Sustained hydrogen peroxide production via MXene-functionalized supramolecular docking

Domain: biology
Published: 2026-03-15
Editorial outcome: major_revision

Abstract
Direct photosynthesis of hydrogen peroxide (H2O2) from air and water using metal/covalent-organic frameworks offers a sustainable alternative to the conventional energy-intensive anthraquinone process. However, current systems suffer from short operational lifetimes typically 10–100 h due to mismatch between O2 capture efficiency and multielectron redox kinetics. Here, we report a supramolecular platform that integrates O2 capture, H2O2 synthesis, and in situ utilization, enabling continuous H2O2 production for over 1,000 hours without sacrificial agents. Mesoporous bromine-substituted COFs are hydrogen-bonded to photothermal MXene, providing organized O2 docking sites and columnar charge transport via σ–σ interactions and π–π stacking. Through a dual-pathway mechanism, the architecture achieves a competitive H2O2 production rate of 2,878 μmol g−1 h−1, alongside complete pollutant removal and durable operation across diverse water sources and outdoor conditions. This work demonstrates a supramolecular design featuring programmable O2 docking, directional charge transport, and localized H2O2 utilization toward decentralized chemical manufacturing.

Introduction
Hydrogen peroxide (H2O2) has been extensively used as a clean oxidant in bleaching, disinfection, environmental remediation, and organic synthesis1. More recently, it has emerged as a promising zero-emission liquid fuel, capable of converting chemical energy into electricity with minimal pollution and high cost-efficiency2. Today’s industrial production of H2O2 is dominated by the conventional anthraquinone oxidation (AO) process, which requires multistep hydrogenation–oxidation cycles at elevated temperatures to activate reagents3 (Supplementary Fig. 1a). This not only incurs substantial energy penalties but also generates large volumes of wastewater, exhaust gases, and solid waste, undermining its environmental credentials and raising downstream treatment costs. Therefore, photocatalytic H2O2 synthesis with green and mild reaction conditions has been considered as an alternative approach. Although inorganic catalysts (TiO2, CdS, and g-C3N4) have been widely explored for electro/photo synthesis4,5, their periodic lattice lacks robust docking sites and efficient transport channels, hindering the material’s ability to capture O2 from open air and rapidly transfer H2O2 molecules, thereby limiting its conversion efficiency (Supplementary Fig. 1b). Covalent organic frameworks (COFs) with donor-acceptor structures offer high porosity, crystallinity, and tunable band structures, and have shown promise for photocatalytic H2O2 production. Despite conventional strategies including band structure tuning and suppression of photogenerated carrier recombination, their photocatalytic activities remain hampered by an inherently weak photoresponse. In particular, harnessing near-infrared light (NIR, > 760 nm), which accounts for ~53 % of solar irradiance, could drastically enhance catalytic performance6, yet few COFs successfully combine NIR photo-absorbers with efficient, well-defined charge transfer pathways.

To mimic the multi-unit architecture of respiratory enzymes in living organisms optimized for O2 and H2O molecules utilization and maintain the same dynamic response as the conventional metal-organic frameworks (MOFs), we proposed a versatile supramolecular system that can be universally employed to integrate various frameworks and functional building units. In specific, we incorporate metallic amine-functionalized MXene (Ti3C2Tx-NH2) photothermal units into rigid COF backbones to construct an integrated supramolecular (COF)x-NH2-M system (where x refers to the mass ratio between COF and MXene, supported by the elemental analysis in Supplementary Tables 1 and 2) for the capture–synthesis–utilization of H2O2 (Fig. 1a), exhibiting a MOFs-like light harvesting characteristics enhanced by the presence of metallic units. Hydrogen-bonded interactions on highly electronegative N atoms links conjugated layers via π–π stacking interactions, while σ–σ stacking interactions7 connect multilayered nanosheets, creating densely organized O2-docking sites and rapid, directional charge pathways (Fig. 1b). To guide supramolecular assembly for controlled crystallinity, surface area and carrier mobility8, we surmise that TAPB (1,3,5-tris(4-aminophenyl)benzene) monomer, among the common ligands9, maximizes hydrogen-bonded interactions by providing the highest density of N sites, thereby promoting intermolecular charge transfer (Fig. 1c). Compared to triazine, the decentralized spatial distribution of N atoms in TAPB further promotes charge separation throughout catalytic reactions.

The highly tunable pore structures in COFs confine guest molecules within their channels through multiple van der Waals interactions, theoretically supporting efficient molecular recognition for selective gas capture. However, O2 and N2 molecules in air have remarkably similar kinetic diameters (3.46 and 3.64 Å, respectively)10, limiting the specificity of O2 capture. To elaborate, O2 is a paramagnetic molecule possessing two unpaired electrons in its π* orbital, which allows it to engage in coordination or charge-transfer complexes with hosts featuring vacant orbitals or donor sites. In contrast, the chemically inert, diamagnetic N2 molecule with its stable triple bond exhibits minimal propensity for similar electron interactions and docking affinity toward supramolecular framework. In addition to the intrinsically higher electron affinity of O2, the presence of electron-deficient centers (such as aromatic nitrogen heterocycles11 and conjugated quinones12) in aromatic molecules have been shown to preferentially adsorb O2. Besides, water molecules serves as proton donors for H2O2 production renders their interaction with the COF structure essential for tailoring the overall reactivity and durability13. To address these challenges, we herein introduce a docking strategy based on the π-conjugated structure of our supramolecular materials and the electron configuration of O2. Although recent advancements have underscored the potential of molecular docking in drug design for predicting ligand-receptor interactions14–16, a comprehensive understanding of docking mechanisms in catalytic reactions remains to be fully established to enable their efficient application.

In this work, we incorporate bromine, a more electronegative substitute for carbon to induce the delocalization of π-electrons, thereby lowering the electron density of benzene rings. The AA-stacked TAPB-TaBr2 COF (where TaBr2 is 2,5-dibromoterephthalaldehyde) exhibits the largest electrostatic potential variation, optimizing distinct molecular docking sites for O2 (Fig. 1d and Supplementary Fig. 2). Our theoretical calculations confirm that O2 adsorption at theses aromatic docking sites is energetically favored within the supramolecular framework. Notably, variations in binding affinity across different sites of supramolecular assemblies are closely related to the adsorption-desorption dynamics underpinning target-molecule capture and release. The intrinsic mesoporous architecture of COF frameworks exposes abundant, spatially defined sites for O2 and H2O adsorption, maximizing opportunities for molecular reactant docking. Thereby, we establish a well-defined supramolecular catalyst, enabling two key advances (i) optimized charge transfer through σ–π hydrogen-bonded connection and (ii) efficient catalytic turnover through strategic reactant-catalyst docking. Simultaneously, (COF)x-NH2-M exhibits a broadened light absorption into the NIR region and harnesses photothermal heating of hot electrons to drive the photosynthesis of H2O2 at elevated local temperatures.

Results
Structure of COF and supramolecular photocatalysts
In the (COF)x-NH2-M supramolecular system, TAPB-TaBr2 COF is introduced with Br substituents derived from TAPB-Ta COF (where Ta is terephthalaldehyde), a selected prototype for H2O2 photocatalysis17. Solvothermal condensation of TAPB with TaBr2 yields an imine-linked COF designed to feature (i) mesopores for efficient mass transfer without requiring additional activation, (ii) electron-donating TAPB “knots” to drive four-electron water oxidation reaction (WOR), and (iii) electron-accepting TaBr2 linkers for two-electron oxygen reduction (ORR)13. The rigid Br substituents in TAPB-TaBr2 COF induce a distortion on Ta backbones (Supplementary Fig. 3), resulting in stronger interplanar interactions, enhancing thermal stability and crystallinity18. To stabilize the MXene and improve its supramolecular interactions, Ti3C2Tx nanosheets are functionalized with 3-aminopropyl-triethoxysilane (APTES), yielding NH2-terminated surfaces that circumvent phase transformation19 under photocatalytic process and boost hydrogen-bonded bridging with TAPB-TaBr2 COF (Supplementary Fig. 4a). To elucidate the local intermolecular interaction on imine linkages, we employed the Independent Gradient Model based on Hirshfeld partitioning (IGMH) to analyze weak interaction (Fig. 2a). The density functional theory (DFT) optimized cluster model clearly reveals the formation of N–H···N hydrogen bonds (2.20 Å). The green IGMH isosurface with faint blue center localized at the hydrogen bonding sites indicates the coexistence of van der Waals interaction and weak hydrogen bonding interaction20. The distribution of most data points between −0.02 and 0.01, together with the relatively larger dg values near 0.02 in the scatter plot, further supports our proposal. N 1s X-ray photoelectron spectroscopy (XPS) results verify the bridging on N atoms, with N–H peak (401.6 eV) significantly enhanced by amino hydrogen bonding, while the N=C peak (399.5 eV)21 remains unchanged (Fig. 2b). Moreover, the Fourier transform infrared (FTIR) spectra of Ti3C2Tx-NH2 composite under TaBr2 monomers presence at varied duration exhibit no detectable enhancement on C=N absorption, confirming the absence of covalent bond formation between Ti3C2Tx-NH2 and TAPB-TaBr2 COF (Supplementary Fig. 5).

The highly ordered π–π stacked COF backbone is evident from its theoretically consistent crystal configuration and mesoporous architecture. The crystal structure of TAPB-TaBr2 COF in AA stacking (Fig. 2a) was optimized by DFT (Supplementary Tables 3–5) and reconstructed by Pawley refinement with lattice parameters of a = b = 3.62 nm, c = 0.419 nm, α = β = 90°, and γ = 120°. Powder X-ray diffraction pattern (PXRD) patterns (Fig. 2c) confirm the AA-stacked hexagonal framework, while other symmetries and stacking modes fail to reproduce the observed intralayer atom distributions and peak positions (Supplementary Figs. 3 and 6). Solid-state 13C cross-polarization magic angle spinning nuclear magnetic resonance (CP/MAS NMR) spectroscopy further verifies the distinct carbon environments along the imine linkages (Supplementary Fig. 7). To assess COF quality, Raman spectroscopy shows the absence of TaBr2 aldehyde C=O stretching vibration around 1690 cm−1, alongside an intense phenyl C=C band at ~1570 cm−1, and a C=N band at 1616 cm−1 (Supplementary Fig. 8), indicating monomer depletion and imine bond formation. Similarly, characteristic peaks for imine COF with highly conjugated aromatic rings are observed at 1615 cm−1 and 1594 cm−1 in FTIR spectrum of TAPB-TaBr2 COF (Supplementary Fig. 9). Nitrogen sorption measurements at 77 K determine the high Brunauer-Emmett-Teller (BET) surface areas of 1289.56 m2 g−1 for TAPB-TaBr2 COF and 1125.70 m2 g−1 for (COF)2.5-NH2-M. Both reveal type VI isotherms accompanied by H2-type hysteresis, confirming the extensive presence of columnar pores and interparticle voids (Supplementary Fig. 10). Barrett-Joyner-Halenda (BJH) analysis shows a dominant micropore width of 3.79 nm (Supplementary Fig. 11), which is consistent with the pore size predicted from the crystal structure (37.274 Å from Supplementary Fig. 3a). The resulting structural stability and mesoporosity expose abundant binding sites, enabling efficient docking of O2 molecules.

In addition, detailed analysis of the chemical states associated with σ–σ units was performed for both the MXene and the supramolecular assembly. APTES grafting on single-layered Ti3C2Tx MXene was verified by solution-state 1H NMR (Supplementary Fig. 12) and Raman spectroscopy (Supplementary Fig. 8b), which show signals attributed to silane hydrolysis and amino (–NH2) groups. XPS survey scans of Ti3C2Tx-NH2, TAPB-TaBr2 COF, and the assembled (COF)x-NH2-M supramolecular catalysts reveal additional N 1s and Si 2p peaks (Supplementary Figs 13–17). The N–H peak in the N 1s XPS spectrum (Supplementary Fig. 15f) and the Si–O/Si–C peak (101.9 eV) in the Si 2p XPS spectrum (Supplementary Fig. 15g) suggest the coexistence of silane chains and amino groups. In addition, the increased intensity of the C–O peak around 286.2 eV in the C 1s XPS spectrum (Supplementary Fig. 15b) and the Ti(VI)–O doublet in the Ti 2p XPS spectrum (Supplementary Fig. 15c) confirms the formation of an oxygen bridge between MXene surface and the silane chain via hydrolysis reaction. The C 1s XPS spectrum of (COF)2.5-NH2-M exhibits characteristic peaks composed of C–Ti (281.8 eV), C=C/C–C (284.6 eV) and C=N (285.4 eV), which were respectively assigned to metallic MXene units, aromatic rings, and imine linkages (Supplementary Figs. 16 and 17). Detection of the Ti 2p XPS spectrum in (COF)2.5-NH2-M sample (Supplementary Fig. 17e), along with the increased intensity of the Ti3C2Tx-NH2 (002) peak at 2θ = 4.3° in the PXRD patterns of (COF)x-NH2-M further confirms the retention of both MXene and COF phases (Supplementary Fig. 18).

Specifically, the reliability of the supramolecular assembly was confirmed through the validation of hydrogen-bonded bridges and morphological characterization. FTIR spectroscopy and NMR analysis distinguish hydrogen bond formation within the supramolecular assembly from covalent linking. As shown in Supplementary Fig. 9, the splitting and shifting22 of the C=N/C–N stretching peaks around 1693/1393 cm−1 in the FTIR spectra reveal the redistribution of electron density around the N center induced by N–H···N hydrogen bonding at the imine linkage in (COF)2.5-NH2-M. Similarly, the signal around 0.6 ppm (–NH2) in 1H NMR of (COF)2.5-NH2-M becomes broader in TAPB-TaBr2 COF and sharper in Ti3C2Tx-NH2, indicating the extensive formation of N–H···N hydrogen bonding at the interface to offset the electron shielding effect by conductive matrix of MXene (Fig. 2d). This assertion is further evidenced by the variable-temperature NMR results under ultrafast MAS conditions, presenting an increasing intensity of –NH peaks due to the weakening hydrogen bonds with temperature rising23 (Fig. 2e and Supplementary Fig. 19). Furthermore, the distinct signal around 40 ppm in 13C NMR spectrum of Ti3C2Tx-NH2 is slightly shifted in (COF)2.5-NH2-M (Fig. 2f), reflecting the effect of hydrogen bonding on the carbon atoms adjacent to the amino terminals. Scanning electron microscopy (SEM) images show that the TAPB-TaBr2 COF forms granules ~2 μm in diameter (Supplementary Figs. 20a and b). With the incorporation of Ti3C2Tx-NH2, COF particles uniformly assembled and stacked onto the metallic MXene nanosheets via supramolecular interactions (Supplementary Figs. 20 c–f). In Fig. 2g, the polycrystalline domains of TAPB-TaBr2 COF appear widely distributed and interspersed with darker Ti3C2Tx-NH2 fringes by high-resolution transmission electron microscopy (HR-TEM). Each COF domain displays a honeycomb-like hexagonal framework with a pore size of 3.52 nm, while the MXene lattice fringes exhibit an interplanar spacing of 3.61 nm (Figs. 2h and 2i). At higher resolution (Supplementary Fig. 21), well-defined boundaries indicate effective supramolecular bridging. Correspondingly, energy-dispersive spectroscopy (EDS) mappings (Supplementary Figs. 22–25) and line scans (Fig. 2j) on different sites corroborate the existence of uniform supramolecular structure arising from hydrogen-bonded connections.

Energy levels and photogenerated carrier dynamics
The electronic structure governs charge carrier dynamics of COFs, which is crucial for evaluating the performance of supramolecular catalysts in practical photosynthesis applications. Theoretical calculations show the highest occupied molecular orbital (HOMO, Fig. 3a) is localized on the donor knots (TAPB), while the lowest unoccupied molecular orbital (LUMO, Fig. 3b) resides on the acceptor linkers (TaBr2), establishing segregated oxidation and reduction sites. To analyze its band structure, the semiconductor energy levels of TAPB-TaBr2 COF and the work function of Ti3C2Tx-NH2 were separately measured (Fig. 3c). The TAPB-TaBr2 COF yields an optical bandgap of 2.50 eV, as determined from the Tauc plot (Supplementary Fig. 26a). The conduction band minimum (CBM) of TAPB-TaBr2 COF was determined to be −1.58 V (versus normal hydrogen electrode (NHE), pH 6.8) from the Mott-Schottky plot (Supplementary Fig. 26b), which indicates sufficient driving force for ORR into H2O2 via the superoxide anion intermediate (O2/•O2−,−0.35 V). Meanwhile, its valence band maximum (VBM) lies at 0.92 V (NHE, pH 6.8), suggesting the involvement of 4e− WOR (0.83 V). Ultraviolet photoemission spectroscopy (UPS) (Supplementary Figs. 26c and d) reveals a work function of 3.97 eV for metallic Ti3C2Tx-NH2, promoting the formation of Schottky junction with accelerated charge transfer24. Based on the band structures predicted by DFT (Fig. 3d, Supplementary Fig. 27, and Supplementary Data 1), the AA-stacked TAPB-TaBr2 COF exhibits the largest bandgap and highest reduction potential to trigger dual H2O2 production pathways. According to the projected density of states (PDOS) for TAPB-TaBr2 COF (Fig. 3d), the energy states near the band edge are primarily contributed by p-orbital electrons. Specifically, the Br, N, C atoms on the acceptor linkers exhibit greater electron deficiency, as evidenced by their significantly higher p-orbital electron density at the conduction band edge (Supplementary Figs. 28 and 29). Moreover, the electrostatic potential calculations reveal that these acceptor linkers carry the most negative average charges which induce photo-generated carrier localization and O2 adsorption (Fig. 1d).

Next, we investigated the dynamics of photogenerated carriers in (COF)x-NH2-M. Nyquist plots from electrochemical impedance spectroscopy (EIS) analysis indicate an obvious light response for (COF)x-NH2-M (Fig. 3e). By further fitting with an equivalent circuit, the charge transfer resistance is determined to reduce due to enhanced charge migration with increasing MXene content, under both dark conditions and 1 sun (standard solar illumination of 100 mW cm−2) irradiation (Supplementary Fig. 30 and Supplementary Table 6). Steady-state photoluminescence (PL) spectra in Fig. 3f show a progressive reduction in emission intensity of (COF)x-NH2-M’s PL around 600 nm to 640 nm, indicative of more efficient exciton dissociation and suppressed electron-hole recombination. Correspondingly, time-resolved fluorescence measurements further corroborate these findings with the average carrier lifetime extending from 0.69 ns to 2.54 ns as MXene loading increases, reflecting enhanced charge extraction by the conductive MXene domains (Fig. 3g, Supplementary Fig. 31, and Supplementary Table 7). Conclusively, integrating metal-like MXene with the COF creates a supramolecular heterostructure with tailored band structures and optimized carrier dynamics, driving dual-route H2O2 production.

Photo-to-thermal conversion performance
Among the (COF)x-NH2-M series samples, obvious color changes of the yellow COF are observed (Supplementary Fig. 32a). Ultraviolet-visible-near-infrared diffuse reflectance spectroscopy (UV-Vis-NIR DRS) was employed to investigate the full-spectrum optical properties of (COF)x-NH2-M. As shown in Fig. 4a, metallic Ti3C2Tx-NH2 nanosheets exhibit a strong absorption bands around 670 nm and 1100 nm due to the LSPR effect25. Compared to the TAPB-TaBr2 COF, (COF)x-NH2-M shows a substantial broadening of absorption across the entire NIR region, which indicates an improved sunlight utilization beyond 250–500 nm. In addition, NIR absorption increases with MXene content in the supramolecular system (Supplementary Figs. 32b–d). Therefore, the MXene units functionalized supramolecular material that we developed provides opportunities for tailoring light response in the NIR region.

A thermal imaging camera and scanning photothermal microscopy (SPThM) were used to evaluate the enhanced photothermal heating capability of (COF)x-NH2-M at both macroscopic and localized scales (Supplementary Fig. 33a). As illustrated in Fig. 4b and Supplementary Figs. 33b–f, the temperature of a self-supported Ti3C2Tx-NH2 film rapidly reached around 72 °C after exposure to simulated 1 sun irradiation. Under identical conditions, the surface temperature of (COF)x-NH2-M rose from ~38 °C (pure COF) to 57 °C (x = 2.5), attributed to the photothermal effect of the Ti3C2Tx-NH2 nanosheets. Under such intentionally controlled MXene loading, the elevated temperature remains within a favorable range for H2O2 synthesis kinetics3. This optimized temperature range, together with the enhanced stability of Ti3C2Tx-NH2, effectively suppresses the secondary decomposition (Supplementary Figs. 34 and 35). For localized photo-to-thermal measurements, SPThM equipped with a UV-NIR light source probed illuminated areas on TAPB-TaBr2 COF and (COF)x-NH2-M samples. The MXene photothermal units induce a more pronounced temperature rise, which in turn produced proportional changes in the tip voltage due to heat flow from the heated samples to the SPThM tip26. By precisely positioning the SPThM tip on the catalyst surface, a higher light-induced temperature increase of 1.8 °C for (COF)2.5-NH2-M nanoparticles were observed versus 1.0 °C for TAPB-TaBr2 COF under the same irradiation conditions, indicating a superior photothermal response (Fig. 4c).

To visualize localized heating effects throughout the supramolecular catalysts, Kelvin probe force microscopy (KPFM) with an integrated light source was employed to map light-induced variations on surface potential27. LSPR-induced hot-electron generation on the MXene surface, together with interfacial charge transfer within (COF)x-NH2-M increases free-electron density and the measured surface potential. As shown in the topography and surface potential maps (Fig. 4d), UV-NIR light illumination on (COF)2.5-NH2-M sample produced a significant increase in surface potential by 51 mV relative to dark conditions, while only marginal change of 12 mV was observed on TAPB-TaBr2 COF sample (Supplementary Fig. 36). Together, the KPFM and SPThM results reveal enhanced localized photo-to-thermal conversion in (COF)x-NH2-M, which indicates both elevated temperature for accelerated O2 activation and enhanced charge transfer for driving photocatalytic reaction.

