Formation of charge-polarized regions at dual single-atom sites for C-H bond activation in methane

Domain: chemistry
Published: 2026-02-21
Editorial outcome: major_revision

Abstract
Direct conversion of CH4 into liquid oxygenates under mild conditions is of great significance but remains challenging due to the high dissociation energy of inert C-H bond. Here we report the fabrication of a dual atomic Fe and Pd catalyst with periodic macroporous structure (Fe-Pd1-Pd1 OMNC) toward the direct CH4 conversion at room temperature. Mechanism studies reveal that a charge polarization region (Oδ−-Fe-Pdδ+) is formed in-situ on Fe-Pd atomic sites upon oxidant activation, wherein the electron-rich Oδ− and electron-deficient Pdδ+ regions can respectively capture the Hδ+ and CH3δ− in CH4 and lead to the activation of C-H bond. As a result, Fe-Pd1-Pd1 OMNC demonstrates attractive photothermal catalytic performance toward the selective oxidation of CH4 under Xe lamp irradiation, achieving the productivities of C1 oxygenates as high as 0.754 mmol h−1 and 0.035 mmol h−1 when using H2O2 or O2 as the oxidant, respectively.

Introduction
Methane (CH4), the primary constituent of natural gas, is one of the most promising C1 building blocks for the synthesis of high-value fuels and chemicals due to its high reserves and relatively low price1,2. Conventionally, the conversion of CH4 to value-added products mainly involves the strongly endothermic steam reforming (CH4 + H2O → 3H2 + CO, ΔH = +206 kJ mol−1) and the subsequent Fischer-Tropsch synthesis or methanol (CH3OH) synthesis process3,4. However, a high temperature (700–1000 °C) is required to destroy the non-polar tetrahedral structure of CH4 with very high dissociation energy of C–H bond (439.3 kJ mol−1). This high energy input will inevitably lead to the formation of more thermodynamically stable over-oxidation products (i.e., CO2) and coke5. In this case, direct conversion of CH4 into liquid oxygenates at low temperatures should be a promising way to substitute the energy-intensive protocols, which, however, remains an enormous challenge.

In nature, methane monooxygenase (MMO) and cytochrome P450 containing single- or dual-metal centers can directly transform CH4 to oxygenates under mild conditions6,7. Inspired by the natural enzyme catalysis, bioinspired heterogeneous catalysts with isolated metal sites have been developed in recent years, which have demonstrated attractive activity toward CH4 conversion at low temperatures (<100 °C) with the assistance of oxidants (e.g., H2O2, O2). Among these biomimetic active sites, d-block element-isolated centers have drawn enormous attention due to the easy orbital hybridization between their inherent d-orbitals (dz2, dxz and dyz orbitals) and the p/s orbitals of CH4 8–12.

Engineering active centers with a high affinity and bond cleavage capability toward the first C–H bond in CH4 is a promising avenue to obtain a high yield of value-added products. Accordingly, the covalent C–H (four covalent bonds) is composed of 74% ground state and 26% ionic resonance structures13,14. During the CH4 activation process, electrons can migrate between the d orbital of catalyst and the σ orbital of a C–H bond, leading to the cleavage of C–H bond. Alternatively, C–H bond can also be activated in the form of electrostatic CH3δ−-Hδ+ polarization by a localized electrostatic field on catalyst surface5,15,16. For example, Zheng et al. found that the transfer of electrons from ZnO to Fe2O3 can induce the charge accumulation on Fe sites, thus reducing the CH4 adsorption energy and facilitating the activation of C–H bond17. In this regard, the activation of C–H bonds in CH4 is highly sensitive to the electronic status of metal centers. Enlightened by these premises, we envisage that a precise design of the electronic configuration of the catalyst surface would provide opportunities in manipulating the cleavage behavior toward C–H bonds to boost the selective conversion of CH4 under mild conditions.

Here, we address the challenge of C–H bond activation in CH4 by introducing a strategy based on the in-situ construction of charge-polarized regions on asymmetric diatomic active sites via oxidant modification. As a proof of concept, we design and fabricate atomically dispersed Fe and Pd on ordered macroporous nitrogen-doped carbon (denoted as Fe-Pd1-Pd1 OMNC) using an encapsulation-pyrolysis strategy. Fe-Pd1-Pd1 OMNC exhibits high photothermal catalytic performance toward the selective oxidation of CH4 when using H2O2 or O2 as the oxidant. Ab-initio molecular dynamics (AIMD) simulations and in-depth in-situ investigations manifest that the oxidant prefers to be activated on Fe site to an axial *O during the photothermal catalytic process, forming a charge polarization region on Oδ−-Fe-Pdδ+. Within this region, the electron-rich Oδ− region captures Hδ+ in CH4, initiating electron transfer that leads to C–H bond cleavage. The electron-deficient Pdδ+ sites stabilize the resulting CH3 species, achieving the complete activation of the CH4 molecule.

Results
Synthesis and characterization of Fe1-Pd1 OMNC
The synthetic route of Fe-Pd1-Pd1 OMNC is briefly illustrated in Fig. 1a. In brief, the ordered polystyrene spheres (PS) arrays were first prepared by assembling the monodisperse PS (270 nm in diameter) (Supplementary Fig. 1)18. Subsequently, ZIF-8 precursors (i.e., Zn2+ and 2-methylimidazole), Fe3+ and Pd(acac)2 were filled in the PS arrays to form the precursors@PS, which was then immersed in a mixture of CH3OH/NH3·H2O to induce the growth of ZIF-8 single crystals within the template (denoted as FePd-ZIF@PS) (Supplementary Fig. 2). The FePd-ZIF@PS was subjected to pyrolysis in Ar atmosphere to carbonize the ZIF and simultaneously remove the PS template (decomposition temperature of ca. 400 °C) and Zn species (vaporization temperature of ca. 900 °C), leaving Fe and Pd sites embedded in the ordered macroporous N-doped carbon matrix19,20.

