Ketyl radical-mediated exfoliation and electron storage for solar hydrogen peroxide production

Domain: physics
Published: 2025-12-12
Editorial outcome: major_revision

Abstract
Efficient photocatalytic production of hydrogen peroxide is a sustainable strategy for green chemical synthesis and environmental remediation. Herein, we report TPM-DADK, a segmented π-conjugation polymer containing redox-active anthrazolines and tetraphenylmethane nodes, enabling visible-light-driven hydrogen peroxide generation through a direct two-electron oxygen reduction reaction pathway. Conjugation breaks promote electron localization and the formation of long-lived ketyl radical anions, which act as both electron reservoirs and triggers light-induced exfoliation into nanosheets with abundant active sites. This structural evolution, together with localized negative charges, enhances oxygen adsorption and activation through proton-coupled electron transfer. Spectroscopic and kinetic analyses reveal more efficient charge separation, longer excited-state lifetimes, and reduced recombination after exfoliation. In this work, we show that TPM-DADK achieves a hydrogen peroxide production rate of 17.22 mmol g-1 h-1 under simulated sunlight with a solar-to-chemical conversion efficiency of 3.07%, demonstrating that precise π-topology control and radical stabilization synergistically enhance solar-to-chemical conversion for sustainable photosynthesis.

Introduction
Hydrogen peroxide (H2O2) is an environmentally friendly oxidant that has been extensively applied in water treatment, green synthesis, and biomedical fields1–5. Industrial production, however, is dominated by the anthraquinone oxidation process, which is energy-intensive, relies on noble metal catalysts, and generates hazardous organic byproducts6–10. These drawbacks have motivated the search for sustainable, low-impact alternatives. Photocatalytic H2O2 synthesis from water and oxygen via solar energy is an attractive option, but suffers from low selectivity, inefficient charge separation, and poor oxygen activation11–16. Current material design strategies, such as constructing donor-acceptor (D-A) frameworks, forming heterojunctions, and extending π-conjugated backbones, have improved charge separation and tuned energy levels for more efficient interfacial redox reactions17–21. However, fully conjugated architectures present inherent trade-offs: while extended π-conjugation promotes charge delocalization, it suppresses the electron localization needed for radical intermediate formation and limits the density of accessible catalytic sites22–26. Moreover, such rigid, static structures lack the capacity to adapt their morphology or interfacial environment during operation27,28.

Parallel approaches, including surface engineering, internal electric field modulation, and supramolecular assembly, have also enhanced oxygen adsorption and charge separation29–33. However, the concept of dynamic, light-triggered structural evolution that couples photophysical and morphological changes remains largely unexplored. Two-dimensional (2D) photocatalysts, with high surface-to-volume ratios, shortened charge transport pathways, and abundant exposed active sites, are attractive for H2O2 production34–36. However, strong interlayer π-π stacking often leads to aggregation and poor dispersion,37,38 whereas mechanical or chemical exfoliation methods39–42 can damage the structure or make scaling difficult43,44.

Here, we introduce a dynamic, light-responsive strategy that integrates conjugation interruption and radical-driven exfoliation to overcome these limitations. As shown in Fig. 1, this work systematically constructs a series of π-conjugated polymers incorporating redox-active anthrazoline (DADK) units and distinct bridging motifs, i.e., tetraphenylmethane (TPM), spirobifluorene (Flu), and pyrene (Py), to systematically modulate backbone conjugation topology and interlayer interactions. In particular, the TPM-DADK polymer introduces well-defined interruptions in π-conjugation via sp3-hybridized TPM nodes, which promote conjugation segmentation and electron localization of the π-conjugated backbone. This architecture promotes electron localization at the redox-active DADK sites under light irradiation, enabling the formation of long-lived ketyl radical anions (TPM-DADK•⁻). These radical anions not only function as electron reservoirs but also generate localized negative charges that induce strong electrostatic repulsion between polymer layers, effectively driving light-induced exfoliation into ultrathin 2D nanosheets under mild sonication. This dynamic exfoliation process simultaneously enhances the surface area, exposes additional catalytic sites, and optimizes charge separation and mass transport. Furthermore, the localized negative charges facilitate oxygen adsorption and activation through proton-coupled electron transfer, steering the system toward a direct two-electron oxygen reduction reaction (2e⁻ ORR) pathway for H2O2 generation. By systematically comparing fully conjugated (Py-DADK), partially conjugated (Flu-DADK), and conjugation-interrupted (TPM-DADK) frameworks, we decouple the effects of π-topology and steric design on charge behavior, radical stabilization, and photocatalytic performance. Overall, this study establishes a generalizable approach for designing light-adaptive polymer photocatalysts for efficient and selective solar-to-chemical energy conversion.

Results
Synthesis and characterization of CMPs
The successful synthesis of the polymers, TPM-DADK, Flu-DADK and Py-DADK, was confirmed through comprehensive structural characterization (Fig. 2 and Supplementary Figs. 1–19). Fourier transform infrared (FT-IR) spectroscopy provided initial evidence of successful polymerization. As shown in Fig. 2a and Supplementary Fig. 9, the characteristic C-Br stretching vibrations at approximately 510 cm−1 present in the monomers (DADK-Br, TPM-Br, Flu-Br, and Py-Br) disappeared in the corresponding polymers, confirming the consumption of terminal bromo groups. The appearance of strong absorption bands at 1614 cm−1 and 1714 cm−1, corresponding to C=N and C=O vibrations, respectively, indicated the formation of imine and carbonyl groups, and the successful incorporation of redox-active DADK units into the polymer backbones.

X-ray photoelectron spectroscopy (XPS) further verified the chemical composition and bonding environment (Fig. 2b and Supplementary Fig. 10). Taking TPM-DADK as a representative example, the high-resolution C1s spectra exhibit peaks at 284.8 eV, 285.8 eV, and 287.8 eV, which are assigned to C=C, C=N, and C=O bonds, respectively, alongside a π-π* satellite peak at ~292.0 eV. The N1s and O1s spectra display signals at 398.8 eV and 532.0 eV, corresponding to pyridinic nitrogen and carbonyl oxygen, respectively. Solid-state 13C NMR spectroscopy provided further structural evidence (Fig. 2c and Supplementary Fig. 11), with characteristic signals for ketocarbonyl carbons (~187 ppm), imine carbons (~161 ppm), sp3-hybridized TPM knots (~65 ppm), and aromatic carbons (120–140 ppm). Comparable XPS and NMR results were obtained for Flu-DADK and Py-DADK.

Powder X-ray diffraction (PXRD) patterns indicate that all the polymers are predominantly amorphous, exhibiting only short-range structural order (Fig. 2d). The peak at 28° corresponds to an interlayer distance of ~0.31 nm, which is characteristic of π-π stacking. Compared with those of TPM-DADK, the diffraction features of Flu-DADK and Py-DADK are slightly stronger, suggesting relatively enhanced short-range ordering and interlayer interactions. The nitrogen adsorption-desorption isotherms at 77 K revealed distinct porosity features (Fig. 2e and Supplementary Fig. 12). TPM-DADK has a predominantly microporous structure with a primary pore diameter of ~2.1 nm, along with a small fraction of larger, irregular mesoporous-macroporous voids, which is consistent with its open 3D structure. Flu-DADK and Py-DADK also display mainly microporous characteristics, with pore diameters at the boundary between the microporous and mesoporous regimes. Thermogravimetric analysis demonstrated good thermal stability (Supplementary Fig. 13), with decomposition temperatures of 526 °C and 538 °C for Flu-DADK and Py-DADK, respectively. In contrast, TPM-DADK has a lower decomposition temperature at 320 °C, which is consistent with its weaker π-π stacking and loose architecture, which are favorable for light-induced exfoliation.

The optical and electronic properties were investigated by UV-vis diffuse reflectance spectra and Mott-Schottky analyses (Fig. 2f, g and Supplementary Figs. 14, 15). All the polymers presented conduction bands that were more negative than the thermodynamic requirements for both the one-step (+1.12 V vs. RHE, pH = 7.47) and two-step ORR pathways (+0.11 V vs. RHE, pH = 7.47), along with valence band maximums (VBMs) exceeding the 4e⁻ water oxidation reaction (WOR) potential (+1.88 V vs. RHE, pH = 7.47), indicating favorable energy alignment for overall H2O2 photosynthesis. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images (Fig. 2h, i and Supplementary Figs. 16–19) revealed bulk layered morphologies with lamellar organization. High-resolution TEM (HRTEM) of TPM-DADK revealed lattice fringes at (0.23–1.14 nm), reflecting weak interlayer interactions conducive to light-triggered exfoliation. In contrast, Flu-DADK and Py-DADK result in smaller fringe distances and stronger crystallinity, which is consistent with enhanced π-π stacking. Collectively, these structural and morphological differences confirm the successful synthesis of the designed polymers.

Photogenerated ketyl radical anion driven exfoliation
As illustrated in Fig. 1 and Fig. 3, photogenerated electrons in polymers are captured by carbonyl groups to form ketyl radical anions under light. This electron storage process significantly alters the negative charges to the photocatalyst surface and substantially alter the local dipole moment from 0.160 Debye in the neutral DADK to 4.995 Debye in the reduced DADKH· species (Fig. 3a). The resulting electrostatic repulsion weakens π-π stacking, enabling light-induced exfoliation into nanosheets with mild sonication (Fig. 1c and Supplementary Fig. 8).

To investigate the formation of photogenerated radical species, electron paramagnetic resonance (EPR) spectroscopy was employed (Fig. 3b and Supplementary Fig. 20). No detectable EPR signal was observed in the dark, whereas light irradiation induced a distinct radical signal for TPM-DADK. A carbonyl-free control polymer (TPM-DADA) exhibited a significantly weaker EPR response under identical conditions, confirming the essential role of carbonyl groups as temporary electron storage sites for radical anion formation.

To directly monitor the light-induced transformation of carbonyl groups, XPS analyses were performed (Fig. 3c and Supplementary Fig. 21). In TPM-DADK, the O1s spectrum before irradiation displays a dominant peak at 532.0 eV (C=O), which decreases under illumination, whereas a new peak emerges at 530.8 eV (C-O), providing strong evidence for the formation of ketyl radical anions and their role in photogenerated charge storage. Zeta potential measurements revealed distinct surface charge responses among the polymers. TPM-DADK, Flu-DADK, and Py-DADK exhibited pronounced negative shifts after irradiation (Fig. 3d), reflecting surface accumulation of ketyl species, whereas TPM-DADA showed negligible changes (from 17.6 to 17.1 mV, Supplementary Fig. 22). The increased negative surface potential strengthens electrostatic proton interactions, promotes hydroxyl group formation, and improves colloidal stability, demonstrating that carbonyl groups facilitate the generation of photogenerated anionic radicals and enhance surface charge modulation. Contact angle measurements further confirm enhanced hydrophilicity after irradiation (Supplementary Fig. 23 and Supplementary Movies 1–6), suggesting improved water adsorption at the photocatalyst surface.

PXRD analysis revealed the light-induced structural changes (Fig. 3e and Supplementary Fig. 24). Upon irradiation, the π-π stacking peak at ~28° was substantially attenuated, which was consistent with enhanced interlayer repulsion and exfoliation. This transformation was further corroborated by atomic force microscopy (AFM), SEM, and TEM images (Fig. 3f, g and Supplementary Figs. 25, 26), which revealed a dramatic reduction in layer thickness from ~1.25 μm to 25 nm after exfoliation. This behavior arises from its architecture with periodic conjugation breaks, introduced by the sp3-hybridized TPM nodes. Such a design promotes the localization of photogenerated electrons at carbonyl sites, while allowing for some degree of delocalization via interchain or π-π interactions. The localized electrons form ketyl radical anions that accumulate negative charges, generating electrostatic repulsion. The resulting electrostatic repulsion, combined with weakened interlayer π-π stacking and vertical extension enforced by the non-conjugated, rigid tetrahedral TPM geometry, effectively drives nanosheet exfoliation and exposes more catalytic sites. In contrast, Flu-DADK and Py-DADK feature more continuous π-conjugation and stronger interlayer stacking, which restrict electron localization and reduces electrostatic repulsion, leading to only moderate photo-thinning. Consistently, UV-vis absorption spectra of the dispersed TPM-DADK suspensions (Supplementary Fig. 27) revealed a slight blue shift after irradiation under air, reflecting weakened π-π interactions and a shortened conjugation length, thereby corroborating the efficient light-driven exfoliation of TPM-DADK. In diluted dispersed suspensions under Ar, a slight red shift was observed (Supplementary Fig. 28), which was consistent with the formation of radicals in oxygen-free conditions. These observations corroborate the efficient light-driven exfoliation of TPM-DADK and the accumulation of surface charges.

Enhanced O2 adsorption driven by photogenerated ketyl radical anions
Oxygen adsorption plays a crucial role in determining the photocatalytic performance of polymers. To evaluate the interaction between O2 and the catalysts, O2 temperature-programmed desorption (O2-TPD) experiments were conducted. As shown in Fig. 4a, compared with its analogs, TPM-DADK exhibited higher O2 uptake and stronger binding affinity. This enhancement is attributed to the formation of protonated ketyl radical anions (TPM-DADKH·) under illumination, which generate localized negative charges and create specific O-H···O interaction sites that promote electrostatic attraction and partial charge transfer with O2 molecules.

To further probe the role of ketyl radical intermediates in O2 adsorption and activation, in situ FT-IR spectroscopy was performed under O2 saturated conditions in 2-propanol (Fig. 4b and Supplementary Figs. 29–32). No oxygen-related signals were observed in the dark. Upon light irradiation, however, a distinct O-O stretching band at 950 cm−1 and broad signals ranging from 1044 to 1204 cm–1 emerged, confirming light-induced Yeager-type O2 adsorption19,45,46. Notably, the O-O signals of TPM-DADK were much stronger and more persistent (Fig. 4b, c and Supplementary Fig. 29) than those of Flu-DADK and Py-DADK, highlighting the synergistic effect of protonated ketyl radical anions and the segmentally conjugated backbone. As schematically depicted in Fig. 4d and Supplementary Fig. 30, photogenerated electrons are captured by surface carbonyl groups, forming ketyl radical anions, which, upon protonation, generate DADKH· species. These radicals retain the ability to adsorb and reduce O2 even in the dark. The presence of the O-O characteristic band at 950 cm−1 under dark conditions confirms that protonated ketyl radicals facilitate O2 adsorption. In sharp contrast, TPM-DADA, which lacks carbonyl groups, did not exhibit these O2-related spectral features or an enhanced O2 adsorption capability, further confirming the essential role of carbonyl-derived ketyl radicals in O2 activation (Supplementary Fig. 32). In contrast to fully conjugated systems, the conjugation breaks in TPM-DADK enable each polymer segment to independently store photogenerated electrons, promoting efficient and localized charge accumulation that enhances O2 adsorption and activation.

To gain further insight, density functional theory (DFT) calculations were performed to evaluate the O2 adsorption configurations and energetics of DADK and DADKH· (Fig. 4e, Supplementary Figs. 33–37 and Supplementary Table 1). The results show that O2 preferentially binds to the O-H sites of DADKH·, forming a Yeager-type endoperoxide intermediate (O-H···O-O···H-C) at site 3. This configuration is thermodynamically favorable for the direct one-step two-electron ORR pathway to H2O2. The calculated O2 adsorption energy at the O-H site of DADKH· is more favorable than that at DADK (−1.74 vs. −0.78 kcal mol−1; Fig. 4f), corresponding to an enhancement of over 100%. Although the absolute energy difference is modest, such an increase is catalytically meaningful because slightly stronger O2 adsorption can facilitate activation while avoiding overly strong binding that impedes product desorption.

Enhanced charge separation and oxygen reduction kinetics
The efficiency of charge separation and transfer is crucial for photocatalytic performance. To elucidate the charge dynamics of the DADK-based polymers, a series of photoelectrochemical and spectroscopic analyses were performed (Fig. 5, Supplementary Figs. 38–48 and Supplementary Table 2–4).

Under photocatalytic conditions, distinct photocurrent responses were observed upon switching from Ar to air atmosphere. Notably, TPM-DADK exhibited a 60.6% decrease in the photocurrent (Fig. 5a), indicating effective electron consumption by the ORR rather than being transferred to the external circuit. In contrast, Flu-DADK and Py-DADK exhibited minimal photocurrent changes (<20%, Supplementary Fig. 38), suggesting limited electron utilization in the ORR. Electrochemical impedance spectroscopy (EIS) further supported these findings, with TPM-DADK showing a significantly reduced charge transfer resistance under air (Fig. 5b), which is consistent with more efficient interfacial electron transfer. Kelvin probe force microscopy (KPFM) revealed that TPM-DADK possessed the highest surface potential (ΔE=200 mV) among the three samples (Fig. 5c and Supplementary Fig. 42), reflecting enhanced charge separation. Unlike continuous conjugated systems, the strategically segmented π-framework in TPM-DADK localizes electrons within discrete domains (Supplementary Table 1 and Supplementary Fig. 37), thereby suppressing recombination and enabling efficient charge separation and storage47. Importantly, the radicals generated in this system are not permanently isolated but remain dynamically coupled with the π-conjugated backbone. This transient interaction induces local polarization that promotes interfacial charge separation and transfer under illumination.

Strikingly, light-induced exfoliation further improved the electron transport properties of TPM-DADK. After photo-exfoliation under air, the photocurrent density increased by 480%, which was attributed to enhanced electron mobility through the thinner, more open nanosheet structure. In contrast, Flu-DADK and Py-DADK resulted in decreased photocurrents after photo-exfoliation, likely due to increased electron consumption by the ORR rather than diminished exciton generation. Temperature-dependent photoluminescence (TD-PL) spectroscopy provided further insight into charge recombination. All polymers exhibited PL quenching with increasing temperature (Fig. 5f, g and Supplementary Figs. 44, 45). Fitting the integrated PL intensity to the Arrhenius equation revealed an exciton binding energy (Eb) of 59.3 meV for TPM-DADK, which was significantly lower than that of Flu-DADK (118.5 meV) and Py-DADK (130.3 meV), confirming superior charge separation.

Furthermore, TPM-DADK displayed strong orange emission at 598 nm, which was significantly quenched upon switching the atmosphere from Ar to air (Fig. 5h and Supplementary Fig. 46), which was consistent with efficient charge transfer to O2. After self-exfoliation, the overall PL intensity became intrinsically much weaker, and the additional quenching by O2 was only slight, reflecting that most photogenerated electrons were already diverted into non-radiative transfer pathways provided by surface-bound anionic radicals. Time-resolved PL measurements of TPM-DADK further revealed that the excited-state lifetime decreased from 4.37 ns to 2.03 ns after exfoliation (Fig. 5i), indicating accelerated interfacial electron transfer and suppressed radiative recombination. The coexistence of weaker initial emission and shorter lifetimes demonstrates that the exfoliated nanosheets possess highly efficient charge separation, which promotes oxygen adsorption and reduction despite the faint luminescence. These results demonstrate that TPM-DADK combines segmented π-conjugation and dynamic exfoliation to enhance charge separation, oxygen adsorption, and interfacial electron transfer. This synergistic design optimizes the balance between charge localization and mobility, highlighting its superior photocatalytic performance for H2O2 production.