Photocatalytic H2O2 production
The photocatalytic activities of (COF)x-NH2-M were assessed under simulated sunlight in an open batch reactor by monitoring H2O2 formation directly from water and air via colorimetry (Supplementary Fig. 37). H2O2 production commenced spontaneously upon the addition of (COF)x-NH2-M dispersion and light irradiation, with no induction period, gas bubbling, pH adjustment, or sacrificial reagents. Under optimized catalyst dosage (Supplementary Fig. 38a) and reaction temperature, (COF)2.5-NH2-M achieved an enhanced H2O2 production of 1.77 mmol g−1 within 30 min, around 1.81 times that of TAPB-TaBr2 COF (Fig. 4e). Notably, H2O2 production rates scaled with MXene content, whereas a pure Ti3C2Tx-NH2 suspension yielded negligible 15 μM over 3 h (Supplementary Fig. 39a), highlighting the superior performance contributed by our supramolecular design on catalysts. Photocatalytic H2O2 yield experiments conducted under irradiation with different wavelength regions revealed a distinct decrease in activity when the NIR and UV components were excluded (Supplementary Fig. 40). This behavior confirms the existence of a synergetic photo- and photothermal-catalytic effect that accelerates the reaction and enhances the overall catalytic efficiency.

Considering the energy band alignment in Fig. 3c, we proceeded to investigate the dual-route pathways with 2e− ORR and 4e− WOR throughout the catalytic process. To probe the role of O2 in the photocatalytic H2O2 production, reactions were performed under different gas atmospheres (Fig. 4f). Continuous Ar/N₂ flow to deoxygenate the dispersion suppressed H2O2 formation for both TAPB-TaBr2 COFs and (COF)2.5-NH2-M dispersions, while O2 flow significantly increased the H2O2 yield. Together with the likewise quenched H2O2 production with electron scavenger (AgNO3) addition (Supplementary Fig. 38b), a more specific rotating ring-disk electrode (RRDE) measurements in an O2-saturated phosphate buffer solution (PBS, pH = 7) confirmed the highly selective 2e− ORR pathway for catalytic process (Supplementary Figs. 41a and b). Noticing the persisted H2O2 generation when the reactor was purged with inert gas only before reaction, ORR is expected to sustain owing to the in situ O2 produced via the 4e− WOR (oxygen evolution reaction, OER, 0.83 V) which is thermodynamically favored over the 2e− WOR (1.36 V). Beyond this, the distinct current response for RRDE curves in Ar-saturated PBS (Supplementary Fig. 41c) coincides with the increasing 18O2/16O2 ratios with irradiation time in isotope labelling experiment for sealed photocatalytic system starting with 16O2 saturated H218O solution (Fig. 5a), confirming the existence of 4e− WOR. Additionally, the 18O2 signal remains detectable when the extracted aqueous phase after irradiation was then purged with Ar and injected into a vial containing MnO2, depicting that the in situ generated O2 from WOR could subsequently participate in ORR toward H2O2.

To verify the possible intermediates involved in photocatalytic production, in situ electron paramagnetic resonance (EPR) spectroscopy was conducted in methanol/H2O using 5,5-dimethyl-1-pyrroline N-oxide (DMPO) as spin-trapping reagent. As depicted in Fig. 5b, the EPR spectra of both TAPB-TaBr2 COF and (COF)2.5-NH2-M dispersion exhibited intensified characteristic peaks of •O2− with increasing irradiation time, while no signals were detected under dark condition, indicating light-induced generation of •O2− intermediate. Meanwhile, the more distinct signals in (COF)2.5-NH2-M system suggest accelerated O2 activation upon light irradiation. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) in a sealed chamber with the presence of O2 and H2O was employed to further elucidate H2O2‐formation pathways and identify reactive sites on (COF)x-NH2-M (Fig. 5c). A broad peak at 886 cm−1 corresponding to O–O bonding13,28,29 gradually increases with irradiation time, suggesting the accumulation of H2O2. Moreover, the concurrent emergence and intensification of the OOH bending mode of surface-adsorbed H2O2 (*H2O2) at 1396 cm−1 further reveal in situ H2O2 generation30,31. Peaks at 1160 cm−1 and 1260 cm−1 assigned to •O2− 28,32 and *OOH30,31,33,34, respectively, further support the formation of key intermediates in a two-step ORR pathway (Supplementary Fig. 27e). Compared to DRIFTS without O2 flow (Supplementary Fig. 42a), enhanced aromatic signals between 1400–1600 cm−1 indicate that the aromatic rings serve as O2 docking site. Notably, in situ Raman spectra corroborate the occurrence of •O2−, evidenced by the signal magnification at 1091 cm−1 over time35 (Supplementary Fig. 42b).

To elucidate the docking mechanism underlying the enhanced H2O2 photosynthesis, we combined DFT analysis with spectroscopic observations and temperature-programmed measurements on TAPB-TaBr2 COF and (COF)x-NH2-M assemblies. The DRIFTS results show time‐dependent variations in the peak intensities of aromatic carbon moieties under photoirradiation, suggesting their likely involvement as active sites (Fig. 5c). Based on this observation and the LUMO distribution of TAPB-TaBr2 COF (Fig. 3b), the imine linkages and adjacent aromatic carbons are selected as candidate O2 adsorption sites for comparative analysis (Supplementary Figs. 43–45). O2 adsorption energy calculations on TAPB-TaBr2 COF (Fig. 5d, red columns) indicate that O2 docking at aromatic carbons (0.36 eV) is energetically more favorable than at imine linkages (0.86 eV). The incorporation of Ti3C2Tx-NH2 units in (COF)x-NH2-M contributes to the electron abundance on COF framework with lower O2 adsorption energy at aromatic carbons (0.06 eV), suggesting the facilitated O2 docking at COF framework (Fig. 5d, blue columns). In comparison, oxygen vacancies of Ti3C2Tx-NH2 exhibit a high adsorption energy (0.81 eV), implying limited likelihood of effective O2 activation at these sites. To experimentally evaluate the O2 docking capability of materials, oxygen temperature-programmed desorption (O2-TPD) was performed to probe the adsorption-desorption behavior of surface oxygen species. Prior to the O2-TPD measurements, thermogravimetric analysis verified the thermal stability of the TAPB-TaBr2 COF over the relevant temperature range (Supplementary Fig. 46). The TPD profiles exhibit a pronounced low-temperature desorption feature (~150 °C), which can be attributed to reversible oxygen species that are weakly bound at π-conjugated aromatic carbon sites36 (Supplementary Fig. 47). Notably, the increasing MXene content leads to a pronounced enhancement of the low-temperature desorption, indicating the improved O2 docking capability in (COF)x-NH2-M. Furthermore, Gibbs free energy calculations disclose a lower energy barrier toward forming the *O intermediate at the aromatic carbon site of (COF)x-NH2-M (Fig. 5e), which is the rate-determining step of ORRs. Similarly, OER is expected to proceed via a single-site (*O/*OOH) pathway at the aromatic carbons located at the TAPB edge, where (COF)x-NH2-M exhibits a lower energy barrier (1.993 eV) than TAPB-TaBr2 COF (2.492 eV) (Fig. 5f). It should be noted that the calculated free-energy profiles serve as thermodynamic descriptors of elementary steps and do not directly represent absolute photocatalytic reaction kinetics. Nevertheless, the consistency between the computed energetic trends and the experimentally established reaction pathways, together with the enhanced catalytic performance of the supramolecular systems, provides qualitative support to the proposed ORR/WOR mechanism and more favorable reaction energetics upon MXene incorporation.

Practical potential assessment
To investigate the stability of (COF)2.5-NH2-M, a recycling test was performed, presenting a negligible H2O2 yield decay and minor structural changes within 5 cycles (Supplementary Fig. 48). To evaluate the scalability and real-world applicability of our photocatalytic system, we designed an integrated flow reactor incorporating (COF)x-NH2-M dispersions. Coupled with a peristaltic pump and a collection reservoir, the aqueous (COF)2.5-NH2-M dispersion was continuously circulated through modular tandem reactors. This setup enabled uninterrupted H2O2 generation over 24 h under laboratory conditions without noticeable activity loss (Supplementary Fig. 49), which can be attributed to the robust π-conjugated framework of (COF)x-NH2-M supramolecular assembly. To further validate practical viability, we deployed a self-powered outdoor system driven by a photovoltaic cell (Fig. 6a), which sustained a steady production of H2O2 at a peak rate of 658 μmol g−1 h−1 under ambient conditions (light intensity < 1 sun) as shown in Supplementary Fig. 50.

Importantly, in many decentralized applications, such as environmental disinfection, food preservation, and green chemistry, the required H2O2 concentration at the point of use is typically below 0.4 wt%37. This stands in stark contrast to conventional AO processes, which generate highly concentrated H2O2 solution that requires subsequent distillation and poses substantial safety risks during transport and storage. To address this, we proposed a modular collection platform (Fig. 6b) to directly produce controllable concentrations of H2O2 on-site, thus eliminating the demands for energy-intensive post-processing and mitigating explosion hazards. In addition, immobilizing (COF)2.5-NH2-M supramolecular catalyst on a solid substrate facilitated continuous replenishment of the reaction medium and prolonged the operational lifespan while maintaining consistent productivity. As a result, the total amount of H2O2 accumulated linearly over time (Supplementary Figs. 51 and 52). Among state-of-the-art photocatalytic H2O2 production system11,13,17,29,34,38–46, our system delivers a competitive production rate of 2,878 μmol g−1 h−1 without requiring O2 bubbling, pH adjustment, or sacrificial agent. Notably, this is the first demonstration of continuous operation for 1,008 h in a fully integrated setup (Fig. 6c and Supplementary Table 8). This combination of operational simplicity, long-term durability, and point-of-use compatibility offers a promising pathway for advancing photocatalytic H2O2 production toward real-world applications.

We also evaluated the photocatalytic performance of (COF)2.5-NH2-M in deionized water, simulated seawater, and real seawater. Only a slight decrease in H2O2 production was observed (Fig. 6d), suggesting that the material retains high activity despite potential interference from competing ions. To further demonstrate practical applicability, we conducted in situ pollutant removal tests using methyl orange (MO) and 2,4,6-triformylphloroglucinol (TFP) as representative dye and phenolic pollutants (Supplementary Fig. 53). Under 1 sun irradiation, rapid degradation of MO (95%) and TFP (77%) was achieved within 60 min (Fig. 6e), confirming not only the reactivity of the produced H2O2 but also the system’s broad potential for decentralized water treatment scenarios. The on-demand generation of dilute H2O2 solutions minimizes the need for transporting, storing, and handling concentrated oxidants, thereby offering an inherently safer and more sustainable disinfection route. As evidenced by the global solar irradiance map (Supplementary Fig. 54), the widespread distribution of solar resources supports the feasibility of deploying (COF)x-NH2-M-integrated systems across diverse regions. Operating under ambient conditions without external energy input or hazardous reagents, this platform offers an environmentally benign, decentralized, and scalable alternative to the conventional AO H2O2 industry.

Methods
Materials
TAPB, TaBr2, mesitylene, 1,4-dioxane, acetic acid, ethanol, acetone, lithium fluoride, hydrochloric acid (HCl, 37%), APTES, potassium hydrogen phthalate (KHP), potassium iodide (KI), and Nafion (5 wt% in the mixture of lower aliphatic alcohols and water) were purchased from Adamas. D2O (≥ 99.9 at% D), Water-18O (≥ 97 at% 18O), and DMPO (≥ 97%) were purchased from Aladdin. Titanium aluminum carbide (Ti3AlC2, MAX) was purchased from Laizhou Kai Kai Ceramic Materials Co. Ltd. All chemicals were used as received without further purification.

Synthesis of TAPB-TaBr2 COF
To synthesize TAPB-TaBr2 COFs, 0.4 mmol TAPB (140.58 mg) and 0.6 mmol TaBr2 (175.15 mg) were added into a Teflon reactor and ultrasonically dispersed for 20 min in 10 mL mixed solvent of mesitylene/1,4-dioxane (v : v = 1:4). Subsequently, 1 mL acetic acid solution (6 M) was added and followed by another 5 min ultrasonication. The reactor was then sealed and transferred to an oven at 120 °C. After 3 days of solvothermal reaction, the precipitate was washed 3 times with acetone and ethanol respectively and collected by suck filtration through hydrophobic membranes. Finally, the product was ground with ethanol and dried in vacuum oven at 60 °C for 12 h.

Synthesis of Ti3C2Tx-NH2
The Ti3C2Tx suspension (30 mg in 3 mL ethanol and 12 mL H2O), obtained by wet etching of HCl/LiF and ethanol addition, was stirred with 1 mL APTES for 12 h at ambient temperature. After centrifuging sequentially in ethanol and H2O, the precipitate was freeze-dried for 2 days to obtain Ti3C2Tx-NH2.

Synthesis of (COF)x-NH2-M
To synthesize (COF)x-NH2-M, Ti3C2Tx-NH2 powder was finely ground and then sonicated to disperse in the mixture of 0.4 mmol TAPB (140.58 mg), 0.6 mmol TaBr2 (175.15 mg), and 10 mL mixed solvent of mesitylene/1,4-dioxane (v : v = 1:4), where the Ti3C2Tx-NH2 content was determined by the mass ratio to the feeding amount of COF monomers (x). After the addition of 1 mL acetic acid solution (6 M), the following sonication time was prolonged to 20 min to further ensure thorough mixing of the COF monomers and Ti3C2Tx-NH2 nanosheets. Finally, the product after subsequent solvothermal reaction and collection were conducted inductively coupled plasma optical emission spectroscopy (ICP-OES) and CHNS measurements for elemental analysis to verify the repeatability.

Photocatalytic H2O2 synthesis and quantification
For batch reactor, 1 mg of photocatalyst was dispersed in 10 mL deionized water. A 300 W Xe lamp (CEL-PE300-3A, China Education Au-light) was calibrated with a light intensity meter and used to drive the photocatalytic reaction with magnetic stirring at 150 rpm. The reaction solution was sampled at certain intervals and passed through hydrophilic syringe filters. The yield of H2O2 was determined by iodometry method (0.5 mL reaction solution + 0.5 mL deionized water + 1 mL 0.1 M KHP + 1 mL 0.4 M KI) and followed by UV-Vis spectroscopy to determine the concentration of I3− oxidized by H2O2. For flow reactor, 15 mg photocatalyst was dispersed in the mixture of 4.5 mL ethanol and 0.5 mL Nafion (binder), subsequently deposited on the substrate. Deionized water was continuously pumped into the reactor and the diluted H2O2 solution was collected in the source container. A controlled amount of catalyst was periodically replenished to offset stripping.

Materials characterization
The valence state and work function of as-prepared samples were measured by XPS (Al Kα source) and UPS (ESCALAB 250Xi, Thermo Fisher Scientific). The PXRD patterns were recorded on a diffractometer (D8 Advance, Bruker, Cu Kα radiation), together with BET test (3Flex, Micromeritics) to further analyze the crystal structure and mesoporosity. The chemical bonding was determined by Raman spectroscopy (WITec alpha300, Oxford Instruments) and FTIR (IRPrestige-21, Shimadzu). The morphology was revealed by SEM (JSM-7001F, JEOL) and HRTEM (JEM-F200, JEOL). Steady-state PL spectra and time-resolved fluorescence lifetime were recorded by spectrofluorometer (FLS1000, Edinburgh) under 364 nm excitation light. The reflectance and absorbance spectra were obtained using an UV-Vis-NIR spectrophotometer (UV-3600, Shimadzu). The chemical adsorption characteristics were evaluated by thermogravimetric analysis (STA200, HITACHI) and O2-TPD (TP-5080B, Xianquan).

Independent gradient model based on Hirshfeld partition (IGMH)
The DFT calculations on molecular cluster model was performed using the Gaussian 16 package47. Geometry optimizations and vibrational frequency calculations were carried out with the BL3YP-D348–50, employing the lanl2dz basis set for Br atom and the 6-31G (d)51 basis set for other elements. Using optimized structure, the IGMH52 was employed to analyze with Multiwfn53 and visualize with Visual Molecular Dynamics54 software.

Nuclear magnetic resonance (NMR) measurements
The solution-state 1H NMR (Varian mercury 400, Agilent, D2O as solvent) was applied to analyze the successful grafting of –NH2 groups on Ti3C2Tx. The solid-state 1H and 13C CP/MAS NMR (Avance Neo 400M, Bruker) were performed to validate the existence of N–H···N hydrogen bonding interactions, which were further verified by the variable-temperature 1H solid-state NMR (Avance Neo 400WB, Bruker) measurements at MAS = 15 kHz.

Electrochemical measurements
The electrochemical impedance spectroscopy (EIS) and Mott-Schottky measurements were conducted using a CHI660E electrochemical workstation configured in a standard three-electrode system. The working electrode was prepared by coating the catalyst on fluorine-doped tin oxide substrates, while a platinum plate and an Ag/AgCl electrode served as the counter and reference electrodes, respectively. All measurements were carried out in the 0.2 M Na2SO4 solution13 (pH = 6.8). EIS was analyzed with a frequency ranging from 100 kHz to 0.1 Hz. The position of conduction band minimum (CBM) can be converted into normal hydrogen electrode (NHE) using the following equation:
ENHE (pH=6.8) = EAgCl/Ag + 0.197 V (1)

Scanning photothermal microscopy (SPThM) and Kelvin probe force microscopy (KPFM)
SPThM and KPFM were carried out on a commercial scanning probe microscopy system (MFP-3D, Asylum Research, Oxford Instruments). During the measurements, the samples were irradiated with a metal halide fiber optic illuminator (Model MH-100), covering a full UV-NIR spectrum.

18O isotope labelling experiments
The 18O isotope was measured on a gas chromatograph mass spectrometer (GC-MS, GCMS-QP2010Ultra, Shimadzu). (COF)2.5-NH2-M photocatalyst (2 mg) and H218O (≥ 97 atom% 18O, 1 mL) were added into a sealed quartz tube and pumped with 16O2 in the dark for 30 min. After 2 h and 12 h irradiation, the 60 μL of gas products in the headspace were extracted and analyzed by GC-MS. The remaining liquid phase of mixture was pumped with Ar for 30 min to remove the remaining O2 and subsequently added with MnO2 to generate O2 by the decomposition of photogenerated H2O2.

Rotating ring-disk electrode (RRDE) measurements
The ORR and WOR were studied by using a RRDE with (COF)2.5-NH2-M, which was coated using a uniformly dispersed mixture (5 mg photocatalyst in 20 μL 5% Nafion and 180 μL isopropanol). The RRDE assembly included a glassy carbon disk (r = 4 mm) and a platinum ring (r = 4.3 mm/6.3 mm). For ORR, 0.1M PBS (pH = 7) saturated with O2 was used as electrolyte, with platinum plate as counter electrode and Ag/AgCl electrode as reference electrode. The ring/disk currents were measured by an SP-150e potentiostat (Biologic). The H2O2 product was detected at the ring potential of 0.6 V (vs. Ag/AgCl). The electron transfer number (n) is calculated as follows:
n = 4Id / (Id + Ir/N) (2)
where Id is the disk electrode current, Ir is the ring electrode current, and N is the collection efficiency.
Similarly, the WOR was analyzed in Ar saturated solution and detected at the ring potential of −0.23 V (vs. Ag/AgCl).

Electron paramagnetic resonance (EPR) spectroscopy
The catalysts (2 mg) were separately dispersed into a methanol/H2O mixture (9/1 v/v, 500 μL) containing 0.1 mmol DMPO as a spin-trapping reagent to detect •O2− intermediate. Before reaction, the dispersion was purged with O2 gas for 5 min. The resulting mixture was extracted and sealed in a capillary tube, followed by Xe lamp irradiation for subsequent testing.

In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS)
In situ DRIFTS measurements were conducted in an in situ reaction cell (Hefei in situ technology) and detected by a modified FTIR spectrometer (Nicolet iS50, Thermo Fisher Scientific) equipped with an MCT detector cooled by liquid N2. Before the measurement, the photocatalyst with a small amount of water was filled into the holder and the chamber was purged with He/O2 gas mixture at a flow rate of 10 mL min−1 for 30 min to record the baseline. Subsequently, the Xe lamp was used to irradiate the reaction cell and the IR spectra were collected with time.

Computational details
The simulation of periodic COF structure was conducted on the BIOVIA Materials Studio suite of programs to perform molecular dynamics and DFT calculations within the generalized gradient approximation (GGA)55 using the Perdew-Burke-Ernzerhof (PBE) functional. The geometry structure was initially established in the Forcite module and followed by optimization in the DMoL3 module. During the structural optimization, we employed an energy convergency smaller than 2×10−5 Ha. Pawley refinement was then predicted using Reflex module with convergent Rwp and Rp. For energy calculation, we used the k-point set of 1×1×4 to sample the electronic structure.
To simulate the H2O2 generation, we employed the Vienna Ab initio Simulation Package (VASP)56,57 at GGA-PBE level with k-points of 1×1×1. The interaction between valence electrons and ionic cores was treated with the projected augmented wave method58 with an energy cutoff of 450 eV. To account for long-range dispersion interactions, the DFT-D3 empirical correction was incorporated59.
More discussions of the DFT calculation are listed in the supplementary information.

Data availability
All data that support the findings of this study are available within the article and Supplementary Information. Source data are provided with this paper.