No diffraction peaks attributed to ZIF-8 are observed in the powder X-ray diffraction (XRD) pattern of Fe-Pd1-Pd1 OMNC (Supplementary Fig. 3). In addition, the Raman spectrum of Fe-Pd1-Pd1 OMNC exhibits the distinct D band (ca. 1350 cm−1) and G band (ca. 1590 cm−1) of graphitized carbon, reflecting the complete carbonization of ZIF (Supplementary Fig. 4). Notably, the ID/IG ratio of Fe-Pd1-Pd1 OMNC is slightly greater than that of OMNC, suggesting that the introduction of metal species can induce the formation of defects in the carbon skeleton (Supplementary Table 1). The scanning electron microscopy (SEM) image unveils the monodispersed tetrakaidekahedral particles of Fe-Pd1-Pd1 OMNC with eight (111) facets and six (100) facets (Fig. 1b–d). The transmission electron microscopy (TEM) and the high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) images reveal the oriented arrangement of 3D-ordered macropores interconnected by the mesoporous channels in Fe-Pd1-Pd1 OMNC (Fig. 1e and Supplementary Fig. 5). The hierarchically porous structure of Fe-Pd1-Pd1 OMNC was further confirmed by the N2 sorption isotherm, which shows a steep increase at relatively low pressures (P/P0 < 0.05) and an obvious hysteresis loop (Fig. 1f). For comparison, isolated Fe and Pd sites embedded in the carriers of mesoporous N-doped carbon matrix (Fe-Pd1-Pd1 MeNC) and disordered macroporous N-doped carbon matrix (Fe-Pd1-Pd1 DOMNC) were designed and prepared in the absence of PS or using the discrete PS as the template, respectively (Supplementary Figs. 6, 7). Significantly, the Brunauer-Emmett-Teller (BET) surface area of Fe-Pd1-Pd1 OMNC (670.18 m2/g) is larger than that of Fe-Pd1-Pd1 MeNC (232.08 m2/g) and Fe-Pd1-Pd1 DOMNC (269.26 m2/g), confirming the virtue of ordered hierarchically porous structure (Supplementary Fig. 8). Considering that CH4 conversion reaction occurs on the surface of catalyst, such periodic porous structure and large BET surface area of Fe-Pd1-Pd1 OMNC should be conducive to improving the accessibility of active sites.

Energy-dispersive X-ray (EDX) elemental mapping images reveal the homogeneous dispersions of Fe and Pd elements over the ordered macroporous framework (Fig. 1g, h). No obvious nanoparticles are observed in the high-resolution TEM (HRTEM) image of Fe1-Pd1 OMNC (Supplementary Fig. 9). Additionally, no characteristic reflections indexed to Fe or Pd metallic phases are detected by XRD, ruling out the presence of large-sized metal species (Supplementary Fig. 3). Aberration-corrected high angle annular dark-field scanning transmission electron microscopy (AC-HAADF-STEM) image clearly reveals the atomic dispersion of Fe and Pd on the NC skeleton, in which the distance of the atomic pairs is estimated to be ca. 0.35 nm (Fig. 1i, j). The contents of Fe and Pd in Fe-Pd1-Pd1 OMNC are measured to be 0.58 and 0.35 wt%, respectively by the inductively coupled plasma atomic emission spectroscopy (Supplementary Table 2).

To clarify the coordination environments of Fe and Pd sites in Fe-Pd1-Pd1 OMNC, X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) analysis were performed. As shown in Fig. 2a, b, the near-edge absorption energy positions of Fe K-edge and Pd K-edge are located between those of Fe foil and Fe2O3 and those of Pd foil and PdO, respectively, suggesting that both Fe and Pd centers are in oxidized states. The positively charged centers of Fe and Pd can also be discerned by X-ray photoelectron spectroscopy (XPS) (Supplementary Fig. 10). The Fe K-edge EXAFS spectrum of Fe-Pd1-Pd1 OMNC exhibits a main peak located at 1.51 Å that is similar to that of FePc, corresponding to the Fe-N scattering path. No Fe-Fe scattering peaks of Fe foil (i.e., 2.17 Å), Fe2O3 (i.e., 2.67 Å) or Fe3O4 (i.e., 2.58 Å) are detected (Fig. 2c and Supplementary Fig. 11a). In addition, the k3χ(k) oscillation curve of Fe-Pd1-Pd1 OMNC differs from that of Fe foil and Fe2O3, ruling out the presence of metallic Fe or Fe oxide nanoparticles (Supplementary Fig. 11b). In the case of the Pd K-edge FT-EXAFS, a dominant peak at 1.5 Å is observed, corresponding to the Pd-N scattering path21. No Pd-Pd scattering peaks of Pd foil (i.e., 2.50 Å) or PdO (i.e., 2.93 Å) are detected (Fig. 2d). The metal-N paths in Fe-Pd1-Pd1 OMNC were also confirmed by the wavelet transform (WT)-EXAFS. As shown in Fig. 2g and supplementary Fig. 12, the WT contour plots of Fe K-edge and Pd K-edge display the intensity maxima at ca. 4 and 6 Å−1, corresponding to the Fe-N and Pd-N scatterings, respectively. Moreover, no Fe-Pd signal is observed in the FT-EXAFS and WT-EXAFS spectra, ruling out the presence of Fe-Pd coordination in Fe-Pd1-Pd1 OMNC. According to the well-matched EXAFS fitting, the coordination numbers of Fe-N and Pd-N in Fe-Pd1-Pd1 OMNC are calculated to be ca. 4 and 3, respectively. Thus, a probable neighboring Fe-N4C and Pd-N3C structure is proposed (Supplementary Fig. 13 and Supplementary Tables 3, 4).

Accordingly, we thermodynamically and kinetically predicted four possible structures of Fe-Pd-NxCy namely Fe-Pd-N6C1, Fe-Pd-N7C1-I, Fe-Pd-N7C1-II and Fe-Pd-N6C1-III in order to accurately characterize the Fe-Pd coordination (Supplementary Fig. 14). Among these structures, Fe-Pd-N6C1 exhibits a simulated Fe-Pd distance of 3.5 Å, which is very close to the experimental result (Fig. 1j). In addition, density functional theory (DFT) calculation results show that the Fe-Pd-N6C1 model is the most thermodynamically favorable structure due to its lowest system energy. Ab-initio molecular dynamics (AIMD) simulations were then performed for a duration of 10 ps to verify the structural feasibility of Fe-Pd-N6C1 model22,23. As shown in Fig. 2e, Supplementary Movie 1 and Supplementary Data 1, the energy of the proposed structure fluctuates within a constant range during the AIMD simulation even at a high temperature of 875 K. In addition, the radial distribution function (RDF) results reveal that the Fe and Pd atoms are directly bonded to the surrounded N atoms with the average metal-N bond lengths of 1.93 and 2.05 Å, which can be well maintained in the AIMD process, reflecting its structural stability (Fig. 2f and Supplementary Fig. 15). Indeed, DFT theoretical calculations indicate that the Fe-Pd-N6C1 model is more favorable for the activation of C–H bond in methane compared to other Fe-Pd models or dual Fe and Pd sites. Therefore, the subsequent calculation of the CH4 oxidation reaction pathway is based on the Fe-Pd-N6C1 structure.