Observation of long-lived charge-separated states
To elucidate the nature and dynamics of the photoinduced intermediates, femtosecond transient absorption (fs-TA) spectroscopy was conducted under various conditions (Fig. 6, Supplementary Figs. 49–53 and Supplementary Table 5). The negative signal at approximately 380 nm, corresponding to ground-state bleaching (GSB), is essentially identical across the three samples, indicating similar ground-state absorption. In contrast, the broad positive band at 450–650 nm, assigned to excited-state absorption (ESA), varies among the samples, reflecting its higher sensitivity to charge-transfer processes. Pristine TPM-DADK under N2 exhibited weak and short-lived ESA, with the signal decaying predominantly within ~100 ps (Fig. 6a, green trace in Fig. 6f), indicating rapid excited-state relaxation and inefficient charge separation. Upon the introduction of air, the ESA signal intensified and persisted for longer durations (Fig. 5b), suggesting that molecular oxygen stabilizes photoexcited species, potentially through electron capture pathways.

Strikingly, after photo-exfoliation, the ESA of TPM-DADK was dramatically enhanced and sustained across 400–700 nm (Fig. 6c), with signals persisting beyond 4.5 ns (Fig. 6d), which is consistent with the formation of long-lived charge-separated states or radical intermediates. A spectral slice at 60 ps (Fig. 6e) revealed pronounced ESA peaks at ~480 and 600 nm, characteristic of stabilized photogenerated species enabled by structural reorganization.

Tri-exponential fitting of the fs-TA decay kinetics (Fig. 6f and Supplementary Table 5) provided insights into the excited-state evolution under different conditions. Under N2, pristine TPM-DADK exhibited ultrafast decay components (τ1 = 1.07 ps, τ2 = 36.6 ps) and a short-lived third component (τ3 = 353 ps), indicative of rapid exciton deactivation and poor charge separation. In air, all lifetime components increased significantly (τ1 = 3.66 ps, τ2 = 100.8 ps, and τ3 = 1701 ps), reflecting efficient electron capture and stabilization by molecular oxygen. Strikingly, photo-exfoliated TPM-DADK in air exhibited further elongation of τ3 (1839 ps) alongside a shortened τ1 (1.48 ps), indicating rapid initial charge separation followed by prolonged stabilization of reactive intermediates. A slight reduction in τ2 (76.95 ps) suggests faster charge migration, likely due to the thinner nanosheet morphology and increased surface accessibility after exfoliation. Collectively, these results demonstrate that photo-exfoliation, combined with oxygen interaction, synergistically promotes fast charge extraction and generates long-lived reactive intermediates in TPM-DADK, contributing to its enhanced photocatalytic performance.

Photocatalytic H2O2 generation
The photocatalytic H2O2 production performance of all the polymers was evaluated under various conditions (Fig. 7, Supplementary Figs. 54–63 and Supplementary Table 6). Among the three polymers, pristine TPM-DADK exhibited superior photocatalytic performance, achieving an exceptional H2O2 production rate of 4.72 mM h–1 in pure water under O2 saturated conditions with visible light irradiation (>420 nm), substantially outperforming Flu-DADK (2.59 mM h−1) and Py-DADK (1.43 mM h−1) (Fig. 7a). Remarkably, after photo-driven exfoliation, these rates further increased, reaching 10.82 mM h−1, 4.19 mM h−1 and 2.11 mM h−1, respectively. Under ambient air, exfoliated TPM-DADK still maintained a high rate of 6.59 mM h−1 under visible light irradiation (Supplementary Fig. 56).

TPM-DADK also demonstrated excellent performance under more practical conditions. Under AM 1.5G simulated sunlight, TPM-DADK achieved a concentration-based H2O2 production rate of 14.60 mM h−1 (Fig. 7b), while the mass-normalized rate reached 17.22 mmol g−1 h−1 (Fig. 7c). It should be noted that these two metrics were obtained at different catalyst concentrations. Together, both values highlight the superior performance of TPM-DADK (Supplementary Tables 6–8).

In outdoor tests under natural sunlight and ambient conditions, the production rate remained robust at 3.99 mM h−1 (Supplementary Fig. 57). The wavelength-dependent apparent quantum yield (AQY) of the polymers aligned well with their absorption spectra (Fig. 7d and Supplementary Fig. 58). Notably, the AQY of TPM-DADK reached a peak value of 46.2% at 405 nm, highlighting its exceptional light-harvesting efficiency.

Moreover, TPM-DADK showed robust activity in real water systems, producing 13.34 mM h−1 in tap water and 13.64 mM h−1 in seawater, indicating strong environmental adaptability (Fig. 7e and Supplementary Fig. 59). Even in relatively contaminated lake water, TPM-DADK retained a high H2O2 production rate of 9.59 mM h−1, while simultaneously contributing to water purification through in situ oxidative processes.

In terms of energy conversion, TPM-DADK achieved an impressive solar-to-chemical conversion (SCC) efficiency of 3.07% under AM 1.5G simulated sunlight, surpassing most previously reported organic photocatalysts, and far exceeding the typical solar-to-biomass conversion efficiency of typical plants (~1%). Long-term recycling experiments demonstrated the excellent stability of these polymers, with negligible performance loss after at least five cycles of testing (Fig. 7f). After the photocatalytic cycle tests, the photostability of the recycled TPM-DADK was evaluated via PXRD and FT-IR analyses (Supplementary Fig. 60), confirming the good durability of the photocatalyst.

Notably, localized photoexcitation at TPM-DADK units favors selective O2 reduction to H2O2, whereas extended charge-transfer excitations across donor-acceptor interfaces in Flu-DADK and Py-DADK are generally more conducive to H2 evolution (Supplementary Figs. 62, 63). This mechanistic divergence between localized excitations and charge-transfer states is consistent with recent studies on organic semiconductor photocatalysts, where exciton localization has been shown to enhance selective two-electron oxygen reduction, whereas delocalized charge-transfer states facilitate proton reduction to H2 48,49.

Mechanistic insights into photocatalytic H2O2 generation
To elucidate the H2O2 production mechanism, a series of trapping experiments were conducted (Fig. 8a and Supplementary Fig. 64). Under O-saturated conditions, TPM-DADK achieved a H2O2 generation rate of 10.82 mM h−1 in pure water. Replacing air with Ar resulted in only trace H2O2 production, confirming that O2 was the essential reactant. The addition of KIO3 as an electron trap completely suppressed H2O2 formation, indicating that the 2e- ORR is the dominant pathway.

To assess the involvement of hydroxyl radicals (·OH) and superoxide radicals (·O2⁻), tert-butanol and p-benzoquinone (p-BQ) were employed as scavengers. Tert-butanol induced only minor inhibition (~9.7%), suggesting negligible ·OH involvement and excluding the WOR pathway. p-BQ caused slight inhibition, implying that the direct one-step 2e⁻ ORR dominated over the conventional two-step route involving ·O2⁻. Similar mechanisms were observed for Flu-DADK and Py-DADK (Supplementary Fig. 64). Nitro blue tetrazolium (NBT) assays quantified ·O2⁻ production (Fig. 8b and Supplementary Fig. 65), revealing yields of 181.03 μM h−1, 319.66 μM h−1 and 554.10 μM h−1 for TPM-DADK, Flu-DADK and Py-DADK, respectively. EPR spectroscopy with 5,5-dimethyl-1-pyrroline N-oxide (DMPO) as a radical trapping agent further supported these findings (Fig. 8c). TPM-DADK exhibited negligible DMPO-·O2⁻ signals compared with strong signals for DADK, confirming suppressed ·O2⁻ intermediate formation in TPM-DADK. These results demonstrate that interrupted π-conjugation in TPM-DADK enhances electron localization and ketyl radical formation, suppresses ·O2⁻ production and favors a direct 2e⁻ ORR pathway.

Koutecky-Levich analysis based on rotating disk electrode (RDE) measurements provided electron-transfer numbers (n) of 1.99, 1.80, and 1.52 for TPM-DADK, Flu-DADK, and Py-DADK, respectively (Fig. 8d and Supplementary Fig. 66), which is consistent with the highly selective 2e⁻ ORR over TPM-DADK. The rotating ring-disc electrode (RRDE) results revealed oxygen evolution via a four-electron WOR pathway for all polymers, with no 2e⁻ WOR products detected (Supplementary Figs. 67, 68). The oxygen evolution rates followed the order Py-DADK > Flu-DADK > TPM-DADK, which is consistent with the structural influence on water oxidation activity.

In-situ FT-IR spectroscopy provided molecular-level evidence for redox processes. Upon light irradiation, the C=O stretching band at 1720 cm−1 diminished, whereas new peaks at 1279 cm−1 (C-O) and 1346 cm−1 (O-H bending) emerged and later reversed in the dark (Fig. 7e and Supplementary Fig. 31). These reversible changes support the formation of protonated ketyl radical intermediates via light-induced reduction of surface ketone groups. Furthermore, a light-Ar/dark-O2 experiment (Supplementary Fig. 69) revealed that upon reintroducing O2 in the dark, approximately 36 μM H2O2 was still produced, indicating that photoinduced radical intermediates formed under illumination can continue reacting with O2 even in the absence of light. Under an O2 atmosphere, these photo-induced ketyl radicals rapidly transfer electrons to the adsorbed oxygen, whereas under Ar, they accumulate and subsequently generate H2O2 upon O2 exposure. These results underscore the critical role of long-lived ketyl intermediates in H2O2 formation.

On the basis of the experimental results and DFT calculations, a photocatalytic mechanism is proposed (Supplementary Fig. 70). Upon visible-light excitation, TPM-DADK generates photogenerated electrons and protons via water oxidation. The electrons reduce surface ketone groups to form TPM-DADKH·, which act as highly active sites for O2 activation. TPM-DADKH· enables Yeager-type dual-site adsorption of O2 at adjacent hydroxyl and benzylic positions, forming an endoperoxide-like intermediate. This structural motif enables a concerted one-step two-electron oxygen reduction pathway, in which the stored electron and the locally generated proton (either as a hydrogen atom, H·, or as H⁺+e⁻) cooperatively reduce O2 to form *H2O2. The generated *H2O2 desorbs from the surface, and TPM-DADK is regenerated, completing the catalytic cycle.

Crucially, the spatial confinement of both photogenerated electrons and protons at the active sites eliminates the need for long-range proton diffusion, accelerating proton-coupled electron transfer (PCET). This precise spatiotemporal control enhances the selectivity for the 2e⁻ ORR to H2O2, while suppressing undesirable ·O2⁻ intermediates or four-electron reduction to water.

Methods
Materials
All starting materials and solvents, unless otherwise specified, were purchased from Energy Chemical, Adamas and Sinopharm Chemical Reagent Co., Ltd and used without prior purification. O2 (99.999%) and Ar (99.999%) were purchased from Shaanxi Qintang New Era Gas Co., Ltd.

Characterization
1H NMR and 13C NMR spectra were recorded on a 400 MHz or a 600 MHz BRUKER spectrometer at room temperature using tetramethylsilane (TMS) as the internal standard. High-resolution mass spectrometry (HRMS) data were collected on a Bruker maxis UHR-TOF mass spectrometer in ESI positive mode. Fourier transform infrared (FT-IR) measurements were carried out using a Bruker Tensor 27 spectrophotometer. X-ray single crystal diffraction data were collected on a Nonius Kappa CCD diffractometer, using MoKα radiation (λ) 0.71073 Å (graphite monochromator). The X-ray photoelectron spectroscopy (XPS) spectrum was recorded on an X-ray spectrometer (ESCALAB 250Xi) equipped with an Al target. The crystallinity was measured via a Bruker D8-advance diffractometer with a rotary Cu target (λ = 0.15418 nm).

UV-vis spectra and UV-Vis diffuse reflectance spectroscopy (DRS) was collected on a Cary 5000 (Varian) spectrometer. Emission spectra and the absolute quantum yields were recorded on a Horiba FluoroMax Plus spectrofluorometer. PL lifetimes were measured using an FLS1000 fluorescence spectrometer (Edinburgh) at room temperature. Zeta potentials were measured on a Horiba SZ-100 analyzer. Thermogravimetric analysis (TGA) was performed on an EXSTAR 6000 under a flow of air by heating from room temperature to 800 oC at a rate of 10 oC min−1. Temperature programmed desorption (TPD) of O2 was measured with an AutoChem II 2920 chemisorption analyzer.

To characterize the morphology of samples, scanning electron microscopy (SEM) was performed using a Hitachi SU8220. Transmission electron microscopy (TEM) micrographs were obtained using a Hitachi TEM HT 7800 operating at 80 kV acceleration voltage. The samples were deposited onto a carbon-coated copper grid and dried. Atomic force microscopy experiments were performed on an Asylum Research Cypher VRS (Oxford instruments) atomic force microscope equipped with a Scan Asyst-HR fast scanning module and a Kelvin probe.

H2O2 photosynthesis
H2O2 photosynthesis was conducted in a 250 mL quartz reactor. Generally, 15.0 mg of photocatalyst was ultrasonically dispersed into 10.0 mL DI water. Then, the suspension was sonicated and irradiated for an hour to conduct the photo-exfoliation. After that, the reactor was illuminated by a 300 W Xe lamp (λ > 420 nm, 100 mW cm−2). The reaction was then initiated under continuous illumination while bubbling O2 to maintain an oxygen-rich environment.

Aliquots were collected every 30 min, filtered through a 0.45 μm polyethersulfone membrane, and mixed with freshly prepared Ce(SO4)2 solution. The H2O2 concentration was determined by UV-vis spectroscopy. For catalyst recycling, the photocatalyst was recovered by filtration, washed thoroughly with water, dried under vacuum at 70 °C, and reused under identical reaction conditions.

Apparent quantum yield (AQY) measurement
The apparent quantum yield (AQY) was determined under monochromatic light irradiation. The measurement was performed in deionized water (10 mL) containing 15.0 mg of photocatalyst. The light intensities at 405, 450, 550, 600 and 650 nm were measured with an optical power meter (CEL-NP2000-2, China).

The AQY (%) was calculated via the following equation:
AQY(%) = [photo H2O2 produced (mol) × 2] / [N × h × c × I × S × t × λ] × 100%

Loading photocatalyst
Solar-to-chemical conversion (SCC) efficiency measurement
The solar-to-chemical energy conversion (SCC) efficiency was tested in pure DI water without any sacrificial agents and calculated via the following equation:
SCC(%) = [ΔG × H2O2 formed (mol)] / [I × A × t] × 100%

Photoelectrochemical measurements
Electrochemical impedance spectroscopy (EIS) measurements, photocurrent response measurements and Mott-Schottky measurements were performed via a CHI-660E electrochemical workstation (CHI Instruments, Shanghai, China). FTO glass coated with prepared samples, platinum wires and SCE electrodes were used as working, counter and reference electrodes, respectively.

A 300 W xenon lamp (λ > 420 nm, light intensity calibrated to 100 mW/cm2 via an optical power meter, CEL-NP2000-2, China) was used as the light source. The measurements were performed in a 0.1 M Na2SO4 aqueous solution (pH = 7.47), with potentials measured against a SCE reference electrode and converted to the RHE scale via the Nernst equation.

Rotating disk electrode (RDE) measurements
RDE measurements, employing a rotating disk electrode (glassy carbon electrode with an area of 0.196 cm2), Ag/AgCl and graphite rod electrode as the working electrode, reference electrode and counter electrode, were conducted on a CHI760E electrochemical workstation (Chenhua, Shanghai). All potentials were measured without iR compensation.

The photocatalyst ink was prepared via ultrasonic dispersion of 5 mg of photocatalyst in 500 μL of a water/ethanol/5% Nafion solution (v/v/v = 33:16:1). The working electrode (0.3 mg photocatalyst) was fabricated by drop-casting 30 μL of a catalyst ink onto its surface, followed by air-drying. Linear sweep voltammetry (LSV) was performed to determine the average electron transfer number (n).

Rotating ring-disk electrode (RRDE) measurements
A ring-disk electrode (PINE Corporation, USA) was used as the working electrode to measure the ORR activity. The working electrode was prepared for RDE measurements. The ORR activity was evaluated in 0.1 M Na2SO4 under an argon atmosphere at a scan rate of 10 mV s−1 and a rotation speed of 1600 rpm. Prior to the measurement, the Na2SO4 solution was purged with argon for 30 min. The potentials of the ring electrode were set to −0.23 and 0.6 V (vs. Ag/AgCl) to detect O2 or H2O2. All potentials were measured without iR compensation.

Quantitative experiment of ·O2-
To quantify the ·O2- concentration, nitro blue tetrazolium (NBT) was used as a ·O2- scavenger, as it can be reduced by ·O2- to form a purple formazan, which is insoluble in water. The photocatalytic activities of TPM-DADK, Flu-DADK and Py-DADK were evaluated in an air-saturated condition and under visible light irradiation (λ > 420 nm). For each test, 10 mg of photocatalyst was added to a 10 mL of 1 mM NBT aqueous solution within a container. After that, the dispersion was stirred in the dark for 30 min. During the irradiation, suspensions were taken from the reaction cell every 15 min, and then filtered to remove the formazan and photocatalysts. The concentration of ·O2- was determined by the degradation of NBT, measured by the absorbance change at the wavelength of 259 nm.

Theoretical calculation
All DFT calculations were performed using the Gaussian 09 software package. All molecular structures were optimized with the B3LYP-D3(BJ) functional and 6-311G* basis set, incorporating an implicit solvent model to account for solvation effects (water as solvent). Frequency calculations at the same theoretical level confirmed the optimized structures as local minima on the potential energy surface. Single-point energy calculations were conducted using the B3LYP-D3(BJ) functional with the extended 6-311+G(2d,p) basis set.

All transition state calculations were performed at the B3LYP-D3(BJ)/6-311G* level. Vibrational frequency analysis confirmed the transition state possesses a single imaginary frequency along the reaction coordinate. Intrinsic reaction coordinate (IRC) calculations verified the topological connectivity between transition states and corresponding reactants/products.

Transient absorption (TA) measurement
Transient absorption measurements were performed via a pump-probe spectrometer. A Ti:sapphire amplifier initially generated a fundamental laser pulse (wavelength: 800 nm, repetition rate: 1 kHz), which was subsequently split into two branches by a beam splitter. One branch was directed to an optical parametric amplifier (OPA) to generate pump pulses covering the 290–2600 nm range, with the pump pulses modulated at 500 Hz, and their intensity adjusted via neutral-density filter wheels. The other branch of the fundamental pulse served as the probe and was focused into a sapphire crystal to produce a white-light continuum spanning 350 nm to 1600 nm. Time delays of up to 8 ns were achieved via a motorized translation stage with a retro-reflecting mirror. Both the pump and probe beams were incident normally on the sample and spatially overlapped at the focal position. The focused spot sizes at the sample were approximately 200 μm for the probe beam and 600 μm for the pump beam.

Electron paramagnetic resonance (EPR) measurements
The EPR test was carried out via EPR (Magnettech MS-5000) with a magnetic field ranging from 330 to 345 mT. 5,5-dimethyl-1-pyrroline N-oxide (DMPO) was selected as the paramagnetic trapping agent of ∙O2-. The measurements were carried out in CH3OH solvent with 2 mg of catalyst, exposed to irradiation with a 300 W xenon lamp (λ > 420 nm) in a Pyrex glass tube. The dispersion was purged with O2 for 15 min before light irradiation. To detect the signal of electrons in the photocatalysts, 20 mg of photocatalyst was loaded into a Pyrex glass tube and then placed in the spectrometer before and after illumination with a xenon lamp for 5 min.

In situ DRIFTS characterization
A Bruker INVENIO R FT-IR spectrometer fitted with an in situ diffuse reflectance cell provided by Harrick was used for the In Situ DRIFTS measurements. Before the measurement, it was necessary to purge with a nitrogen purge to eliminate impurities. Subsequently, water and O2 were added to the reactor in the dark until the sample reached O2 adsorption equilibrium within 1 h. Then, illumination was provided via a 300 W xenon lamp (λ > 420 nm).