Peer review rounds
[{"round": 1, "reviewer_comments": {"reviewer_1": "This manuscript reports a supramolecular assembly platform that integrates oxygen (O₂) capture, hydrogen peroxide (H₂O₂) synthesis, and in situ utilization, enabling continuous H₂O₂ production. While the authors have addressed certain structural aspects of the material in the Discussion section, the investigation into the underlying mechanisms remains insufficient. The data interpretation is overly superficial, failing to thoroughly explore the various influencing factors and their interrelationships. Based on the following considerations, I cannot recommend the acceptance of this manuscript in its current form.\n1.The authors propose that the integration of metallic amine-functionalized MXene (Ti₃C₂Tₓ–NH₂) photothermal units into a rigid covalent organic framework (COF) backbone leads to the formation of an integrated supramolecular system, denoted as (COF)ₓ–NH₂–M. However, the preparation strategy for such composite materials has been previously reported in the literature, and the innovation in this regard appears limited. Moreover, the specific structure of the composite material is not clearly elucidated in the manuscript.\n2.Typically, Ti₃C₂Tₓ synthesized via the method described in this work is expected to exhibit a large, sheet-like morphology rather than the small nanostructures connected to each nitrogen site as illustrated in the schematic diagram. Was the structural compatibility between the COF and Ti₃C₂Tₓ nanostructures taken into account when constructing the schematic model? Furthermore, does this affect the validity of the proposed supramolecular architecture?\n3.It is well established that COFs are excellent candidates for photocatalytic H₂O₂ production. In this study, the integration of Ti₃C₂Tₓ raises concerns regarding H₂O₂ decomposition. Ti species in Ti₃C₂Tₓ can catalytically decompose the generated H₂O₂, potentially reducing the overall yield. Therefore, the loading ratio of Ti₃C₂Tₓ is a critical parameter that significantly affects the system's performance. Unfortunately, this important aspect is not addressed in the manuscript.\n4.The surface of Ti₃C₂Tₓ modified with APTES contains a large number of –NH₂ groups. When this modified MXene is introduced into the monomer solution for COF synthesis—specifically, 2,5-dibromoterephthalaldehyde—it is more plausible that imine bonds are formed, leading to in situ growth of the COF on the Ti₃C₂Tₓ surface. This contradicts the claim in the manuscript that hydrogen bonding is the primary interaction mechanism.\n5.Ti₃C₂Tₓ is highly prone to oxidation in reactions involving molecular oxygen (O₂). This contradicts the authors’ assertion that NH₂-terminated surfaces prevent phase transformation during the photocatalytic process and enhance hydrogen bonding with the TAPB-TaBr₂ COF.\n6.The manuscript claims that N 1s X-ray photoelectron spectroscopy (XPS) results confirm the bridging of nitrogen atoms, with a significant enhancement of the N–H peak at 401.6 eV due to hydrogen bonding, while the N=C peak at 399.5 eV remains unchanged, suggesting the absence of covalent linkages to the TAPB-TaBr₂ COF. However, this interpretation does not adequately address the structural concerns raised above, and the investigation into the material's architecture remains superficial and incomplete.", "reviewer_2": "This work by Sun et al. presents a long-term of 1000 hours H2O2 photosynthesis from air and water. A H2O2 production rate of 2,878 μmol g−1 h−1 was reported over the developed supramolecular photocatalyst comprises microporous bromine-substituted COFs conjugated to metallic MXene. However, the photothermal-photocatalytic mechanism has not been investigated enough. Although this work is well-organized, there are still many problems need to be solved. More evidence is needed to support the reaction mechanism and the authors'conclusions. Besides, the reasonability of the conclusions drawn is unconvincing based on the incorrect use of foundational concepts.\n1.In the photocatalysts preparation and characterization, there are still many troubles to be addressed. The -NH2 plays a vital part in the COF/MXene preparation. While, the, the 1H NMR spectrum of COF-NH2-M in Figure 2d was absent. More specific characterizations are needed. According to the XPS data from the Supplementary Fig. 8-12, the presence of halogen elements such as Cl and Br is sometimes observed in the spectra. Do these elements play a role in catalysis? The preparation of MXene was absent. In the name of (COF)x-NH2-M, what the x refers to? The describe is unclear.\n2.As we know, in COF materials, different stacking patterns typically correspond to different types of semiconductors. In this Figure 3d and Supplementary Fig. 22a, we can see the obvious character of indirect bandgap semiconductor. However, the subsequent band structure analysis was based on a direct bandgap of the COF. The conclusion drawn based on this analysis may be ambiguous.\n3.For H2O2 photosynthesis, a O2-seal an O2-flow should be added to further verify the reaction pathway. In addition, the results in Supplementary Fig. 30 seems inconsistent with that in Figure 4f. More important, the photothermal MXene and photocatalytic COF, what roles did each play and how were they coupled? More evidence and specific work are needed.\n4.Relatively high temperatures are not conducive to the formation of H2O2 and may even accelerate its decomposition. H2O2 decomposition experiments over various catalysts and under various related temperature should be also carried out.\n5.The scale-up reactor under ambient environment is well designed, however, the record of real-time temperature of the catalyst under natural sunlight is absent.", "reviewer_3": "This work presents a supramolecular assembly composed of covalent organic frameworks (COFs) integrated with metallic MXene for sustained photocatalytic hydrogen peroxide (H₂O₂) production. The (COF)x-NH2-M heterostructure enables O₂ capture and H₂O₂ production under ambient conditions without scavengers, achieving a record operational lifetime of over 1,000 hours. Additionally, theoretical and experimental studies support mechanistic insight into H2O2 production. While the study demonstrates impressive performance, there are some issues that should be addressed before acceptance.\n1) Based on the SEM images of (COF)x-NH2-M, the MXene content in the composite appears relatively high. However, the near-complete disappearance of MXene diffraction peaks in the XRD data (Supplementary Fig. 13) is somewhat unexpected. Could you provide a more detailed explanation for this observation? Additionally, please include the quantitative ratio between MXene and COF using ICP-MS or SEM-EDS when controlling the (COF)x content.\n2) In Supplementary Fig. 4, please highlight and provide zoom-in image to clarify the difference between synthesized COF, AA stacking, and AB stacking.\n3) Fig. 2h is not clear for me. It seems white dash line is where you scanned. However, the middle section appears completely dark, even though MXene is present there. Additionally, the carbon signal appears uniformly distributed, while the left region is completely dark and the right region seems to be covered by some particles. Could you clarify if this interpretation is correct and provide more explanation regarding the image?\n4) The explanation of the ATR-FTIR data is unclear. Do you mean that the presence of hydrogen bonding leads to splitting and shifting of the imine vibration band? If so, it seems contradictory that the splitting disappears after hydrogen bond formation. Since this data is critical for confirming the supramolecular structure, the interpretation should be explained more clearly and in greater detail.\n5) Regarding the UPS data, my understanding is that for metallic materials, the low binding energy edge should indicate that the electronic bands cross the Fermi level (at 0 eV binding energy). However, your UPS spectrum appears more characteristic of a semiconducting material. Could you please clarify this.\n6) The interpretation of the EIS data is not sufficiently clear. Please provide a more detailed explanation of the EIS results. In Fig. 3e, which specific point represents the reduced charge transfer resistance? It would be helpful to include a zoomed-in image highlighting the differences in resistance and to provide a more thorough discussion of these observations.\n7) Regarding the PL data, where does the peak at 620 nm originate? It does not appear to correspond to the COF’s band gap emission. Additionally, if the coordination between the COF and MXene is sufficiently strong, I would expect a more pronounced quenching effect, especially given the metallic nature of MXene. Could you clarify these points?\n8) You mentioned that Addition of the electron scavenger (AgNO3) likewise quenched H2O2 production, confirming that the ORR is the primary pathway for the catalytic process. However, adding hole scavenger also showed decrease of yield. Usually, yield should increase after scavenger addition due to prolonged electron lifetime. Please clarify it.\n9) There is no explanation on Fig. 5d.\nMinor issues\n1) In Fig. 1a, for the supramolecular structure, please indicate what each color represents.", "reviewer_4": "In this work, Sun and coworkers present a supramolecular assembled platform that integrates O2 capture, H2O2 synthesis, and in situ utilization, enabling continuous H2O2 production for over 1000 hours without sacrificial agents. Although the results seem encouraging and characterization are decent, there are many critical issues and mistakes that have to be comprehensively addressed. Thus, its current form falls below the standards required for publication in Nature Communications and should be rejected.\n1. Line 108-109, “In the (COF)x-NH2-M supramolecular photocatalysts, metallic MXene nanosheets are grafted onto the COF backbone’s imine linkages via hydrogen bonds”. How do the authors accurately quantify the amount of the MXene nanosheets and how about the repeatability, it should be addressed.\n2. Line 111-1122, “solvothermal condensation of TAPB with TaBr2 yields an imine-linked COF designed to feature (i) micropores..”. However, the pore size in Fig. 2a is claimed to be 37.3 Å, which is undoubtful mesopore. The authors should explain this. The same mistake for the description of the N2 sorption results (Line 143).\n3. Line 133. The lattice parameters of TAPB-TaBr2-COF, c = 0.419 nm, however, in table S1, c = 3.8685 Å. The authors should explain this.\n4. FT-IR spectra measurements should be given to assess COF quality instead of Raman spectroscopy.\n5. The N2 sorption isotherm seems quite strange, why no N2 uptake at low relative pressure region? It is really uncommon for COFs. The authors should explain this. Furthermore, for comparison, the N2 sorption isotherms after the grafting of MXene should be given.\n6. Line 193-194, “Meanwhile, its valence band maximum (VBM) lies at 1.01 V (NHE, pH 6.8), suggesting the involvement of four-electron water oxidation (0.83 V)..” It can only prove that four-electron WOR is thermodynamic feasibility, how can the author know the involvement of four-electron WOR?\n7. Line 206, what’s the meaning of “1 sun”?\n8. Line 277-279, the authors claimed the in situ O2 produced via four-electron WOR pathway, more experiments should be performed to prove this, such as isotope experiments and RRDE measurements.\n9. Electron paramagnetic resonance (EPR) spectroscopy was performed to identify the possible intermediates.\n10. The recycling tests (at least 5 repeated cycles) of the studied materials toward H2O2 photosynthesis should be given. And the general characterization of the materials after repeated cycles should be given to prove the stability of the studied materials, such as PXRD, SEM, FT-IR etc.\nAll in all, the writing of this manuscript is quite confusing, the characterization of the materials is not sufficient and there are still lots of unsolved problems in this study. It is not recommended to be published in its current form."}, "author_response": "Point-by-point response for Nature Communications manuscript\n(ID: NCOMMS-25-52770)\nManuscript Type: Article\nTitle: Sustained hydrogen peroxide production via metallic unit-functionalized supramolecular docking\nAuthor(s): Jiaxun Sun†, Yuanming Zhang†, Wanheng Lu, Wei Li Ong, Xinglong Pan, Wentao Song,\nZhonghua Li, Zhaosheng Li, Ghim Wei Ho*\nGeneral response: We sincerely appreciate the editor, editorial staff and all reviewers for their valuable and\ncritical comments. The manuscript has been greatly improved by addressing all the suggestions with points-\nby-points responses as listed below.\n(Our response is given in blue, the corrections in the revised manuscript are shown in red, and some key points\nare highlighted in yellow.)\nPoints-by-points responses to Reviewer(s):\nReviewer #1:\nThis manuscript reports a supramolecular assembly platform that integrates oxygen (O ) capture, hydrogen\n2\nperoxide (H O ) synthesis, and in situ utilization, enabling continuous H O production. While the authors\n2 2 2 2\nhave addressed certain structural aspects of the material in the Discussion section, the investigation into the\nunderlying mechanisms remains insufficient. The data interpretation is overly superficial, failing to thoroughly\nexplore the various influencing factors and their interrelationships. Based on the following considerations, I\ncannot recommend the acceptance of this manuscript in its current form.\nResponse: We are grateful for the reviewer’s constructive feedback on our manuscript.\nWe sincerely appreciate the reviewer’s recognition of our work on utilizing TAPB-TaBr COF (TAPB =\n2\n1,3,5-tris(4-aminophenyl)benzene and TaBr = 2,5-dibromoterephthalaldehyde) for well-designed\n2\nphotocatalytic H O production, integrating photothermal unit via supramolecular engineering, and realizing\n2 2\nlong-term oxygen capture, in situ synthesis and utilization for the first time. Also, the suggestions and concerns\non data interpretation help us to substantially improve the quality of our manuscript. In response to the\nreviewer’s comments, we have conducted a series of additional experiment and expanded the corresponding\nanalysis as follows.\n(i) In terms of material design, we characterized the sample with Fourier transform infrared (FTIR)\nspectroscopy and variable-temperature solid-state 1H nuclear magnetic resonance (NMR), together with the\npreviously presented X-ray photoelectron spectroscopy (XPS) and 13C solid-state NMR results, systematically\ndemonstrating the presence of hydrogen bonding interactions we proposed within the supramolecular\nassembly.\n(ii) Regarding the reaction mechanism, we thoroughly analyzed the effects of temperature and light\nirradiation on the possible decomposition of H O and decoupled the photothermal and photocatalytic\n2 2\ncontributions. In addition, we supplemented the study with isotope labelling and rotating ring-disk electrode\n(RRDE) methods to further deepen the analysis of dual reaction pathways; we employed in situ electron\nparamagnetic resonance (EPR) spectroscopy to detect the possible intermediates. These results can be found\nin our revised manuscript and the following points-by-points responses. We hope our revision will address the\nreviewer’s concern on the depth of our analysis.\n1. The authors propose that the integration of metallic amine-functionalized MXene (Ti C T -NH )\n3 2 x 2\nphotothermal units into a rigid covalent organic framework (COF) backbone leads to the formation of an\nintegrated supramolecular system, denoted as (COF) -NH -M. However, the preparation strategy for such\nx 2\ncomposite materials has been previously reported in the literature, and the innovation in this regard appears\nlimited. Moreover, the specific structure of the composite material is not clearly elucidated in the manuscript.\nResponse: Thanks for the reviewer’s attentive comments. We have addressed the reviewer’s concerns\nseparately as follows.\n(i) We present the first supramolecular material exhibiting efficient photothermal H O generation, in\n2 2\nwhich aminated MXene is assembled with TAPB-TaBr COF (TAPB = 1,3,5-tris(4-aminophenyl)benzene and\n2\nhave focused on designing composite materials that connecting MXene and COF components via covalent\nbonds. For instance, Wang et al. constructed a photocatalytic material by covalently linking β-ketoenamine-\nCOFs onto Ti C T -NH , which enhanced photocatalytic H production in a sacrificial system (J. Am. Chem.\n3 2 x 2 2\nSoc. 2020, 142, 4862−4871). He et al. developed an amino-functionalized MXene composite featuring a two-\ndimensional iron covalent organic framework on the MXene via covalent bond, demonstrating its efficacy for\nelectrocatalytic nitrogen reduction (Adv. Sci. 2023, 10, 2206933). Similar with the composite materials\nDABA-TFP COF/MXene (DABA = 4,4’-diaminobiphenyl; TFP = 1,3,5-triformylphloroglucinol) via covalent\nassembly (ACS Nano, 2025, 19, 11058–11074) in lithium-sulfur batteries. So, our material design and\nfunctionality markedly differ from previous reports. We demonstrate a TAPB-TaBr COF capable of\n2\nphotocatalytic H O generation for the first time, with its band alignment and electronic structure\n2 2\ncomprehensively elucidated. In addition, aminated MXene with intrinsic photothermal activity is assembled\nwith TAPB-TaBr COF through hydrogen bonding, substantially enhancing O capture from ambient air and\n2 2\nestablishing an integrated supramolecular platform for in situ capture, synthesis, and utilization.\n(ii) We focus on the design of COF backbones and MXene photothermal units to realize supramolecular\nassembly at macroscopic level through hydrogen bonding. To further clarify our hydrogen-bonded\nsupramolecular structure, we have now revised figures including in Fig. R1 (this figure corresponds to revised\nFig. 1) a conceptual illustration of our supramolecular design, and in Fig. R2 (this figure corresponds to revised\nFig. 2) the depiction of local hydrogen-bonding connections between the two components. Furthermore, we\nhave added the synthetic route and relevant structural schemes in the Fig. R3 (this figure corresponds to revised\nSupplementary Fig. 4) to facilitate the reviewer’s understanding of the overall structure. Based on these\nconsiderations, we also supplemented FTIR and variable-temperature solid-state NMR to further elucidate the\nhydrogen bonding interactions in supramolecular assembly, which can be found in the following responses.\nFig. R1 | Molecular design of metallic unit-functionalized hydrogen-bonded supramolecular assemblies with docking sites.\na, Schematic of integrated supramolecular design featuring enzyme-like docking sites for various frameworks and functional units.\nb, -assembly contributed by the connection of - and -stacking interactions (dash line on the chain represents hydrogen\nbonds). c, Molecular design of N-rich ligands with steric effects (blue, metallic MXene units; red, COF ligands). d, Electrostatic\npotential distribution maps of TAPB-Ta COF in AA stacking, TaPB-TaBr COF in AA stacking, and TAPB-TaBr COF in AB\n2 2\nstacking, the unit of scale bar is Hartree/e.\nFig. R2 | Structural characteristics of TAPB-TaBr COF and supramolecular (COF) -NH -M. a, Molecular structures of\n2 x 2\nTAPB-TaBr COF and (COF)-NH -M. b, N 1s XPS spectra of Ti C T-NH , TAPB-TaBr COF, and (COF) -NH -M. c,\n2 x 2 3 2 x 2 2 2.5 2\nExperimental PXRD pattern of TAPB-TaBr COF with Pawley refinement fit. d, f, Solid-state NMR spectra of Ti C T-NH (dark\n2 3 2 x 2\nblue), TAPB-TaBr COF (red), and (COF) -NH -M (blue) (d) 1H and (f) 13C. e, Variable-temperature 1H solid-state NMR spectra\n2 2.5 2\nof (COF) -NH -M (from −40 °C to 20 °C with an increment of 20 °C). g, h, HR-TEM image of (COF) -NH -M in different\n2.5 2 2.5 2\nmagnification. i, Fourier transform of the COF domains, showing lattice fringes of the COF networks and MXene multilayers. j,\nEDS line scan profiles of selected elements across the (COF) -NH -M.\n2.5 2\nFig. R3 | Synthesis and structures of supramolecular (COF) -NH -M.\nx 2\n2. Typically, Ti C T synthesized via the method described in this work is expected to exhibit a large, sheet-\n3 2 x\nlike morphology rather than the small nanostructures connected to each nitrogen site as illustrated in the\nschematic diagram. Was the structural compatibility between the COF and Ti C T nanostructures taken into\n3 2 x\naccount when constructing the schematic model? Furthermore, does this affect the validity of the proposed\nsupramolecular architecture?\nResponse: Thanks for the reviewer’s valuable comments.\nOur target is to integrate photothermal unit into COF networks via hydrogen bonding. The\nsupramolecular design of (COF) -NH -M does not involve small molecular monomers. Instead, consistent\nx 2\nwith strategies reported (J. Am. Chem. Soc., 2022, 144, 2468–2473; Adv. Mater., 2025, 37, 2417374), our\napproach achieves a macroscopic assembly that incorporates functional units into photocatalytic frameworks,\nwhich is highly tunable for various system. Although the MXene content is relatively low, its sheet-like\nmorphology is preserved and assembled with COF nanostructure by non-covalent interaction, rather than\ninsertion of MXene into the mesopores of COF network. Unlike previous studies focusing on COF nanosheets\nnucleation on MXene surfaces, we designed TAPB-TaBr COF with abundant N-sites for supramolecular\n2\nassembly and decentralized distribution for efficient charge separation. In this design, TaBr monomers\n2\npreferentially assemble through hydrogen bonding rather than covalent linkage, ensuring effective integration\nof MXene units within the proposed supramolecular architecture and allowing precise regulation of\nphotothermal properties by controlling the MXene mass fraction.\n3. It is well established that COFs are excellent candidates for photocatalytic H O production. In this study,\n2 2\nthe integration of Ti C T raises concerns regarding H O decomposition. Ti species in Ti C T can\n3 2 x 2 2 3 2 x\ncatalytically decompose the generated H O , potentially reducing the overall yield. Therefore, the loading\n2 2\nratio of Ti C T is a critical parameter that significantly affects the system's performance. Unfortunately, this\n3 2 x\nimportant aspect is not addressed in the manuscript.\nResponse: Thanks for the reviewer’s insightful comments. I will explain our design in response to the\nreviewer’s concern in several aspects with supplemented experiments results.