Photocatalytic performance of Fe1-Pd1 OMNC
The selective oxidation of CH4 was performed in an autoclave under the irradiation of Xenon arc lamp using H2O2 as oxidant without external heat (Supplementary Fig. 16). All the possible liquid (e.g., alcohols, hydroperoxide, and organic acids) and gas products (e.g., CO, C2H4, C2H6 and CO2) were quantitatively analyzed by 1H nuclear magnetic resonance (1H NMR), gas chromatography (GC) and ultraviolet-visible spectrophotometer (Supplementary Figs. 17–19). As shown in Supplementary Figs. 20, 21, C1 oxygenates including HCOOH, CH3OH and CH3OOH are detected as the main products, apart from the trace amount of overoxidized products. Notably, the as-prepared Fe-Pd1-Pd1 OMNC exhibit high catalytic performance toward the selective oxidation of CH4, delivering a total C1 oxygenates evolution rate as high as 0.754 mmol h−1 with a selectivity of 100%. The turnover frequency (TOF) is calculated to be 1106.4 h−1, corresponding to 16.2 mol gmetal−1 h−1. The apparent quantum yield (AQY) at 450 nm is estimated to be 3.34%. Notably, the yield of oxygenates achieved in this work is competitive with prior studies (Supplementary Table 5).

For comparison, three control samples namely Fe1 OMNC, Pd1 OMNC and OMNC were synthesized (Supplementary Figs. 22–24). As shown in Fig. 3a and Supplementary Fig. 25, Fe-Pd1-Pd1 OMNC reveals a higher evolution rate of total oxygenates than Fe1 OMNC (0.455 mmol h−1), Pd1 OMNC (0.330 mmol h−1) and OMNC (0.138 mmol h−1). Notably, the yield of C1 oxygenates over the physical mixture of Fe1 OMNC and Pd1 OMNC (0.552 mmol h−1) is significantly lower than that over Fe-Pd1-Pd1 OMNC (0.754 mmol h−1) (Supplementary Fig. 26), suggesting that the enhanced catalytic activity of the bimetallic system originates from the synergistic effect between the adjacent Fe and Pd dual-atom sites. In addition, OMNC without metal species displays lower oxygenates evolution rate compared with the atomic metal samples, suggesting that metal species may be the active sites for CH4 conversion and Fe-Pd synergy plays an indispensable role in improving the catalytic activity. Notably, both Fe-Pd1-Pd1 DOMNC with disordered macropores and Fe-Pd1-Pd1 MeNC without macropores show poor catalytic activities with the C1 oxygenates evolution rates of 0.444 and 0.325 mmol h−1, respectively, pointing out the virtue of ordered macroporous structure in realizing the full catalytic potentials of Fe-Pd atomic catalyst (Fig. 3b). The sequential cycling test demonstrates that the catalytic performance of Fe-Pd1-Pd1 OMNC can be maintained at a high level with a C1 oxygenated products yield of 0.743 mmol h−1 after eight consecutive cycles (Fig. 3c). Moreover, the SEM, HAADF-STEM, EDX mapping images, XRD pattern and XPS spectra indicate that the morphology and structure of Fe-Pd1-Pd1 OMNC remain intact after the catalytic reactions, highlighting its good stability (Supplementary Fig. 27).

Control experiments reveal that the partial pressure of CH4 is conductive to the catalytic performance toward CH4 conversion (Supplementary Fig. 28). In addition, CH4 conversion is terminated in the absence of Fe-Pd1-Pd1 OMNC or H2O2, reflecting the essential roles of catalyst and oxidant in CH4 oxidation (Fig. 3d, columns 1–2). The effect of the amounts of H2O2 and catalysts on the catalytic activity was then explored. As shown in Supplementary Fig. 29, increasing the H2O2 content promotes the formation of oxygenated products. However, excessive H2O2 results in decreased oxygenate yields, which may be ascribed to the overoxidation of liquid products24. Moreover, the yields of C1 oxygenated products significantly increase as the dosage of Fe-Pd1-Pd1 OMNC changes from 1 to 5 mg. Nevertheless, further increments in catalyst dosage will attenuate the rate of performance enhancement (Supplementary Fig. 30).

No detectable oxygenates are observed when replacing CH4 feedstock gas with Ar, indicating that the oxygenated products are originated from the oxidation of CH4 (Fig. 3d, column 3). The carbon balance of the present photothermal catalytic system is higher than 97%, suggesting that the C1 oxygenated products came from the transformation of CH4 (Supplementary Fig. 31). To confirm the source of the product, we further conducted the 13C isotope labeling experiment using 13CH4 as the feedstock. As shown in Fig. 3e, the 13C NMR spectra reveal that the featured peaks match well with the 13C-labeled formic acid (H13COOH), methyl hydroperoxide (13CH3OOH), and methanol (13CH3OH), indicating that the C1 oxygenated products came from the oxidation of 13CH4 rather than from the catalyst itself.

The reaction in the absence of Xe lamp irradiation gave unsatisfactory oxygenate yield of 0.030 mmol h−1, suggesting the essential role of light irradiation (Fig. 3d, column 5). In contrast, the generation rate of C1 oxygenated products increases gradually with an increase in the light intensity (Supplementary Fig. 32). Interestingly, further increasing the light intensity leads to an increase in the selectivity of CH3OH and a decrease in CH3OOH yield, indicating that intense light irradiation may promote the conversion process of CH3OOH to CH3OH25,26.