Photocatalytic oxygen evolution reaction
The photocatalytic oxygen evolution reaction was performed in a Pyrex top-irradiation reacting vessel, which was connected to a glass closed gas system with a constant temperature of 5 oC (Labsolar-6A, Beijing Perfectlight). As for oxygen evolution, 5.0 mg photocatalyst was dispersed in 20 mL distilled water with 0.02 M AgNO3 as electron scavenger; 5 wt% Co co-catalyst was loaded via the in-situ photo-deposition of CoCl2. The suspension was thoroughly degassed and irradiated by a 300 W Xe lamp (full spectrum, 300 mW cm–2). The evolved gases were analyzed at a 0.5 h interval by an online gas chromatograph (GC-2002N/TFF, TCD detector, Ar carrier, 5 Å molecular sieve column).

Degradation of H2O2
Photocatalyst (10.0 mg) was suspended in H2O2 solution (2 mM, 10.0 mL) and dispersed by sonication for 30 min. The resulting mixture was bubbled Ar for 30 min in darkness, then irradiated under 300 W Xe lamp (λ > 420 nm, light intensity: 100 mW·cm–2) for 1 h. The H2O2 concentration was measured as described in Supplementary Information.

ICP-OES Analysis
The content of Pd in the polymer was determined by inductively coupled plasma optical emission spectroscopy (ICP-OES, iCAP 7400, Thermo). 50 mg of TPM-DADK was digested in a mixed acid solution of HNO3/H2O2 (3:1, v/v) under heating until complete dissolution. The solution was further evaporated to a volume of less than 0.5 mL, cooled to room temperature, and then diluted to 10 mL with ultrapure water for ICP-OES measurement. The Pd concentration, determined using a calibration curve prepared from standard Pd solutions, was 0.1588 wt%.

Data availability
All other data supporting the findings of this study are available within this article and its Supplementary Information. Source data are provided in this paper.