\nFirstly, although metal elements raise the concern of promoting the decomposition of H O , many studies\n2 2\n(Nat. Commun., 2023, 14, 2493; Nat. Commun., 2024, 15, 3212) have reported the use of semiconductor\ncatalysts containing transition metal elements or noble metal cocatalysts for H O production owing to their\n2 2\nmoderate and tunable adsorption on metal sites. In our system, the grafted silane chains on MXene surface are\ndesigned to minimize the exposure of Ti sites, thereby effectively reducing the H O decomposition. To\n2 2\nvalidate our assumption, we performed H O decomposition tests (using equivalent concentration to those in\n2 2\nour photocatalytic system) under both dark and light with existence of Ti C T and Ti C T -NH . As shown\n3 2 x 3 2 x 2\nin Figs. R4a and b (these figures correspond to revised Supplementary Figs. 35a and b), the decomposition of\nH O occurs within 3 hours for all samples, and the effect is more pronounced under light irradiation but\n2 2\nclearly reduced in grafted samples. These results confirm that our surface modification significantly supressed\nthe undesired H O decomposition. More importantly, our design discussed the collection of diluted H O\n2 2 2 2\nseparately in a continuous flow reactor, which will not suffer from in situ H O decomposition on MXene\n2 2\nduring storage and long-term reaction.\nIn regard to the loading ratio control of MXene, this is an important point to design an optimal loading\nin our supramolecular assembly. We would like to point out that, compared with the direct H O\n2 2\nphotodecomposition on MXene surface, the photothermal heating effect induced by MXene may play a more\ndominant role in promoting H O decomposition. To clarify this, we have presented the thermal\n2 2\ndecomposition profiles at different temperature (Fig. R4c, this figure corresponds to revised Supplementary\nFig. 35c), revealing that the decomposition becomes significant at temperature above 55 °C. As discussed in\nthe manuscript, the photothermal temperature of our supramolecular system reached the limit of 55°C in\n(COF) -NH -M. Considering that further increasing the MXene content would inevitably lead to higher local\n2.5 2\ntemperatures and thereby accelerate H O decomposition, we intentionally avoided increasing the\n2 2\nphotothermal component loading beyond this point. This design choice ensures that the reaction proceeds\nefficiently without excessive loss of H O due to thermal decomposition.\n2 2\nFig. R4 | H O decomposition tests. a–c, Relative H O concentration which is comparable to photosynthesis process (a) dark\n2 2 2 2\ncondition, (b) photodecomposition, and (c) thermodecomposition.\nAction: We have expanded upon the above discussion in the main text and Supplementary information as\nfollows:\n“Under such intentionally controlled MXene loading, the elevated temperature remains within a\nfavorable range for H O synthesis kinetics3. This optimized temperature range, together with the enhanced\n2 2\nstability of Ti C T -NH , effectively suppresses the secondary decomposition (Supplementary Figs. 34 and\n3 2 x 2\n35).”\n4. The surface of Ti C T modified with APTES contains a large number of –NH groups. When this modified\n3 2 x 2\nMXene is introduced into the monomer solution for COF synthesis—specifically, 2,5-\ndibromoterephthalaldehyde—it is more plausible that imine bonds are formed, leading to in situ growth of the\nCOF on the Ti C T surface. This contradicts the claim in the manuscript that hydrogen bonding is the primary\n3 2 x\ninteraction mechanism.\nResponse: Thanks for the reviewer’s insightful comments.\nBased on extensive literature comparison and our supplemented experiment results, we have thoroughly\nverified that hydrogen bonding is the primary interaction mechanism of our supramolecular assembly. To\nverify that no covalent bonds were formed between the components, we conducted a control experiment in\nwhich the TaBr monomer was mixed with MXene under the same reaction conditions. As shown in Fig. R5\n2\n(this figure corresponds to revised Supplementary Fig. 5), the FTIR spectra of Ti C T -NH and Ti C T -\n3 2 x 2 3 2 x\nNH @TaBr after solvothermal reaction are essentially identical with no detectable signals around 1615 cm−1\n2 2\nto support imine bonds in such composites. Herein, we specially design our TAPB-TaBr COF with abundant\nanalysis of XPS results, we have provided solid evidence supporting the presence of hydrogen-bonding\ninteractions in the following responses.\nFig. R5 | FTIR spectra of pristine Ti C T -NH and Ti C T -NH @TaBr .\n3 2 x 2 3 2 x 2 2\nAction: We have added the above discussion in the main text and Supplementary information as follows:\n“Moreover, combined with the Fourier transform infrared (FTIR) results, the identical spectrum of\nTi C T -NH composite under TaBr monomers presence along with the absence of any detectable C=N\n3 2 x 2 2\nstretching signal confirms that almost no covalent linkages are formed between Ti C T -NH and TAPB-TaBr\n3 2 x 2 2\nCOF (Supplementary Fig. 5).”\n5. Ti C T is highly prone to oxidation in reactions involving molecular oxygen (O ). This contradicts the\n3 2 x 2\nauthors’ assertion that NH -terminated surfaces prevent phase transformation during the photocatalytic\n2\nprocess and enhance hydrogen bonding with the TAPB-TaBr COF.\nFirstly, we would like to clarify that as a type of commonly used photothermal material (Nature, 2024,\n634, 1103–1110; Nat. Sustain., 2025, 8, 1058–1067), MXene seldom suffer from the photothermal\nperformance decay under slight oxidation. Also, APTES functionalization has been reported to prevent the\ncontact of exposed Ti atom with molecular oxygen and water, which play important roles in MXene oxidation\n(FlatChem, 2019, 17, 100128). To further verify our assertion, we dispersed Ti C T and Ti C T -NH in\n3 2 x 3 2 x 2\ndilute H O solution with comparable concentrations to photosynthesis process, thereby better simulating the\n2 2\nactual reaction environment. After standing for 2 weeks, the dispersion with Ti C T turned into white TiO ,\n3 2 x 2\nwhile the one with Ti C T -NH was still in dark black, which indicates that the photothermal property of\n3 2 x 2\nTi C T -NH was well-preserved. We have added the photothermal temperature measurement of Ti C T -NH\n3 2 x 2 3 2 x 2\nsample after long-term standing (Fig. R6, this figure corresponds to revised Supplementary Fig. 34). Our DFT\ncalculation also reveal the lower oxygen adsorption energy on Ti C T -NH than the docking site on COF,\n3 2 x 2\nwhich can be attribute to the enhanced oxygen abundance on surface terminations (Fig. R7, this figure\ncorresponds to revised Fig. 5d).\nFig. R6 | Stability of Ti C T -NH . a, Digital photo of Ti C T and Ti C T-NH sample after dispersed in diluted H O solution\n3 2 x 2 3 2 x 3 2 x 2 2 2\nfor 2 weeks. b, The photothermal temperature of Ti C T-NH sample after long-term standing.\n3 2 x 2\nFig. R7 | O adsorption energies on aromatic carbon (linker), imine linkage, and oxygen vacancies of MXene (red column,\n2 x 2\n6. The manuscript claims that N 1s X-ray photoelectron spectroscopy (XPS) results confirm the bridging of\nnitrogen atoms, with a significant enhancement of the N–H peak at 401.6 eV due to hydrogen bonding, while\nthe N=C peak at 399.5 eV remains unchanged, suggesting the absence of covalent linkages to the TAPB-\nTaBr COF. However, this interpretation does not adequately address the structural concerns raised above,\n2\nand the investigation into the material’s architecture remains superficial and incomplete.\nResponse: Thanks for the reviewer’s insightful comment.\nThe observation in N 1s XPS (Fig. R2b, this figure corresponds to revised Fig. 2b) indicates the\npreservation of –NH group from Ti C T -NH . As evidenced in Fig. R5 (this figure corresponds to revised\n2 3 2 x 2\nSupplementary Fig. 5), the FTIR spectra reveals the absence of covalent bonding between Ti C T -NH and\n3 2 x 2\nTaBr monomer. To further address the reviewer’s concern on deepen the structural analysis of supramolecular\n2\n(COF) -NH -M, we performed additional characterizations of FTIR and solid-state NMR to obtain more\nx 2\ncomprehensive insights.\nAs shown in Fig. R8 (this figure corresponds to revised Supplementary Fig. 9), the significant peaks at\n1615 cm−1 and 1594 cm−1 could be attributed to the C=N stretching of imine and C=C stretching of aromatic\nrings, which substantially verify the successful synthesis of high-quality imine-linked COF. The subsequent\npeaks observed at 1503 cm−1, 1456 cm−1, 1442 cm−1, and 1359 cm−1 are typical characteristics of aromatic\nstructures and extended conjugated systems, corresponding to the C=C stretching, C–H in-plane bending, and\nC–N stretching. Considering the multiple aromatic rings and complex conjugated structure, the peaks at 1393\ncm−1 and 1697 cm−1 slightly deviate from the original peak position, which can sensitively characterize the\nchemical interaction with imine group. The existence of N–H···N hydrogen bonding is predicted to affect the\nstretching vibration of the C=N linkage, thereby causing a slight shift toward higher wavenumbers in the\nspectrum (J. Am. Chem. Soc. 2024, 146, 2663–2672; Nat. Photon. 2023, 17, 478–484). As shown in the blue\ncolumns in the figure, both two peaks split for all samples with MXene presence, indicating the existence of\nhydrogen bonding in our supramolecular assembly.\nFig. R8 | FTIR analysis of TAPB-TaBr COF and (COF) -NH -M. a, FTIR spectra. The orange columns verify the successful\n2 2.5 2\nsynthesis of imine COF and the blue columns verify the existence of hydrogen bonding. b, Peak table and relevant description.\nAs shown in Fig. R9 (this figure corresponds to revised Fig. 2d), the signals ~0.6 ppm in 1H solid-state\nNMR spectra (400 MHz) are attributed to the –NH groups, which is expected to be sharp in Ti C T -NH due\n2 3 2 x 2\nto the electron shielding effect by conductive matrix, whereas becomes broader in COF. Thereby, the extensive\nformation of N–H···N hydrogen bonding at the interface will offset the shielding effect of MXene, resulting\nin a higher peak intensity (not as sharp as pristine Ti C T -NH ) in (COF) -NH -M compared with TAPB-\n3 2 x 2 2.5 2\nTaBr COF. To further support this assertion, variable-temperature NMR under ultrafast MAS (15 kHz)\n2\nconditions reveal a shaper and more distinct –NH peak (Fig. R10, this figure corresponds to revised Fig. 2e).\n2\nfree, resulting in an enhanced peak intensity (Nat. Chem., 2012, 4, 711–717; J. Am. Chem. Soc., 2025, 147,\n39623–39631). Moreover, the distinct signal around 40 ppm in 13C NMR spectrum of Ti C T -NH is slightly\n3 2 x 2\nshifted in (COF) -NH -M (Fig. R2e, this figure corresponds to revised Fig. 2e), reflecting a chemical\n2.5 2\nenvironment change of the carbon atoms adjacent to the amino terminals caused by the formation of hydrogen\nbonding. These findings offer direct and compelling evidence for the existence for hydrogen bonding\ninteractions within the supramolecular structure.\nFig. R9 | 1H solid-state NMR of TAPB-TaBr COF, (COF) -NH -M and Ti C T -NH .\n2 2.5 2 3 2 x 2\nFig. R10 | Variable-temperature 1H solid-state NMR spectra of (COF) -NH -M (from −40 °C to 20 °C with an increment\n2.5 2\nof 20 °C).\nAction: We have elaborated the above discussion on hydrogen bonding in the main text and Supplementary\ninformation as follows:\n“Specifically, the reliability of the supramolecular assembly was confirmed through the validation of\nhydrogen-bonded bridges and morphological characterization. FTIR spectroscopy and NMR analyses\ndistinguish hydrogen bond formation within the supramolecular assembly from covalent linking. As shown in\nSupplementary Fig. 9, the splitting and shifting21 of the C=N/C–N stretching peaks around 1693/1393 cm−1 in\nthe FTIR spectra reveal the N–H···N hydrogen bonding at the imine linkage in (COF) -NH -M. Similarly,\n2.5 2\nthe signal around 0.6 ppm (–NH ) in 1H NMR of (COF) -NH -M becomes broader in TAPB-TaBr COF and\n2 2.5 2 2\nsharper in Ti C T -NH , indicating the extensive formation of N–H···N hydrogen bonding at the interface to\n3 2 x 2\noffset the electron shielding effect by conductive matrix of MXene (Fig. 2d). This assertion is further\nevidenced by the variable-temperature NMR results under ultrafast MAS conditions, presenting an increasing\nintensity of –NH peaks due to the weakening hydrogen bonds with temperature rising (Fig. 2e and\n3 2 x\nNH is slightly shifted in (COF) -NH -M (Fig. 2f), reflecting the effect of hydrogen bonding on the carbon\n2 2.5 2\natoms adjacent to the amino terminals.”\nReviewer #2:\nThis work by Sun et al. presents a long-term of 1000 hours H O photosynthesis from air and water. A H O\n2 2 2 2\nproduction rate of 2,878 μmol g−1 h−1 was reported over the developed supramolecular photocatalyst comprises\nmicroporous bromine-substituted COFs conjugated to metallic MXene. However, the photothermal-\nphotocatalytic mechanism has not been investigated enough. Although this work is well-organized, there are\nstill many problems need to be solved. More evidence is needed to support the reaction mechanism and the\nauthors' conclusions. Besides, the reasonability of the conclusions drawn is unconvincing based on the\nincorrect use of foundational concepts.\nResponse: We are grateful for the reviewer’s thoughtful comment and insightful suggestions. We sincerely\nappreciate the reviewer’s recognition of our work that “this work is well-organized” towards designing a\nsupramolecular photocatalyst comprising photothermal units for photocatalytic H O production, realizing\n2 2\nlong-term oxygen capture, in situ H O synthesis and utilization for the first time. Also, the suggestions and\n2 2\nconcerns on data interpretation for photothermal-photocatalytic mechanism help us to substantially improve\nthe quality of our manuscript. In response to the reviewer’s comments, we have improved our work with\nsupplementary experimental results and careful corrections on mechanism explanation. To enhance the\nanalysis on supramolecular material design, we conducted variable-temperature solid-state NMR and FTIR to\ncharacterize the existence of hydrogen bonding interaction we proposed. To further deepen our mechanistic\nunderstanding of both the material system and H O photosynthesis, we performed both H O decomposition\n2 2 2 2\ntests and analysis on H O synthetic routes (including isotope labelling and rotating ring-disk electrode (RRDE)\n2 2\nmethods to reveal dual production pathways; in situ electron paramagnetic resonance (EPR) spectroscopy to\ndetect the possible intermediates). Furthermore, the dual routes of H O photosynthesis have been evaluated\n2 2\nby DFT calculations. These results can be found in our revised manuscript and the following points-by-points\nresponses. We hope our revision will address the reviewer’s concern on the reliability of our mechanistic\ninvestigation.\n1. In the photocatalysts preparation and characterization, there are still many troubles to be addressed. The –\nNH plays a vital part in the COF/MXene preparation. While the 1H NMR spectrum of COF-NH -M in Figure\n2 2\n2d was absent. More specific characterizations are needed. According to the XPS data from the Supplementary\nFig. 8–12, the presence of halogen elements such as Cl and Br is sometimes observed in the spectra. Do these\nelements play a role in catalysis? The preparation of MXene was absent. In the name of (COF) -NH -M, what\nx 2\nthe x refers to? The describe is unclear.\nResponse: Thanks for the reviewer’s important comments. The detailed responses are as follows.\nFor reviewer’s concern on 1H NMR characterization, we would like to clarify that this spectrum was\nprimarily intended to confirm the successful grafting of –NH groups on MXene (Fig. R11, this figure\n2\ncorresponds to revised Supplementary Fig. 12 and original Fig. 2d). In addition, this experiment was\nperformed with deuterium water, which can only dissolve hydrophilic MXene components. Most solvents\ncannot dissolve COF powder without disrupting the imine bonds. To further address the reviewer’s concern,\nwe have performed solid-state NMR to provide complementary evidence supporting the formation of N–H···N\nhydrogen bonding (Nat. Chem., 2012, 4, 711–717; J. Am. Chem. Soc., 2025, 147, 39623–39631). The distinct\nsignal around 0.6 ppm (–NH ) in 1H NMR of (COF) -NH -M, which is broader in TAPB-TaBr COF and\n2 2.5 2 2\nsharper in Ti C T -NH (Fig. R12, this figure corresponds to revised Fig. 2d), rises with temperature due to\n3 2 x 2\nthe weakening of hydrogen bonds (Fig. R13, this figure corresponds to revised Fig. 2e).\nFig. R11 | Solution-state 1H NMR spectra of Ti C T and Ti C T -NH .\n3 2 x 3 2 x 2\nFig. R12 | 1H solid-state NMR spectra of Ti C T -NH , TAPB-TaBr COF, and (COF) -NH -M.\n3 2 x 2 2 2.5 2\nFig. R13 | Variable-temperature 1H solid-state NMR spectra of (COF) -NH -M (from −40 °C to 20 °C with an increment\n2.5 2\nof 20 °C).\nFor reviewer’s concern on halogen elements (Figs. R14–18, these figures correspond to revised\nSupplementary Figs. 13–17 and original Supplementary Figs. 8–12), we will discuss separately as follows.\nThe Cl signals are primarily detected in MXene samples, which originates from the commonly used wet-\netching (hydrochloric acid + lithium fluoride) synthesis of Ti C T . In this process, a trace amount of Cl atoms\n3 2 x\ncan be inevitably incorporated into MXene’s surface termination (Nat. Synth. 2022, 1, 601–614). This minor\nincorporation does not affect the electrical conductivity or photothermal performance of MXene and therefore\nhas no influence on the catalytic process. The Br signals are primarily detected in COF samples, which\noriginates from the monomer (TaBr ) of bromine-substituted COF. As we discussed in our material design,\n2\nthe electronegative bromine substitutes lower the electron density of benzene rings, thereby contributing to\nthe distinct molecular docking sites for O .\n3 2 x\nFig. R15 | XPS spectrum of Ti C O MXene. a, XPS survey. b, C 1s. c, Ti 2p. d, O 1s. e, F 1s.\n3 2 2\nFig. R16 | XPS spectrum of Ti C T -NH MXene. a, XPS survey. b, C 1s. c, Ti 2p. d, O 1s. e, F 1s. f, N 1s. g, Si 2p.\n3 2 x 2\nFig. R17 | XPS spectrum of TAPB-TaBr COF. a, XPS survey. b, C 1s. c, N 1s. d, O 1s. e, Br 3d.\n2.5 2\nFor the MXene preparation part, this method was included in the section of “Synthesis of (COF) -NH -\nx 2\nM”. We have now put it in an individual section. In our work, x represents the mass ratio between COF and\nMXene. We have now revised the manuscript to explicitly define x in the main text to avoid any confusion.\nAction: We have clarified the above discussion in the main text and Supplementary information as follows:\n“Synthesis of Ti C T -NH\n3 2 x 2\nThe Ti C T suspension (30 mg in 3 mL ethanol and 12 mL H O), obtained by wet etching of HCl/LiF\n3 2 x 2\nand ethanol addition, was stirred with 1 mL APTES for 12 h at ambient temperature. After centrifuging\nsequentially in ethanol and H O, the precipitate was freeze-dried for 2 days to obtain Ti C T -NH .”\n2 3 2 x 2\n“(where x refers to the mass ratio between COF and MXene, supported by the elemental analysis in\nSupplementary Tables 1 and 2)”\n2. As we know, in COF materials, different stacking patterns typically correspond to different types of\nsemiconductors. In this Figure 3d and Supplementary Fig. 22a, we can see the obvious character of indirect\nbandgap semiconductor. However, the subsequent band structure analysis was based on a direct bandgap of\nthe COF. The conclusion drawn based on this analysis may be ambiguous.\nResponse: Thanks for the reviewer’s insightful critics.\nA clear character of indirect bandgap of TAPB-TaBr COF is verified. We have conducted a\n2\ncomprehensive analysis of both direct and indirect bandgap concepts. However, we overlooked this distinction\nwhen organizing the manuscript. We have now corrected the mislabeling in both Fig. R19 (this figure\ncorresponds to revised Fig. 3c) and Fig. R20 (this figure corresponds to revised Supplementary Fig. 26a).\nImportantly, the value of bandgap was corrected from 2.59 eV to 2.50 eV, which does not affect our\ninterpretation of the band alignment and thermodynamic analysis on reaction path.\nFig. R19 | Experimentally derived energy band alignments of TAPB-TaBr COF and Ti C T -NH .\n2 3 2 x 2\nFig. R20 | Tauc plot of TAPB-TaBr COF.\n“The TAPB-TaBr COF yields an optical bandgap of 2.50 eV, as determined from the Tauc plot\n2\n(Supplementary Fig. 26a). The conduction band minimum (CBM) of TAPB-TaBr COF was determined to\n2\nbe −1.58 V (versus normal hydrogen electrode (NHE), pH 6.8) from the Mott-Schottky plot (Supplementary\nFig. 26b), which indicates sufficient driving force for ORR into H O via the superoxide anion intermediate\n2 2\n(O /•O −,−0.35 V). Meanwhile, its valence band maximum (VBM) lies at 0.92 V (NHE, pH 6.8), suggesting\n2 2\nthe involvement of 4e− WOR (0.83 V).”\n3. For H O photosynthesis, a O -seal an O -flow should be added to further verify the reaction pathway. In\n2 2 2 2\naddition, the results in Supplementary Fig. 30 seems inconsistent with that in Figure 4f. More important, the\nphotothermal MXene and photocatalytic COF, what roles did each play and how were they coupled? More\nevidence and specific work are needed.\nResponse: Thanks for the reviewer’s valuable suggestions.\nFor the concern on H O photosynthesis verification, we had already included control experiments under\n2 2\ndifferent gas atmosphere (open system, Ar, and N ) and with various sacrificial agents to identify the reactant\n2\ninvolved, as well as in situ DRIFTS measurements confirming the participation of O . Nevertheless, we fully\n2\nunderstand the reviewer’s valuable suggestion and have now supplemented the control experiments under O -\n2\nseal and O -flow conditions. For clarity, we have also added explicit definitions of the “seal” (reaction solution\n2\nis purged with relevant gas for 30 min before reaction and then sealed during the reaction) and “flow” (reaction\nsolution is purged with relevant gas for 30 min before reaction and continuously purged throughout the\nreaction process). As shown in Fig. R21 (this figure corresponds to revised Fig. 4f), the H O yield of O -seal\n2 2 2\nsample was significantly higher than other gas atmosphere, while still slightly lower than the open system.\nWe attribute this to the limited initial solubility of oxygen in the seal condition, which probably restricts the\nreaction kinetics. In contrast, the O -flow sample yielded approximately twice the amount of H O compared\n2 2 2\nwith the open system, further supporting our interpretation of the oxygen-involved reaction pathway. Beyond\nthis, the detection of 18O with MnO presence (Fig. R22, this figure corresponds to revised Fig. 5a) and RRDE\n2 2\nmeasurements in O -saturated solution (Figs. R23a and b, these figures correspond to revised Supplementary\n2\ntime in isotope labelling experiment, together with the detection of O current for RRDE in Ar-saturated\n2\nsolution (Fig. R23c, this figure corresponds to revised Supplementary Fig. 41c), directly proved the existence\nof 4e− water oxidation.