We thus investigated the optical properties of the catalysts by diffuse reflection spectrometer. As shown in Supplementary Fig. 33, Fe-Pd1-Pd1 OMNC exhibits intensive light absorption across the UV-Vis-IR region. In addition, the infrared thermal images demonstrate that the temperature of the surface of Fe-Pd1-Pd1 OMNC immediately raises from room temperature to 195.9 °C upon the irradiation of Xe light, implying its good photothermal conversion property (insert of Supplementary Fig. 33). We thus monitored the temperature variation of the homogeneous reaction solution during the catalytic process (Supplementary Figs. 34, 35). The results show that the temperature of the reaction solution in the presence of Fe-Pd1-Pd1 OMNC rapidly increases from room temperature to a maximum temperature of 62.8 °C following the irradiation of Xe lamp, which is significantly higher than that without catalyst (48.2 °C).

To further identify the role of light irradiation, the oxidation of CH4 was performed under the photocatalytic (with 25 °C circulating water) and thermal catalytic conditions (only electric heating). Interestingly, both the solely photocatalytic and thermal catalytic systems display lower oxygenated products yields of 0.286 and 0.233 mmol h−1, respectively compared with the photothermal catalytic system (Fig. 3d, columns 6–7). We further performed the thermal catalytic CH4 oxidation experiments at different temperatures under dark condition. As shown in Supplementary Fig. 36, the generation rate of C1 oxygenates increases gradually from 0.030 to 0.233 mmol h−1 when increasing the temperature from 25 to 63 °C. However, kinetic analysis demonstrates that the apparent activation energy for CH4 oxidation under photothermal condition (27.73 KJ mol−1) is significantly lower than that under purely thermal condition (48.84 KJ mol−1) (Fig. 3f). These results indicate that the oxidation of CH4 is facilitated by photothermal synergy, rather than by simple light-induced thermal catalysis alone.

To further distinguish between purely thermal and photo-assisted thermal process, we measured the reaction rate at a constant temperature (i.e., 63 °C) while varying the light intensity. As shown in Fig. 3g and Supplementary Fig. 37, the yield of C1 oxygenates in Fe‑Pd1-Pd1 OMNC system increases significantly from 0.416 to 0.798 mmol h−1 as the light intensity increases from 100 to 600 mW cm−2, while the temperature is maintained at 63 °C by external heating. Combined with the results of a series of controlled experiments (Fig. 3f, g, Supplementary Figs. 35–40 and Supplementary Table 7), it can be fully demonstrated that light primarily generates photoexcited electrons and directly participates in the catalytic steps, while the photo-driven heat accelerates the overall reaction kinetics.

In fact, the catalytic performance of Fe‑Pd1-Pd1 OMNC photothermal system decreases by 50.36% after adding an electron scavenger (i.e., AgNO3) (Supplementary Fig. 39a)27. In addition, an obvious photocurrent signal is observed in Fe-Pd1-Pd1 OMNC upon light irradiation, confirming the generation of excited electrons. Significantly, the photocurrent increases while the electron transfer resistance of Fe‑Pd1-Pd1 OMNC decreases as the solution temperature rises from 25 to 63 °C (Supplementary Figs. 39b, c, 40 and Supplementary Table 7). These results unambiguously demonstrate that photo-induced heat in Fe‑Pd1-Pd1 OMNC plays an indispensable role in promoting the generation and lowering the migration resistance of photoexcited electrons. In addition, Fe-Pd1-Pd1 OMNC exhibits a higher current density and smaller semicircle diameter in electrochemical impedance spectroscopy than OMNC, suggesting that the presence of dual Fe-Pd metals sites can promote the formation of photo-induced electron (Supplementary Figs. 41, 42).

In-situ irradiated XPS was then carried out to explore the charge transfer within Fe-Pd1-Pd1 OMNC. As shown in Supplementary Fig. 43, both the high-resolution Fe 2p and Pd 3d XPS spectra display the distinct positive shifts upon light irradiation, while the N 1s spectrum exhibits a negative shift. Such shifts in binding energy under light irradiation confirm the migration of photo-induced electrons between N and metal sites. The above results unambiguously reveal that heat and photo-induced electrons generated by Fe-Pd1-Pd1 OMNC under light irradiation would jointly participate in the oxidation of CH4, instead of undergoing a simple photo-derived thermal catalysis (Supplementary Fig. 44). On the one hand, the formed photoexcited charge carriers and thermal energy are able to directly participate the activation of CH4. On the other hand, the photo-induced heat can also promote the generation and migration dynamics of photoexcited charge carriers, thereby enhancing the efficiency of electron-involved activation process.

We also conducted the photothermal catalytic CH4 oxidation over Fe-Pd1-Pd1 OMNC by using both O2 and H2O2 as the oxidants. As shown in Fig. 3h, the introduction of O2 significantly increased the total C1 oxygenates evolution rate from 0.754 to 1.480 mmol h−1. Considering the high cost and safety issues of hydrogen peroxide during the catalytic process, we subsequently employed sole O2 as the oxidant for the selective oxidation of CH4. Satisfyingly, the as-prepared Fe-Pd1-Pd1 OMNC demonstrates high catalytic performance in the selective oxidation of CH4 with a methanol production rate of 0.035 mmol h−1 (Supplementary Fig. 45). Further, we pre-treated the Fe-Pd1-Pd1 OMNC with H2O2 at room temperature (denoted as O/Fe-Pd1-Pd1 OMNC) and performed the photothermal catalytic CH4 oxidation under O2 to avoid the formation of deep-oxidized product (i.e., HCOOH)28. Unexpectedly, the as-prepared O/Fe-Pd1-Pd1 OMNC exhibit high total C1 oxygenates evolution rate of 0.996 mmol h−1 with a methanol yield of 0.787 mmol h−1, highlighting the structural virtue of Fe-Pd1-Pd1 OMNC in CH4 oxidation (Fig. 3i). Notably, the oxygenate yield in this work demonstrates competitiveness compared to previously reported CH4 conversion catalysts under comparable conditions (Supplementary Table 6).