Peer review rounds
[{"round": 1, "reviewer_comments": {"reviewer_1": "The authors report a π-conjugated polymer with deliberately segmented conjugation that delivers efficient photocatalytic H₂O₂ production. A central claim is that long-lived ketyl radical anions trigger light-induced exfoliation, thereby increasing O₂ adsorption/activation and enabling high SCC efficiency. The concept is original, the materials chemistry is thoughtfully executed, and the performance is compelling. In my view, this work represents a notable advance for polymer-based photocatalysis and is suitable for publication in Nature Communications.\nHopefully the following comments could further refine this study:\n1. In Figure 1e, the N2 adsorption/desorption isotherms of TPM-DADK show no obvious hysteresis loop, which is inconsistent with typical mesoporous characteristics. Meanwhile, in Supplementary Fig. 10, the calculated pore size distributions of Flu-DADK and Py-DADK indicate mesoporosity, whereas the manuscript describes that Flu-DADK and Py-DADK predominantly display microporous characteristics. This inconsistency requires further characterization and explanation.\n2. In the PXRD spectra, the position of the π-π stacking diffraction peak typically reflects the interlayer distance. According to the authors, the interlayer distances of TPM-DADK, Flu-DADK, and Py-DADK are not identical; however, in Fig. 1d, the corresponding π-π stacking diffraction peaks appear at the same position.\n3. It is recommended that the authors perform in-situ FTIR spectroscopy on TPM-DADA to further substantiate the pivotal role of photogenerated ketyl radical anions in the reaction process.\n4. In Fig. 4a, the authors attribute the decrease in photocurrent of TPM-DADK to the effective electron consumption by the ORR. However, it is not clear whether the production from ORR has been verified.\n5. The authors state that “the strategically segmented π-framework in TPM-DADK localizes electrons within discrete domains”, yet this claim is not sufficiently supported by computational evidence.\n6. The authors report that the SCC efficiency of TPM-DADK reaches 3.49%, which is close to the highest level in the field. However, during the SCC measurements, the actual illumination area was less than 1 cm2 and the irradiation time was only 20 minutes, which may lead to an overestimation of the results. Authors should report a more reliable SCC value with much larger irradiation area and longer irradiation time.\n7. In Supplementary Fig. S45, when the dosage of TPM-DADK was 1 g/L under pure water conditions, the H2O2 generation rate was 9.95 mM h-1. However, in Supplementary Fig. S46, under the same dosage conditions, the H2O2 generation rate of TPM-DADK reached 10.82 mM h-1\n9. There are some apparent errors in the manuscript. For instance, in Fig. 6d and Supplementary Fig. S49, AQY and AQE are used interchangeably, which may cause conceptual confusion. Supplementary Fig. S37 lacks the corresponding data figure. In addition, Supplementary Fig. S61-62 are not mentioned in the manuscript.", "reviewer_2": "This manuscript by Zhu et al. reports an impressive and innovative advance in photocatalytic hydrogen peroxide production. The authors designed a novel π-conjugated polymer (TPM-DADK) with a segmented conjugation structure that enables two key functions: stabilization of long-lived ketyl radical anions as electron reservoirs and light-induced exfoliation into 2D nanosheets. This creative concept of using photogenerated intermediates to drive in situ morphological transformation represents a notable step forward in adaptive photocatalysis. The study is thorough, integrating sophisticated synthesis, comprehensive characterization (EPR, in situ FT-IR, XPS, fs-TA, etc.), and theoretical calculations to elucidate the mechanism. TPM-DADK delivers outstanding H2O2 production rates and solar-to-chemical efficiencies under both simulated and natural sunlight, with activity further demonstrated in real water sources. Overall, the work is rigorous, the conclusions are well supported, and the findings are broadly relevant. I strongly recommend acceptance after minor revisions to improve clarity and impact.\n1.While the light-induced exfoliation is well documented, the manuscript would benefit from a clearer discussion of why TPM-DADK shows superior exfoliation compared to Flu-DADK and Py-DADK. The authors attribute this to the “segmented conjugated structure,” but it would be valuable to elaborate on how this specifically enhances electrostatic repulsion.\n2.The proposed mechanism in the conclusion and preceding discussion is excellent. To enhance accessibility, the authors might consider adding a simple schematic, even in the Supplementary Information, that visually summarizes the catalytic cycle—from light absorption and radical formation to O2 adsorption, one-step 2e⁻ reduction, and H2O2 desorption.\n3.The synthesis appears to require specific conditions that may limit scalability. A brief discussion of potential scale-up considerations and cost implications would further strengthen the practical relevance of this work.\n4.Typically, H2O2 stability and production efficiency are pH-dependent. Testing across different pH ranges would demonstrate the robustness of the system and optimal operating conditions.\n5.H2 evolution data are provided in Fig. S62, but no corresponding discussion is included. It would strengthen the manuscript to briefly address these results—either to clarify their relevance to the photocatalytic process, or to explain why H2 evolution is negligible compared to H2O2 production. This would help avoid potential confusion and provide a more comprehensive picture of the system’s selectivity.\n6.Some figures, such as Figure 1, could be improved for readability. Please ensure that all labels and abbreviations (e.g., TPM, Flu, Py, DADK) are consistently defined and that font sizes are large enough to be easily legible.\n7.The English is generally very good, but there are a few minor grammatical errors and awkward phrasings that should be corrected during proofreading (e.g., “reflecting indicating” in the results section; “further increasement” in the photocatalytic performance section).", "reviewer_3": "Han and colleagues report a conceptually elegant and rigorously executed study on the π-conjugated polymer photocatalyst TPM-DADK. They propose a novel photoinduced ketyl radical anion-driven self-exfoliation and electron storage mechanism, enabling the bulk polymer to transform into nanosheets, which enhances charge utilization, oxygen adsorption, and selectivity for the two-electron oxygen reduction reaction. The catalyst achieves excellent H2O2 production of 14.60 mM·h-1 with a solar-to-chemical efficiency of 3.45%, among the highest for organic systems.\nThe study is both innovative and thorough. Conjugation segmentation effectively balances electron localization with structural exfoliation, and comparison with Flu-DADK and Py-DADK underscores the role of π-topology. Mechanistic insights are strongly supported by multiple techniques, convincingly identifying ketyl radical anions as key intermediates. Overall, this is a systematic, high-quality study, and I recommend publication after addressing the following minor points.\n1.Please clarify how the completion of the Suzuki coupling reaction was confirmed (e.g., by solid-state NMR or FT-IR spectroscopy) and whether any catalytic metal residues or unreacted monomers remained after Soxhlet purification.\n2.The BET surface area of TPM-DADK is notably lower than that of Flu-DADK and Py-DADK. A deeper discussion on how this inverse correlation with catalytic activity arises (potentially due to differences in charge separation efficiency, active site density, or substrate adsorption energy) would be valuable.\n3.To confirm the morphological stability of the exfoliated material, please provide SEM images of TPM-DADK after repeated catalytic cycles to verify whether the nanosheet structure is retained or if reaggregation occurs.\n4.Please indicate whether solvent effects were incorporated in the computational models used to calculate O2 adsorption energies, as this would affect their practical relevance.\n5.The DADKH· radical intermediate is calculated to possess a markedly higher dipole moment than the parent DADK molecule. A brief discussion on the origin of this change would strengthen the narrative.\n6.The explanation for why TPM-DADK undergoes more efficient light-induced exfoliation than its counterparts could be expanded. Specifically, elaborating on how its “segmented conjugation” structure enhances electrostatic repulsion between nanosheets would provide clearer mechanistic insight.", "reviewer_4": "The manuscript by Han and co-workers addresses a timely and important topic in solar hydrogen peroxide generation by organic semiconductors. They study three different porous organic polymers, obtained through cross-coupling reaction between anthrazoline (DADK) photocatalysts and different bridging motifs (tetraphenylmethane, spirobifluorene and pyrene). The authors furthermore irradiate the polymers to obtain the radical anions, attributed to the formation ketyl radical anions. The polymers are also tested to produce hydrogen peroxide under light irradiation, in water without additional sacrificial donors, and report high efficiencies for H2O2 production (solar to chemical, SCC, efficiency of almost 4%). This reviewer is of the opinion that the manuscript could be potentially of interest to the readership of Nature Communications, but several critical issues should be addressed before the manuscript can be accepted.\n- Some mechanistic claims that are central to the manuscript are, in my opinion, not fully corroborated. The authors claim several times that the production of radicals is leading to the dynamic exfoliation. More experiments and controls need to be performed to back-up this claim. For example, the authors also sonicate while the radical also photogenerated so control experiments (such as no sonication) need to be performed. Additionally, dynamic implies that after catalysis (or radicals being quenched) the materials return to the initial stage.\n- Another mechanistic aspect to improve is the \"isolation” of radicals. While the authors claim the formation of discrete radicals, identified as ketyl radicals, the EPR spectra presented in the manuscript do not corroborate this claim. The EPR spectra of the solids (at room temperature presumably) shows a broad signal, typical of organic semiconductors and polymers. I would expect, for isolated radicals, to see a well-structured and resolved signal (with assigned hyperfine splitting). Therefore, spin quantification and further experiments are suggested (such as low temperature, variable temperature,) etc.) to confirm the formation of the proposed radicals. A minor point is that the EPR spectra are recorded as solid so it is unclear where the PCET hydrogen sources is from and whether the observed signal is a carbon-based or oxygen-based radical.\n- In connection to the point above, it appears that other optoelectronic characterization (for example photoconductivity) shows that radicals behave as I would expect for a conjugated organic radical polymer. In my opinion, isolated radicals and improved electron/charge transports should not go hand in hand.\n- The authors mention their polymers to accumulate charge and the fate of the radicals is unclear, but this aspect has been relatively unexplored. Control experiments in which for example, air is introduced into the reactor with radical present and H2O2 checked (under dark) is suggested. Similarly, comparison of radicals before and after photocatalysis is suggested.\n- Since several properties of the polymers change (porosity, water contact, etc.) further experiments and comparisons should be performed. For example, the authors should report absorption spectra before and after irradiation. The data presented in Supplementary Fig. 24 should be discussed as the authors claim that blue-shift indicated decreased pi-pi stacking. However, such similar absorbance is not what I would expect when radicals are formed, which are expected to absorb well into to NIR. Similar comparisons (before and after radicals) would be expected also in determination in energy levels, for example, as these could also contribute to the photocatalytic properties.\nMinor points:\n- -C=N signal in the solid-state 13C NMR appears different in the three polymers. 13C NMR spectrum of DADK alone should be shown as comparison and further proofs of the obtainment of the polymers should be provided.\n- Zeta potential after irradiation of TPM-DADA should be provided.\n- The authors refer to a “significantly lower” O2 adsorption energy for a difference minor than a kcal mol-1.\n- Provide an explanation of why PL quenching is less pronounced for the self-exfoliated sample compared to the as-synthesised. How do the lifetimes change under Ar and air in both conditions? Have the samples been irradiated at the same wavelenght?\n- Photocatalytic experiments should be done in replicates and error bars should be reported.\n- For Py-DADK, H2O2 production is inhibited more than 20% in presence of p-BQ, so superoxide photo-production should not be ignored.\n- For semiconductors, H2O2 production is usually reported as (mol of hydrogen peroxide)/(g of material). The authors should add a column with mM h-1 and mol/g, in order to have a direct comparison with other systems reported in literature.\n- XPS spectrum of TPM-DADK in Fig. 1b refers to C 1s. The caption should be modified accordingly.\n- Figure S19 b. should be updated with the correct reference to the molecule. It refers to Py-DADK?\n- References should be provided for the attribution of O2 Yeager-type adsorption in DRIFTS experiments. Apparently, the O-O is not observed in DRIFTS experiments (or reported at different wavelenghts?) so indicating potentially a different mechanism?\n- There is a mismatch between text and data in Fig. 6a\n- NBT assays usually quantify the amount of superoxide produced by monitoring the formazan formation at 560 nm.\n- AQY compared to UV-Vis absorption spectrum should be plotted in water, the actual photocatalytic condition.", "reviewer_5": "Han et al. demonstrate a novel, intelligent, design principle in which pi-pi interactions are weakened through chemical structure of the catalyst. By sonication under illumination in H2O, the morphology appears to change, supported by a number of characterization techniques; in the presence of air, the observance that O2 has bound to the catalyst has been shown convincingly. The \"charges\" are remarkably long lived, and it is shown that O2 can be bound to the catalyst after several minutes in the dark under Ar - I find this truly fascinating, and emphasizes the importance in stabilization of charges through chemical reactions, in this case, formation of the \"protonated anion intermediate\".\nThere are several points which I feel should be clarified however.\n1) It is not clear to me what excitation wavelength was used for the PL and TA experiments - my guess is ~500 nm for PL and 355 nm for the TA experiments. If this is correct, it would have profound effects on the photophysics. Can the authors clarify this?\n2) The assignment of the spectral features in the TA spectra should be clarified. Significant weight is placed upon these results (i.e. Lifetime, degree of charge separation) but these conclusions depend on their assignment. An additional peak is observed at ~440 nm in the presence of air in all cases, can the authors comment on this band. The bands at ~440, 480, and 600 nm all appear to show different kinetics \"by-eye\" in Figure 5 for the exfoliated sample - significantly more insight would be provided from global lifetime analysis rather than fitting the kinetic trace at 480 nm. As is, i agree the spectra show increased lifetimes for the exfoliated sample in air, but there is little evidence that this is because of increased charge-separation, a local excited state may have a longer lifetime just because of difference in morphology. Similarly the difference in shape of the TA spectra may be expected from changing morphology based on the shape of PL spectra. Showing the evolution of the spectra using GLA will enhance the manuscript considerably.\n3) I found the Pseudo-colour maps of the TA spectra hard to interpret, I suggest figures analogous to Figure 5d be added.\n4) Is there residual Pd present within the catalyst from the synthesis - can this play a role in possible redox chemistries?\n5)Figure S51 is accompanied by \"The PXRD and FT-IR spectra of TPM-DADK remained virtually unchanged before and after photocatalysis, suggesting its excellent structural stability.\" The robust functional groups remain, however, the broad band at ~1050 cm-1 appears to have changed significantly, can the authors comment on this.\n6) It is not always clear what the conditions the characterisations were performed in, (suspension, concentration, dry powder etc.) this should be clairfied.", "reviewer_6": "I co-reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co-review manuscripts."}, "author_response": "Response to Referee 1:\nThe authors report a π-conjugated polymer with deliberately segmented conjugation\nthat delivers efficient photocatalytic H O production. A central claim is that long-lived\n2 2\nketyl radical anions trigger light-induced exfoliation, thereby increasing O\n2\nadsorption/activation and enabling high SCC efficiency. The concept is original, the\nmaterials chemistry is thoughtfully executed, and the performance is compelling. In my\nview, this work represents a notable advance for polymer-based photocatalysis and is\nsuitable for publication in Nature Communications.\nReply: We are delighted to receive the reviewer’s support for the publication of our\nwork. We sincerely thank the reviewer for the positive evaluation and thoughtful\nsummary of our work. We also greatly appreciate the reviewer’s constructive\nsuggestions for improving the manuscript. Below, we provide detailed responses to\neach comment and outline the revisions made to the manuscript accordingly.\nHopefully the following comments could further refine this study:\n1. In Figure 1e, the N adsorption/desorption isotherms of TPM-DADK show no\n2\nobvious hysteresis loop, which is inconsistent with typical mesoporous characteristics.\nMeanwhile, in Supplementary Fig. 10, the calculated pore size distributions of Flu-\nDADK and Py-DADK indicate mesoporosity, whereas the manuscript describes that\nFlu-DADK and Py-DADK predominantly display microporous characteristics. This\ninconsistency requires further characterization and explanation.\nReply: We sincerely thank the reviewer for this insightful comment on the porosity\ncharacterization of our materials. We agree that the apparent discrepancy between the\nN adsorption/desorption isotherms and the reported pore‐size distributions warrants\n2\nclarification.\nTPM-DADK exhibits a Type I isotherm with no obvious hysteresis, while the BET\nsurface area is moderate (~65.98 m2 g-1) and the pore-size distribution (Figure 1d)\nreveals a main pore diameter of ~2.1 nm together with some larger pores. This\ncombination indicates a mesoporous-macroporous architecture with irregular or\ninterparticle voids rather than ordered mesopores, which explains the absence of a\npronounced hysteresis loop.\nWe apologize for the oversight in the pore-size labeling of Py-DADK in\nSupplementary Fig. 8. The corrected dominant pore diameter of Py-DADK should be\n~2.38 nm, while that of Flu-DADK is ~2.14 nm. These values fall at the boundary of\nmicroporous–mesoporous regimes and thus reconcile the apparent inconsistency with\nthe text, where both Flu-DADK and Py-DADK are described as predominantly\nmicroporous. We have corrected the figure and clarified this point in the revised\nmanuscript and SI.\nThe revised manuscript: “TPM-DADK shows a predominantly microporous\nstructure with a primary pore diameter of ~2.1 nm, along with a small fraction of larger,\nirregular mesoporous-macroporous voids, consistent with its open 3D structure. Flu-\nDADK and Py-DADK also display mainly microporous characteristics, with pore\ndiameters at the boundary between microporous and mesoporous regimes.”\nThe updated SI: “Nitrogen adsorption-desorption measurements were performed at\nDADK, and Py-DADK. TPM-DADK exhibits a Type I isotherm with a BET surface\narea of ~65.98 m2 g-1 and a primary pore diameter of ~2.1 nm, together with a small\nfraction of larger pores (Figure 1d). The absence of a pronounced hysteresis loop\nindicates the presence of irregular mesoporous-macroporous voids rather than ordered\nmesopores. Flu-DADK and Py-DADK display BET surface areas of 313.48 and\n262.82 m2 g-1, with dominant pore diameters of ~2.14 and ~2.38 nm, respectively\n(Supplementary Figure 8). These pore sizes lie at the boundary between microporous\nand mesoporous regimes.”\nSupplementary Fig. 8 | (a, b, c) Pore size distribution curves for TPM-DADK, Flu-DADK and\nPy-DADK.\n2. In the PXRD spectra, the position of the π-π stacking diffraction peak typically\nreflects the interlayer distance. According to the authors, the interlayer distances of\nTPM-DADK, Flu-DADK, and Py-DADK are not identical; however, in Fig. 1d, the\ncorresponding π-π stacking diffraction peaks appear at the same position.\nReply: We thank the reviewer for highlighting this important point regarding the PXRD\npatterns. Although these polymers are predominantly amorphous and exhibit only\nlimited long‐range order, weak diffraction features associated with π-π stacking can still\nbe observed. In Fig. 1d, the broad diffraction peaks of TPM-DADK, Flu-DADK, and\nPy-DADK all appear at nearly the similar position (26~28°), suggesting that their\naverage π-π stacking distances are very similar within the resolution limit of PXRD.\nThe interlayer distances were further estimated to be 0.31, 0.36, and 0.31 nm for TPM-\nDADK, Flu-DADK, and Py-DADK, respectively (Supplementary Figs. 14-16), as\nderived from high-resolution TEM and supported by structural simulations. These\nsubtle variations are below the detection limit of PXRD but can be resolved by HRTEM.\nWe have revised the text to clarify this point and to avoid any misleading impression\nof high crystallinity or inconsistency. Both PXRD and HRTEM consistently indicate\nthe presence of local π-π stacking, which is crucial for efficient charge transport despite\nthe overall amorphous character of the polymers. Therefore, we have revised the\nmanuscript and Supplementary Information accordingly.\nRevised manuscript text: “Powder X-ray diffraction (PXRD) patterns indicate that\nall polymers are predominantly amorphous, exhibiting only short-range structural order\n(Fig. 1d). The peak at 28° corresponds to an interlayer distance of ~0.31 nm,\ncharacteristic of π-π stacking. Flu-DADK and Py-DADK exhibit slightly stronger\ndiffraction features than TPM-DADK, suggesting relatively enhanced short-range\nordering and interlayer interactions.”\nUpdated Supplementary Information: “The interlayer distances were estimated to\nbe approximately 0.31, 0.36, and 0.31 nm for TPM-DADK, Flu-DADK, and Py-\nDADK, respectively (Supplementary Figs. 14-16), corresponding to the local\nintermolecular π-π stacking. Although these polymers are largely amorphous and lack\nlong-range crystallinity, a broad diffraction feature is observed at around 26~28° in the\nPXRD patterns (Fig. 1d), which reflects the average d-spacing associated with π-π\nstacking. The subtle variations in interlayer distance revealed by high-resolution TEM\nare below the detection limit of PXRD but consistently support the presence of short-\nrange π-π interactions that facilitate charge transport.”\n3. It is recommended that the authors perform in-situ FTIR spectroscopy on TPM-\nDADA to further substantiate the pivotal role of photogenerated ketyl radical anions in\nthe reaction process.\nReply: We sincerely appreciate the reviewer’s insightful suggestion. In fact, we have\nperformed in-situ FTIR spectroscopy, and the corresponding results are presented in\nFig. 3 (for TPM-DADK), Supplementary Fig. 27 (for Flu-DADK and Py-DADK) and\nSupplementary Fig. 28 (for SA-DADK and TPM-DADA). Under O -saturated\n2\nconditions in 2-propanol, no oxygen-related signals were detected in the dark. Upon\nlight irradiation, however, a distinct O-O stretching band at ~950 cm-1 together with\nbroad signals from 1044 to 1204 cm-1 emerged, confirming light-induced Yeager-type\nO₂ adsorption. Notably, TPM-DADK exhibited much stronger and more persistent O-\nO signals than Flu-DADK and Py-DADK, highlighting the synergistic effect of\nprotonated ketyl radical anions and the segmentally conjugated backbone. These\nradicals can even retain O adsorption ability in the dark, as evidenced by the\n2\npersistence of the 950 cm-1 O-O band. In sharp contrast, TPM-DADA, which lacks\ncarbonyl groups, did not show such spectral features or enhanced O adsorption,\n2\nfurther confirming that the carbonyl-derived ketyl radical anions play a pivotal role in\nfacilitating O adsorption and activation.