\nFig. R21 | H O production of TAPB-TaBr COF and (COF) -NH -M over 60 min under different gas conditions.\n2 2 2 2.5 2\nFig. R22 | 18O isotope labelling experiment for (COF) -NH -M system dispersed in 16O saturated H 18O.\n2 2.5 2 2 2\nFor the concern on figure inconsistence, the H O production of TAPB-TaBr COF “blank” sample in\n2 2 2\nFigs. R21 (this figure corresponds to revised Fig. 4f) and 22 (this figure corresponds to revised Supplementary\nFig. 38 and original Supplementary Fig. 30) are strictly same.\nFig. R24 | H O production in batch reactor. a, Photocatalytic performance of TAPB-TaBr COF at different dosage. b,\n2 2 2\nPhotocatalytic performance of TAPB-TaBr COF in the presence of sacrificial agent.\nprovide detailed explanation and supplementary experiment to address. Photocatalytic TAPB-TaBr COF is\n2\ndesigned as a promising candidate for direct H O photosynthesis from air and water with following advances\n2 2\n(i) mesoporous COF backbone towards rapid mass transfer, (ii) energetically favored and spatially organized\nO docking sites for in situ capture, and (iii) well-designed donor-acceptor structure for dual route reaction.\nimprove sunlight utilization and synergistically enhance photocatalytic H O production in 2 aspects (i)\n2 2\nelevated temperature for accelerated O activation and reaction kinetics that promote surface chemistry with\n2\neffective O adsorption on docking sites and (ii) hot electron generation and enhanced charge transfer for\n2\ndriving photocatalytic reaction. To provide more sufficient and convincing evidence, we revised our analysis\nin the section of “Photo-to-thermal conversion performance” and closely connected to the DFT calculations\nin the section of “Photocatalytic H O production” in our manuscript. Also, we uniquely employed scanning\n2 2\nphotothermal microscopy (SPThM) and Kelvin probe microscopy (KPFM) to investigate the local heat\nvariations induced by the photothermal units within the supramolecular catalyst (Fig. R25, this figure\ncorresponds to revised Fig. 4). The corresponding results and discussions are provided in the section of\n“Photo-to-thermal conversion performance” in original manuscript. In addition, we provide a\nsupplemented H O photosynthesis performance comparison under Xe light irradiation with different filter\n2 2\nand the same current to decouple the contribution of photothermal MXene and photocatalytic COF (Fig. R26,\nthis figure corresponds to revised Supplementary Fig. 40). The remarkable improvement in H O production\n2 2\ncould be attributed to the synergetic photo and photothermo-catalytic effect. The negligible H O production\n2 2\nin MXene suspension (Fig. R27, this figure corresponds to revised Supplementary Fig. 39) further proved that\nthe activity under Vis-NIR light irradiation was contributed by the photothermal-enhanced photocatalysis\nfrom part of the visible light adsorption in COF.\nFig. R25 | Light response and photocatalytic performance of supramolecular (COF) -NH -M. a, Solid-state light absorption\nx 2\nspectra of Ti C T-NH (dark blue),TAPB-TaBr COF (red), and(COF)-NH -M (orange for x = 50; green for x = 5; blue for x =\n3 2 x 2 2 x 2\n2.5) produced by Kubelka-Munk function. b, Photothermal temperature profiles of thin film samples under 100 mW cm−2 light\nirradiation. c, Localized temperature variation induced by light-to-heat conversion at a selected spot of (COF) -NH -M. d,\n2.5 2\nTopography and surface potential maps of a selected area of (COF) -NH -M at dark condition and UV-NIR irradiation (scale bar:\n2.5 2\n200 nm). e, H O production of TAPB-TaBr COF and (COF)-NH -M over 90 min (peak light intensity: 200 mW cm−2). f, H O\n2 2 2 x 2 2 2\nproduction of TAPB-TaBr COF and (COF) -NH -M over 60 min under different gas conditions.\n2 2.5 2\nFig. R26 | H O production under different light sources.\n2 2\nFig. R27 | Ti C T properties. a, Photocatalytic performance of Ti C T compared with TAPB-TaBr COF. b, Absorbance of\n3 2 x 3 2 x 2\nTi C T suspension in different concentration.\n3 2 x\nAction: We have expanded upon the above discussion on verifying ORR/WOR pathways in the main text and\nSupplementary information as follows:\n“Considering the energy band alignment in Fig. 3c, we proceeded to investigate the dual-route pathways\nwith 2e− ORR and 4e− WOR throughout the catalytic process. To probe the role of O in the photocatalytic\n2 2\nto deoxygenate the dispersion suppressed H O formation for both TAPB-TaBr COFs and (COF) -NH -M\n2 2 2 2.5 2\ndispersions, while O flow significantly increased the H O yield. Together with the likewise quenched H O\n2 2 2 2 2\nproduction with electron scavenger (AgNO ) addition (Supplementary Fig. 38b), a more specific rotating ring-\n3\ndisk electrode (RRDE) measurements in an O -saturated phosphate buffer solution (PBS, pH = 7) confirmed\n2\nthe highly selective 2e− ORR pathway for catalytic process (Supplementary Figs. 41a and b). Noticing the\npersisted H O generation when the reactor was purged with inert gas only before reaction, ORR is expected\n2 2\nto sustain owing to the in situ O produced via the 4e− WOR (oxygen evolution reaction, OER, 0.83 V) which\n2\nis thermodynamically favored over the 2e− WOR (1.36 V). Beyond this, the distinct current response for\nRRDE curves in Ar-saturated PBS (Supplementary Fig. 41c) coincides with the increasing 18O /16O ratios\n2 2\nwith irradiation time in isotope labelling experiment for sealed photocatalytic system starting with 16O\n2\nsaturated H 18O solution (Fig. 5a), confirming the existence of 4e− WOR. Additionally, the 18O signal remains\n2 2\ndetectable when the extracted aqueous phase after irradiation was then purged with Ar and injected into a vial\ncontaining MnO , depicting that the in situ generated O from WOR could subsequently participate in ORR\n2 2\ntowards H O .”\n2 2\nWe have also supplemented the above discussion on photothermal-photocatalytic mechanism to the main\ntext and Supplementary information as follows:\n“Together, the KPFM and SPThM results reveal enhanced localized photo-to-thermal conversion in\n(COF) -NH -M, which indicates both elevated temperature for accelerated O activation and enhanced charge\nx 2 2\ntransfer for driving photocatalytic reaction.”\n“Photocatalytic H O yield experiments conducted under irradiation with different wavelength regions\n2 2\nrevealed a distinct decrease in activity when the NIR and UV components were excluded (Supplementary Fig.\n40). This behavior confirms the existence of a synergetic photo- and photothermal-catalytic effect that\naccelerates the reaction and enhances the overall catalytic efficiency.”\n4. Relatively high temperatures are not conducive to the formation of H O and may even accelerate its\n2 2\ndecomposition. H O decomposition experiments over various catalysts and under various related temperature\n2 2\nshould be also carried out.\nResponse: Thanks for the reviewer’s valuable comment.\nOur observations are consistent with the accelerated decomposition of H O at elevated temperatures. As\n2 2\nwe discussed in the evaluation of photothermal behaviors (Fig. R25b, this figure corresponds to revised 4b),\nwe intentionally controlled the loading amount of photothermal units to maintain the photothermal\ntemperature within the range of 50–60 °C, which is consistent with the reported accelerated H O production\n2 2\nwith elevated temperature (Angew. Chem. Int. Ed., 2006, 45, 6962–6984; Nat. Energy, 2023, 8, 361–371). To\nverify our design concept, we examined the thermal decomposition of H O at different temperatures and the\n2 2\nphotodecomposition behavior of H O over different supramolecular components. As shown in Fig. R28c (this\n2 2\nfigure corresponds to revised Supplementary Fig. 35c), obvious thermodecomposition is observed within 3 h\nabove 55 °C, which is consistent with our designed photothermal temperature. Besides, the decomposition in\nboth dark and light condition (Figs. R28a and b, these figures correspond to revised Supplementary Figs. 35a\nand b) is supressed in amino-grafted MXene (Ti C T -NH ) compared with pristine MXene (Ti C T ).\n3 2 x 2 3 2 x\nMoreover, given the relatively low MXene content in the supramolecular catalyst, the intrinsic decomposition\ncan be negligible in the (COF) -NH -M dispersion (Fig. R28b, this figure corresponds to revised\n2.5 2\nSupplementary Fig. 35b).\nFig. R28 | H O decomposition tests. a–c, Relative H O concentration which is comparable to photosynthesis process (a) dark\n2 2 2 2\ncondition, (b) photodecomposition, and (c) thermodecomposition.\nAction: We have expanded upon the above discussion in the main text and Supplementary information as\nfollows:\n“Under such intentionally controlled MXene loading, the elevated temperature remains within a\nfavorable range for H O synthesis kinetics3. This optimized temperature range, together with the enhanced\n2 2\nstability of Ti C T -NH , effectively suppresses the secondary decomposition (Supplementary Figs. 34 and\n3 2 x 2\n35).”\n5. The scale-up reactor under ambient environment is well designed, however, the record of real-time\ntemperature of the catalyst under natural sunlight is absent.\nResponse: We appreciate the reviewer’s suggestion to include the record of real-time temperature of the\ncatalyst under natural sunlight.\nIn our earlier outdoor multi-channel measurements, we noticed that the catalyst temperature increased\nconcurrently with both light intensity and ambient temperature, although these data were not documented or\nincluded in the initial manuscript. To confirm the reproducibility of this photothermal effect, we have repeated\nthe measurement of catalyst temperature and ambient temperature under natural sunlight and supplemented in\nFig. R29 (this figure corresponds to revised Supplementary Fig. 48d). The photothermal temperature in\nambient environment is comparable to the results under simulated solar irradiation (1 sun).\nFig. R29 | Temperature measurement of the (COF) -NH -M catalyst under ambient light.\n2.5 2\nReviewer #3:\nThis work presents a supramolecular assembly composed of covalent organic frameworks (COFs) integrated\nwith metallic MXene for sustained photocatalytic hydrogen peroxide (H O ) production. The (COF) -NH -M\n2 2 x 2\nheterostructure enables O capture and H O production under ambient conditions without scavengers,\n2 2 2\nachieving a record operational lifetime of over 1,000 hours. Additionally, theoretical and experimental studies\nsupport mechanistic insight into H O production. While the study demonstrates impressive performance,\n2 2\nthere are some issues that should be addressed before acceptance.\nResponse: We appreciate the reviewer’s positive view on our work that “The (COF) -NH -M heterostructure\nx 2\nenables O capture and H O production under ambient conditions without scavengers, achieving a record\n2 2 2\noperational lifetime of over 1,000 hours” and “the study demonstrate impressive performance”. Our work\nachieves following advances (i) utilizing TAPB-TaBr COF (TAPB for (1,3,5-tris(4-aminophenyl)benzene)\n2\nand TaBr for 2,5-dibromoterephthalaldehyde) for well-designed photocatalytic H O production, (ii)\n2 2 2\nintegrating photothermal unit via supramolecular engineering, and (iii) realizing long-term oxygen capture, in\nsitu synthesis and utilization for the first time. Also, the reviewer’s suggestions and criticisms help us to\nsubstantially improve the quality of our manuscript with revised discussion and supplemented experiments.\nWe hope these improvements, which can be found in the following points-to-points responses, could address\nthe reviewer’s concern and meet the standard for publication.\n1) Based on the SEM images of (COF) -NH -M, the MXene content in the composite appears relatively high.\nx 2\nHowever, the near-complete disappearance of MXene diffraction peaks in the XRD data (Supplementary Fig.\n13) is somewhat unexpected. Could you provide a more detailed explanation for this observation? Additionally,\nplease include the quantitative ratio between MXene and COF using ICP-MS or SEM-EDS when controlling\nthe (COF) content.\nx\nResponse: Thanks for the reviewer’s insightful comment.\nIn our work, x represents the mass ratio between COF and MXene. For the presented (COF) -NH -M,\nx 2\ndespite MXene with sheet-like morphology was observed, the weight ratio of MXene was not very high. In\nthe PXRD patterns (Fig. R30, this figure corresponds to revised Supplementary Fig. 18 and original\nSupplementary Fig. 13), the characteristic (002) peak of Ti C T -NH (2 = 4.3°) were detected for (COF) -\n3 2 x 2 2.5\nNH -M and (COF) -NH -M. In response to the reviewer’s suggestion on quantitative analysis, we conducted\n2 5 2\ninductively coupled plasma optical emission spectroscopy (ICP-OES) and CHNS measurements for elemental\nanalysis. The relevant element content and mass ratio between COF and MXene have been listed in Tables\nR1 and 2 (these tables correspond to revised Supplementary Tables 1 and 2). The results show that, as the\nMXene feed amount increased during synthesis, the MXene mass ratio in the resulting supramolecular\ncomposites increased proportionally, confirming the successful incorporation of MXene into supramolecular\nassembly. It is noteworthy that for the (COF) -NH -M sample, the calculated MXene mass ratio was slightly\n2.5 2\nlower than the theoretical value of 0.4. This deviation can be attributed to several factors. On the one hand,\nICP-OES analysis of metallic elements requires aqua regia digestion. However, the COF phase is insoluble in\nsuch solution, leaving yellow precipitation during digestion. It is therefore possible that a small fraction of Ti\nremained undissolved. On the other hand, ICP-OES is conducted on a very small amount of the sample, which\nmay not perfectly represent the macroscopic composition. Thus, the discrepancy is within acceptable range.\nTo further verify the mass ratio between the components, we also conducted quantitative analysis based on\nour XPS results. Among all samples, only (COF) -NH -M exhibited a detectable characteristic signal in the\n2.5 2\nTi 2p spectrum. The calculated MXene to COF mass ratio was approximately 0.37, which closely matches the\ntheoretical value of 0.4.\nFig. R30 | PXRD patterns of (COF)\nx\n-NH\n2\n-M and Ti\nx\n-NH\n2\n.\nTable R1 | Elemental analysis based on ICP-OES and CHNS measurements.\nTi (wt%) C (wt%) H (wt%) N (wt%) Mass ratio (w/w)\nCOF 0 58.48 2.92 5.77 0\n(COF) -NH -M 1.16 56.06 2.81 5.48 0.04317\n50 2\n(COF) -NH -M 7.67 48.08 2.61 4.72 0.21631\n5 2\n(COF) -NH -M 9.18 45.25 2.47 4.56 0.29238\n2.5 2\nTable R2 | Elemental analysis based on XPS quantification.\nC (at%) N (at%) O (at%) Br (at%) Ti (at%) Si (at%) Mass ratio (w/w)\nCOF 81.45 7.35 4.17 7.04 0 0 0\nTi C T -NH 39.23 5.11 31.03 0 18.95 5.67 1\n3 2 x 2\n(COF) -NH -M 80.75 7.13 3.87 7.58 0.33 0.34 /\n50 2\n(COF) -NH -M 77.88 7.04 5.68 7.74 1.12 0.53 /\n5 2\n(COF) -NH -M 72.36 6.33 11.06 5.19 2.99 1.53 0.37632\n2.5 2\nAction: We have added the above discussion in the main text and Supplementary information as follows:\n“In specific, we incorporate metallic amine-functionalized MXene (Ti C T -NH ) photothermal units\n3 2 x 2\ninto rigid COF backbones to construct an integrated supramolecular (COF) -NH -M system (where x refers to\nx 2\nthe mass ratio between COF and MXene, supported by the elemental analysis in Supplementary Tables 1 and\n2) for the capture–synthesis–utilization of H O (Fig. 1a), exhibiting a MOFs-like light harvesting\n2 2\ncharacteristics enhanced by the presence of metallic units.”\n2) In Supplementary Fig. 4, please highlight and provide zoom-in image to clarify the difference between\nsynthesized COF, AA stacking, and AB stacking.\nResponse: Thanks for the reviewer’s comment.\nThe pattern marked “COF (Synthesis)” refers to the XRD pattern of our synthetic TAPB-TaBr COF.\nTAPB-TaBr COF in AA stacking (each layer is perfectly aligned) and AB stacking (each layer is laterally\n2\nshifted) modes based on the 𝑝3̅ crystal structure we created in Fig. R31 (this figure corresponds to revised\nSupplementary Fig. 3), while Fig. R32 (this figure corresponds to revised Supplementary Fig. 6 and original\nSupplementary Fig. 4) aims to verify the successful synthesis of COF in AA stacking mode. The relevant\natomic coordinates are provided in revised Supplementary Tables 3–5. We clarified the caption and added the\nzoom-in image in Fig. R32b (this figure corresponds to revised Supplementary Fig. 6b) with asterisk marking\nthe matched peaks. The slight shift in peak position (< 0.2°) could be attributed to the increase in distance\nbetween the diffraction planes at finite temperatures, which is acceptable corresponding to the natural\ndynamics of the atoms at operando conditions (Angew. Chem. Int. Ed. 2021, 60, 8913–8922).\nFig. R31 | Crystal structures. a–c, The top view of unit cells of (a) TAPB-TaBr COF in AA stacking, (b) TAPB-TaBr COF in\n2 2\nAB stacking, and (c) TAPB-Ta COF in AA stacking with the space group of 𝑝3̅. d–f, The side view of unit cells in the space group\nof 𝑝3̅. g, h, The side view of TAPB-TaBr COF in AA stacking unit cell in the space group of (g) 𝑝6 and (h) 𝑝6𝑚.\n3) Fig. 2h is not clear for me. It seems white dash line is where you scanned. However, the middle section\nappears completely dark, even though MXene is present there. Additionally, the carbon signal appears\nuniformly distributed, while the left region is completely dark and the right region seems to be covered by\nsome particles. Could you clarify if this interpretation is correct and provide more explanation regarding the\nimage?\nResponse: Thanks for the reviewer’s careful observation.\nWe apologize for the figure distortion during processing that led to the reviewer’s misunderstanding. We\nhave revised Fig. R33 (this figure corresponds to revised Fig. 2h) and Fig. R34 (this figure corresponds to\nrevised Supplementary Fig. 24) according to the raw date. For the concern on carbon signal, it cannot be\nclearly distinguished from the completely dark region due to the carbon substrate of TEM. As can be seen in\nthe revised image, the particles and stripes can be separately attributed to COF and MXene, which exhibit\ndifferent contrast to distinguish. Based on this conclusion, we can clearly observe the distribution of MXene\nfrom Ti, and COF from Br.\nFig. R33 | EDS line scan profiles of selected elements across the (COF) -NH -M.\n2.5 2\nFig. R34 | Line scan of EDS mapping. a, Line scan on bright field image. b, Line profile of C, N, Br, Ti, Si, F and O atoms.\n4) The explanation of the ATR-FTIR data is unclear. Do you mean that the presence of hydrogen bonding\nleads to splitting and shifting of the imine vibration band? If so, it seems contradictory that the splitting\ndisappears after hydrogen bond formation. Since this data is critical for confirming the supramolecular\nstructure, the interpretation should be explained more clearly and in greater detail.\nResponse: Thanks for the reviewer’s insightful comment.\nWe apologize for the ambiguous interpretation on the noisy data due to the intrinsic limitation of ATR-\nFTIR. To further address the reviewer’s concern, we remeasured the FTIR spectra using the KBr pellet method\nto obtain higher spectral quality and clearer characteristic peaks (Fig. R35, this figure corresponds to revised\nSupplementary Fig. 9). The significant peaks at 1615 cm−1 and 1594 cm−1 could be attributed to the C=N\nstretching of imine and C=C stretching of aromatic rings, which substantially verify the successful synthesis\nof high-quality imine-linked COF. The subsequent peaks observed at 1503 cm−1, 1456 cm−1, 1442 cm−1, and\n1359 cm−1 are typical characteristics of aromatic structures and extended conjugated systems, corresponding\nto the C=C stretching, C–H in-plane bending, and C–N stretching. Considering the multiple aromatic rings\nand complex conjugated structure, the peaks at 1393 cm−1 and 1697 cm−1 slightly deviate from the original\npeak position, which can sensitively characterize the chemical interaction with imine group. The existence of\nN–H···N hydrogen bonding is predicted to affect the stretching vibration of the C=N linkage, thereby causing\na slight shift toward higher wavenumbers in the spectrum (J. Am. Chem. Soc. 2024, 146, 2663–2672; Nat.\nPhoton. 2023, 17, 478–484). As shown in the blue columns in the figure, both two peaks split for all samples\nwith MXene presence, indicating the existence of hydrogen bonding in our supramolecular assembly. The\nvalidity of hydrogen bonding interaction is also further characterized by variable-temperature 1H solid-state\nNMR.\nFig. R35 | FTIR analysis of TAPB-TaBr COF and (COF) -NH -M. a, FTIR spectra. The orange columns verify the successful\n2 2.5 2\nsynthesis of imine COF, and the blue columns verify the existence of hydrogen bonding. b, Peak table and relevant description.\nAction: We have expanded upon the above discussion in the main text and Supplementary information as\nfollows:\n“Specifically, the reliability of the supramolecular assembly was confirmed through the validation of\nhydrogen-bonded bridges and morphological characterization. FTIR spectroscopy and NMR analyses\ndistinguish hydrogen bond formation within the supramolecular assembly from covalent linking. As shown in\nSupplementary Fig. 9, the splitting and shifting21 of the C=N/C–N stretching peaks around 1693/1393 cm−1 in\nthe FTIR spectra reveal the N–H···N hydrogen bonding at the imine linkage in (COF) -NH -M. Similarly,\n2.5 2\nthe signal around 0.6 ppm (–NH ) in 1H NMR of (COF) -NH -M becomes broader in TAPB-TaBr COF and\n2 2.5 2 2\nsharper in Ti C T -NH , indicating the extensive formation of N–H···N hydrogen bonding at the interface to\n3 2 x 2\noffset the electron shielding effect by conductive matrix of MXene (Fig. 2d). This assertion is further\nevidenced by the variable-temperature NMR results under ultrafast MAS conditions, presenting an increasing\nintensity of –NH peaks due to the weakening hydrogen bonds with temperature rising (Fig. 2e and\n3 2 x\nNH is slightly shifted in (COF) -NH -M (Fig. 2f), reflecting the effect of hydrogen bonding on the carbon\n2 2.5 2\natoms adjacent to the amino terminals.”\n5) Regarding the UPS data, my understanding is that for metallic materials, the low binding energy edge\nshould indicate that the electronic bands cross the Fermi level (at 0 eV binding energy). However, your\nUPS spectrum appears more characteristic of a semiconducting material. Could you please clarify this.