To gain insights into the catalytic mechanism of CH4 conversion, in-situ electron paramagnetic resonance (EPR) spectra with the spin-electron trap (i.e., 5,5-dimethyl-1-pyrroline N-oxide, DMPO) were conducted to monitor the formed free radicals29,30. As shown in Supplementary Fig. 46, DMPO-OOH and DMPO-OH were detected in the presence of Fe-Pd1-Pd1 OMNC under irradiation, suggesting that •OOH and •OH radicals were formed during the photothermal catalytic process. Notably, a new sextet signal emerges after the introduction of CH4 in the reaction solution (Fig. 4a), which could be assigned to the •CH3 radical31. These results manifest that the •OOH and •OH radicals generated from H2O2 decomposition are able to attack CH4 to form the •CH3 radical under the irradiation of Xe lamp.

In-situ diffuse Fourier-transform infrared spectroscopy (FTIR) was employed to probe the reaction intermediates on Fe-Pd1-Pd1 OMNC during the photothermal CH4 conversion process. As shown in Fig. 4b, c, two peaks appear at 881 and 1643 cm−1 as the reaction proceeds, corresponding to the *OOH and *OH species, respectively32. Additional peak responsible for methyl (*CH3) emerges at 1354, 1455 and 1410 cm−1, reflecting the activation of C–H bond in CH4 to give rise of *CH3 on Fe-Pd1-Pd1 OMNC33,34. It is noted that two adsorption bands belonged to *O=COOH and *CH3O appear at 1340 and 2820 cm−1, suggesting the formation of HCOOH and CH3OH in the reaction system35. Accordingly, a possible pathway for the photothermal conversion of CH4 over Fe-Pd1-Pd1 OMNC is deduced as follow: *CH4 → *CH3 → *CH3OH/*CH3OOH/*HCOOH.

Density functional theory (DFT) calculations were intervened to explore the catalytic mechanism for the selective oxidation of CH4 on Fe-Pd1-Pd1 OMNC. Three calculation models, i.e., Fe single-atom site (Fe-N4C3), Pd single-atom site (Pd-N4C3), and Fe-Pd dual-single-atomic sites (Fe-Pd-N6C1), were constructed based on the results of EXAFS (Supplementary Figs. 14, 47, Supplementary Data 1). We studied the dissociation behavior of H2O2 on catalyst surface. It is observed in Supplementary Fig. 48 that H2O2 can be readily adsorbed on the metal atomic sites and activated into •OH or •OOH species. Significantly, H2O2 prefers to be activated on the Fe site in Fe-Pd-N6C1 with a lower energy barrier compared with that on Fe-N4C3 and Pd-N4C3, signifying the synergistic effect of Fe-Pd diatomic sites on H2O2 activation. Interestingly, we found that the activation of O2 molecule on Fe-Pd diatomic center is consistent with the activation process of H2O2. As observed in Supplementary Fig. 49, O2 can be easily captured by the Fe site in Fe-Pd-N6C1 and activated into *OOH with a gibbs free energy difference of as small as 0.48 eV. Subsequently, the formed *OOH can be further activated into *O species to formed the O-Fe-Pd structure.

AIMD simulations were then conducted to gain insight into the activation behavior of H2O2 on Fe-Pd-N6C1. Interestingly, the results of AIMD simulations demonstrate that the active O species can be formed on the Fe site in Fe-Pd-N6C1 via a hydrogen transfer process between two OH* groups during the H2O2 activation process (Supplementary Fig. 50, Supplementary Movie 2 and Supplementary Data 1). The formed in-situ axially coordinated O species on Fe site is able to stabilize the Fe-Pd-N6C1 structure with a total energy decrease of 2.50 eV, which is well in line with previous works (Supplementary Fig. 51)36,37. Actually, the formation of O species on Fe-Pd1-Pd1 OMNC has been confirmed by XPS spectra, which show that the proportion of Fe–O bond (529.5 eV) in O 1s increases significantly after the treatment of H2O2 (Supplementary Fig. 52).

Subsequently, we proposed the plausible reaction pathways of CH4 conversion to C1 oxygenates on Fe-Pd1-Pd1 OMNC and further gained in-depth insight into these steps via DFT calculations, in which Fe-Pd-N6C1 structure was selected as the models of Fe-Pd1-Pd1 OMNC (Supplementary Fig. 53a). As shown in the energy profile diagrams (Fig. 4d and Supplementary Figs. 53, 54), the dissociation of C–H bond on Fe-Pd-N6C1 is endothermic (ΔG = 1.44 eV), suggesting the C–H bond activation process should be the rate-limiting step in CH4 conversion. The generated methyl species after the activation of C–H bond can combine with •OH and •OOH easily to form the CH3OH, CH3OOH, and HCOOH products as these steps are exothermic. It is clear that the activation energy required for C–H bond dissociation on the pristine Fe-Pd-N6C1 is calculated to be 2.72 eV (Supplementary Fig. 55a). In contrast, the activation energy barrier significantly decreases to 1.82 eV upon the implantation of axially coordinated O species on Fe site, pointing out the essential role of O species in CH4 activation (Fig. 4e and Supplementary Fig. 55b). In addition, a higher energy barrier of 2.23 eV is required to activate the C–H bond on the single atom Fe site (i.e., Fe-N4C3) in the absence of Pd (Fig. 4e and Supplementary Fig. 55c). These results demonstrate that the co-existing dual atomic sites and O species, namely O-Fe-Pd structure is beneficial for the activation of CH4.

To delve into the roles of O-Fe-Pd structure on C–H bond activation, we conducted AIMD simulations to investigate the dynamic adsorption and activation process of CH4. In the case of the pristine Fe-Pd-N6C1, CH4 molecule tends to approach and circle around the Fe site via a weak physical interaction (Supplementary Movie 3 and Supplementary Fig. 56a). During the AIMD simulations, the bond-length of C–H in CH4 molecule keeps stable at ca. 0.13 Å and only 0.003 e− of electron transformation between CH4 and pristine Fe-Pd-N6C1 is observed, revealing its non-activated state (Supplementary Fig. 56b, c and Supplementary Table 8). By contrary, when CH4 approaches the O-Fe-Pd sites formed by O coordination, the H atom in CH4 can be captured by the axial O atom to form a Fe-OH ensemble and the residual CH3 group is stabilized by the Pd site (Fig. 4f, g and Supplementary Movie 4). During the activation process, one of the C–H bond lengths in CH4 molecule dynamically elongates from 0.98 Å to 3.02 Å, suggesting the complete activation of CH4 molecule (Supplementary Fig. 57).