\nDADA, which lacks carbonyl groups, did not exhibit these O -related spectral features\n2\nor enhanced O adsorption capability, further confirming the essential role of carbonyl-\n2\nderived ketyl radicals in O activation. (Supplementary Fig. 28)”\ngroups at 1720 cm-1 decreased under the light condition and reverted to the original\nstate under the dark condition, and the formation and disappearance of the peak at 1279\ncm-1 was attributed to the C-O group. The peak at 1346 cm-1 corresponding to O-H\nbending displayed a similar trend to that of the C-O group, indicating that the\nphotogenerated electrons reduced the carbonyl group to the protonated anion\nintermediate. A new peak at 1651 cm-1 attributed to C=N-H+ gradually appears for\npolymers, due to the oxidation of water, resulting in the formation of protonated\npyridine substituents. Thus, *HOOH signal can be observed as well.”\nSupplementary Fig. 27 | In situ FTIR spectrum of (a) Flu-DADK and (b) Py-DADK with Ar\natmosphere under irradiation and O gas purging in the dark at 1200-2100 cm-1.\natmosphere under 300 W Xe lamp and then O gas purging in the dark at 900-1300 cm-1. (b, d)\nsitu FTIR spectra of (b) SA-DADK and (d) TPM-DADA during photoreaction in a 2-propanol\naqueous solution with saturated oxygen (2-propanol as electron donor, 10% v/v).\n4. In Fig. 4a, the authors attribute the decrease in photocurrent of TPM-DADK to the\neffective electron consumption by the ORR. However, it is not clear whether the\nproduction from ORR has been verified.\nReply: We sincerely thank the reviewer for this important comment. To verify the ORR\ncontribution, we attempted to measure the H O concentration in the electrolyte after\n2 2\nphotocurrent tests. However, the results were not ideal. During these tests, the sample\nis coated on an FTO substrate rather than dispersed in solution, which significantly\nlimits the catalytic reaction activity, O adsorption, and effective photoreaction area. In\n2\naddition, the measurement requires the addition of Nafion to ensure electrical contact,\nwhich can block surface pores and further reduce catalytic activity. These factors lead\nto very low H O production, making it difficult to quantitatively confirm ORR under\n2 2\nphotocurrent testing conditions. Nevertheless, the observed decrease in photocurrent\nunder O -saturated conditions compared to Ar-saturated conditions still strongly\n2\nindicates that electron consumption is dominated by ORR.\n5. The authors state that “the strategically segmented π-framework in TPM-DADK\nlocalizes electrons within discrete domains”, yet this claim is not sufficiently supported\nby computational evidence.\nReply: We sincerely thank the reviewer for this valuable comment. We fully agree that\nthe statement regarding “π-framework segmentation and electron localization” requires\nmore substantial computational evidence. To address this point, we have carried out a\ndetailed analysis from both the ground and excited state perspectives:\nFrontier Molecular Orbital Analysis (Supplementary Table 1):\nThe calculated frontier orbitals of TPM-DADK show that both the HOMO and\nLUMO are predominantly localized on the DADK unit, with negligible orbital\ncontribution from the peripheral benzene rings of the TPM moiety (highlighted in red\ncircles). In contrast, the HOMO and LUMO of Flu-DADK and Py-DADK extend over\nthe entire molecular skeleton (green circles), reflecting their more delocalized\nelectronic structures. This visual evidence clearly indicates that the incorporation of the\nTPM unit restricts electron delocalization, consistent with the concept of a “segmented\nπ-framework.”\nExcited-State Electron-Hole Analysis (Supplementary Fig. 33):\nWe further examined the low-lying excited states of the three polymer fragments.\nFor TPM-DADK, the dominant excitation (S →S at 376 nm) exhibits a relatively\n0 6\nsmall Δσ index of 2.221 Å, indicating localized excitation. The corresponding electron-\nhole distribution is confined within the DADK unit and the directly connected TPM\nbranch, without extending to the other branches of the TPM moiety (red circles). In\ncontrast, both Py-DADK and Flu-DADK display much larger Δσ values (7.099 Å and\n5.364 Å, respectively) and delocalized electron-hole distributions across the entire π-\nconjugated framework (green circles), indicative of strong charge-transfer character.\nIn summary, the combined frontier orbital distributions and electron-hole analyses\nprovide direct and complementary computational evidence that the segmented π-\nframework of TPM-DADK effectively localizes electrons within discrete domains. We\nhave incorporated these results into the revised manuscript and Supplementary\nInformation.\nMain text: “Unlike continuous conjugated systems, the strategically segmented π-\nframework in TPM-DADK localizes electrons within discrete domains\n(Supplementary Table 1, Supplementary Fig. 33), thereby suppressing recombination\nand enabling efficient charge separation and storage.[45] Importantly, the radicals\ngenerated in this system are not permanently isolated but remain dynamically coupled\nwith the π-conjugated backbone. This transient interaction induces local polarization\nthat facilitates interfacial charge separation and transfer under illumination.”\nUpdated SI: “Frontier Molecular Orbital Analysis (Supplementary Table 1):\nThe HOMO and LUMO of TPM-DADK are predominantly localized on the\ncentral DADK core, with negligible orbital contribution from the peripheral benzene\nrings of the TPM substituent. In contrast, both Flu-DADK and Py-DADK show\nfrontier orbitals delocalized across the entire molecular skeleton. This clearly indicates\nthat the TPM unit enforces orbital confinement, consistent with the concept of a\n“segmented π-framework.”\nExcited-State Electron-Hole Distribution (Supplementary Fig. 33)\nElectron-hole analyses of the lowest-lying excited states further confirm this\nlocalization. For TPM-DADK, the excitation with the largest oscillator strength\n(S →S , 376 nm) yields a Δσ index of only 2.221 Å, well within the range of localized\n0 6\nexcitations (< ~3 Å). The corresponding electron-hole density is confined to the DADK\nunit and the directly attached TPM branch, with no distribution observed on the other\nbranches. In contrast, Flu-DADK (S →S , 413 nm, f = 0.6664, Δσ = 5.364 Å) and Py-\n0 3\nDADK (S →S , 371 nm, f = 1.1646, Δσ = 7.099 Å) show strong charge-transfer\n0 8\ncharacter, with holes and electrons separated over distant molecular fragments.\nTogether, these complementary results provide direct computational evidence that\nthe strategically segmented π-framework in TPM-DADK effectively localizes\nelectrons within discrete domains.”\nSupplementary Table 1 | Frontier Molecular Orbital Analysis of TPM-DADK, Flu-DADK and\nPy-DADK\nSupplementary Fig. 33 | Electron-Hole Distribution of Excited-State in (a) TPM-DADK, (b) Flu-\nDADK and (c) Py-DADK\n6. The authors report that the SCC efficiency of TPM-DADK reaches 3.49%, which is\nclose to the highest level in the field. However, during the SCC measurements, the\nactual illumination area was less than 1 cm2 and the irradiation time was only 20\nminutes, which may lead to an overestimation of the results. Authors should report a\nmore reliable SCC value with much larger irradiation area and longer irradiation time.\nReply: We thank the reviewer for pointing out the potential influence of illumination\narea and irradiation time on the SCC efficiency measurement. We fully agree that\ntesting under a larger illumination area and extended irradiation time provides a more\nreliable and practically relevant assessment of photocatalytic performance. In our initial\nstudy, the reported SCC value of 3.49% was obtained under controlled laboratory\nconditions following the mainstream methodology currently adopted in the literature\nfor evaluating photocatalytic materials.\nTo further address the reviewer’s concern, we have now conducted additional\nexperiments under a larger illumination area (~3.14 cm2) and longer irradiation time (1\nh). The SCC efficiency remained high at ~3.07 %, confirming the robustness and\nstability of TPM-DADK. These updated results have been included in the revised\nSupporting Information and used in the main text for accuracy.\nThe solar-to-chemical energy conversion (SCC) efficiency was tested in pure D.I.\nwater without any sacrificial agents and calculated by the following equation:\n∆𝐺 ×𝐻 𝑂 𝑓𝑜𝑟𝑚𝑒𝑑 (𝑚𝑜𝑙)\n2 2\n𝑆𝐶𝐶(%) = ×100% = 3.07%\n𝐼 ×𝐴×𝑡\nWhere ΔG is 117 kJ mol−1, the light intensity is 300 W m−2 and the irradiated area\nis 3.14 × 10−4 m2. The total input energy was therefore 0.0942 W. Reaction time is 3600\ns. The average H O production of TPM-DADK over three tests was 88.95 μmol.\n2 2\n7. In Supplementary Fig. S45, when the dosage of TPM-DADK was 1 g/L under pure\nwater conditions, the H O generation rate was 9.95 mM h-1. However, in\n2 2\nSupplementary Fig. S46, under the same dosage conditions, the H O generation rate\n2 2\nof TPM-DADK reached 10.82 mM h-1.\nReply: We thank the reviewer for pointing out this inconsistency. The discrepancy\narises from a mislabeling of the optimal TPM-DADK dosage under pure water\nconditions. The actual optimal dosage is 1.5 g/L, not 1 g/L as previously indicated.\nUnder this corrected condition, the measured H O generation rate reaches its\n2 2\nmaximum value, and the relevant data have been corrected and updated in the revised\nSupplementary Figures.\n8. There are some apparent errors in the manuscript. For instance, in Fig. 6d and\nSupplementary Fig. S49, AQY and AQE are used interchangeably, which may cause\nconceptual confusion. Supplementary Fig. S37 lacks the corresponding data figure. In\naddition, Supplementary Fig. S61-62 are not mentioned in the manuscript.\nReply: We thank the reviewer for carefully pointing out these issues. We have carefully\nchecked the manuscript and made the following corrections:\n(a) In the updated Fig. 6d and Supplementary Fig. 55 (previously Supplementary\nFig. 49), the terms AQY and AQE have been standardized throughout the manuscript\nto avoid confusion.\n(b) The missing data for updated Supplementary Fig. 40 (previously\nSupplementary Fig. 37) has been added.\n(c) References to Supplementary Figs. 59-60 (previously Supplementary Figs. 61-\n62) have been included in the revised manuscript.\nIn addition, we have taken this opportunity to systematically reorganize and re-\nsequence the supplementary figures to enhance overall clarity and coherence. All\ncorrections and improvements have been incorporated into the revised manuscript and\nthe updated Supplementary Information.\nResponse to Referee 2:\nThis manuscript by Zhu et al. reports an impressive and innovative advance in\nphotocatalytic hydrogen peroxide production. The authors designed a novel π-\nconjugated polymer (TPM-DADK) with a segmented conjugation structure that enables\ntwo key functions: stabilization of long-lived ketyl radical anions as electron reservoirs\nand light-induced exfoliation into 2D nanosheets. This creative concept of using\nphotogenerated intermediates to drive in situ morphological transformation represents\na notable step forward in adaptive photocatalysis. The study is thorough, integrating\nsophisticated synthesis, comprehensive characterization (EPR, in situ FT-IR, XPS, fs-\nTA, etc.), and theoretical calculations to elucidate the mechanism. TPM-DADK\ndelivers outstanding H O production rates and solar-to-chemical efficiencies under\n2 2\nboth simulated and natural sunlight, with activity further demonstrated in real water\nsources. Overall, the work is rigorous, the conclusions are well supported, and the\nfindings are broadly relevant. I strongly recommend acceptance after minor revisions\nto improve clarity and impact.\nReply: We are truly grateful for the reviewer’s positive assessment and strong support\nfor the publication of our work. We sincerely thank the reviewer for the thoughtful\nsummary and encouraging evaluation of our study. We also greatly appreciate the\nconstructive suggestions, which have helped us to further improve the manuscript.\nBelow, we provide detailed responses to each comment and describe the corresponding\nrevisions made.\n1. While the light-induced exfoliation is well documented, the manuscript would benefit\nfrom a clearer discussion of why TPM-DADK shows superior exfoliation compared to\nFlu-DADK and Py-DADK. The authors attribute this to the “segmented conjugated\nstructure,” but it would be valuable to elaborate on how this specifically enhances\nelectrostatic repulsion.\nReply: We thank the reviewer for this insightful comment. We agree that a more\ndetailed discussion on the superior light-induced exfoliation of TPM-DADK is\nnecessary. In TPM-DADK, the strategically segmented π-conjugated framework,\nintroduced by the sp3-hybridized tetraphenylmethane (TPM) nodes, plays a decisive\nrole. This periodic conjugation interruption localizes photogenerated electrons at the\ncarbonyl sites, forming stable ketyl radical anions (DADK·⁻). The accumulated\nnegative charges generate strong electrostatic repulsion between adjacent layers, which\nefficiently drives the light-induced exfoliation process.\nBeyond this electrostatic effect, the segmented π-system also prolongs the excited-\nstate lifetime and reduces electron-hole recombination, enabling independent electron\nstorage in discrete domains. Meanwhile, the rigid tetrahedral geometry of TPM\nweakens interlayer π-π stacking and promotes vertical extension of the layered structure,\nso that both the upper and lower surfaces of each layer are accessible to reactants. As a\nresult, TPM-DADK can achieve much more effective nanosheet exfoliation and\nexposure of catalytic sites under mild conditions.\nIn contrast, Flu-DADK and Py-DADK possess more continuous π-conjugation\nand stronger interlayer stacking, leading to less localized charge accumulation and\nweaker electrostatic repulsion, thereby limiting their exfoliation efficiency. The detailed\ndiscussion has been included in the revised manuscript.\n“This outstanding performance originates from its segmented π-conjugated\narchitecture, introduced by the sp3-hybridized TPM nodes. The periodic conjugation\ninterruption localizes photogenerated electrons at carbonyl sites, forming ketyl radical\nanions that accumulate negative charges. The resulting electrostatic repulsion,\ncombined with weakened interlayer π-π stacking and vertical extension enforced by the\nnon-conjugated, rigid tetrahedral TPM geometry, effectively drives nanosheet\nexfoliation and exposes more catalytic sites. In contrast, Flu-DADK and Py-DADK\nfeature more continuous π-conjugation and stronger interlayer stacking, which restrict\nelectron localization and reduce electrostatic repulsion, leading to only moderate photo-\nthinning.”\n2. The proposed mechanism in the conclusion and preceding discussion is excellent. To\nenhance accessibility, the authors might consider adding a simple schematic, even in\nthe Supplementary Information, that visually summarizes the catalytic cycle—from\nlight absorption and radical formation to O adsorption, one-step 2e⁻ reduction, and\n2 2\nReply: We sincerely appreciate your recognition of our proposed mechanism and your\nvaluable suggestion. We fully agree that a clear schematic can intuitively summarize\nthe complex catalytic cycle and improve the manuscript’s readability. Accordingly, we\nhave added a schematic in Supplementary Fig. 67a, illustrating the overall process:\nfrom light absorption and radical formation to O adsorption, one-step 2e⁻ reduction,\n2\nand H O desorption. We believe this addition makes the proposed mechanism more\n2 2\naccessible and enhances the clarity of our discussion.\nSupplementary Fig. 67 | Schematic of (a) the one-step 2e- ORR, and (b) two-step 2e- ORR\nmechanism over DADKH∙.\n3.The synthesis appears to require specific conditions that may limit scalability. A brief\ndiscussion of potential scale-up considerations and cost implications would further\nstrengthen the practical relevance of this work.\nReply: We acknowledge that scaling up the synthesis of TPM-DADK may present\ncertain technical challenges, such as maintaining uniform reaction conditions and\ncontrolling material quality. However, the primary focus of the current work is on\nfundamental research, including the design of the TPM-DADK system, its structural\ncharacterization, and the mechanistic exploration of its superior photocatalytic\nperformance. These studies provide essential insights that form the foundation for\nfuture practical applications. In subsequent work, we plan to investigate strategies to\naddress scale-up challenges, such as optimizing reaction parameters, exploring\ncontinuous-flow synthesis, and evaluating cost-effective approaches for larger-scale\nproduction.\n4. Typically, H O stability and production efficiency are pH-dependent. Testing across\n2 2\ndifferent pH ranges would demonstrate the robustness of the system and optimal\noperating conditions.\nReply: We thank the reviewer for this valuable suggestion. In this work, we focused on\nneutral water conditions to reflect environmentally relevant scenarios. To further\nevaluate the pH effect, we carried out additional experiments under air atmosphere in\nacidic conditions. The results show that TPM-DADK exhibits the highest H O\n2 2\nproduction efficiency near neutral pH, whereas acidic conditions lead to somewhat\nreduced performance. This trend can be attributed to the fact that excess protons in\nacidic media electrostatically interact with the ketyl radical anion intermediates,\nweakening their electron-donating ability for O reduction. In alkaline solutions, the\n2\nabundance of hydroxide ions may accelerate the decomposition of H O or destabilize\n2 2\nintermediate species. These findings confirm the robustness of the system and provide\npractical guidance for selecting optimal operating conditions. The detailed results are\nprovided in the revised Supplementary Information (Supplementary Fig. 52).\n“Photocatalytic experiments conducted under different pH conditions indicate that\nTPM-DADK achieves the highest H O production efficiency near neutral conditions,\n2 2\nwhereas acidic environments result in somewhat reduced performance. This trend can\nbe rationalized by the electrostatic interaction of excess protons with ketyl radical anion\nintermediates, which weakens their electron-donating ability for O reduction.\n2 2\nreactive intermediates. These results highlight neutral pH as the most favorable\ncondition for maintaining radical stability and achieving efficient H O accumulation.”\n2 2\nSupplementary Fig. 52 | (a) Photocatalytic H O generation performances of TPM-DADK using\n2 2\ndifferent sacrificial reagents under O atmosphere. (b) Photocatalytic H O generation performance\n2 2 2\nof TPM-DADK in HCl aqueous solution under air atmosphere at different pH conditions. (c)\nPhotocatalytic H O generation of TPM-DADK under air atmosphere with or without 1.0 mg\n2 2\nPd(PPh ) . Reaction condition: 1.5 mg/mL photocatalyst, visible light (> 420 nm, 100 mW cm-2)\n3 4\n5. H evolution data are provided in Fig. S62, but no corresponding discussion is\n2\nincluded. It would strengthen the manuscript to briefly address these results—either to\nclarify their relevance to the photocatalytic process, or to explain why H evolution is\n2\nnegligible compared to H O production. This would help avoid potential confusion\n2 2\nand provide a more comprehensive picture of the system’s selectivity.\nReply: We thank the reviewer for this valuable suggestion. As shown in Supplementary\nFig. 61, in 1 M L-ascorbic acid (AA) solution, the H evolution rates of DADK, TPM-\nrespectively. In 10 wt% TEOA solution, the corresponding rates were 0.5, 5.7, 7.3, and\n19.1 mmol g-1 h-1. These results correlate well with the relative strength of the built-in\nelectric fields (Supplementary Fig. 40), indicating that photocatalytic H evolution is\n2\nprimarily governed by the intrinsic electronic structure and charge transfer efficiency\nof the polymers. Importantly, H production can only be observed in the presence of\n2\nsacrificial agents, further suggesting that it is not the dominant reaction pathway under\nneutral conditions.\nIn contrast, H O production proceeds efficiently under neutral conditions without\n2 2\nsacrificial reagents, requiring not only electron transfer but also effective O adsorption,\n2\nmass transport, and electron storage processes, which follow distinct mechanistic\npathways. Thus, the H evolution data serve as a useful reference for understanding\n2\ncharge transfer behavior, while emphasizing that H O formation is the primary\n2 2\nphotocatalytic pathway. A brief discussion highlighting these points and the\nexperimental conditions has been added to the Supplementary Information, clarifying\nthe system’s selectivity and mechanistic distinction.\nSupplementary Fig. 40 | Internal electric field intensities of TPM-DADK, Flu-DADK and Py-DADK.\nRevised Supplementary Discussion:\n“Photocatalytic H O production occurs efficiently under neutral conditions\n2 2\nwithout sacrificial reagents, relying on electron transfer, O adsorption, mass transport,\n2\nand electron storage processes. In contrast, H₂ evolution is observed only in the\npresence of sacrificial agents. As shown in Supplementary Fig. 59, in 1 M AA solution,\nthe H₂ evolution rates of DADK, TPM-DADK, Py-DADK, and Flu-DADK are 0.01,\n3.8, 28.8, and 43.9 mmol g-1 h-1, respectively; in 10 wt% TEOA solution, the rates are\n0.5, 5.7, 7.3, and 19.1 mmol g-1 h-1. These results correlate with the relative strengths\nof the built-in electric fields (Supplementary Fig. 40), indicating that their intrinsic\nelectronic structures critically influence photocatalytic H production. Importantly, H\n2 2\nevolution differs markedly from H O formation, which relies on O adsorption and the\n2 2 2\noxygen reduction reaction, following a distinct mechanistic pathway.”\n6. Some figures, such as Figure 1, could be improved for readability. Please ensure that\nall labels and abbreviations (e.g., TPM, Flu, Py, DADK) are consistently defined and\nthat font sizes are large enough to be easily legible.\nReply: We thank the reviewer for this helpful suggestion. We have carefully revised the\nfigures (e.g., Figure 1) to improve readability by enlarging the font size and ensuring\nthat all labels and abbreviations are consistently defined.\nScheme 1. Design principles and functional implications of DADK-based photocatalysts. (a)\nSchematic diagram of anion radical intermediate DADK·⁻ and protonated anion intermediate\nDADKH· formation via photogenerated electron transfer and reduction. (b) Rational design and\nfunctional tuning of DADK-based frameworks from full conjugation to segmented π-systems via\nnode modulation. (c) Schematic illustration for photogenerated ketyl radical anion driven\nexfoliation.\n7. The English is generally very good, but there are a few minor grammatical errors and\nawkward phrasings that should be corrected during proofreading (e.g., “reflecting\nindicating” in the results section; “further increasement” in the photocatalytic\nperformance section).\nReply: We thank the reviewer for the careful reading and constructive suggestions. We\nhave thoroughly proofread the manuscript and corrected the minor grammatical errors\nand awkward phrasings, including the specific examples mentioned (“reflecting\nindicating” and “further increasement”), as well as other similar issues throughout the\ntext. We believe that these revisions have improved the clarity and readability of the\nmanuscript.\nResponse to Referee 3:\nHan and colleagues report a conceptually elegant and rigorously executed study on the\nπ-conjugated polymer photocatalyst TPM-DADK. They propose a novel photoinduced\nketyl radical anion-driven self-exfoliation and electron storage mechanism, enabling\nthe bulk polymer to transform into nanosheets, which enhances charge utilization,\noxygen adsorption, and selectivity for the two-electron oxygen reduction reaction. The\ncatayst achieves excellent H O production of 14.60 mM·h-1 with a solar-to-chemical\n2 2\nefficiency of 3.49%, among the highest for organic systems. The study is both\ninnovative and thorough. Conjugation segmentation effectively balances electron\nlocalization with structural exfoliation, and comparison with Flu-DADK and Py-\nDADK underscores the role of π-topology. Mechanistic insights are strongly supported\nby multiple techniques, convincingly identifying ketyl radical anions as key\nintermediates. Overall, this is a systematic, high-quality study, and I recommend\npublication after addressing the following minor points.\nReply: We sincerely thank the reviewer for the encouraging evaluation and strong\nsupport for the publication of our work. We are grateful for the thoughtful summary and\npositive assessment, as well as the constructive suggestions that helped us improve the\nmanuscript. Detailed responses to each comment and the corresponding revisions are\nprovided below.