\nResponse: Thanks for the reviewer’s concern.\nAs the reviewer pointed out, in conventional metallic materials such as Au and Ag, the lower edge crosses\nthe 0 eV binding energy. Although Ti C T MXene exhibit metallic properties, the naturally functionalized\n3 2 x\nsurface termination strongly influences the density of states of MXene, thereby influencing the work function\nand the position of binding energy edge (Nat. Mater. 2019, 18, 1228–1234). In this work, Ti C T -NH\n3 2 x 2\npossesses many oxygen terminations with abundant 3-aminopropyl-triethoxysilane grafting on the surface,\nwhich substantially alter the electronic environment and lead to notable differences in UPS compared with\nconventional metals (Fig. R36, this figure corresponds to revised Supplementary Figs. 26c and d).\nFig. R36 | UPS of Ti C T -NH .\n3 2 x 2\n6) The interpretation of the EIS data is not sufficiently clear. Please provide a more detailed explanation of\nthe EIS results. In Fig. 3e, which specific point represents the reduced charge transfer resistance? It would be\nhelpful to include a zoomed-in image highlighting the differences in resistance and to provide a more thorough\ndiscussion of these observations.\nResponse: Thanks for the review’s valuable comment.\nWe have provided a zoomed-in image of the EIS result and conducted equivalent circuit fitting in Fig.\nR37 (this figure corresponds to revised Supplementary Fig. 30). As shown in the Nyquist plot of TAPB-TaBr\n1\ndouble-layer capacitance (C ), charge transfer/diffusion of electroactive species (R -W ) near electrode\n1 2 1\nsurface. This part of response is essentially unrelated to the intrinsic charge transfer capability and light\nresponse of the catalyst, which is the focus of our study. In conclusion, the charge transfer capability of\n(COF) -NH -M is evaluated by the value of R , which explains the reason for plotting EIS results in kΩ-scale\nx 2 3\nto analyze low-frequency performance. The curves in Fig. R37b and c and the fitting values in Table R3 (this\ntable corresponds to revised Supplementary Table 6) reveal a pronounced decrease in charge transfer\nresistance under light irradiation. This effect becomes more evident with the increasing proportion of MXene,\nindicating enhanced charge transfer capability in supramolecular assembly.\nFig. R37 | Electrochemical impedance spectra and fitting results of (COF) -NH -M. a, Equivalent circuit and zoom-in Nyquist\nx 2\nplot of COF-coated electrode at high-frequency region (dark condition: solid circle for experimental data and solid line for fitting\nresults; light irradiation: hollow circle for experimental data and dash line for fitting results). b, Fitting results of TAPB-TaBr COF\n2\n(red) and (COF) -NH -M (blue). c, Fitting results of (COF) -NH -M (orange) and (COF) -NH -M (green).\n2.5 2 50 2 5 2\nTable R3 | Fitting parameters of electrochemical impedance for (COF) -NH -M.\nx 2\nCOF COF (COF) -NH -M (COF) -NH -M\n50 2 50 2\nParameters\ndark light dark light\nR\n1\n6.764 7.593 0.004 1.484×10−6\n()\nR\n2\n15.76 15.13 18.37 17.91\n()\nW -R\n1\n15.15 17.16 735.3 172.6\n()\nW -T\n1\n0.00454 0.00471 0.02181 0.00342\n(s)\nW -P 0.3851 0.41483 0.61427 0.56083\n1\n(− s)\nR\n3\n996570 782250 859870 161830\n()\nCPE -T\n1\n1.028×10−5 1.0459×10−5 1.1798×10−5 1.2012×10−5\n(− sP−1)\nCPE -P 0.97533 0.97457 0.93586 0.92623\n1\n(COF) -NH -M (COF) -NH -M (COF) -NH -M (COF) -NH -M\n5 2 5 2 2.5 2 2.5 2\nParameters\ndark light dark light\nR\n1\n11.91 10.31 12.15 7.3724×10−8\n()\nR\n2\n10.77 10.73 7.637 18.98\n()\nW -R\n1\n7.158×10−10 9.384 159.5 159.7\n()\nW -T\n1 3.2182×10−5 4.8951×10−5 0.01171 0.00445\n(s)\nW -P 0.49799 0.40312 0.56375 0.57176\n1\n1.0805×10−8 7.908×10−9 1.0846×10−8 1.358×10−9\n(− s)\nR\n3\n465700 102930 328920 101790\n()\nCPE -T\n1\n3.7006×10−6 3.5965×10−6 1.21×10−5 1.1276×10−5\n(− sP−1)\nCPE -P 0.81141 0.8678 0.87309 0.91074\n“Nyquist plots from electrochemical impedance spectroscopy (EIS) analysis indicate an obvious light\nresponse for (COF) -NH -M (Fig. 3e). By further fitting with an equivalent circuit, the charge transfer\nx 2\nresistance is determined to reduce due to enhanced charge migration with increasing MXene content, under\nboth dark conditions and 1 sun (standard solar illumination of 100 mW cm−2) irradiation (Supplementary Fig.\n30 and Supplementary Table 6).”\n7) Regarding the PL data, where does the peak at 620 nm originate? It does not appear to correspond to the\nCOF’s band gap emission. Additionally, if the coordination between the COF and MXene is sufficiently strong,\nI would expect a more pronounced quenching effect, especially given the metallic nature of MXene. Could\nyou clarify these points?\nResponse: Thanks for the review’s insightful observation.\nWe also note that imine COF has been reported to exhibit PL peak due to intrinsic - transition (J. Am.\nChem. Soc. 2024, 146, 35098–35108), which is expected to align with the band gap emission (~550 nm).\nNevertheless, the donor-acceptor configuration of TAPB-TaBr COF promotes efficient charge transfer (J.\nC=N bond rotation (J. Am. Chem. Soc. 2023, 145, 14417–14426; Angew. Chem. Int. Ed. 2023, 62, e202310794)\ninduced by adjacent bromine substitute, thereby leading to a significant red shift (~620 nm) in the PL emission\nspectrum (Fig. R38, this figure corresponds to revised Fig. 3f). Besides, we agree with the reviewer that\nquenching effect is theoretically expected in COF-MXene supramolecular assembly. However, such\nquenching does not necessarily lead to a complete disappearance of the PL peak. First, the intrinsic PL\nintensity of the imine-COF is relatively low. In addition, not all COF networks are connected to MXene units,\nremaining unbound COF that can still emit detectable PL signals. Therefore, we observe a gradual attenuation\nof the PL peak intensity with increasing MXene loading, rather than a complete quenching of the PL spectrum.\nFig. R38 | Steady-state photoluminescence of (COF) -NH -M.\nx 2\n8) You mentioned that addition of the electron scavenger (AgNO ) likewise quenched H O production,\n3 2 2\nconfirming that the ORR is the primary pathway for the catalytic process. However, adding hole scavenger\nalso showed decrease of yield. Usually, yield should increase after scavenger addition due to prolonged\nelectron lifetime. Please clarify it.\nResponse: Thanks for the reviewer’s comment.\nTo address the reviewer’s concern on the scavenger control experiments, we would like to clarify first\nabout dual route of photocatalytic production of H O in this work: (i) two-electron oxygen reduction reaction\n2 2\n(ORR) from O to H O and (ii) four-electron water oxidation reaction (WOR) from H O to O . The reaction\n2 2 2 2 2\npathways have already been verified by both the thermodynamic analysis on band alignment of TAPB-TaBr\nincluding control tests under various gas atmosphere, isotope labelling experiments, and rotating ring-disk\nelectrode measurements, etc. Given the confirmed ORR pathway from the quenched H O production by\n2 2\nelectron scavenger, although the presence of a hole scavenger can theoretically prolong the electron lifetime\nand enhanced H O production, it simultaneously supresses the WOR process, which provides in situ O for\n2 2 2\nfurther H O production. As a result, the overall H O decreases based on the balance of these two effects (Fig.\n2 2 2 2\nR40, this figure corresponds to revised Supplementary Fig. 38).\nFig. R39 | Experimentally derived energy band alignments of TAPB-TaBr COF and Ti C T -NH .\n2 3 2 x 2\nFig. R40 | H O production in batch reactor. a, Photocatalytic performance of TAPB-TaBr COF at different dosage. b,\n2 2 2\nPhotocatalytic performance of TAPB-TaBr COF in the presence of sacrificial agent.\n2\n9) There is no explanation on Fig. 5d.\nResponse: Thanks for the reviewer’s careful reminder. We apologize for missing the mark of Fig. R41 (this\nfigure corresponds to revised Fig. 5f and original Fig. 5d) in manuscript. We have labelled at the correct place\nand revise our discussion.\nFig. R41 | Gibbs free energy diagram for all intermediates in the oxygen evolution reaction over aromatic carbon (knot) site\n(red line, TAPB-TaBr COF; blue line, (COF) -NH -M).\n2 x 2\nAction: We have revised the main text as follows:\n“Similarly, OER is expected to proceed via a single-site (*O/*OOH) pathway at the aromatic carbons\nlocated at the TAPB edge, where (COF) -NH -M exhibits a lower energy barrier (1.993 eV) than TAPB-TaBr\nx 2 2\nCOF (2.492 eV) (Fig. 5f).”\nMinor issues\n1) In Fig. 1a, for the supramolecular structure, please indicate what each color represents.\nResponse: Thanks for the reviewer’s comment.\nIn our original Fig. 1a, the color of atoms is in accord with Fig. 2a. Nevertheless, this figure intended to\nillustrate the conceptual design of our supramolecular assembly, which can be extensively applied to various\ncatalytic backbones and functional units, rather than limited to the specific TAPB-TaBr COF and Ti C T -\n2 3 2 x\nNH MXene in our work. We acknowledge that the original illustration may have led to some\n2\nmisunderstanding and have therefore redrawn this figure (Fig. R42, this figure corresponds to revised Fig. 1a).\nFig. R42 | Schematic of integrated supramolecular design featuring enzyme-like docking sites for various frameworks and\nfunctional units.\nReviewer #4:\nIn this work, Sun and coworkers present a supramolecular assembled platform that integrates O capture, H O\n2 2 2\nsynthesis, and in situ utilization, enabling continuous H O production for over 1000 hours without sacrificial\n2 2\nagents. Although the results seem encouraging and characterization are decent, there are many critical issues\nand mistakes that have to be comprehensively addressed. Thus, its current form falls below the standards\nrequired for publication in Nature Communications and should be rejected.\nResponse: Thanks for the reviewer’s recognition that “the results seem encouraging and characterization are\ndecent”. We also appreciate the reviewer’s insightful suggestions that substantially help us to improve the\nquality of our manuscript with revised explanations and supplemented experiments (including elemental\nanalysis, Fourier transform infrared (FTIR) spectroscopy, and Brunauer-Emmett-Teller (BET) test for material\nanalysis; isotope labelling experiment, rotating ring-disk electrode measurement, in situ electron paramagnetic\nresonance (EPR) spectroscopy, and catalyst recycling test for reaction mechanism analysis). We hope our\nrevision and supplemented contents will satisfactorily address the reviewer’s concerns.\n1. Line 108–109, “In the (COF) -NH -M supramolecular photocatalysts, metallic MXene nanosheets are\nx 2\ngrafted onto the COF backbone’s imine linkages via hydrogen bonds”. How do the authors accurately quantify\nthe amount of the MXene nanosheets and how about the repeatability, it should be addressed.\nResponse: Thanks for the reviewer’s critical comment.\nIn our work, x represents the mass ratio between COF and MXene, which was determined by the feeding\nratio of MXene during synthesis process. To address the reviewer’s concern on the accurate quantification\nand the repeatability, we have now revised the manuscript to explicitly define x and conducted supplemented\nelemental analysis experiments, including inductively coupled plasma optical emission spectrometry (ICP-\nOES) and CHNS measurements. The relevant element content and mass ratio between COF and MXene have\nbeen listed in Tables R4 and 5 (these tables correspond to revised Supplementary Tables 1 and 2). The results\nshow that, as the MXene feed amount increased during synthesis, the MXene mass ratio in the resulting\nsupramolecular composites increased proportionally, confirming the successful incorporation of MXene into\nsupramolecular assembly. It is noteworthy that for the (COF) -NH -M sample, the calculated MXene mass\n2.5 2\nratio was slightly lower than the theoretical value of 0.4. This deviation can be attributed to several factors.\nOn the one hand, ICP-OES analysis of metallic elements requires aqua regia digestion. However, the COF\nphase is insoluble in such solution, leaving yellow precipitation during digestion. It is therefore possible that\na small fraction of Ti remained undissolved. On the other hand, ICP-OES is conducted on a very small amount\nof the sample, which may not perfectly represent the macroscopic composition. Thus, the discrepancy is within\nacceptable range. To further verify the mass ratio between the components, we also conducted quantitative\nanalysis based on our XPS results. Among all samples, only (COF) -NH -M exhibited a detectable\n2.5 2\ncharacteristic signal in the Ti 2p spectrum (Fig. R43, this figure corresponds to revised Supplementary Fig.\n17). The calculated MXene to COF mass ratio was approximately 0.37, which closely matches the theoretical\nvalue of 0.4.\nTable R4 | Elemental analysis based on ICP-OES and CHNS measurements.\nTi (wt%) C (wt%) H (wt%) N (wt%) Mass ratio (w/w)\nCOF 0 58.48 2.92 5.77 0\n(COF) -NH -M 1.16 56.06 2.81 5.48 0.04317\n50 2\n(COF) -NH -M 7.67 48.08 2.61 4.72 0.21631\n5 2\n(COF) -NH -M 9.18 45.25 2.47 4.56 0.29238\n2.5 2\nTable R5 | Elemental analysis based on XPS quantification.\nC (at%) N (at%) O (at%) Br (at%) Ti (at%) Si (at%) Mass ratio (w/w)\nCOF 81.45 7.35 4.17 7.04 0 0 0\nTi C T -NH 39.23 5.11 31.03 0 18.95 5.67 1\n3 2 x 2\n(COF) -NH -M 80.75 7.13 3.87 7.58 0.33 0.34 /\n50 2\n(COF) -NH -M 77.88 7.04 5.68 7.74 1.12 0.53 /\n5 2\n(COF) -NH -M 72.36 6.33 11.06 5.19 2.99 1.53 0.37632\n2.5 2\nFig. R43 | XPS spectrum of (COF) -NH -M. a, XPS survey. b, C 1s. c, N 1s. d, O 1s. e, Ti 2p.\n2.5 2\nAction: We have added the above discussion in the main text and Supplementary information as follows:\n“In specific, we incorporate metallic amine-functionalized MXene (Ti C T -NH ) photothermal units\n3 2 x 2\ninto rigid COF backbones to construct an integrated supramolecular (COF) -NH -M system (where x refers to\nx 2\nthe mass ratio between COF and MXene, supported by the elemental analysis in Supplementary Tables 1 and\n2) for the capture–synthesis–utilization of H O (Fig. 1a), exhibiting a MOFs-like light harvesting\n2 2\ncharacteristics enhanced by the presence of metallic units.”\n2. Line 111–112, “solvothermal condensation of TAPB with TaBr2 yields an imine-linked COF designed to\nfeature (i) micropores.”. However, the pore size in Fig. 2a is claimed to be 37.3 Å, which is undoubtful\nmesopore. The authors should explain this. The same mistake for the description of the N sorption results\n2\n(Line 143).\nResponse: Thanks for the reviewer’s comment. We have replaced relevant descriptions on micropore (< 2\nnm) with mesopore (2–50 nm).\nAction: We have revised the main text and Supplementary information as follows:\n“Besides, water molecules serves as proton donors for H O production renders their interaction with the\n2 2\nmeso-porous COF structure essential for tailoring the overall reactivity and durability13.”\n“The intrinsic meso-porous architecture of COF frameworks exposes abundant, spatially defined sites\nfor O and H O adsorption, maximizing opportunities for molecular reactant docking.”\n2 2\n3. Line 133. The lattice parameters of TAPB-TaBr -COF, c = 0.419 nm, however, in table S1, c = 3.8685 Å.\nResponse: Thanks for the reviewer’s careful observation.\nThe lattice parameter of TAPB-TaBr COF in the manuscript was determined by further Pawley\n2\nrefinement according to the PXRD results, while the lattice parameter in Supplementary Table 1\n(Supplementary Table 3 in revised manuscript) was determined by DFT geometry optimization. This deviation\ncould be attributed to the increase in distance between the diffraction planes at finite temperatures, which is\nacceptable corresponding to the natural dynamics of the atoms at operando conditions (Angew. Chem. Int. Ed.,\n2021, 60, 8913–8922). We apologize for missing of the detailed explanation on given lattice parameters in the\nmanuscript and supplementary information.\nAction: We have revised the description in the main text according to the simulated crystal structure to avoid\nmisunderstanding as follows:\n“The crystal structure of TAPB-TaBr COF in AA stacking (Fig. 2a) was optimized by density functional\n2\ntheory (DFT) (Supplementary Tables 3–5) and reconstructed by Pawley refinement with lattice parameters of\na = b = 3.62 nm, c = 0.419 nm, α = β = 90°, and γ = 120°. Powder X-ray diffraction pattern (PXRD) patterns\n(Fig. 2c) confirm the AA-stacked hexagonal framework, while other symmetries and stacking modes fail to\nreproduce the observed intralayer atom distributions and peak positions (Supplementary Figs. 3 and 6).”\n4. FT-IR spectra measurements should be given to assess COF quality instead of Raman spectroscopy.\nResponse: Thanks for the reviewer’s insightful comment.\nRaman spectroscopy can provide evidence to assess COF quality by detecting the characteristic peaks of\nCOF and monomers. Nevertheless, we understand the reviewer’s concern on COF quality assessment by the\noriginal attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectra, which were limited by\nthe quality of ATR measurement. To address this issue, we improve the quality of FTIR result by KBr pellet\nmethod in Fig. R44 (this figure corresponds to revised Supplementary Fig. 9). The distinct C=N stretching\npeak at 1615 cm−1 and aromatic C=C stretching peak at 1594 cm−1 provides strong evidence for the successful\nsynthesis of high quality TAPB-TaBr COF. Also, the disappearance of TAPB characteristic peak around\n2\n1360 cm−1 further verified the depletion of monomers. The peak table with detailed description of FTIR is\ncollected in Fig. R44b.\nFig. R44 | FTIR analysis of TAPB-TaBr COF and (COF) -NH -M. a, FTIR spectra. The orange columns verify the successful\n2 2.5 2\nsynthesis of imine COF and the blue columns verify the existence of hydrogen bonding. b, Peak table and relevant description.\nAction: We have expanded upon the above discussion on COF quality evaluation in the main text and\nSupplementary information as follows:\n“To assess COF quality, Raman spectroscopy shows the absence of TaBr aldehyde C=O stretching\n2\nvibration around 1690 cm−1, alongside an intense phenyl C=C band at ~1570 cm−1, and a C=N band at 1616\ncm−1 (Supplementary Fig. 8), indicating monomer depletion and imine bond formation. Similarly,\ncharacteristic peaks for imine COF with highly conjugated aromatic rings are observed at 1615 cm−1 and 1594\ncm−1 in FTIR spectrum of TAPB-TaBr COF (Supplementary Fig. 9).”\n2\n5. The N sorption isotherm seems quite strange, why no N uptake at low relative pressure region? It is really\n2 2\nuncommon for COFs. The authors should explain this. Furthermore, for comparison, the N sorption isotherms\n2\nafter the grafting of MXene should be given.\nResponse: Thanks for the reviewer’s valuable comment.\nThe original BET data points start from a relative pressure of ~0.05, which is due to the characteristics\nof the instrument we used (Quantachrome Nova 2200e). In fact, the adsorption volume at this time had already\nreached nearly 200 cm3 g−1, indicating that N uptake did occur, contrary to the reviewer’s concern. To further\n2\naddress the reviewer’s comment, we repeated the N sorption measurements for both the TAPB-TaBr COF\n2 2\nand (COF) -NH -M samples using a different instrument (Micromeritics 3Flex). The results in Fig. R45 (this\n2.5 2\nfigure corresponds to revised Supplementary Fig. 10) reveal type VI isotherms accompanied by H2-type\nhysteresis loops for both samples. The BET surface areas were determined to be 1289.56 m2 g−1 for TAPB-\nTaBr COF and 1125.70 m2 g−1 for (COF) -NH -M. These findings confirm the presence of the columnar\n2 2.5 2\npores within the COF, the interparticle voids arising from densely packed granules, as well as the excellent\nstructural integration between the COF and MXene in the composite.\nFig. R45 | Nitrogen sorption isotherms. a, TAPB-TaBr COF. b, (COF) -NH -M.\n2 2.5 2\nAction: We have elaborated the above discussion in the main text and Supplementary information as follows:\n“Nitrogen sorption measurements at 77 K determine the high Brunauer-Emmett-Teller (BET) surface\nareas of 1289.56 m2 g−1 for TAPB-TaBr COF and 1125.70 m2 g−1 for (COF) -NH -M. Both reveal type VI\n2 2.5 2\nisotherms accompanied by H2-type hysteresis, confirming the extensive presence of columnar pores and\ninterparticle voids (Supplementary Fig. 10). Barrett-Joyner-Halenda (BJH) analysis shows a dominant\nmicropore width of 3.79 nm (Supplementary Fig. 11), which is consistent with the pore size predicted from\nthe crystal structure (37.274 Å from Supplementary Fig. 3a). The resulting structural stability and\nmesoporosity expose abundant binding sites, enabling efficient docking of O molecules.”\n2\n6. Line 193–194, “Meanwhile, its valence band maximum (VBM) lies at 1.01 V (NHE, pH 6.8), suggesting\nthe involvement of four-electron water oxidation (0.83 V)..” It can only prove that four-electron WOR is\nthermodynamic feasibility, how can the author know the involvement of four-electron WOR?\nResponse: Thanks for the reviewer’s comment.\nIn the section of “Energy levels and photogenerated carrier dynamics”, we intended to discuss the\nband alignment of the supramolecular assembly to verify our design thermodynamically favors the expected\nreaction pathways. The experimental verification of the actual reaction mechanisms is presented separately in\nthe section of “Photocatalytic H O production”, where we explained the results of control experiments\n2 2\nunder different gas atmospheres and with various sacrificial agents. As shown in Fig. R46 (this figure\ncorresponds to revised Fig. 4f), H O yield could still be detected within 1 h when the system was purged with\n2 2\nN /Ar and then sealed, while quenched with continuous N /Ar flow. This observation indicates that WOR\n2 2\ngenerates in situ O which can be subsequently participate in H O production. Furthermore, the yield\n2 2 2\ndecreases upon addition of a hole scavenger (Fig. R47, this figure corresponds to revised Supplementary Fig.\n38) further support this conclusion. Nevertheless, to address the reviewer’s concern, we have supplemented\nisotope labelling experiment and rotating ring-disk electrode (RRDE) measurements to prove WOR\ninvolvement, which can be found in the following response.\nFig. R46 | H O production of TAPB-TaBr COF and (COF) -NH -M over 60 min under different gas conditions.\n2 2 2 2.5 2\nFig. R47 | Photocatalytic performance of TAPB-TaBr COF in the presence of sacrificial agent.\n2\n7. Line 206, what’s the meaning of “1 sun”\nResponse: Thanks for the reviewer’s question.