Notably, the C–H activation behavior on O assisted single atomic Fe-N4C3 (i.e., O-Fe site) is similar to that on O-Fe-Pd site except that the residual CH3 group tends to be captured by Fe site (Fig. 4e and Supplementary Fig. 55c). In this case, the *H atom and *CH3 on O-Fe site will inevitably undergo a recombination process due to their close distance. Such a reverse activation is also observed by the climbing image nudged elastic band (CI-NEB) calculation, which reveals that the reaction barrier for the recombination of *CH3 and *H on O-Fe site (2.09 eV) is significantly lower than that on O-Fe-Pd site (2.23 eV) and even the CH4 activation on O-Fe site (2.23 eV) (Supplementary Fig. 58). The aforementioned results unambiguously confirm the virtue of the as-formed O-Fe-Pd structure in CH4 activation.

To further confirm the activation process of CH4 on Fe-Pd1-Pd1 OMNC, time-resolved FTIR spectra over Fe1 OMNC and Pd1 OMNC were performed (Fig. 4h and Supplementary Fig. 59). The results show that the intensity of the *CH3 signals on Pd1 OMNC is significantly higher than that on Fe1 OMNC (Fig. 4i). Additionally, the FTIR band of *CH3 on Pd1 OMNC exhibits a blue shift from 1417 to 1435 cm−1 compared with that on Fe1 OMNC (Supplementary Table 9). The intense signals of *CH3 and the blue shift of the FTIR bands indicate a stronger interaction of Pd-CH3 than Fe-CH338. Additionally, the FTIR bands of *CH3 on Fe-Pd1-Pd1 OMNC are closer to that on Pd1 OMNC but farther away from that on Fe1 OMNC, suggesting that the generated *CH3 intermediate during the CH4 activation process is more readily captured by Pd sites.

We then performed CH4-temperature programmed desorption (CH4-TPD) measurements to further understand the chemical adsorption behavior of CH4. As shown in Fig. 4j and Supplementary Fig. 60, Fe-Pd1-Pd1 OMNC exhibits a larger desorption quantity and higher desorption temperature (256 °C) of CH4 compared with that of single atom catalysts (i.e., Fe1 OMNC and Pd1 OMNC), suggesting a stronger CH4 adsorption on Fe-Pd diatomic sites. In addition, the CH4 desorption peak over Fe-Pd1-Pd1 OMNC shifts to a higher temperature (265 °C) and becomes more intense when decorated with O species, pointing out the significant role of O-Fe-Pd structure in enhancing the interaction between CH4 and catalyst.

To further disclose the activation mechanism of C–H bond on the O-Fe-Pd structure, we analyzed the local structure of Fe-Pd1-Pd1 OMNC. As shown in Supplementary Figs. 61–63, both the single atom models of Fe-N4C3 and Pd-N4C3 display the perfectly symmetrical configurations with metal-N bond in length of 1.88 and 1.94 Å, respectively. Electron localization function (ELF) and charge density difference further illustrate the symmetrical distributions of charge densities for Fe-N4C3 and Pd-N4C3. Upon the construction of Fe-Pd dual-single-atomic structure, the symmetrical metal-N geometry and electronic structures are broken. The unbalanced electron configuration in Fe-Pd-N6C1 may be attributed to the differences in electronegativity between Fe and Pd.

The charge density difference was then calculated to quantify the variation of electronic structure induced by axial O species, where its planar average along the Z-direction is plotted. Clearly, Fig. 5a reveals an obvious electron transfer from metal sites to O with the charge of ca. 0.58 e−. Such a migration of electrons should induce the aggregation of electrons on O site. Thus, a charge polarization region should be formed on the O-Fe-Pd structure with the electron-rich and electron-deficient regions located on O and Pd sites, respectively (i.e., Oδ−-Fe-Pdδ+).

Actually, the variation in the surface charge of Fe-Pd1-Pd1 OMNC by O implanting is observed by the Zeta potential test, which shows that the charge is changed from −0.60 to −31.5 mV upon the treatment of H2O2 (Fig. 5b). Moreover, the charge of Fe1 OMNC is reduced significantly by 13 mV upon the treatment of H2O2. In contrast, H2O2 treatment displays negligible alter on the charge of Pd1 OMNC and OMNC (Supplementary Fig. 64). The variation in the surface charge of Fe-Pd1-Pd1 OMNC by O implanting is also observed by Kelvin probe force microscopy (KPFM), which show that the surface potential increases significantly upon the treatment of H2O2 (Supplementary Fig. 65). These results suggest that the Fe sites in Fe-Pd1-Pd1 OMNC should be the active centers for H2O2 activation and a electron-rich region (Fe–O) is generated after H2O2 treatment. In addition, the contact potential difference (CPD) increases significantly after Xe lamp irradiation, indicating that the charge polarization within Fe-Pd1-Pd1 OMNC can be strengthen upon illumination (Supplementary Fig. 66).

To gain more insights into the electron transfer mechanism within O-Fe-Pd structure, the partial density of states (PDOS) and projected crystal orbital Hamilton population (pCOHP) calculations were performed. It is clearly that the 3d orbital (dz2) of Fe site exhibits a large extent of overlap with the p orbital of O site, pointing out their strong bonding via d-p interaction (Fig. 5c and Supplementary Figs. 67, 68). Fragment orbital analysis show that the electrons in metal d orbitals are partially transferred to the singly occupied 2p orbitals of O via the dz2-pz interaction (Supplementary Fig. 69). In addition, since the d band center of Fe site in Fe-Pd-N6C1 (−2.41 eV) is more positive than that in Fe-N4C3 (−2.76 eV), the antibonding state of d-p in O-Fe-Pd structure shows less electron occupancy compared with that in O-Fe structure (Supplementary Figs. 70, 71). Thus, the electron transfer between O and dual atomic Fe-Pd-N6C1 should be more frequent and the degree of charge polarization is more distinctly than that between O and single atomic Fe-N4C3, which is confirmed by the charge density difference and Bader charge analysis of O-Fe structure (Supplementary Fig. 72a and Supplementary Table 8)39–41.