\n1. Please clarify how the completion of the Suzuki coupling reaction was confirmed\n(e.g., by solid-state NMR or FT-IR spectroscopy) and whether any catalytic metal\nresidues or unreacted monomers remained after Soxhlet purification.\nReply: We thank the reviewer for this valuable comment. The completion of the Suzuki\ncoupling reaction was confirmed by the disappearance of the characteristic C-Br\nstretching vibrations of the monomers in the FT-IR spectra (Supplementary Fig. 5),\nindicating the full conversion of the reactants into the corresponding polymers. No\nsignals attributable to unreacted monomers were detected after Soxhlet extraction.\nTo evaluate possible residual catalytic metal species, both XPS and ICP-OES\nanalyses were conducted. XPS spectra of TPM-DADK showed no detectable signals\ncorresponding to Pd0 (335.0 eV) or Pd2+ (337.0 eV), confirming the absence of\ncatalytically active Pd species such as metallic Pd or PdO nanoparticles. ICP-OES\nmeasurements further revealed that the Pd content in TPM-DADK is 0.1588 wt%,\nwhich agrees well with the theoretical amount of Pd introduced from Pd(PPh ) during\n3 4\npolymer synthesis. Considering this low Pd loading and the absence of Pd nanoparticles\nor clusters in all characterization results, residual Pd is unlikely to contribute to the\nobserved photocatalytic redox activity.\nMoreover, all polymers (TPM-DADK, Flu-DADK, and Py-DADK) were\nsynthesized via the same protocol but exhibit markedly distinct photocatalytic\nperformances. This systematic variation strongly supports that the photocatalytic\nactivity originates from the intrinsic electronic structures of the designed π-conjugated\nframeworks rather than from trace Pd residues. The Supporting Information has been\nupdated accordingly.\n“1.22 ICP-OES Analysis\nThe content of Pd in the polymer was determined by inductively coupled plasma\noptical emission spectroscopy (ICP-OES, iCAP 7400, Thermo). 50 mg of TPM-DADK\nwas digested in a mixed acid solution of HNO /H O (3:1, v/v) under heating until\n3 2 2\ncomplete dissolution. The solution was further evaporated to a volume of less than 0.5\nmL, cooled to room temperature, and then diluted to 10 mL with ultrapure water for\nICP-OES measurement. The Pd concentration, determined using a calibration curve\nprepared from standard Pd solutions, was 0.1588 wt%.”\n“Critically, no signals corresponding to Pd0 (335.0 eV) or Pd2+ (337.0 eV) were\ndetected, confirming the absence of residual palladium from synthesis in any\ncatalytically relevant form. In addition, ICP-OES analysis showed that the Pd content\nin TPM-DADK is 0.1588 wt%, which agrees well with the theoretical amount of Pd\nintroduced from Pd(PPh ) during polymer synthesis. Considering this low Pd loading\n3 4\nand the absence of Pd nanoparticles or clusters in all characterization results, it is\nreasonable to conclude that Pd species do not play a significant role in the observed\nphotocatalytic redox behavior.\nMoreover, all polymers (TPM-DADK, Flu-DADK, Py-DADK) were prepared\nusing the same synthetic protocol. Despite this, they exhibit markedly distinct\nphotocatalytic performances. This systematic variation clearly indicates that the\nphotocatalytic activity originates from the designed π-conjugated frameworks, rather\nthan from trace Pd residues.”\n2. The BET surface area of TPM-DADK is notably lower than that of Flu-DADK and\nPy-DADK. A deeper discussion on how this inverse correlation with catalytic activity\narises (potentially due to differences in charge separation efficiency, active site density,\nor substrate adsorption energy) would be valuable.\nReply: We appreciate the reviewer’s insightful comment. TPM-DADK exhibits a Type\nI isotherm with a BET surface area of ~65.98 m2 g-1 and a primary pore diameter of\n~2.1 nm, together with a small fraction of larger, irregular mesoporous–macroporous\nvoids, reflecting its open 3D architecture. Flu-DADK and Py-DADK display higher\nBET surface areas of 313.48 and 262.82 m2 g-1, respectively, with pore diameters at the\nboundary between microporous and mesoporous regimes. Despite its lower surface area,\nTPM-DADK achieves superior photocatalytic H O production, predominantly driven\n2 2\nby the formation of long-lived ketyl radical anions and light-induced exfoliation into\n2D nanosheets, which generate abundant active sites and enhance O adsorption and\n2\nactivation. These effects, together with efficient charge separation, demonstrate that π-\nconjugation segmentation and radical stabilization synergistically boost solar-to-\nchemical conversion efficiency for H O photosynthesis.\n2 2\n3. To confirm the morphological stability of the exfoliated material, please provide\nSEM images of TPM-DADK after repeated catalytic cycles to verify whether the\nnanosheet structure is retained or if reaggregation occurs.\nReply: We thank the reviewer for this helpful suggestion. SEM images of TPM-DADK\nafter repeated catalytic cycles have been added (Supplementary Fig. 57c), confirming\nthat the nanosheet morphology is well retained without obvious reaggregation.\nMoreover, PXRD patterns, FT-IR spectra, and SEM analyses of TPM-DADK before\nand after photocatalysis remain virtually unchanged, further demonstrating its excellent\nstructural stability.\n4. Please indicate whether solvent effects were incorporated in the computational\nmodels used to calculate O adsorption energies, as this would affect their practical\n2\nrelevance.\nReply: We sincerely thank the reviewer for raising this important question. Regarding\nyour inquiry about solvent effects, we confirm that solvation effects were explicitly\nconsidered in our calculations of O adsorption energy. Specifically, we employed the\n2\nimplicit solvation model IEFPCM as implemented in Gaussian, with water selected as\nthe solvent to simulate the actual aqueous reaction environment. This approach allows\na more realistic representation of the influence of solvent on O adsorption behavior,\n2\nthereby enhancing the practical relevance of our computational results.\nWhile the original Supporting Information only briefly mentioned solvation in\nSection 1.5 Theoretical calculation, we have now clarified the details by adding the\nfollowing sentence to Section 1.9 Adsorption Energy Analysis: “For O adsorption, the\n2\nsolvation effects were accounted for using the built-in IEFPCM (Integral Equation\nFormalism Polarizable Continuum Model) implicit solvation model in Gaussian, with\nwater as the solvent.”\n5. The DADKH· radical intermediate is calculated to possess a markedly higher dipole\nmoment than the parent DADK molecule. A brief discussion on the origin of this change\nwould strengthen the narrative.\nReply: We sincerely thank the reviewer for this insightful observation and valuable\nsuggestion. We fully agree that a discussion on the origin of the significantly higher\ndipole moment of the DADKH· radical intermediate compared to the parent DADK\nmolecule would strengthen the narrative. The notable increase in dipole moment\nprimarily arises from the breaking of electronic structure symmetry. The DADK\nmolecule possesses a centrosymmetric structure, leading to a relatively even charge\ndistribution and consequently a small dipole moment. In contrast, the formation of the\nDADKH· radical disrupts this symmetry, resulting in a significant redistribution of\nmolecular charge density and rearrangement of electronic and electrostatic potentials,\nwhich collectively contribute to the enhanced dipole moment. This change also reflects\nthe higher polarity and reactivity of the radical intermediate, which is closely correlated\nwith its subsequent chemical behavior.\n6.The explanation for why TPM-DADK undergoes more efficient light-induced\nexfoliation than its counterparts could be expanded. Specifically, elaborating on how\nits “segmented conjugation” structure enhances electrostatic repulsion between\nnanosheets would provide clearer mechanistic insight.\nReply: We thank the reviewer for this insightful comment. We agree that a more\ndetailed discussion on the superior light-induced exfoliation of TPM-DADK is\nnecessary. In TPM-DADK, the strategically segmented π-conjugated framework,\nintroduced by the sp3-hybridized TPM nodes, plays a decisive role. This periodic\nconjugation interruption localizes photogenerated electrons at the carbonyl sites,\nforming stable ketyl radical anions (DADK·⁻). The accumulated negative charges\ngenerate strong electrostatic repulsion between adjacent layers, which efficiently drives\nthe light-induced exfoliation process.\nBeyond this electrostatic effect, the segmented π-system also prolongs the excited-\nstate lifetime and reduces electron-hole recombination, enabling independent electron\nstorage in discrete domains. Meanwhile, the rigid tetrahedral geometry of TPM\nweakens interlayer π-π stacking and promotes vertical extension of the layered structure,\nso that both the upper and lower surfaces of each layer are accessible to reactants. As a\nresult, TPM-DADK can achieve much more effective nanosheet exfoliation and\nexposure of catalytic sites under mild conditions.\nIn contrast, Flu-DADK and Py-DADK possess more continuous π-conjugation\nand stronger interlayer stacking, leading to less localized charge accumulation and\nweaker electrostatic repulsion, thereby limiting their exfoliation efficiency. The detailed\ndiscussion has been included in the revised manuscript.\n“This outstanding performance originates from its segmented π-conjugated\narchitecture, introduced by the sp3-hybridized TPM nodes. The periodic conjugation\ninterruption localizes photogenerated electrons at carbonyl sites, forming ketyl radical\nanions that accumulate negative charges. The resulting electrostatic repulsion,\ncombined with weakened interlayer π-π stacking and vertical extension enforced by the\nnon-conjugated, rigid tetrahedral TPM geometry, effectively drives nanosheet\nexfoliation and exposes more catalytic sites. In contrast, Flu-DADK and Py-DADK\nfeature more continuous π-conjugation and stronger interlayer stacking, which restrict\nelectron localization and reduce electrostatic repulsion, leading to only moderate photo-\nthinning.”\nResponse to Referee 4:\nThe manuscript by Han and co-workers addresses a timely and important topic in solar\nhydrogen peroxide generation by organic semiconductors. They study three different\nporous organic polymers, obtained through cross-coupling reaction between\nanthrazoline (DADK) photocatalysts and different bridging motifs (tetraphenylmethane,\nspirobifluorene and pyrene). The authors furthermore irradiate the polymers to obtain\nthe radical anions, attributed to the formation ketyl radical anions. The polymers are\nalso tested to produce hydrogen peroxide under light irradiation, in water without\nadditional sacrificial donors, and report high efficiencies for H O production (solar to\n2 2\nchemical, SCC, efficiency of almost 4%). This reviewer is of the opinion that the\nmanuscript could be potentially of interest to the readership of Nature Communications,\nbut several critical issues should be addressed before the manuscript can be accepted.\nReply: We sincerely thank the reviewer for the careful evaluation of our manuscript\nand for recognizing the potential interest of our work to the readership of Nature\nCommunications. We appreciate the thoughtful summary of our study and the\nconstructive feedback provided. We have carefully addressed all the concerns raised, as\ndetailed in our point-by-point responses below, and have revised the manuscript\naccordingly.\n1. Some mechanistic claims that are central to the manuscript are, in my opinion, not\nfully corroborated. The authors claim several times that the production of radicals is\nleading to the dynamic exfoliation. More experiments and controls need to be\nperformed to back-up this claim. For example, the authors also sonicate while the\nradical also photogenerated so control experiments (such as no sonication) need to be\nperformed. Additionally, dynamic implies that after catalysis (or radicals being\nquenched) the materials return to the initial stage.\nReply: We sincerely thank the reviewer for this critical and insightful comment\nregarding the mechanistic evidence for radical-induced dynamic exfoliation. We agree\nthat this central claim requires robust experimental support. Based on your suggestions,\nwe have performed additional control experiments and refined our discussion\naccordingly.\nSpecifically, we performed exfoliation experiments under three distinct conditions:\n1) Sonication only, 2) Irradiation only, and 3) Simultaneous sonication and irradiation.\nThe results (Supplementary Fig. 51b) demonstrate a remarkable synergistic effect.\nNeither individual condition alone was effective, but their combination efficiently\nproduced exfoliated nanosheets. This indicates that photogenerated radicals (chemical\neffect) and sonication (physical effect) are both indispensable, working in concert to\nenable exfoliation.\nImportantly, post-catalysis characterizations, including XRD, SEM, and FT-IR,\nreveal no detectable changes in the crystalline framework or chemical functionalities,\nconfirming that the so-called “dynamic” exfoliation is a reversible, radical-driven\nprocess rather than irreversible structural damage. We have incorporated these results\ninto the revised Supplementary Information.\n“To further elucidate the mechanism of the radical-driven dynamic exfoliation\nprocess, control experiments were carried out under three different conditions: (i)\nsonication only, (ii) visible-light irradiation only, and (iii) simultaneous sonication and\nirradiation. As shown in Supplementary Fig. 51b, neither sonication nor irradiation\nalone induced significant exfoliation of TPM-DADK, whereas the combined treatment\nresulted in efficient formation of nanosheets. This observation highlights a synergistic\nrelationship between the physical agitation provided by sonication and the chemical\nactivation by photogenerated radicals.\nPost-catalysis characterizations, including XRD, SEM, and FT-IR analyses, reveal\nno discernible changes in the crystalline framework or chemical functionalities. This\nconfirms that the exfoliation is reversible and does not involve permanent structural\ndamage, thereby justifying the term “dynamic” used in the main text.”\nSupplementary Fig. 51 | (a) Photocatalytic H O generation performance of TPM-DADK with\n2 2\ndifferent catalyst concentrations; (b) Comparison of photocatalytic H O generation performance of\n2 2\nTPM-DADK under different exfoliation and activation conditions: simultaneous sonication and\nirradiation, sonication only, and irradiation only. Photocatalytic condition: 15.0 mg TPM-DADK,\n10.0 mL H O, O , Xe lamp with a 420 nm cutoff filter (100 mW cm-2).\n2 2\n2. Another mechanistic aspect to improve is the “isolation” of radicals. While the\nauthors claim the formation of discrete radicals, identified as ketyl radicals, the EPR\nspectra presented in the manuscript do not corroborate this claim. The EPR spectra of\nthe solids (at room temperature presumably) shows a broad signal, typical of organic\nsemiconductors and polymers. I would expect, for isolated radicals, to see a well-\nstructured and resolved signal (with assigned hyperfine splitting). Therefore, spin\nquantification and further experiments are suggested (such as low temperature, variable\ntemperature,) etc.) to confirm the formation of the proposed radicals. A minor point is\nthat the EPR spectra are recorded as solid so it is unclear where the PCET hydrogen\nsources is from and whether the observed signal is a carbon-based or oxygen-based\nradical.\nReply: We sincerely thank the reviewer for the insightful comments. We would like to\nclarify that TPM-DADK is a conjugated polymer, and the term “discrete radicals”\nrefers to the radicals being localized at each repeating unit, rather than delocalized over\nthe entire polymer backbone. In conjugated polymer matrices, however, π-π\ninteractions, exchange coupling between neighbouring radical sites, and heterogeneous\nlocal environments commonly produce broad EPR envelopes at room temperature even\nwhen the underlying radical species are localized; therefore a broad line does not by\nitself rule out the presence of localized ketyl (or carbon-centered) radicals.\nTo address the reviewer’s specific points, we performed variable-temperature X-\nband continuous-wave EPR on solid samples (293 K to 100 K). Both the room-\ntemperature (293 K) and low-temperature (100 K) spectra show a single, broad\nderivative envelope centered at ≈3355-3360 G with a linewidth substantially larger than\nthose of small-molecule radicals. The 100 K spectrum exhibits only slight narrowing\nand a marginal field shift relative to 293 K, and no resolved hyperfine structure emerges\n(Supplementary Fig. 16d). The corresponding g values (2.0043 at 293 K and 2.0068 at\nsignificantly lower than those characteristic of oxygen-centered species (usually >2.01).\nThese observations indicate that the observed signal arises predominantly from\ncarbon-centered radicals, and that exchange broadening and g-strain dominate the line\nshape in the solid polymer, rather than simple unresolved hyperfine from a single,\nisolated small radical. Such g-value evolution and line-broadening behavior are fully\nconsistent with localized carbon-centered (ketyl-type) radicals confined within a π-\nconjugated polymer matrix, where residual intersite coupling and environmental\ndisorder broaden the signal even at cryogenic temperatures.\nRegarding the proton-coupled electron transfer (PCET) process, we consider that\nthe hydrogen source in the solid-state EPR measurements originates mainly from\nadsorbed moisture in ambient air. We therefore attribute the observed signal primarily\nto carbon-centered (ketyl-type) radical species formed following photoinduced PCET,\nwhile acknowledging that a minor oxygen-centered contribution cannot be entirely\nexcluded. Given that the photocatalytic reaction itself is carried out in aqueous media,\nthis is unlikely to affect the interpretation of the radical species. We have added this\nclarification to the updated SI as follows:\n“Both room temperature (293 K) and low temperature (100 K) spectra display a\nsingle, broad derivative envelope centered at ≈ 3355-3360 G. The 100 K spectrum\nshows only slight narrowing and a marginal field shift compared to 293 K without the\nemergence of resolved hyperfine structure. The corresponding g values (2.0043 at 293\nK and 2.0068 at 100 K) are characteristic of carbon-centered radicals rather than\noxygen-centered ones. These features indicate that exchange broadening, g-strain and\nmicroenvironment heterogeneity in the solid polymer are the dominant broadening\nmechanisms; such broadened envelopes are commonly observed for localized radicals\nin conjugated polymer matrices.”\nSupplementary Fig. 16 | (d) EPR spectra of TPM-DADK in the solid-state at 293 K and 100 K.\n3. In connection to the point above, it appears that other optoelectronic characterization\n(for example photoconductivity) shows that radicals behave as I would expect for a\nconjugated organic radical polymer. In my opinion, isolated radicals and improved\nelectron/charge transports should not go hand in hand.\nReply: We thank the reviewer for raising this insightful comment. We agree that, in\ngeneral, localized organic radicals tend to disrupt electronic delocalization and would\nnot typically enhance charge transport. However, in our system, the radicals are not\npermanently isolated but remain dynamically coupled with the π-conjugated backbone.\nSuch transient interactions induce local polarization, which in turn promotes interfacial\ncharge separation and transfer under illumination, thereby giving rise to an apparent\nenhancement in photoconductivity. This interpretation is well supported by our\nphotocurrent, EIS, and PL dynamics data, all of which demonstrate light-enhanced\ninterfacial electron transfer. To avoid potential misunderstanding, we have clarified this\nmechanism in the revised manuscript as follows:\n“Unlike continuous conjugated systems, the strategically segmented π-framework\nin TPM-DADK localizes electrons within discrete domains (Supplementary Table 1,\nSupplementary Fig. 33), thereby suppressing recombination and enabling efficient\ncharge separation and storage.[45] Importantly, the radicals generated in this system are\nnot permanently isolated but remain dynamically coupled with the π-conjugated\nbackbone. This transient interaction induces local polarization that facilitates interfacial\ncharge separation and transfer under illumination.”\n4. The authors mention their polymers to accumulate charge and the fate of the radicals\nis unclear, but this aspect has been relatively unexplored. Control experiments in which\nfor example, air is introduced into the reactor with radical present and H O checked\n2 2\n(under dark) is suggested. Similarly, comparison of radicals before and after\nphotocatalysis is suggested.\nReply: We thank the reviewer for this insightful comment. To clarify the fate of the\nradicals, we performed electron paramagnetic resonance (EPR) measurements to\nmonitor radical species before and after irradiation (Fig. 2b). The results reveal that\nradicals in TPM-DADK are relatively stable and accumulate on the polymer surface,\nconsistent with enhanced charge separation and hydrophilicity.\nComplementary XPS analyses (Fig. 2c, Supplementary Fig. 17) provide direct\nevidence of light-induced carbonyl transformation: the dominant O 1s peak at 532.0 eV\n(C=O) decreases upon irradiation while a new peak appears at 530.8 eV (C-O),\nconfirming the formation of ketyl radical anions as photogenerated charge-storage sites.\nZeta-potential measurements show a pronounced negative shift after irradiation (Fig.\n2d), reflecting surface accumulation of these ketyl species and strengthened\nelectrostatic proton interactions. Contact-angle measurements reveal increased\nhydrophilicity (Supplementary Fig. 19; Supplementary Video 1-6), indicating improved\nwater adsorption and dispersion stability. Together, these results demonstrate that the\nradicals persist beyond illumination and play a critical role in charge storage and\ncatalytic activity.\nIn response to the reviewer’s suggestion, we also carried out a “Light-Ar/Dark-O ”\n2\ncontrol experiment (Supplementary Fig. 66). After rigorous Ar purging for 60 min in\nthe dark, a trace amount of H O was still detected under Ar irradiation, likely due to\n2 2\nresidual O . When O was subsequently reintroduced under dark conditions,\n2 2\napproximately 36 μM H O continued to form, confirming that photoinduced radical\n2 2\nintermediates generated under illumination can react with O even in the absence of\n2\nlight. This finding underscores the persistence of these reactive species in driving H O\n2 2\nformation.\nTogether, these results substantiate that charge accumulation and radical formation\nin TPM-DADK are key contributors to its high photocatalytic activity, with long-lived\nradicals serving as active charge-storage centers capable of reacting with O post-\n2\nillumination.\nTherefore, we have revised the manuscript accordingly as follows:\n“Furthermore, a Light-Ar/Dark-O experiment (Supplementary Fig. 66) revealed\n2\nthat upon reintroducing O in the dark, approximately 36 μM H O was still produced,\n2 2 2\nindicating that photoinduced radical intermediates formed under illumination can\ncontinue to react with O even without light. This observation underscores the\n2\nremarkable persistence of these reactive species in promoting H O formation.”\n2 2\nSupplementary Fig. 66 | H O production of TPM-DADK under different control conditions.\n2 2\nReaction conditions: TPM-DADK (20 mg), water (10 mL), Ar atmosphere in the light or O\n2\natmosphere in the dark.\n5. Since several properties of the polymers change (porosity, water contact, etc.) further\nexperiments and comparisons should be performed. For example, the authors should\nreport absorption spectra before and after irradiation. The data presented in\nSupplementary Fig. 24 should be discussed as the authors claim that blue-shift indicated\ndecreased pi-pi stacking. However, such similar absorbance is not what I would expect\nwhen radicals are formed, which are expected to absorb well into to NIR. Similar\ncomparisons (before and after radicals) would be expected also in determination in\nenergy levels, for example, as these could also contribute to the photocatalytic\nproperties.\nReply: We thank the reviewer for raising the important comments. Indeed, we have\nprovided the water contact angle patterns of TPM-DADK, Flu-DADK, and Py-DADK\nbefore and after irradiation in Supplementary Fig. 19, together with Supplementary\nvideos showing the changes. TPM-DADK shows a significant change in contact angle\n(~90° before irradiation, ~24° after irradiation), indicating a remarkable increase in\nsurface hydrophilicity. In contrast, Flu-DADK and Py-DADK exhibit only minor\nchanges, further confirming that TPM-DADK accumulates a large amount of surface\ncharge upon illumination.