\n“1 sun” refers to the standard solar illumination, which corresponds to an irradiance of 100 mW/cm2 (AM\n1.5G spectrum). This is the commonly accepted standard used to simulate natural sunlight in photocatalytic\nresearch (Nature, 2023, 613, 66–70). To avoid the misunderstanding, we have marked it in the revised\nmanuscript.\nAction: We have added the above discussion in the main text as follows:\n“Nyquist plots from electrochemical impedance spectroscopy (EIS) analysis indicate an obvious light\nresponse for (COF) -NH -M (Fig. 3e). By further fitting with an equivalent circuit, the charge transfer\nx 2\nresistance is determined to reduce due to enhanced charge migration with increasing MXene content, under\nboth dark conditions and 1 sun (standard solar illumination of 100 mW cm−2) irradiation (Supplementary Fig.\n30 and Supplementary Table 6).”\n8. Line 277–279, the authors claimed the in situ O produced via four-electron WOR pathway, more\n2\nexperiments should be performed to prove this, such as isotope experiments and RRDE measurements.\nResponse: Thanks for the reviewer’s valuable suggestions.\nWe have conducted isotope labelling experiments by gas chromatography-mass spectrometer (GC-MS)\nand RRDE measurements. For isotope labelling experiments, the supramolecular catalyst was dispersed in\nH 18O and purged with 16O . As shown in Fig. R48 (this figure corresponds to revised Fig. 5a), 18O was\n2 2 2\ndetected directly from the headspace of the sealed photocatalytic system after reaction with the intensity\nincreasing with time, which indicated the involvement of four-electron WOR pathway. Thereafter, the\nextracted aqueous phase was purged with Ar and decomposed with MnO . The detection of 18O verifies that\n2 2\nthe in situ generated O can be utilize for further H O production. For RRDE measurement, the\n2 2 2\nsupramolecular catalyst was casted on disk electrode and measured in phosphate buffer solution (pH = 7) with\ndifferent gas conditions. As shown in Figs. R49a and b (these figures correspond to revised Supplementary\nFigs. 41a and b), the measurement in O saturated solution shows an estimated electron transfer number of\n2\n2.283 with apparent ring current plateau, verifying the two-electron ORR pathway. Besides, the current\nresponse at −0.23 V (ring potential) at Ar saturated solution indicates obvious O generation via four-electron\nFig. R48 | 18O isotope labelling experiment for (COF) -NH -M system dispersed in 16O saturated H 18O.\n2 2.5 2 2 2\nFig. R49 | RRDE tests in phosphate buffer solution (PBS) solution at 1600 rpm. a, RRDE curves in an O -saturated solution for\ncurves in an Ar-saturated solution for WOR verification (Pt ring at −0.23 V vs. Ag/AgCl).\nAction: We have expanded upon the above discussion on ORR/WOR in the main text and Supplementary\ninformation as follows:\n“Considering the energy band alignment in Fig. 3c, we proceeded to investigate the dual-route pathways\nwith 2e− ORR and 4e− WOR throughout the catalytic process. To probe the role of O in the photocatalytic\n2 2\nto deoxygenate the dispersion suppressed H O formation for both TAPB-TaBr COFs and (COF) -NH -M\n2 2 2 2.5 2\ndispersions, while O flow significantly increased the H O yield. Together with the likewise quenched H O\n2 2 2 2 2\nproduction with electron scavenger (AgNO ) addition (Supplementary Fig. 38b), a more specific rotating ring-\n3\ndisk electrode (RRDE) measurements in an O -saturated phosphate buffer solution (PBS, pH = 7) confirmed\n2\nthe highly selective 2e− ORR pathway for catalytic process (Supplementary Figs. 41a and b). Noticing the\npersisted H O generation when the reactor was purged with inert gas only before reaction, ORR is expected\n2 2\nto sustain owing to the in situ O produced via the 4e− WOR (oxygen evolution reaction, OER, 0.83 V) which\n2\nis thermodynamically favored over the 2e− WOR (1.36 V). Beyond this, the distinct current response for\nRRDE curves in Ar-saturated PBS (Supplementary Fig. 41c) coincides with the increasing 18O /16O ratios\n2 2\nwith irradiation time in isotope labelling experiment for sealed photocatalytic system starting with 16O\n2\nsaturated H 18O solution (Fig. 5a), confirming the existence of 4e− WOR. Additionally, the 18O signal remains\n2 2\ndetectable when the extracted aqueous phase after irradiation was then purged with Ar and injected into a vial\ncontaining MnO , depicting that the in situ generated O from WOR could subsequently participate in ORR\n2 2\ntowards H O .”\n2 2\n9. Electron paramagnetic resonance (EPR) spectroscopy was performed to identify the possible intermediates.\nResponse: Thanks for the reviewer’s insightful suggestion.\nWe have supplemented EPR measurements for both TAPB-TaBr COF and (COF) -NH -M, which\n2 2.5 2\nwere dispersed in methanol/water mixture (9/1 v/v) containing DMPO as spin-trapping reagent. As shown in\nrevised Fig. R50 (this figure corresponds to revised Fig. 5b), the characteristic signals indicative of superoxide\n(•O −) are detected for both TAPB-TaBr COF and (COF) -NH -M within 0.5 min and increase with time.\n2 2 2.5 2\nBesides, the clearer multiple peak features and the higher overall intensity in (COF) -NH -M confirm our\n2.5 2\ndesign on superior oxygen activation ability.\nFig. R50 | In situ EPR spectra of TAPB-TaBr COF and (COF) -NH -M reaction solution under dark and light irradiation\n2 2.5 2\nfor different time to capture •O − intermediate with DMPO.\nSupplementary information as follows:\n“To verify the possible intermediates involved in photocatalytic production, in situ electron paramagnetic\nresonance (EPR) spectroscopy was conducted in methanol/H O using 5,5-dimethyl-1-pyrroline N-oxide\n2\n(DMPO) as spin-trapping reagent. As depicted in Fig. 5b, the EPR spectra of both TAPB-TaBr COF and\n2\n(COF) -NH -M dispersion exhibited intensified characteristic peaks of O − with increasing irradiation time,\n2.5 2 2\nwhile no signals were detected under dark condition, indicating light-induced generation of O − intermediate.\n2.5 2 2\nirradiation.”\n10. The recycling tests (at least 5 repeated cycles) of the studied materials toward H O photosynthesis should\n2 2\nbe given. And the general characterization of the materials after repeated cycles should be given to prove the\nstability of the studied materials, such as PXRD, SEM, FT-IR etc.\nResponse: Thanks for the reviewer’s suggestion.\nWe have already conducted a long-term continuous test for more than 1,000 h to verify our systematic\nstability. Despite, we have added the recycling test to further address the reviewer’s concern. As shown in Fig.\nR51a (this figure corresponds to revised Supplementary Fig. 46a), the H O yield exhibits negligible decay\n2 2\nwithin 5 cycles. To further assess the stability of supramolecular (COF) -NH -M, the PXRD, SEM, and FTIR\n2.5 2\nmeasurements were conducted (Figs. R51b–d, these figures correspond to revised Supplementary Figs. 46b–\nd), revealing no obvious changes in crystal structure, morphology, and chemical bonding during reaction.\nFig. R51 | Recycling test of (COF) -NH -M. a, Catalyst activity in 5 cycles of 1 h reaction. b–d, Characterization of\n2.5 2\nsupramolecular catalyst before and after 5 cycles (b) PXRD patterns, (c) SEM images, and (d) FTIR spectra.\nAction: We have added the above discussion in the main text and Supplementary information as follows:\n“To investigate the stability of (COF) -NH -M, a recycling test was performed, presenting a negligible\n2.5 2\nH O yield decay and minor structural changes within 5 cycles (Supplementary Fig. 46).”\n2 2\nAll in all, the writing of this manuscript is quite confusing, the characterization of the materials is not sufficient\nand there are still lots of unsolved problems in this study. It is not recommended to be published in its current\nform.\nPoint-by-point response for Nature Communications manuscript\n(ID: NCOMMS-25-52770A-Z)\nManuscript Type: Article\nTitle: Sustained hydrogen peroxide production via metallic unit-functionalized supramolecular docking\nAuthor(s): Jiaxun Sun†, Yuanming Zhang†, Wanheng Lu, Wei Li Ong, Xinglong Pan, Wentao Song, Zhonghua\nLi, Zhaosheng Li, Ghim Wei Ho*\nGeneral response: We sincerely appreciate the editor, editorial staff and all reviewers for their valuable and\ncritical comments. The manuscript has been greatly improved by addressing all the suggestions with points-by-\npoints responses as listed below.\n(Our response is given in blue, the corrections in the revised manuscript are shown in red, and some key points\nare highlighted in yellow.)\nPoints-by-points responses to Reviewer(s):\nReviewer #1:\nThe authors have made efforts to address the previous reviewers’ concerns. However, critical issues remain\nunresolved, which undermine the validity of the central claims. First, there is insufficient evidence for key\nconclusion material structure. The revised manuscript still lacks the characterization of the materials and there\nare still lots of unsolved problems in the resubmitted version. Also, there is insufficient experimental or theoretical\nevidence to substantiate the proposed reaction mechanism. Questionable interpretation stemming from a\nmisapplication of fundamental concepts, which undermines the validity of the central conclusions. This falls\nbelow the standards required for publication in Nature Communications and should be rejected in its present form.\nResponse:\nWe sincerely appreciate the reviewer’s careful evaluation and feedback regarding structural characterization,\nreaction mechanism, and conceptual interpretation. Our work presents the first supramolecular material exhibiting\nefficient and long-term stable photothermal H O generation, in which aminated MXene is connected to TAPB-\n2 2\nTaBr COF (TAPB = 1,3,5-tris(4-aminophenyl)benzene and TaBr = 2,5-dibromoterephthalaldehyde) via\n2 2\nhydrogen bonding. We understand that the central concerns lie in the adequacy of structural characterization,\nproposed mechanism, and the conceptual clarity of our interpretations. To further elucidate the rationale of our\nwork, we have systematically addressed these concerns by clearly presenting the existing evidence chain and,\nimportantly, supplementing it with additional experiments and analyses to further substantiate our conclusions,\nincluding Independent Gradient Model based on Hirshfeld partitioning (IGMH) calculations to quantify\nhydrogen-bond interactions, oxygen temperature-programmed desorption (O -TPD) measurements to confirm O\n2 2\ndocking, and time-dependent solvothermal reaction to demonstrate the absence of covalent bond formation.\nStructural characterization: The material structure has been rigorously verified using multiple complementary\ntechniques: X-ray diffraction (XRD), Raman spectroscopy, solid-state nuclear magnetic resonance (NMR), and\ntransmission electron microscopy (TEM) to elucidate the composition and structural framework. In addition,\nFourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and variable-\ntemperature solid-state 1H nuclear magnetic resonance (VT-ssNMR) were employed to confirm the presence of\nhydrogen-bonding interactions. These combined analyses establish a clear and robust understanding of the\nmaterial’s supramolecular architecture and the absence of covalent bonding.\nReaction mechanism: To substantiate the mechanism, we conducted isotope labelling experiments, rotating ring-\ndisk electrode (RRDE), in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), in situ\nelectron paramagnetic resonance (EPR) spectroscopy, and gas reference experiments. The experimental\nobservations are further supported by density functional theory (DFT) calculations, including adsorption energies\nand reaction pathway analysis, providing both experimental and theoretical validation of the reaction mechanism.\nWe hope that the revised manuscript now addresses the reviewer’s concerns thoroughly and strengthens the\nvalidity of our findings.\nIn the newly revised version, we focus on clearly elucidating and in-depth analyzing the optimization of\nsupramolecular structures, quantum chemical calculations of hydrogen-bond interactions, and oxygen docking\nwithin these supramolecular frameworks.\nSupramolecular architecture\nTo address the reviewer’s confusion on supramolecular architecture, we have supplemented a molecular-\nlevel synthesis pathway of the assembly of TAPB-TaBr COF fragment on Ti C T -NH surface via hydrogen\n2 3 2 x 2\nbonding interactions in Fig. R1a (this figure corresponds to revised Supplementary Fig. 4a). Besides, we\nreconstructed a lattice-matched supercell with associated local hydrogen bonding interaction details in Fig. R1b\n(this figure corresponds to revised Supplementary Fig. 4b) to visualize the three-dimensional crystalline structure,\nwhich is highly consistent with sheet-like morphology highlighted by the reviewer.\nFig. R1 | Synthesis and structures of supramolecular (COF) -NH -M. a, Synthetic route of (COF)-NH -M in molecular level. b, 3D\nx 2 x 2\ncrystalline structure of (COF)-NH -M with details of COF network and hydrogen bonding interaction in supramolecular assembly.\nx 2\nAbsence of covalent bonding\nTo directly address the reviewer’s concern about potential covalent bonding, we performed time-dependent\nsolvothermal reactions between TaBr monomers and Ti C T -NH matrix. The resulting products were extracted\n2 3 2 x 2\nand analyzed by Fourier transform infrared (FTIR) spectroscopy. As shown in Fig. R2 (this figure corresponds to\nrevised Supplementary Fig. 5), the characteristic imine-related absorption near 1610 cm−1 exhibits no detectable\ntendency toward covalent bond formation under employed reaction, suggesting the noncovalent interaction\nthroughout the synthesis.\nFig. R2 | FTIR spectra of pristine Ti C T -NH and Ti C T -NH @TaBr .\n3 2 x 2 3 2 x 2 2\nVisual analysis and clarification of hydrogen bonding interaction\nWe conducted supplementary weak interaction analysis using IGMH method. The DFT-optimized cluster\nmodel (B3LYP-D3/6-31G(d)+lanl2dz) reveals the formation of N–H···N hydrogen bonds (2.20 Å) on imine\nlinkage. Based on the wave function of cluster model, the interfragment interaction could be analyzed with both\nvisualized interaction region from g isosurface and interaction properties from sign( ). As shown in Fig. R3a\n2\n(this figure corresponds to revised Fig. 2a), the green IGMH isosurface with faint blue center localized at the\nhydrogen bonding sites is reflected in the scatter plot (this figure corresponds to revised Fig. 2a). The distribution\nof most data points between −0.02 and 0.01 and the relatively larger g values near 0.02 elucidate the coexistence\nof van der Waals interaction and weak hydrogen bonding interaction (Nat Commun., 2025, 16, 6481; J. Comput.\nChem. 2012, 33, 580−592).\nAs shown in Fig. R3b (this figure corresponds to revised Fig. 2b), the N 1s X-ray photoelectron spectroscopy\n(XPS) results show no additional intensity corresponding to C=N formation (399.5 eV), which is consistent with\nthe absence of covalent bonding formation inferred from the FTIR spectra of Ti C T -NH composite under TaBr\n3 2 x 2 2\nmonomers presence at varied duration.\nBased on these results, the hydrogen bonding interactions in the supramolecular material are further\nexperimentally investigated by FTIR and solid-state nuclear magnetic resonance (NMR) measurements. As\nshown in Fig. R4 (this figure corresponds to revised Supplementary Fig. 9), the significant peaks at 1615 cm−1\nand 1594 cm−1 could be attributed to the C=N stretching of imine and C=C stretching of aromatic rings, which\nsubstantially verify the successful synthesis of high-quality imine-linked COF. The subsequent peaks observed at\n1503 cm−1, 1456 cm−1, 1442 cm−1, and 1359 cm−1 are typical characteristics of aromatic structures and extended\nconjugated systems, corresponding to the C=C stretching, C–H in-plane bending, and C–N stretching.\nConsidering the multiple aromatic rings and complex conjugated structure, the peaks at 1393 cm−1 and 1697 cm−1\nslightly deviate from the original peak position, which can sensitively characterize the chemical interaction with\nimine group. The existence of N–H···N hydrogen bonding is predicted to affect the stretching vibration of N–H\nmoieties and further extend to the adjacent C–N/C=N bonds through the conjugated framework, thereby causing\na slight shift toward higher wavenumbers in the spectrum (J. Am. Chem. Soc. 2024, 146, 2663–2672; Nat. Photon.\n2023, 17, 478–484). As shown in the blue columns in the figure, both two peaks split for all samples with MXene\npresence, indicating the existence of hydrogen bonding in our supramolecular assembly.\nComplementary solid-state NMR spectroscopy provides direct insight into the hydrogen bonding\nenvironment of the –NH groups. As shown in Fig. R3d (this figure corresponds to revised Fig. 2d), the signals\n2\n~0.6 ppm in 1H solid-state NMR spectra (400 MHz) are attributed to the –NH groups, which is expected to be\n2\nsharp in Ti C T -NH due to the electron shielding effect by conductive matrix, whereas becomes broader in COF.\n3 2 x 2\nThereby, the extensive formation of N–H···N hydrogen bonding at the interface will offset the shielding effect of\nMXene, resulting in a higher peak intensity (not as sharp as pristine Ti C T -NH ) in (COF) -NH -M compared\n3 2 x 2 2.5 2\nwith TAPB-TaBr COF. To further support this assertion, variable-temperature NMR under ultrafast MAS (15\n2\nkHz) conditions reveal a shaper and more distinct –NH peak (Fig. R3e, this figure corresponds to revised Fig.\n2\n2e). As temperature increases, the weakening of hydrogen bonding renders the –NH groups more dynamically\n2\nfree, resulting in an enhanced peak intensity (Nat. Chem., 2012, 4, 711–717; J. Am. Chem. Soc., 2025, 147, 39623–\n39631). Moreover, the distinct signal around 40 ppm in 13C NMR spectrum of Ti C T -NH is slightly shifted in\n3 2 x 2\n(COF) -NH -M (Fig. R3f, this figure corresponds to revised Fig. 3f), reflecting a chemical environment change\n2.5 2\nof the carbon atoms adjacent to the amino terminals caused by the formation of hydrogen bonding. Together with\nthe intimate interfacial morphology between MXene and COF domains revealed by high-resolution transmission\nelectron microscopy (Fig. R3g–j, these figures correspond to revised Fig. 2g–j), these findings offer direct and\ncompelling evidence for the existence for hydrogen bonding interactions within the supramolecular structure.\nFig. R3 | Structural characteristics of TAPB-TaBr COF and supramolecular (COF) -NH -M. a, IGMH analysis on molecular\n2 x 2\nclusters of TAPB-TaBr COF and Ti C T-NH (grey for C; blue for N; red for Br; light orange for Si). b, N 1s XPS spectra of Ti C T-\n2 3 2 x 2 3 2 x\nNH , TAPB-TaBr COF, and (COF) -NH -M. c, Experimental PXRD pattern of TAPB-TaBr COF with Pawley refinement fit. d, f,\n2 2 2.5 2 2\nSolid-state NMR spectra of Ti C T-NH (dark blue), TAPB-TaBr COF (red), and (COF) -NH -M (blue) (d) 1H and (f) 13C. e, Variable-\n3 2 x 2 2 2.5 2\ntemperature 1H solid-state NMR spectra of (COF) -NH -M (from −40 °C to 20 °C with an increment of 20 °C). g, h, HR-TEM image\n2.5 2\nof (COF) -NH -M in different magnification. i, Fourier transform of the COF domains, showing lattice fringes of the COF networks\n2.5 2\nand MXene multilayers. j, EDS line scan profiles of selected elements across the (COF) -NH -M.\n2.5 2\nFig. R4 | FTIR analysis of TAPB-TaBr COF and (COF) -NH -M. a, FTIR spectra. The orange columns verify the successful\n2 2.5 2\nsynthesis of imine COF and the blue columns verify the existence of hydrogen bonding. b, Peak table and relevant description.\nAction: We have added the above discussion in the main text and Supplementary information as follows:\n“To elucidate the local intermolecular interaction on imine linkages, we employed the Independent Gradient\nModel based on Hirshfeld partitioning (IGMH) to analyze weak interaction (Fig. 2a). The density functional\ntheory (DFT) optimized cluster model clearly reveals the formation of N–H···N hydrogen bonds (2.20 Å). The\ngreen IGMH isosurface with faint blue center localized at the hydrogen bonding sites indicates the coexistence of\nvan der Waals interaction and weak hydrogen bonding interaction20. The distribution of most data points between\n−0.02 and 0.01, together with the relatively larger dg values near 0.02 in the scatter plot, further supports our\nproposal. N 1s X-ray photoelectron spectroscopy (XPS) results verify the bridging on N atoms, with N–H peak\n(401.6 eV) significantly enhanced by amino hydrogen bonding, while the N=C peak (399.5 eV)21 remains\nunchanged (Fig. 2b). Moreover, the Fourier transform infrared (FTIR) spectra of Ti C T -NH composite under\n3 2 x 2\nTaBr monomers presence at varied duration exhibit no detectable enhancement on C=N absorption, confirming\n2\nthe absence of covalent bond formation between Ti C T -NH and TAPB-TaBr COF (Supplementary Fig. 5).”\n3 2 x 2 2\n“Specifically, the reliability of the supramolecular assembly was confirmed through the validation of\nhydrogen-bonded bridges and morphological characterization. FTIR spectroscopy and NMR analysis distinguish\nhydrogen bond formation within the supramolecular assembly from covalent linking. As shown in Supplementary\nFig. 9, the splitting and shifting22 of the C=N/C–N stretching peaks around 1693/1393 cm−1 in the FTIR spectra\nreveal the redistribution of electron density around the N center induced by N–H···N hydrogen bonding at the\nimine linkage in (COF) -NH -M. Similarly, the signal around 0.6 ppm (–NH ) in 1H NMR of (COF) -NH -M\n2.5 2 2 2.5 2\nbecomes broader in TAPB-TaBr COF and sharper in Ti C T -NH , indicating the extensive formation of N–\n2 3 2 x 2\nH···N hydrogen bonding at the interface to offset the electron shielding effect by conductive matrix of MXene\n(Fig. 2d). This assertion is further evidenced by the variable-temperature NMR results under ultrafast MAS\nconditions, presenting an increasing intensity of –NH peaks due to the weakening hydrogen bonds with\n2\ntemperature rising23 (Fig. 2e and Supplementary Fig. 19). Furthermore, the distinct signal around 40 ppm in 13C\nNMR spectrum of Ti C T -NH is slightly shifted in (COF) -NH -M (Fig. 2f), reflecting the effect of hydrogen\n3 2 x 2 2.5 2\nbonding on the carbon atoms adjacent to the amino terminals.”