The formation of charge polarization region on O-Fe-Pd sites may facilitate the activation process of C–H bond. Thus, the electron transfer behavior during the activation of CH4 on O-Fe-Pd sites was analyzed. According to the Mulliken charge analysis, the C and H atoms in CH4 possess the negative (−1.03 e−) and positive charges (+0.25 e−), respectively, before activation (Supplementary Table 8). During the activation process, the positively charged H atom of CH4 is readily captured by the negatively charged O atom of O-Fe-Pd sites, which is witnessed by charge density difference and spin density distribution analysis (Fig. 5d and Supplementary Fig. 72b, c)42. The Bader charge calculation further elucidates that the charge of CH3 fragment far from O atom increases by 0.25 e− (Supplementary Table 8). This formed electron-rich region will induce the CH3δ− fragment to be landed on the electron-deficient region (i.e., Pdδ+ site), thus leading to the hetero-cleavage of C–H bond (CH4 + Fe–Oδ− + Pdδ+ → Fe–Oδ−-Hδ+ + CH3δ−-Pdδ+). Actually, the charge of *CH3 fragment decreases by 0.48 e− when bonding to the Pd site.

Further, quasi in-situ XPS was then performed to monitor the variation of chemical states and surface eletrons during the C–H activation process, where Fe-Pd1-Pd1 OMNC was first treated with H2O2 (i.e., O/Fe-Pd1-Pd1 OMNC) and then subjected to CH4 and light treatment in an in-situ chamber. As shown in Fig. 5e, the surface OH species (531.5 eV) in the O 1s spectrum increases significantly upon light irradiation under CH4 atmosphere, signifying that the H species in CH4 may combine with the surface O species on Fe-Pd1-Pd1 OMNC to form the OH species during the C–H bond activation process43. Moreover, the binding energy of Pd 3d significantly shifts towards lower binding energies by 0.4 eV after CH4 and light treatment, suggesting that Pd sites tend to gain electrons during the CH4 activation process44,45. Considering that negative electron nature of the carbon center in *CH3 (Supplementary Table 10), we speculate that the electrons obtained by the Pd sites during CH4 activation are likely to come from the *CH3 fragment.

Fragment orbital analysis was further conducted to explore the orbital interactions and electron transfer mechanisms in the activation process of CH4 on the Oδ−-Fe-Pdδ+ charge-polarized region (Fig. 5f, g and Supplementary Figs. 73–77). The results show that the constructed Oδ−-Fe-Pdδ+ charge polarization region is able to capture CH4, giving rise to the formation of s-p obital interaction between O and H atoms. This s-p orbital interaction then serves as an electronic transport bridge to inject electrons from electron-rich Oδ− sites into the σ* antibonding orbital of CH4, facilitating the breakage of C–H bond. Meanwhile, the electrons in the remained CH3 fragment transfer to the electron-deficient Pd site via p-d coordination interactions, achieving the complete activation of CH4. Nevertheless, due to the inherent simplifications of DFT, there are limitations in modeling the precise electronic structure and dynamic evolution of the charge-polarized region under actual photothermal conditions.

To prove the feasibility of in-situ formed O-Fe-Pd sites for C–H activation, in-situ EPR and in-situ FTIR have been conducted on a precatalyst O/Fe-Pd1-Pd1 OMNC with O-Fe-Pd sites to explore the activation of CH4 under H2O2 free conditions. As shown in Fig. 5h, a stable CH3 radical signal is detected over O/Fe-Pd1-Pd1 OMNC without externally added H2O2. In addition, in-situ FTIR spectra exhibit the distinct FTIR bands of *CH3 and *OH on O/Fe-Pd1-Pd1 OMNC upon CH4 and light treatment, while neglectable signals are observed on the surface of Fe-Pd1-Pd1 OMNC without H2O2 treatment (Fig. 5i and Supplementary Figs. 78, 79). These results demonstrate that the in-situ formed O-Fe-Pd sites on Fe-Pd1-Pd1 OMNC can drive the activation of C–H bond in CH4 under illumination.

Taken together, our findings clearly illustrate that a charge polarization region is formed on Fe-Pd1-Pd1 OMNC upon the construction of O-Fe-Pd structure, which enables the stabilization of *H and *CH3 fragments and thus promotes the activation of CH4. In addition, the periodic macroporous structure of Fe-Pd1-Pd1 OMNC with large external surface area can efficiently improve the accessibility of Fe-Pd dual single-atom sites and enhance the mass transfer efficiency toward substrate and products, which contribute to the high photothermal catalytic efficiency toward CH4 conversion. In addition, the ordered macroporous stucture can also enhance the light absorption due to the slow light effects and the band-stop reflection generated by coherent Bragg diffraction19. Particularly, both the light absorption capability and mass transfer efficiency can be significantly amplified if the macropores are periodically arranged into the three-dimensional ordered array.

Methods
Materials
All chemicals were commercially purchased and directly used without purification. The following chemicals were purchased and used without any further treatments: ammonium hydroxide (NH3·H2O, 28–30%, Shanghai Macklin Biochemical Co., Ltd.), ferric nitrate (Fe(NO3)3·9H2O, 99.9%, Shanghai Macklin Biochemical Co., Ltd.), potassium persulfate (K2S2O8, 99.5%, Shanghai Macklin Biochemical Co., Ltd.), palladium acetylacetonate (C10H14O4Pd, 99.95%, Shanghai Macklin Biochemical Co., Ltd.), sodium hydroxide pellets (NaOH, 95%, Shanghai Macklin Biochemical Co., Ltd.), zinc nitrate hexahydrate (Zn(NO3)2∙6H2O, 99%, Shanghai Chemical Reagent Co., Ltd.), hydrogen peroxide (H2O2, 6 wt.% in H2O, Shanghai Macklin Biochemical Co., Ltd.), deuterated water (D2O, 99.9%, Shanghai Macklin Biochemical Co., Ltd.), N, N-dimethylformamide (DMF, 99.8%, Shanghai Macklin Biochemical Co., Ltd.) and 2-methylimidazole (2-MeIM, 98%, Shanghai Macklin Biochemical Co., Ltd.).