\nSupplementary Fig. 19 | Water contact angle patterns of (a, d) TPM-DADK, (b, e) Flu-DADK\nand (c, f) Py-DADK before and after irradiation.\nWe also attempted to measure porosity and perform O -TPD on the samples after\n2\nirradiation. However, these experiments were unsuccessful because such measurements\nrequire solid-state samples. After light-induced exfoliation, the recovered and dried\nsamples lose their exfoliated morphology and revert to bulk-like structures, making\nthese tests unfeasible.\nWe agree that, for many small organic molecules, radical formation often gives\nnew broad absorptions extending toward the NIR. In our polymeric systems, however,\nthe intrinsic absorption is already strong, which can mask small changes. To test the\nsolid-state response we sealed polymer powders in NMR tubes under Ar in a glovebox\nand irradiated them for 30 min. No obvious color or absorption change was observed\nbefore vs. after irradiation (Supplementary Fig. 24 i-j), indicating that in the compact\nsolid state light exposure does not produce large, readily observable changes in the\noptical absorption.\nBy contrast, when the polymers were dispersed (1 mg in 20 mL DMF/H O) and the\n2\nsupernatants were irradiated, we observed clear spectral evolution: in several cases a\nred-shift (and increased visible absorption) appears (Supplementary Fig. 24 a-f). This\nbehaviour is consistent with partial exfoliation/formation of radicals in the dispersed\nstate, where polymer chains are more isolated and interactions with solvent permit\nmodulation of electronic structure.\nThe UV-vis spectra and photographs show that suspensions irradiated under Ar are\ndarker and display a slight red shift relative to those irradiated in air (Supplementary\nFig. 24 a-f). We attribute this to stabilization of photogenerated radicals in oxygen-free\nconditions. Whereas in air/O photogenerated electrons are more readily scavenged,\n2\npromoting H O formation and placing the catalyst in a dynamic balance between\n2 2\nradical and molecular states. For the concentrated aqueous experiment (20 mg TPM-\nDADK in 10 mL H O, Supplementary Fig. 24 g-h) the Ar-irradiated sample is darker\n2\nthan the O -irradiated one, though the difference is subtle and requires strict comparison\n2\nto observe.\nTaken together, (i) the large decrease in contact angle, (ii) reproducible UV-vis\nevolution in dispersed samples under controlled atmospheres, and (iii) reproducible\noptical colour changes (Supplementary Fig. 24) support our interpretation of light-\ninduced exfoliation and accumulation of surface charges in TPM-DADK. The limited\nresponse in the compact solid state likely reflects strong interchain interactions and the\nintense intrinsic coloration of the polymers that mask small radical-induced features.\nTherefore, we have revised the manuscript and Supplementary Information\naccordingly as follows:\nMain text: “Consistently, UV-vis absorption spectra of dispersed TPM-DADK\nsuspensions (Supplementary Fig. 23) showed a slight blue shift after irradiation under\nair, reflecting weakened π-π interactions and shortened conjugation length, thereby\ncorroborating the efficient light-driven exfoliation of TPM-DADK. In diluted\ndispersed suspensions under Ar, a slight red shift was observed, consistent with\nformation of radicals in oxygen-free conditions. These observations corroborate the\nefficient light-driven exfoliation of TPM-DADK and the accumulation of surface\ncharges.”\nSupplementary Fig. 24 | Photographs (a-c) and normalized UV-vis absorption spectra (d-f) of (a,\nd) TPM-DADK, (b, e) Flu-DADK, and (c, f) Py-DADK dispersed in mixed solvent (DMF/ H O =\n2\n9:1, v/v, concentration: 1.0 mg/20 mL), recorded after light irradiation under air and Ar atmospheres.\n(g) Photographs TPM-DADK (20 mg) in 10 mL of water under Ar or O atmosphere with light\n2\nirradiation for 30 min. (i,j) Photographs of TPM-DADK, Flu-DADK, and Py-DADK powders (i)\nbefore and (j) after 30 min of light irradiation under Ar atmosphere, sealed in an Ar-filled glovebox.\nUpdated SI: “When the polymers (TPM-DADK, Flu-DADK, Py-DADK) were\ndispersed in a DMF/H O mixed solvent (9:1, v/v; 1.0 mg in 20 mL) to form dilute\n2\nsuspensions, the supernatants were irradiated for 30 min. Under these conditions,\ndistinct spectral evolution was observed, including slight red shifts in UV-vis\nabsorption (Supplementary Fig. 24a-f). This is attributed to partial light-induced\nexfoliation and formation of photogenerated radicals in oxygen-free conditions,\nfacilitated by polymer chain isolation and solvent interaction.\nIn concentrated aqueous suspensions (20 mg TPM-DADK in 10 mL H O), the\n2\ncolor difference between Ar- and O -irradiated samples is subtle (Supplementary Fig.\n2\n24g-h) but detectable under strict comparison.\nPolymer powders (TPM-DADK, Flu-DADK, Py-DADK) were sealed in NMR\ntubes under Ar atmosphere in a glovebox and irradiated for 30 min. No observable\nchange in color was detected before vs. after irradiation (Supplementary Fig. 24i-j),\nsuggesting that light exposure in the solid state does not induce significant alterations\nin optical absorption due to the strong intrinsic coloration and limited exciton mobility\nin compact polymer solids.”\nMinor points:\n1. -C=N signal in the solid-state 13C NMR appears different in the three polymers. 13C\nNMR spectrum of DADK alone should be shown as comparison and further proofs of\nthe obtainment of the polymers should be provided.\nReply: We thank the reviewer for the suggestion. We have carried out the solid-state\n13C NMR of DADK. The characteristic resonances of the DADK monomer (115-160\nppm for aromatic carbons, 185-190 ppm for the carbonyl carbon) are fully retained in\nthe polymers, confirming that the DADK backbone remains intact. Minor variations\nnear the carbonyl region are due to MAS spinning sidebands (spacing: 66.39 ppm),\ncausing partial overlap of the C=O resonance and giving the appearance of small\ndifferences.\nIn fact, the -C=N signals are in fact essentially consistent across the three polymers.\nThe previously provided solid-state 13C NMR spectra may not have clearly shown this\nconsistency. To better illustrate this, a comparison figure has now been included in the\nSI (Supplementary Fig. 7). In addition, complementary FT-IR, XRD, and XPS analyses\nfurther corroborate the successful synthesis of the polymers.\nTherefore, we have revised the SI accordingly as follows: “Solid-state 13C NMR\nspectra further support this assignment. The characteristic resonances of the DADK\nmonomer (115-160 ppm for aromatic carbons, 185-190 ppm for the carbonyl carbon)\nare fully retained in the polymers, confirming that the DADK backbone remains intact.\nMinor variations near the carbonyl region are due to MAS spinning sidebands (spacing:\n66.39 ppm), which partially overlap with the C=O resonance and give the appearance\nof slight differences. Importantly, the –C=N resonances are essentially consistent across\nDADK and all three polymers.”\nSupplementary Fig. 7 | (a) Solid-state 13C NMR spectrum of DADK, (b) Solid-state 13C NMR\nspectra of TPM-DADK, Flu-DADK, Py-DADK and DADK.\n2. Zeta potential after irradiation of TPM-DADA should be provided.\nReply: We thank the reviewer for the suggestion. The zeta potential of TPM-DADA\nadditionally measured and found to remain nearly unchanged before and after\nirradiation (from 17.6 to 17.1 mV). In contrast, TPM-DADK, Flu-DADK, and Py-\nDADK exhibited a pronounced negative shift in zeta potential after irradiation (Fig. 2d),\nindicating the surface accumulation of ketyl species. This comparison highlights the\ncrucial role of carbonyl functionalities in facilitating the generation of photogenerated\nanionic radicals and modulating surface charge properties. Therefore, we have revised\nthe manuscript as follows:\n“Zeta potential measurements revealed distinct surface charge responses among the\npolymers. TPM-DADK, Flu-DADK, and Py-DADK exhibited pronounced negative\nshifts after irradiation (Fig. 2d), reflecting surface accumulation of ketyl species,\nwhereas TPM-DADA showed negligible change (from 17.6 to 17.1 mV,\nSupplementary Fig. 18). The increased negative surface potential strengthens\nelectrostatic proton interactions, promotes hydroxyl group formation, and improves\ncolloidal stability, demonstrating that carbonyl groups facilitate the generation of\nphotogenerated anionic radicals and enhance surface charge modulation.”\nSupplementary Fig. 18 | Zeta potential of TPM-DADA in the dark and under irradiation. The error\nbars mean values are standard deviation of three independent experiments.\n3. The authors refer to a “significantly lower” O adsorption energy for a difference\n2\nminor than a kcal mol-1.\nReply: We sincerely appreciate the reviewer’s comment regarding the description of\nthe O adsorption energy. We acknowledge that the absolute difference in adsorption\n2\nenergy is less than 1 kcal/mol; however, we referred to the change as “significant”\nconsidering that the adsorption energy increased by over 100%, from -0.78 kcal/mol\nbefore activation to -1.74 kcal/mol after activation. From a catalytic perspective, even\nsuch a modest enhancement is meaningful, as excessively strong O adsorption may\n2\nhinder product desorption and slow down the overall reaction kinetics. To more\naccurately convey this perspective, we have revised the relevant statement in the\nmanuscript to:\n“The calculated O adsorption energy at the O-H site of DADKH· is more\n2\nfavorable than that on DADK (-1.74 vs -0.78 kcal mol-1; Fig. 3f), corresponding to an\nenhancement of over 100%. Although the absolute energy difference is modest, such\nan increase is catalytically meaningful because slightly stronger O adsorption can\n2\nfacilitate activation while avoiding overly strong binding that would impede product\ndesorption.”\n4. Provide an explanation of why PL quenching is less pronounced for the self-\nexfoliated sample compared to the as-synthesized. How do the lifetimes change under\nAr and air in both conditions? Have the samples been irradiated at the same wavelength?\nReply: We thank the reviewer for this insightful comment. The self-exfoliated TPM-\nDADK, Flu-DADK, and Py-DADK exhibit intrinsically much weaker\nphotoluminescence than the as-synthesized material, which is attributed to its higher\ndegree of charge separation and the presence of abundant surface-bound anionic radical\nspecies formed during exfoliation. These radicals provide efficient non-radiative\nelectron transfer pathways and serve as active sites for O adsorption and reduction.\nintroducing O causes only a slight additional decrease in PL intensity, whereas the as-\n2\nsynthesized sample, with stronger initial emission and fewer radical quenching centers,\nshows a more pronounced quenching under air. Consistently, time-resolved PL\nmeasurements reveal that the lifetimes of the self-exfoliated sample change only\nslightly between Ar and air, while the as-synthesized sample exhibits a clear lifetime\nshortening under air, reflecting more efficient oxygen quenching of radiative\nrecombination. All PL measurements were performed using the same excitation\nwavelength (420 nm) to ensure direct comparability.\nAttempts to measure lifetimes of the exfoliated samples under air were\nunsuccessful due to their extremely weak PL signals. Nevertheless, the existing data\nclearly demonstrate enhanced charge separation of the exfoliated samples. This\ndiscussion has been incorporated into the revised manuscript and Supplementary\nInformation, and the figure captions have been refined accordingly.\nMain text: “Furthermore, TPM-DADK displayed a strong orange emission at\n598 nm, which was significantly quenched upon switching the atmosphere from Ar to\nair (Fig. 4h, Supplementary Fig. 43), consistent with efficient charge transfer to O .\nthe additional quenching by O was only slight, reflecting that most photogenerated\n2\nelectrons were already diverted into non-radiative transfer pathways provided by\nsurface-bound anionic radicals. Time-resolved PL measurements of TPM-DADK\nfurther showed that the excited-state lifetime decreased from 4.37 ns to 2.03 ns after\nexfoliation (Fig. 4i), indicating accelerated interfacial electron transfer and suppressed\nradiative recombination. The coexistence of weaker initial emission and shorter\nlifetimes demonstrates that the exfoliated nanosheets possess highly efficient charge\nseparation, which promotes oxygen adsorption and reduction despite the faint\nluminescence. These results demonstrate that TPM-DADK combines segmented π-\nconjugation and dynamic exfoliation to enhance charge separation, oxygen adsorption,\nand interfacial electron transfer. This synergistic design optimizes the balance between\ncharge localization and mobility, underpinning its superior photocatalytic performance\nfor H O production.”\n2 2\nSupplementary Information: “Time‐resolved photoluminescence (PL)\nmeasurements were performed for TPM-DADK, Flu-DADK, and Py-DADK in H O\n2\nunder Ar and air atmospheres using an excitation wavelength of 420 nm. As shown in\nFigure 4h-4i and Supplementary Fig. 43-45, the self-exfoliated samples display\nintrinsically much weaker PL intensity and shorter lifetimes than their as-synthesized\ncounterparts under Ar, revealing highly efficient charge separation and rapid interfacial\nelectron transfer. The weak emission originates from abundant surface-bound anionic\nradical species generated during exfoliation, which act as active sites for O adsorption\n2\nand reduction. Because the photoluminescence of the self-exfoliated samples is already\nstrongly suppressed, introducing O produces only a slight additional decrease, whereas\n2\nthe as-synthesized samples, with stronger initial emission and fewer radical quenching\ncenters, show a more pronounced PL quenching under air. This limited oxygen-induced\nquenching, together with the shorter lifetimes, indicates that most photogenerated\nelectrons in the self-exfoliated samples are promptly transferred to surface radicals and\nO acceptors rather than undergoing radiative recombination, accounting for their\n2\nmarkedly higher photocatalytic H O production efficiency despite the weak\n2 2\nluminescence.”\nFigure 4. Charge transport properties and photo-induced modulation of TPM-DADK. (a)\nPhotocurrent response, and (b) Electrochemical impedance spectra (EIS) of as-synthesized TPM-\nDADK under Ar and Air atmosphere; (c) KPFM image of as-synthesized TPM-DADK under\nirradiation; (d) Photocurrent of TPM-DADK as-synthesized and after photo-exfoliation under Air;\n(e) EIS of TPM-DADK as-synthesized and after photo-exfoliated in air; (f) Temperature-dependent\nPL spectra of TPM-DADK; (g) Fitting curve of the temperature-dependent PL (TD-PL) intensity\nfor TPM-DADK; (h) Steady-state PL spectra of as-synthesized TPM-DADK under Ar and O with\n2\nan excitation wavelength of 420 nm; (i) PL decay dynamics of TPM-DADK before and after photo-\nexfoliation under Ar with an excitation wavelength of 420 nm.\nSupplementary Fig. 43 | PL spectra of as-synthesized (a) Flu-DADK and (b) Py-DADK under Ar\nand O with an excitation wavelength of 420 nm.\nAr and O with an excitation wavelength of 420 nm.\nPy-DADK in H O under Ar in the as-synthesized state and after exfoliation with an excitation\n2\nwavelength of 420 nm.\n5. Photocatalytic experiments should be done in replicates and error bars should be\nreported.\nReply: We thank the reviewer for this valuable suggestion. We apologize for the\noversight of not including error bars in the original figures. As the reviewer correctly\npointed out, this is essential for representing data variability. The photocatalytic\nperformance data presented in our manuscript were indeed obtained from at least three\nindependent replicate experiments. In accordance with your suggestion, we have now\nre-plotted all relevant figures (Fig. 6 and Supplementary Fig. 55) to include error bars\n(representing standard deviation). We believe these revisions have significantly\nimproved the clarity and statistical rigor of our data presentation. Thank you again for\nthis helpful suggestion.\nFigure 6. Photocatalytic H O generation performance. (a) Comparison of H O production of\n2 2 2 2\nTPM-DADK, Flu-DADK and Py-DADK before and after photo-exfoliation. Conditions: 15.0 mg\nphotocatalyst, 10.0 mL H O, saturated O , under visible light (λ > 420 nm, 100 mW cm-2); (b)\n2 2\nPhotocatalytic H O generation performances of TPM-DADK under varied conditions; (c)\n2 2\nPerformance comparison of TPM-DADK with other photocatalysts; (d) UV-vis absorption\nspectrum and apparent quantum yield of TPM-DADK; (e) H O generation by TPM-DADK using\n2 2\ndifferent water sources under AM 1.5G; (f) Long-term photocatalytic H O production under\n2 2\nsaturated O by TPM-DADK, Flu-DADK and Py-DADK under simulated sunlight (AM 1.5G,\n2\n100 mW cm-2). The error bars mean values are standard deviation of three independent experiments.\nSupplementary Fig. 55 | Absorption spectrum (curves) and apparent quantum yield (columns) of\n(a) Flu-DADK and (b) Py-DADK. Photocatalytic condition: 1.5 mg/mL photocatalyst in H O, O ,\n2 2\nvisible light (> 420 nm, 100 mW cm-2). The error bars mean values are standard deviation of three\nindependent experiments.\n6. For Py-DADK, H O production is inhibited more than 20% in presence of p-BQ, so\n2 2\nsuperoxide photo-production should not be ignored.\nReply: We thank the reviewer for this comment. We agree that superoxide formation\ncontributes to H O production in Py-DADK, as evidenced by the >20% inhibition in\n2 2\nthe presence of p-BQ. However, this does not change the overall conclusion that the 2e⁻\nORR pathway dominates H O generation. This point has been clarified in the revised\n2 2\nmanuscript.\n7. For semiconductors, H O production is usually reported as (mol of hydrogen\n2 2\nperoxide)/(g of material). The authors should add a column with mM h-1 and mol/g,\nin order to have a direct comparison with other systems reported in literature.\nReply: We sincerely thank the reviewer for this valuable suggestion. We fully agree\nthat providing the H O production rate in commonly used units such as mM h-1 and\n2 2\nmmol g-1 h-1 is essential for direct comparison with previously reported semiconductor\nsystems. In the original version of our manuscript, we primarily reported the\nconcentration-based rate (mM h-1), as our main focus was to demonstrate the ability of\nTPM-DADK to achieve high H₂O₂ concentrations, which is a critical prerequisite for\npractical applications such as chemical synthesis and water treatment. Nevertheless,\nfollowing the reviewer’s suggestion, we have now supplemented the mass-normalized\nproduction rates (mmol g-1 h-1) and included them in the revised manuscript (Table S5),\nallowing direct comparison with previously reported systems.\n8. XPS spectrum of TPM-DADK in Fig. 1b refers to C 1s. The caption should be\nmodified accordingly.\nReply: We thank the reviewer for pointing this out. The caption of Fig. 1b has been\ncorrected to specify that the XPS spectrum corresponds to the C 1s signal of TPM-\nDADK. This correction has been made in the revised manuscript.\n9. Figure S19 b. should be updated with the correct reference to the molecule. It refers\nto Py-DADK?\nReply: We thank the reviewer for carefully noting this error. Figure S17b (previously\nFigure S19 b) indeed contained an incorrect label. The correct reference should be to\nPy-DADK. We have updated the figure accordingly in the revised Supporting\nInformation.\nSupplementary Fig. 17 | XPS spectra of O 1s on (a, c) Flu-DADK and (b, d) Py-DADK before\nand under irradiation.\n10. References should be provided for the attribution of O Yeager-type adsorption in\nreported at different wavelengths?) so indicating potentially a different mechanism?\nReply: We sincerely thank the reviewer for this valuable comment. We fully agree on\nthe necessity of providing appropriate references for the assignment of O Yeager-type\n2\nadsorption in in situ DRIFTS experiments.\nThe Yeager-type adsorption configuration of O as determined by in-situ DRIFTS,\n2\nhas been extensively reported in photocatalytic systems for hydrogen peroxide\nsynthesis. Key references supporting this assignment include: Chi, W. et al., Nat.\nCommun. 15, 5316 (2024); Luo, Y. et al., Angew. Chem. Int. Ed. 62, e202305355 (2023);\nLuo, L. et al., Angew. Chem. Int. Ed. 64, e202507415 (2025). In these studies, the -O-\nO- vibration (ca. 1050-1200 cm-1) and the O-O characteristic peak (ca. 950 cm-1) were\nassigned to the Yeager-type adsorption of oxygen.\nOur experimental results (Fig. 3b, Fig. 3d) are consistent with these literature\nreports. We have therefore clarified in the manuscript that the assignment of the O\n2\nadsorption mode is based on both our experimental data and previously reported studies.\nFollowing your suggestion, we have added the relevant references regarding O Yeager-\n2\ntype adsorption in DRIFTS experiments to the main text.\nReferences\n[19] Chi, W. et al. A photocatalytic redox cycle over a polyimide catalyst drives\nefficient solar-to-H O conversion. Nat. Commun. 15, 5316 (2024).\n2 2\n[45] Luo, Y. et al. Sulfone-modified covalent organic frameworks enabling efficient\nphotocatalytic hydrogen peroxide generation via one-step two-electron O reduction.\n[46] Luo, L. et al. Defective poly(heptazine imide) nanosheets for efficient one-step\ntwo-electron photocatalytic O reduction to medical-like H O . Angew. Chem. Int. Ed.\n2 2 2\n64, e202507415 (2025).\n11. There is a mismatch between text and data in Fig. 6a.\nReply: We thank the reviewer for carefully examining our manuscript and for pointing\nout this error. We apologize for the oversight. We have carefully rechecked the original\ndata, figures, and related descriptions in the text. The corrected description now reads:\nsubstantially outperforming Flu-DADK (2.59 mM h-1) and Py-DADK (1.43 mM h-1)\n(Fig. 6a). Additionally, the figure caption has been corrected to indicate that the catalyst\namount is 15 mg. We sincerely apologize for this mistake and greatly appreciate the\nreviewer’s careful reading.\n12. NBT assays usually quantify the amount of superoxide produced by monitoring the\nformazan formation at 560 nm.\nReply: We thank the reviewer for this comment. While NBT assays are often performed\nby monitoring formazan formation at 560 nm to quantify superoxide production. In our\nstudy, however, we followed an alternative protocol cited from recent high-profile\nworks (Ref. 20, Angew. Chem. Int. Ed. 2024, 63, e202320218; Nat. Catal. 2024, 7, 195-\n206; Angew. Chem. Int. Ed. 2024, 63, e202319216), which measures absorbance at 259\nnm, a method validated for the accurate quantification of superoxide radicals. To\nprevent any confusion, we have now explicitly specified the detection wavelength in\nthe Experimental Section of the SI.\nThe concentration of ·O - was determined by the degradation of NBT, measured\n2\nby the absorbance change at the wavelength of 259 nm. The mole ratio of the generated\n·O - and the degraded NBT was 4:1 according to the following equation:\n2\n𝑁𝐵𝑇+4∙𝑂− +2𝐻+ → 𝐹𝑜𝑟𝑚𝑎𝑡𝑖𝑜𝑛+𝑂\n2 2\n13. AQY compared to UV-vis absorption spectrum should be plotted in water, the actual\nphotocatalytic condition.\nReply: We thank the reviewer for this valuable comment. We agree that the comparison\nbetween AQY and the UV-vis absorption spectrum should be performed under\nconditions consistent with the actual photocatalytic environment. In our study, the AQY\nvalues were indeed measured in water under the real photocatalytic conditions. The\nUV-Vis absorption spectrum, however, was recorded in the solid powder state in order\nto reveal the intrinsic optical absorption properties of the material itself. We believe that\npresenting the intrinsic absorption together with the AQY results provides\ncomplementary information: the UV-Vis spectrum reflects the fundamental light-\nharvesting ability of TPM-DADK, while the AQY measurements demonstrate its\nactual performance under photocatalytic conditions.\nResponse to Referee 5:\nHan et al. demonstrate a novel, intelligent, design principle in which pi-pi interactions\nare weakened through chemical structure of the catalyst. By sonication under\nillumination in H O, the morphology appears to change, supported by a number of\n2\ncharacterization techniques; in the presence of air, the observance that O has bound to\n2\nthe catalyst has been shown convincingly. The “charges” are remarkably long lived,\nand it is shown that O can be bound to the catalyst after several minutes in the dark\n2\nunder Ar - I find this truly fascinating, and emphasizes the importance in stabilization\nof charges through chemical reactions, in this case, formation of the “protonated anion\nintermediate”.