\nEvaluation of oxygen docking behavior\nTo further address the reviewer’s concern on reaction mechanism, we employed the oxygen temperature-\nprogrammed desorption (O -TPD) measurements to probe the chemical adsorption characteristics of (COF) -\n2 x\nNH -M surfaces. Prior to the O -TPD measurements, thermogravimetric analysis verified the thermal stability of\n2 2\nthe TAPB-TaBr COF over the relevant temperature range (Fig. R5, this figure corresponds to revised\npristine TAPB-TaBr COF exhibits two distinct desorption regions in the O -TPD profiles, corresponding to low-\n2 2\ntemperature (approximately 50–200 °C) and high-temperature (approximately 300–400 °C) features. The low-\ntemperature behavior originates from reversible O docking on -conjugated aromatic carbon sites, instead of\n2\nstrong binding at nitrogen-containing sites (Nat Commun., 2025, 16, 6297). This interpretation is fully consistent\nwith our DFT calculations, which reveal a thermodynamically favored adsorption behavior according to the\nsignificantly lower O adsorption energy on aromatic than that on imine sites (Fig. R7, this figure corresponds to\n2\nrevised Fig. 5d). Moreover, a pronounced increase in the low-temperature desorption contribution in (COF) -\nx\nNH -M is observed with MXene content increasing, suggesting a substantially enhanced capability for O docking.\n2 2\nCompared with strongly bound oxygen species, weakly adsorbed oxygen is more readily available to participate\nin the 2e− oxygen reduction reaction, thereby favoring H O photoproduction in (COF) -NH -M.\n2 2 x 2\nFig. R5 | Thermogravimetric analysis of TAPB-TaBr COF.\n2 x 2 2\nFig. R7 | O adsorption energies on aromatic carbon (linker), imine linkage, and oxygen vacancies of MXene (red column, TAPB-\n2 x 2\nAction: We have expanded upon the above discussion in the main text and Supplementary information as follows:\n“The oxygen temperature-programmed desorption (O -TPD) was widely used to evaluate the O docking\n2 2\ncapability of materials by probing the adsorption-desorption behavior of surface oxygen species. Prior to the O -\n2\nrelevant temperature range (Supplementary Fig. 46). The TPD profiles exhibit a pronounced low-temperature\ndesorption feature (~150 °C), which can be attributed to reversible oxygen species that are weakly bound at -\nconjugated aromatic carbon sites36 (Supplementary Fig. 47). Notably, the increasing MXene content leads to a\npronounced enhancement of the low-temperature desorption, indicating the improved O docking capability in\n2\n(COF) -NH -M.”\nx 2\nWe sincerely thank the reviewers once again for the time and effort to the careful evaluation of our\nmanuscript. We have rigorously validated the material structure and systematically clarified the relationship\nbetween structure and performance. We believe that these comprehensive analyses clearly elucidate the\nsignificance of the study.\nReviewer #2:\nAll my concerns have been solved.\nResponse: We sincerely thank the reviewer for accepting our manuscript and for their time and constructive\ncomments again.\nReviewer #3:\nThe authors have well addressed the questions, and the quality of the revised manuscript has been significantly\nimproved. Publish without any changes.\nResponse: We sincerely thank the reviewer for their positive feedback and acceptance of our manuscript.\nReviewer #4:\nThe authors have thoroughly revised the manuscript and addressed the previously raised concerns. The overall\nquality of the manuscript has been improved. This reviewer has no additional comments and supports its\npublication in its current form.\nResponse: We appreciate the reviewer’s constructive comments, which led to the acceptance of the manuscript."}, {"round": 2, "reviewer_comments": {"reviewer_1": "The authors have made efforts to address the previous reviewers’ concerns. However, critical issues remain unresolved, which undermine the validity of the central claims. First, there is insufficient evidence for key conclusion material structure. The revised manuscript still lacks the characterization of the materials and there are still lots of unsolved problems in the resubmitted version. Also, there is insufficient experimental or theoretical evidence to substantiate the proposed reaction mechanism. Questionable interpretation stemming from a misapplication of fundamental concepts, which undermines the validity of the central conclusions. This falls below the standards required for publication in Nature Communications and should be rejected in its present form.", "reviewer_2": "All my concerns have been solved.", "reviewer_3": "The authors have well addressed the questions, and the quality of the revised manuscript has been significantly improved. Publish without any changes.", "reviewer_4": "The authors have thoroughly revised the manuscript and addressed the previously raised concerns. The overall quality of the manuscript has been improved. This reviewer has no additional comments and supports its publication in its current form."}, "author_response": "Point-by-point response for Nature Communications manuscript\n(ID: NCOMMS-25-52770A-Z)\nManuscript Type: Article\nTitle: Sustained hydrogen peroxide production via metallic unit-functionalized supramolecular docking\nAuthor(s): Jiaxun Sun†, Yuanming Zhang†, Wanheng Lu, Wei Li Ong, Xinglong Pan, Wentao Song, Zhonghua\nLi, Zhaosheng Li, Ghim Wei Ho*\nGeneral response: We sincerely appreciate the editor, editorial staff and all reviewers for their valuable and\ncritical comments. The manuscript has been greatly improved by addressing all the suggestions with points-by-\npoints responses as listed below.\n(Our response is given in blue, the corrections in the revised manuscript are shown in red, and some key points\nare highlighted in yellow.)\nPoints-by-points responses to Reviewer(s):\nReviewer #1:\nThe authors have made efforts to address the previous reviewers’ concerns. However, critical issues remain\nunresolved, which undermine the validity of the central claims. First, there is insufficient evidence for key\nconclusion material structure. The revised manuscript still lacks the characterization of the materials and there\nare still lots of unsolved problems in the resubmitted version. Also, there is insufficient experimental or theoretical\nevidence to substantiate the proposed reaction mechanism. Questionable interpretation stemming from a\nmisapplication of fundamental concepts, which undermines the validity of the central conclusions. This falls\nbelow the standards required for publication in Nature Communications and should be rejected in its present form.\nResponse:\nWe sincerely appreciate the reviewer’s careful evaluation and feedback regarding structural characterization,\nreaction mechanism, and conceptual interpretation. Our work presents the first supramolecular material exhibiting\nefficient and long-term stable photothermal H O generation, in which aminated MXene is connected to TAPB-\n2 2\nTaBr COF (TAPB = 1,3,5-tris(4-aminophenyl)benzene and TaBr = 2,5-dibromoterephthalaldehyde) via\n2 2\nhydrogen bonding. We understand that the central concerns lie in the adequacy of structural characterization,\nproposed mechanism, and the conceptual clarity of our interpretations. To further elucidate the rationale of our\nwork, we have systematically addressed these concerns by clearly presenting the existing evidence chain and,\nimportantly, supplementing it with additional experiments and analyses to further substantiate our conclusions,\nincluding Independent Gradient Model based on Hirshfeld partitioning (IGMH) calculations to quantify\nhydrogen-bond interactions, oxygen temperature-programmed desorption (O -TPD) measurements to confirm O\n2 2\ndocking, and time-dependent solvothermal reaction to demonstrate the absence of covalent bond formation.\nStructural characterization: The material structure has been rigorously verified using multiple complementary\ntechniques: X-ray diffraction (XRD), Raman spectroscopy, solid-state nuclear magnetic resonance (NMR), and\ntransmission electron microscopy (TEM) to elucidate the composition and structural framework. In addition,\nFourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and variable-\ntemperature solid-state 1H nuclear magnetic resonance (VT-ssNMR) were employed to confirm the presence of\nhydrogen-bonding interactions. These combined analyses establish a clear and robust understanding of the\nmaterial’s supramolecular architecture and the absence of covalent bonding.\nReaction mechanism: To substantiate the mechanism, we conducted isotope labelling experiments, rotating ring-\ndisk electrode (RRDE), in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), in situ\nelectron paramagnetic resonance (EPR) spectroscopy, and gas reference experiments. The experimental\nobservations are further supported by density functional theory (DFT) calculations, including adsorption energies\nand reaction pathway analysis, providing both experimental and theoretical validation of the reaction mechanism.\nWe hope that the revised manuscript now addresses the reviewer’s concerns thoroughly and strengthens the\nvalidity of our findings.\nIn the newly revised version, we focus on clearly elucidating and in-depth analyzing the optimization of\nsupramolecular structures, quantum chemical calculations of hydrogen-bond interactions, and oxygen docking\nwithin these supramolecular frameworks.\nSupramolecular architecture\nTo address the reviewer’s confusion on supramolecular architecture, we have supplemented a molecular-\nlevel synthesis pathway of the assembly of TAPB-TaBr COF fragment on Ti C T -NH surface via hydrogen\n2 3 2 x 2\nbonding interactions in Fig. R1a (this figure corresponds to revised Supplementary Fig. 4a). Besides, we\nreconstructed a lattice-matched supercell with associated local hydrogen bonding interaction details in Fig. R1b\n(this figure corresponds to revised Supplementary Fig. 4b) to visualize the three-dimensional crystalline structure,\nwhich is highly consistent with sheet-like morphology highlighted by the reviewer.\nFig. R1 | Synthesis and structures of supramolecular (COF) -NH -M. a, Synthetic route of (COF)-NH -M in molecular level. b, 3D\nx 2 x 2\ncrystalline structure of (COF)-NH -M with details of COF network and hydrogen bonding interaction in supramolecular assembly.\nx 2\nAbsence of covalent bonding\nTo directly address the reviewer’s concern about potential covalent bonding, we performed time-dependent\nsolvothermal reactions between TaBr monomers and Ti C T -NH matrix. The resulting products were extracted\n2 3 2 x 2\nand analyzed by Fourier transform infrared (FTIR) spectroscopy. As shown in Fig. R2 (this figure corresponds to\nrevised Supplementary Fig. 5), the characteristic imine-related absorption near 1610 cm−1 exhibits no detectable\ntendency toward covalent bond formation under employed reaction, suggesting the noncovalent interaction\nthroughout the synthesis.\nFig. R2 | FTIR spectra of pristine Ti C T -NH and Ti C T -NH @TaBr .\n3 2 x 2 3 2 x 2 2\nVisual analysis and clarification of hydrogen bonding interaction\nWe conducted supplementary weak interaction analysis using IGMH method. The DFT-optimized cluster\nmodel (B3LYP-D3/6-31G(d)+lanl2dz) reveals the formation of N–H···N hydrogen bonds (2.20 Å) on imine\nlinkage. Based on the wave function of cluster model, the interfragment interaction could be analyzed with both\nvisualized interaction region from g isosurface and interaction properties from sign( ). As shown in Fig. R3a\n2\n(this figure corresponds to revised Fig. 2a), the green IGMH isosurface with faint blue center localized at the\nhydrogen bonding sites is reflected in the scatter plot (this figure corresponds to revised Fig. 2a). The distribution\nof most data points between −0.02 and 0.01 and the relatively larger g values near 0.02 elucidate the coexistence\nof van der Waals interaction and weak hydrogen bonding interaction (Nat Commun., 2025, 16, 6481; J. Comput.\nChem. 2012, 33, 580−592).\nAs shown in Fig. R3b (this figure corresponds to revised Fig. 2b), the N 1s X-ray photoelectron spectroscopy\n(XPS) results show no additional intensity corresponding to C=N formation (399.5 eV), which is consistent with\nthe absence of covalent bonding formation inferred from the FTIR spectra of Ti C T -NH composite under TaBr\n3 2 x 2 2\nmonomers presence at varied duration.\nBased on these results, the hydrogen bonding interactions in the supramolecular material are further\nexperimentally investigated by FTIR and solid-state nuclear magnetic resonance (NMR) measurements. As\nshown in Fig. R4 (this figure corresponds to revised Supplementary Fig. 9), the significant peaks at 1615 cm−1\nand 1594 cm−1 could be attributed to the C=N stretching of imine and C=C stretching of aromatic rings, which\nsubstantially verify the successful synthesis of high-quality imine-linked COF. The subsequent peaks observed at\n1503 cm−1, 1456 cm−1, 1442 cm−1, and 1359 cm−1 are typical characteristics of aromatic structures and extended\nconjugated systems, corresponding to the C=C stretching, C–H in-plane bending, and C–N stretching.\nConsidering the multiple aromatic rings and complex conjugated structure, the peaks at 1393 cm−1 and 1697 cm−1\nslightly deviate from the original peak position, which can sensitively characterize the chemical interaction with\nimine group. The existence of N–H···N hydrogen bonding is predicted to affect the stretching vibration of N–H\nmoieties and further extend to the adjacent C–N/C=N bonds through the conjugated framework, thereby causing\na slight shift toward higher wavenumbers in the spectrum (J. Am. Chem. Soc. 2024, 146, 2663–2672; Nat. Photon.\n2023, 17, 478–484). As shown in the blue columns in the figure, both two peaks split for all samples with MXene\npresence, indicating the existence of hydrogen bonding in our supramolecular assembly.\nComplementary solid-state NMR spectroscopy provides direct insight into the hydrogen bonding\nenvironment of the –NH groups. As shown in Fig. R3d (this figure corresponds to revised Fig. 2d), the signals\n2\n~0.6 ppm in 1H solid-state NMR spectra (400 MHz) are attributed to the –NH groups, which is expected to be\n2\nsharp in Ti C T -NH due to the electron shielding effect by conductive matrix, whereas becomes broader in COF.\n3 2 x 2\nThereby, the extensive formation of N–H···N hydrogen bonding at the interface will offset the shielding effect of\nMXene, resulting in a higher peak intensity (not as sharp as pristine Ti C T -NH ) in (COF) -NH -M compared\n3 2 x 2 2.5 2\nwith TAPB-TaBr COF. To further support this assertion, variable-temperature NMR under ultrafast MAS (15\n2\nkHz) conditions reveal a shaper and more distinct –NH peak (Fig. R3e, this figure corresponds to revised Fig.\n2\n2e). As temperature increases, the weakening of hydrogen bonding renders the –NH groups more dynamically\n2\nfree, resulting in an enhanced peak intensity (Nat. Chem., 2012, 4, 711–717; J. Am. Chem. Soc., 2025, 147, 39623–\n39631). Moreover, the distinct signal around 40 ppm in 13C NMR spectrum of Ti C T -NH is slightly shifted in\n3 2 x 2\n(COF) -NH -M (Fig. R3f, this figure corresponds to revised Fig. 3f), reflecting a chemical environment change\n2.5 2\nof the carbon atoms adjacent to the amino terminals caused by the formation of hydrogen bonding. Together with\nthe intimate interfacial morphology between MXene and COF domains revealed by high-resolution transmission\nelectron microscopy (Fig. R3g–j, these figures correspond to revised Fig. 2g–j), these findings offer direct and\ncompelling evidence for the existence for hydrogen bonding interactions within the supramolecular structure.\nFig. R3 | Structural characteristics of TAPB-TaBr COF and supramolecular (COF) -NH -M. a, IGMH analysis on molecular\n2 x 2\nclusters of TAPB-TaBr COF and Ti C T-NH (grey for C; blue for N; red for Br; light orange for Si). b, N 1s XPS spectra of Ti C T-\n2 3 2 x 2 3 2 x\nNH , TAPB-TaBr COF, and (COF) -NH -M. c, Experimental PXRD pattern of TAPB-TaBr COF with Pawley refinement fit. d, f,\n2 2 2.5 2 2\nSolid-state NMR spectra of Ti C T-NH (dark blue), TAPB-TaBr COF (red), and (COF) -NH -M (blue) (d) 1H and (f) 13C. e, Variable-\n3 2 x 2 2 2.5 2\ntemperature 1H solid-state NMR spectra of (COF) -NH -M (from −40 °C to 20 °C with an increment of 20 °C). g, h, HR-TEM image\n2.5 2\nof (COF) -NH -M in different magnification. i, Fourier transform of the COF domains, showing lattice fringes of the COF networks\n2.5 2\nand MXene multilayers. j, EDS line scan profiles of selected elements across the (COF) -NH -M.\n2.5 2\nFig. R4 | FTIR analysis of TAPB-TaBr COF and (COF) -NH -M. a, FTIR spectra. The orange columns verify the successful\n2 2.5 2\nsynthesis of imine COF and the blue columns verify the existence of hydrogen bonding. b, Peak table and relevant description.\nAction: We have added the above discussion in the main text and Supplementary information as follows:\n“To elucidate the local intermolecular interaction on imine linkages, we employed the Independent Gradient\nModel based on Hirshfeld partitioning (IGMH) to analyze weak interaction (Fig. 2a). The density functional\ntheory (DFT) optimized cluster model clearly reveals the formation of N–H···N hydrogen bonds (2.20 Å). The\ngreen IGMH isosurface with faint blue center localized at the hydrogen bonding sites indicates the coexistence of\nvan der Waals interaction and weak hydrogen bonding interaction20. The distribution of most data points between\n−0.02 and 0.01, together with the relatively larger dg values near 0.02 in the scatter plot, further supports our\nproposal. N 1s X-ray photoelectron spectroscopy (XPS) results verify the bridging on N atoms, with N–H peak\n(401.6 eV) significantly enhanced by amino hydrogen bonding, while the N=C peak (399.5 eV)21 remains\nunchanged (Fig. 2b). Moreover, the Fourier transform infrared (FTIR) spectra of Ti C T -NH composite under\n3 2 x 2\nTaBr monomers presence at varied duration exhibit no detectable enhancement on C=N absorption, confirming\n2\nthe absence of covalent bond formation between Ti C T -NH and TAPB-TaBr COF (Supplementary Fig. 5).”\n3 2 x 2 2\n“Specifically, the reliability of the supramolecular assembly was confirmed through the validation of\nhydrogen-bonded bridges and morphological characterization. FTIR spectroscopy and NMR analysis distinguish\nhydrogen bond formation within the supramolecular assembly from covalent linking. As shown in Supplementary\nFig. 9, the splitting and shifting22 of the C=N/C–N stretching peaks around 1693/1393 cm−1 in the FTIR spectra\nreveal the redistribution of electron density around the N center induced by N–H···N hydrogen bonding at the\nimine linkage in (COF) -NH -M. Similarly, the signal around 0.6 ppm (–NH ) in 1H NMR of (COF) -NH -M\n2.5 2 2 2.5 2\nbecomes broader in TAPB-TaBr COF and sharper in Ti C T -NH , indicating the extensive formation of N–\n2 3 2 x 2\nH···N hydrogen bonding at the interface to offset the electron shielding effect by conductive matrix of MXene\n(Fig. 2d). This assertion is further evidenced by the variable-temperature NMR results under ultrafast MAS\nconditions, presenting an increasing intensity of –NH peaks due to the weakening hydrogen bonds with\n2\ntemperature rising23 (Fig. 2e and Supplementary Fig. 19). Furthermore, the distinct signal around 40 ppm in 13C\nNMR spectrum of Ti C T -NH is slightly shifted in (COF) -NH -M (Fig. 2f), reflecting the effect of hydrogen\n3 2 x 2 2.5 2\nbonding on the carbon atoms adjacent to the amino terminals.”\nEvaluation of oxygen docking behavior\nTo further address the reviewer’s concern on reaction mechanism, we employed the oxygen temperature-\nprogrammed desorption (O -TPD) measurements to probe the chemical adsorption characteristics of (COF) -\n2 x\nNH -M surfaces. Prior to the O -TPD measurements, thermogravimetric analysis verified the thermal stability of\n2 2\nthe TAPB-TaBr COF over the relevant temperature range (Fig. R5, this figure corresponds to revised\npristine TAPB-TaBr COF exhibits two distinct desorption regions in the O -TPD profiles, corresponding to low-\n2 2\ntemperature (approximately 50–200 °C) and high-temperature (approximately 300–400 °C) features. The low-\ntemperature behavior originates from reversible O docking on -conjugated aromatic carbon sites, instead of\n2\nstrong binding at nitrogen-containing sites (Nat Commun., 2025, 16, 6297). This interpretation is fully consistent\nwith our DFT calculations, which reveal a thermodynamically favored adsorption behavior according to the\nsignificantly lower O adsorption energy on aromatic than that on imine sites (Fig. R7, this figure corresponds to\n2\nrevised Fig. 5d). Moreover, a pronounced increase in the low-temperature desorption contribution in (COF) -\nx\nNH -M is observed with MXene content increasing, suggesting a substantially enhanced capability for O docking.\n2 2\nCompared with strongly bound oxygen species, weakly adsorbed oxygen is more readily available to participate\nin the 2e− oxygen reduction reaction, thereby favoring H O photoproduction in (COF) -NH -M.\n2 2 x 2\nFig. R5 | Thermogravimetric analysis of TAPB-TaBr COF.\n2 x 2 2\nFig. R7 | O adsorption energies on aromatic carbon (linker), imine linkage, and oxygen vacancies of MXene (red column, TAPB-\n2 x 2\nAction: We have expanded upon the above discussion in the main text and Supplementary information as follows:\n“The oxygen temperature-programmed desorption (O -TPD) was widely used to evaluate the O docking\n2 2\ncapability of materials by probing the adsorption-desorption behavior of surface oxygen species. Prior to the O -\n2\nrelevant temperature range (Supplementary Fig. 46). The TPD profiles exhibit a pronounced low-temperature\ndesorption feature (~150 °C), which can be attributed to reversible oxygen species that are weakly bound at -\nconjugated aromatic carbon sites36 (Supplementary Fig. 47). Notably, the increasing MXene content leads to a\npronounced enhancement of the low-temperature desorption, indicating the improved O docking capability in\n2\n(COF) -NH -M.”\nx 2\nWe sincerely thank the reviewers once again for the time and effort to the careful evaluation of our\nmanuscript. We have rigorously validated the material structure and systematically clarified the relationship\nbetween structure and performance. We believe that these comprehensive analyses clearly elucidate the\nsignificance of the study.\nReviewer #2:\nAll my concerns have been solved.\nResponse: We sincerely thank the reviewer for accepting our manuscript and for their time and constructive\ncomments again.\nReviewer #3:\nThe authors have well addressed the questions, and the quality of the revised manuscript has been significantly\nimproved. Publish without any changes.\nResponse: We sincerely thank the reviewer for their positive feedback and acceptance of our manuscript.\nReviewer #4:\nThe authors have thoroughly revised the manuscript and addressed the previously raised concerns. The overall\nquality of the manuscript has been improved. This reviewer has no additional comments and supports its\npublication in its current form.\nResponse: We appreciate the reviewer’s constructive comments, which led to the acceptance of the manuscript."}]

Decision letter