\nReply: We sincerely thank the reviewer for the thoughtful and encouraging comments,\nespecially for recognizing our work as “truly fascinating.” We are delighted that the\nreviewer found our design strategy and mechanistic insights compelling, particularly\nthe stabilization of long-lived charges through the formation of the protonated anion\nintermediate. We greatly appreciate the reviewer’s thoughtful recognition of the\nstructural design, morphological evolution, and oxygen binding behavior demonstrated\nin our study. These encouraging comments further strengthen our confidence in the\nsignificance of this work.\nThere are several points which I feel should be clarified, however.\n1) It is not clear to me what excitation wavelength was used for the PL and TA\nexperiments - my guess is ~500 nm for PL and 355 nm for the TA experiments. If this\nis correct, it would have profound effects on the photophysics. Can the authors clarify\nthis?\nReply: We thank the reviewer for raising this important point. Regarding the question\non excitation wavelengths, we used 420 nm for PL and 350 nm for the TA experiments.\nThe selection of these wavelengths was based on the laser sources available in our\nlaboratories. As shown in the absorption spectra (Fig. 1f), the samples exhibit strong\nabsorption in the 300-440 nm range, with no significant difference between 420 nm and\n350 nm. Therefore, the choice of excitation wavelengths does not affect the reliability\nof our conclusions. To clarify this, we have now explicitly included the excitation\nwavelengths in the captions of Figure 4, Figure 5 and Supplementary Figs. 43-47.\n2) The assignment of the spectral features in the TA spectra should be clarified.\nSignificant weight is placed upon these results (i.e. Lifetime, degree of charge\nseparation) but these conclusions depend on their assignment. An additional peak is\nobserved at ~440 nm in the presence of air in all cases, can the authors comment on this\nband. The bands at ~440, 480, and 600 nm all appear to show different kinetics “by-\neye” in Figure 5 for the exfoliated sample - significantly more insight would be\nprovided from global lifetime analysis rather than fitting the kinetic trace at 480 nm.\nAs is, i agree the spectra show increased lifetimes for the exfoliated sample in air, but there\nis little evidence that this is because of increased charge-separation, a local excited state\nmay have a longer lifetime just because of difference in morphology. Similarly the\ndifference in shape of the TA spectra may be expected from changing morphology based\non the shape of PL spectra. Showing the evolution of the spectra using GLA will\nenhance the manuscript considerably.\nReply: We thank the reviewer for the valuable and insightful comments, which helped\nus to clarify the assignment of the spectral features and better explain the underlying\nmechanism in the revised manuscript. We have carefully analyzed the transient\nabsorption (TA) spectra of TPM-DADK under three different conditions (pristine in\nN , pristine in air, and photoexfoliated in air) as follows.\nspectral curves in Supplementary Fig. 48 and Supplementary Fig. 49a, a negative\nground-state bleaching (GSB) signal is observed around 380 nm. The decay dynamics\nof the GSB signal are nearly identical under all three conditions. This indicates that the\nfundamental bandgap transition is largely unaffected by morphological changes, and\ntherefore the observed increase in TA lifetimes for the photoexfoliated sample cannot\nbe attributed solely to morphology.\nSecond, the broad positive bands observed at 440-650 nm can be attributed to\nexcited-state absorption (ESA), arising from promotion of carriers from the first excited\nstate to higher-lying electronic states. These ESA features are sensitive to charge-\ntransfer processes and, therefore, more responsive to sample modulation. For the\nphotoexfoliated TPM-DADK in air, the decay curves at 440, 480, and 600 nm\n(Supplementary Fig. 50c) overlap almost completely, indicating highly consistent\nkinetics; the same trend is observed for the other two states (Supplementary Fig. 50a-\nb). This consistency across wavelengths demonstrates that the dynamics are uniform\nthroughout the ESA region, justifying the use of the 480 nm trace for kinetic fitting.\nAlthough we have not performed a full global lifetime analysis (GLA), the TA results\ncombined with EPR, PL, TRPL, and EIS measurements consistently indicate that\nphotoexfoliation in the presence of oxygen promotes initial charge separation and\nstabilizes long-lived charge carriers.\nIn the revised manuscript, we have clarified the assignment of the characteristic\npeaks in the TA spectra: “The negative signal around 380 nm, corresponding to ground-\nstate bleaching (GSB), is essentially identical across the three samples, indicating\nsimilar ground-state absorption. In contrast, the broad positive band at 450 - 650 nm,\nassigned to excited-state absorption (ESA), varies among the samples, reflecting its\nhigher sensitivity to charge-transfer processes.”\nSupplementary Fig. 48 | Normalized spectral curves of TPM-DADK under three different states\nand different delay times. (a) Pristine in N , (b) Pristine in air, (c) Photoexfoliated in air.\nTPM-DADK in three different states.\nSupplementary Fig. 50 | Normalized dynamic curves of TPM-DADK in positive signal region at\ndifferent wavelengths under three conditions. (a) Pristine in N , (b) Pristine in air, (c)\n3) I found the Pseudo-colour maps of the TA spectra hard to interpret, I suggest figures\nanalogous to Figure 5d be added.\nReply: We sincerely thank the reviewer for the valuable comments. To improve clarity,\nwe have supplemented the pseudo-colour TA maps with time-resolved TA spectra\nanalogous to Figure 5d, allowing readers to more clearly observe and compare the\nspectral evolution under different conditions. The newly added data are shown in\nSupplementary Fig. 49b-c, presenting the TA spectra of pristine TPM-DADK in air and\nN at various delay times.\ndifferent conditions: (b) pristine in air, (c) pristine in N , recorded at various delay times.\n2\n4) Is there residual Pd present within the catalyst from the synthesis - can this play a\nrole in possible redox chemistries?\nReply: We thank the reviewer for raising this important question. To address this point,\nwe carefully re-examined the XPS spectra of the TPM-DADK. No discernible peaks\nwere observed at 335.0 eV (Pd0) or 337.0 eV (Pd2+), confirming the absence of\ncatalytically active Pd species such as metallic Pd or PdO nanoparticles. This indicates\nthat any residual palladium is present at a concentration below the detection limit of\nXPS and, more importantly, is not in a form expected to contribute to photocatalytic\nactivity.\nFurthermore, ICP-OES analysis showed that the residual Pd content in TPM-\nDADK is 0.1588 wt%. Considering this low Pd content and the lack of Pd nanoparticles\nor clusters in all characterizations, it is unlikely that Pd contributes significantly to the\nobserved redox activity.\nTo further exclude potential Pd-related effects, we performed an additional\nexperiment under standard photocatalytic conditions by adding 1.0 mg of Pd(PPh ) ,\nas\n3 4\nshown in Supplementary Fig. 52c. The addition of Pd had negligible impact on the\nreaction rate, confirming that Pd does not play a decisive role in the photocatalytic\nprocess.\nMoreover, all three polymers were synthesized using the same protocol yet display\ndistinct photocatalytic performances, strongly supporting that the observed activity\noriginates from the intrinsic electronic structures of the designed π-conjugated\nframeworks rather than from trace Pd residues. The Supporting Information has been\nupdated accordingly.\n“1.22 ICP-OES Analysis\nThe content of Pd in the polymer was determined by inductively coupled plasma\noptical emission spectroscopy (ICP-OES, iCAP 7400, Thermo). 50 mg of TPM-DADK\nwas digested in a mixed acid solution of HNO /H O (3:1, v/v) under heating until\n3 2 2\ncomplete dissolution. The solution was further evaporated to a volume of less than 0.5\nmL, cooled to room temperature, and then diluted to 10 mL with ultrapure water for\nICP-OES measurement. The Pd concentration, determined using a calibration curve\nprepared from standard Pd solutions, was 0.1588 wt%.”\n“Critically, no signals corresponding to Pd0 (335.0 eV) or Pd2+ (337.0 eV) were\ndetected, confirming the absence of residual palladium from synthesis in any\ncatalytically relevant form. In addition, ICP-OES analysis showed that the Pd content\nin TPM-DADK is 0.1588 wt%, which agrees well with the theoretical amount of Pd\nintroduced from Pd(PPh ) during polymer synthesis. Considering this low Pd loading\n3 4\nand the absence of Pd nanoparticles or clusters in all characterization results, it is\nreasonable to conclude that Pd species do not play a significant role in the observed\nphotocatalytic redox behavior.\nMoreover, all polymers (TPM-DADK, Flu-DADK, Py-DADK) were prepared\nusing the same synthetic protocol. Despite this, they exhibit markedly distinct\nphotocatalytic performances. This systematic variation clearly indicates that the\nphotocatalytic activity originates from the designed π-conjugated frameworks, rather\nthan from trace Pd residues.”\n“Importantly, Supplementary Fig. 52c demonstrates that Pd has a negligible effect\non the photocatalytic reaction. Addition of 1.0 mg Pd(PPh ) under standard conditions\n3 4\ndid not noticeably alter the reaction rate.”\nSupplementary Fig. 52 | (a) Photocatalytic H O generation performances of TPM-DADK using\n2 2\ndifferent sacrificial reagents under O atmosphere. (b) Photocatalytic H O generation performance\n2 2 2\nof TPM-DADK in HCl aqueous solution under air atmosphere at different pH conditions. (c)\nPhotocatalytic H O generation of TPM-DADK under air atmosphere with or without 1.0 mg\n2 2\nPd(PPh ) . Reaction condition: 1.5 mg/mL photocatalyst, visible light (> 420 nm, 100 mW cm-2)\n3 4\n5) Figure S51 is accompanied by “The PXRD and FT-IR spectra of TPM-DADK\nremained virtually unchanged before and after photocatalysis, suggesting its excellent\nstructural stability.” The robust functional groups remain, however, the broad band at\n~1050 cm-1 appears to have changed significantly, can the authors comment on this.\nReply: We thank the reviewer for carefully examining our data and for this valuable\ncomment. We agree with the observation that the IR absorption band at ~1050 cm-1\ndecreases in intensity after photocatalysis. This variation is most likely caused by the\nremoval of surface-adsorbed species (e.g., water or residual solvent), which can interact\nwith C-O related groups and enhance absorption in this region. After the reaction and\nrecovery processes (washing and drying), these adsorbates are removed, leading to\nreduced intensity. Such C-O related bands are known to be sensitive to surface\nenvironments, rather than indicative of framework degradation. Importantly, the\ncharacteristic skeletal vibrations, including C=O (~1710 cm-1), C=N (~1650 cm-1), and\naromatic C=C (1200-1600 cm-1), remain unchanged, in agreement with the PXRD and\nSEM results that confirm the nanosheet morphology and crystal framework are well\npreserved. Therefore, the local variation at ~1050 cm-1 reflects reversible surface effects\nrather than chemical decomposition of TPM-DADK. In accordance with this\ninterpretation, we have updated the manuscript as follows:\n“The PXRD, FT-IR spectra and SEM image of TPM-DADK remained virtually\nunchanged before and after photocatalysis, suggesting its excellent structural stability.\nThe decreased intensity at ~1050 cm-1 after photocatalysis can be ascribed to the\nremoval of surface-adsorbed species (e.g., water or residual solvent) that interact with\nC-O related groups. Importantly, the characteristic skeletal vibrations (C=O, C=N, and\naromatic C=C) remain unchanged, further confirming that the TPM-DADK framework\nis well preserved and the variation at ~1050 cm-1 arises from reversible surface effects\nrather than structural degradation.”\n6) It is not always clear what the conditions the characterizations were performed in,\n(suspension, concentration, dry powder etc.) this should be clarified.\nReply: We sincerely thank the reviewer for this important suggestion. We fully agree\nwith the reviewer’s comment and apologize for the omission of such details in the initial\nsubmission. According to the reviewer’s advice, we have carefully checked and revised\nthe manuscript to provide explicit descriptions of the experimental conditions for key\ncharacterization techniques. These additions greatly improve the reproducibility and\nscientific rigor of our work. We are grateful to the reviewer for helping us improve the\nquality of the manuscript.\nResponse to Referee 6:\nI co-reviewed this manuscript with one of the reviewers who provided the listed reports.\nThis is part of the Nature Communications initiative to facilitate training in peer review\nand to provide appropriate recognition for Early Career Researchers who co-review\nmanuscripts.\nReply: We thank the reviewer for the note and greatly appreciate the contribution of\nboth reviewers in evaluating our manuscript. We value the Nature Communications\ninitiative to support Early Career Researchers in the peer-review process and are\ngrateful for the constructive feedback provided.\nResponse to Referee 2:\nThe revised manuscript robustly demonstrates a novel and intelligent materials design\nstrategy that integrates electronic structure modulation with dynamic morphological\ncontrol. The insights provided will be of great interest to the broader communities in\nphotocatalysis, materials science, and energy conversion. I recommend acceptance after\nthe incorporation of the minor points outlined below.\nReply: We sincerely thank the reviewer for the positive and encouraging evaluation of\nour revised manuscript. We are glad that the reviewer recognizes the novelty and\nsignificance of our materials design strategy and its broader relevance to the\nphotocatalysis, materials science, and energy conversion communities. We also\nappreciate the constructive minor points provided, which have helped us further refine\nthe manuscript. Detailed responses to each comment are provided below.\nLanguage and Typographical Refinements:\n1. Page 5, Line 78-79: \"...introduces well-defined conjugation breaks via sp3-\nhybridized TPM nodes, segmenting the π-conjugated backbone.\" This is clear.\nReply: We thank the reviewer for this comment. The sentence has been refined for\nclarity and precision:\n“In particular, the TPM-DADK polymer introduces well-defined interruptions in\nthe π-conjugation via sp3-hybridized TPM nodes, promoting conjugation segmentation\nand electron localization the π-conjugated backbone.”\n2. Page 17, Line 484: \"This structural design localizes photoexcited electrons at DADK\nunits, facilitating the formation of long-lived ketyl radical anions (TPM-DADKH-)\" –\nEnsure consistency in the radical notation. Sometimes it's TPM-DADKH-, other times\nDADKH-. Consider standardizing to TPM-DADK^- or TPM-DADK•⁻ for the radical\nanion and TPM-DADKH• for the protonated form for clarity, if this aligns with the\nchemical reality.\nReply: We thank the reviewer for the careful reading and for pointing out the\ninconsistent radical notation. You are correct — the species on Page 17, Line 484 should\nbe denoted as TPM-DADK•⁻ (ketyl radical anion). We have corrected it accordingly.\nFurthermore, we have standardized the radical/protonation notation throughout the\nmanuscript: TPM-DADK•⁻ for the ketyl radical anion and TPM-DADKH• for the\nprotonated radical species.\n3. Page 23, Line 524: The SCC equation is presented clearly. It would be helpful to\ndefine 'A' (area) in the variable list beneath the equation for absolute clarity.\nReply: We thank the reviewer for the helpful suggestion. We have revised the variable\nlist beneath the SCC equation to explicitly define A as the irradiated area. The revised\ntext now reads as follows:\nSolar-to-chemical conversion (SCC) efficiency measurement\nThe solar-to-chemical energy conversion (SCC) efficiency was tested in pure D.I.\nwater without any sacrificial agents and calculated by the following equation:\n∆𝐺 ×𝐻 𝑂 𝑓𝑜𝑟𝑚𝑒𝑑 (𝑚𝑜𝑙)\n2 2\n𝑆𝐶𝐶(%) = ×100% = 3.07%\n𝐼 ×𝐴×𝑡\nWhere ΔG is 117 kJ mol−1, I is the light intensity (300 W m−2), A is the irradiated\narea (3.14 × 10−4 m2), and t is the reaction time (3600 s). The total input energy was\ntherefore 0.0942 W. The average H O production of TPM-DADK over three tests was\n2 2\n88.95 μmol.\nResponse to Referee 4:\nThe authors have addressed all major criticisms with new data and more nuanced\ndiscussion. The mechanistic picture, wherein light-induced ketyl radical formation and\npartial exfoliation cooperatively enhance oxygen activation and hydrogen peroxide\nproduction, now has more backing to the statements. I have only minor suggestions left:\nReply: We sincerely thank the reviewer for the careful re-evaluation and positive\nassessment of our revised manuscript. We appreciate the insightful minor suggestions,\nwhich have helped us further clarify and refine the discussion. Our detailed responses\nare as follows:\n1. In regard to authors reply, I would suggest minor re-write (either toning down or\nclarification) to the following two points (1) discussion regarding localized radicals to\nbe more consistent. As the authors replied also interpolymer interaction and pi-pi\nstacking can lead to delocalization. Therefore I would be less absolute in the\nsegmentation claim.\nReply: We fully agree with the reviewer’s suggestion. The description regarding the\nlocalization of photogenerated radicals has been refined to better reflect the coexistence\nof localized and partially delocalized electronic states. We have revised the manuscript\naccordingly.\n“In particular, the TPM-DADK polymer introduces well-defined interruptions in\nthe π-conjugation via sp3-hybridized TPM nodes, promoting conjugation segmentation\nand electron localization the π-conjugated backbone.”\n“This behavior arises from its architecture with periodic conjugation breaks,\nintroduced by the sp3-hybridized TPM nodes. Such a design promotes the localization\nof photogenerated electrons at carbonyl sites, while allowing for some degree of\ndelocalization via interchain or π-π interactions. The localized electrons form ketyl\nradical anions that accumulate negative charges, generating electrostatic repulsion.”\n2. The role of ketyl radical and accumulation. Now it seems more clear that ketyl\nradicals readily interact with oxygen and cannot be accumulated. Irradiation under Ar,\nunderstandably, presents a different picture, where these radical can be accumulated\nand react when exposed to O2, to produce H2O2.\nReply: We thank the reviewer for this insightful comment. Regarding the accumulation\nof ketyl radicals, we have clarified their transient nature and the influence of the\nreaction atmosphere as follows.\n“Under O atmosphere, these photoinduced ketyl radicals rapidly transfer\n2\nelectrons to adsorbed oxygen, whereas under Ar, they accumulate and subsequently\ngenerate H O upon O exposure. These results underscore the critical role of long-\n2 2 2\nlived ketyl intermediates in H O formation.”\n2 2\n3. The response to reviewer 2 about H2 and H2O2 brings out actually an interesting\npoint. It seems that the authors here observe that localized excitation are important for\nH2O2 production, while charge-transfer reactions are important for H2 production. It\ncould be interesting to contextualise with similar observations in organic\nsemiconductors (eg. Nature Nanotechnology 2023, 18, 307–315 and Adv. Funct. Mater.\n2025, 2505835)\nReply: We sincerely appreciate this insightful suggestion, which allows us to situate\nour observations within the broader context of exciton dynamics in organic and polymer\nphotocatalysts. Indeed, our results indicate that localized excitations at DADK sites\nfavor selective O reduction to H O , whereas extended charge-transfer excitations\n2 2 2\nacross the donor-acceptor interface promote H evolution. This distinction aligns well\n2\nwith recent studies on organic semiconductors (Nature Nanotechnology 2023, 18, 307-\n315; Adv. Funct. Mater. 2025, 2505835), which similarly highlight the decisive role of\nexciton localization and charge-transfer pathways in determining photocatalytic\nselectivity. We have accordingly added the following contextual discussion to the\nrevised manuscript:\n“It is noteworthy that the localized photoexcitation at TPM-DADK units favors\nselective O reduction to H O , whereas extended charge-transfer excitations across\n2 2 2\ndonor-acceptor interfaces in Flu-DADK and Py-DADK are generally more conducive\nto H evolution (Supplementary Fig. 59-60). This mechanistic divergence between\n2\nlocalized excitations and charge-transfer states is consistent with recent studies on\norganic semiconductor photocatalysts, where exciton localization has been shown to\nenhance selective two-electron oxygen reduction, while delocalized charge-transfer\nstates facilitate proton reduction to H .[48,49]”\n[48] Yang, H. et al. Packing-induced selectivity switching in molecular nanoparticle\nphotocatalysts for hydrogen and hydrogen peroxide production. Nat. Nanotechnol. 18,\n307-315 (2023).\n[49] Barbieri, M. et al. Controlled aggregation of pyrene-based supramolecular\nnanostructures for light-driven switchable H or H O production. Adv. Funct. Mater.\n2 2 2\n2505835 (2025)."}, {"round": 2, "reviewer_comments": {"reviewer_1": "Authors have addressed all the concerns. This manuscript is recommended for publication.", "reviewer_2": "The revised manuscript robustly demonstrates a novel and intelligent materials design strategy that integrates electronic structure modulation with dynamic morphological control. The insights provided will be of great interest to the broader communities in photocatalysis, materials science, and energy conversion. I recommend acceptance after the incorporation of the minor points outlined below.\nLanguage and Typographical Refinements:\nPage 5, Line 78-79: \"...introduces well-defined conjugation breaks via sp3-hybridized TPM nodes, segmenting the π-conjugated backbone.\" This is clear.\nPage 17, Line 484: \"This structural design localizes photoexcited electrons at DADK units, facilitating the formation of long-lived ketyl radical anions (TPM-DADKH-)\" – Ensure consistency in the radical notation. Sometimes it's TPM-DADKH-, other times DADKH-. Consider standardizing to TPM-DADK^- or TPM-DADK•⁻ for the radical anion and TPM-DADKH• for the protonated form for clarity, if this aligns with the chemical reality.\nPage 23, Line 524: The SCC equation is presented clearly. It would be helpful to define 'A' (area) in the variable list beneath the equation for absolute clarity.", "reviewer_3": "I recommend that this manuscript be accepted without any revisions.", "reviewer_4": "The authors have addressed all major criticisms with new data and more nuanced discussion. The mechanistic picture, wherein light-induced ketyl radical formation and partial exfoliation cooperatively enhance oxygen activation and hydrogen peroxide production, now has more backing to the statements. I have only minor suggestions left:\n- In regard to authors reply, I would suggest minor re-write (either toning down or clarification) to the following two points (1) discussion regarding localized radicals to be more consistent. As the authors replied also interpolymer interaction and pi-pi stacking can lead to delocalization. Therefore I would be less absolute in the segmentation claim. (2) The role of ketyl radical and accumulation. Now it seems more clear that ketyl radicals readily interact with oxygen and cannot be accumulated. Irradiation under Ar, understandably, presents a different picture, where these radical can be accumulated and react when exposed to O2, to produce H2O2.\n- the response to reviewer 2 about H2 and H2O2 brings out actually an interesting point. It seems that the authors here observe that localized excitation are important for H2O2 production, while charge-transfer reactions are important for H2 production. It could be interesting to contextualise with similar observations in organic semiconductors (eg. Nature Nanotechnology 2023, 18, 307–315 and Adv. Funct. Mater. 2025, 2505835)", "reviewer_5": "Thank you for addressing the comments so robustly, all of my comments were addressed and the manuscript is improved significantly upon revision.", "reviewer_6": "I co-reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co-review manuscripts."}, "author_response": ""}, {"round": 3, "reviewer_comments": {"reviewer_2": "I would recommend that this manuscript can be accepted without any further revisions.", "reviewer_4": "The authors have revised the manuscript in a satisfactory manner according the the suggestion. Thank you.", "reviewer_6": "I co-reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co-review manuscripts."}, "author_response": ""}]

Decision letter