Catalysts synthesis
Synthesis of 3D-PS template. The uniformly monodisperse colloidal PS spheres with a diameter of ~270 nm were first synthesized via a soap-free method. Typically, a mixture of 500 mL of deionized water, 65 mL of styrene, and 2.5 g of polyvinylpyrrolidone (PVP) was sequentially added to a 1 L round-bottom flask, which was purged with nitrogen for 15 min and stirred mechanically at 75 °C. Subsequently, 50 mL of aqueous solution containing 0.1 g of K2S2O8 was added to initiate the polymerization of styrene. After stirring for 24 h under nitrogen atmosphere, monodispersed PS spheres were obtained. The 3D-PS template was prepared by filtering the as-synthesized monodispersed PS spheres.

Synthesis of Fe-Pd1-Pd1 OMNC. 3.0 g of 2-methylimidazole was dissolved in 6.0 mL of methanol to obtain solution A. 3.62 g of Zn(NO3)2·6H2O, 300 mg of Fe(NO3)3·9H2O, and 20 mg of acetylacetone palladium Pd(acac)2 were dissolved in 14 mL of methanol to obtain solution B. The precursor solution was then obtained via mixing the solutions of A and B. Subsequently, a piece of 3D-PS template was added to the precursor solution and impregnated for 1 h, followed by vacuum treatment for 10 min to make sure that the metal species and organic ligands fill the gaps of template. Following impregnation, the precursor@PS was dried at 50 °C overnight. To crystallize the ZIF-8 phase, the dried precursor@PS was then treated with a CH3OH/NH3·H2O (2:1 v/v) solution under vacuum degassing for 5 min, and aged for 24 h at room temperature. The obtained FePd-ZIF@PS was collected and dried at 50 °C prior to pyrolysis. The pyrolysis was conducted in a tubular furnace under flowing Ar, with the temperature programmed to increase at 5 °C/min to 950 °C and held there for 2 h. After cooling to room temperature, the obtained black power was subjected to acid treatment (0.1 M HCl) to remove the residual Zn species and any impurity. In addition, the 3DOM FePd-ZIF with ordered macroporous structure was prepared via soaking FePd-ZIF@PS in N, N-Dimethylformamide to remove the PS template. The synthetic process of OMNC was similar to that of Fe-Pd1-Pd1 OMNC except for the absence of Fe(NO3)3·9H2O and Pd(acac)2. The synthetic process of the Fe-Pd1-Pd1 DOMNC with disordered microporous structure was similar to the synthesis of Fe-Pd1-Pd1 OMNC except for using the crushed PS filter cake as the template.

Synthesis of Fe-Pd1-Pd1 MeNC. 3.62 g of Zn(NO3)2·6(H2O), 100 mg of Fe(NO3)3·9H2O, and 20 mg of acetylacetone palladium were dissolved in 14 mL of methanol, which was then poured into 6 mL of methanol solution containing 3.0 g of 2-methylimidazole. The mixture was stirred for 5 min and let stand at room temperature for 24 h to obtain FePd-ZIF. A pyrolysis and subsequent acid treatment processes similar to the synthesis of Fe-Pd1-Pd1 OMNC were adopted to transfer FePd-ZIF into Fe-Pd1-Pd1 MeNC.

Material characterizations
The morphology observations were conducted on a scanning electron microscopy (SEM, HITACHI SU8220) and a transmission electron microscope (TEM, JEOL, JEM 2100F) equipped with an EDX analyzer (Bruker Xflash 5030T). A FEI Titan Themsis Z high-resolution transmission electron microscope with voltage of 300 kV was utilized to obtain the spherical aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (AC-HAADF-STEM) images. A Bruker D8 Advance diffractometer was used to characterize the crystal structures. A Thermo Scientific NEXSA X-ray photoelectron spectrometer was applied to determined the chemical states of catalysts, where where C 1s peak (284.8 eV) was selected as the ref. 46. Raman spectra were recorded on a Raman spectrometer (HORIBA Jobin Yvon). The Brunauer-Emmett-Teller (BET) surface areas and porosity were analyzed on an automatic rapid comparison surface and porosity analyzer (Micromeritics, ASAP 2460). The 3D structural model of catalysts in Fig. 1a was created by Blender 5.0, a software package released under the GNU General Public License that grants users full free usage rights (https://www.blender.org/).

X-ray absorption spectroscopy (XAS) measurements, encompassing both XANES and EXAFS, were carried out at the Singapore Synchrotron Light Source (SSLS). A Si (111) double-crystal monochromator was used to monochromatize the white light. Spectra for Fe and Pd were calibrated against foil and oxide standards (Fe, FeO, Fe2O3, Pd, PdO). All measurements were performed with the storage ring at 2.5 GeV and an electron current maintained below 200 mA. The collected EXAFS data were analyzed via the ATHENA module47.

In-situ Fourier transform infrared (FTIR) tests were conducted on a Thermo Fisher iS50 with a KBr plate as the infrared window, in which CH4 bubbled with H2O2 aqueous solution was adopted as the carrier gas. A 300 W xenon lamp was used as the light source. Free radical capture experiment on electron paramagnetic resonance (EPR). 5 mg of sample was dispersed in 4.5 mL water or methanol containing 0.5 mL DMPO solution (1 M). Then, an appropriate amount of solution was taken and loaded into an EPR test tube and purged with CH4 or Ar gas for 5 min before adding 0.5 mL of 30% hydrogen peroxide. EPR spectra were recorded after illumination for 0 minutes (i.e., in the dark), 5 min, and 10 min with a 300 W xenon lamp. The Kelvin probe force microscopy (KPFM) analyses were performed using an atomic force microscope (AFM, Bruker Dimension Icon). The Zeta potential information was obtained using a Malvern Zetasizer Nano series. The contents of Fe and Pd in different catalysts were determined by an inductively coupled plasma atomic emissions spectroscopy (ICP-OES) of PerkinElmer 7300DV instrument.

Photothermal catalytic selective oxidation of CH4
The photothermal catalytic oxidation of methane was conducted in a 230 mL batch reactor equipped with a quartz window to allow light exposure. Typically, 5 mg of catalyst, 5 mL of water and a certain amount of H2O2 or O2 (0.2 MPa) were added to the reactor vessel. The reactor was purged with CH4 multiple times to remove air, and then pressurized with Ar or CH4 (purity of 99.9995%) to reach 2 MPa. A 300 W xenon lamp (CEL-HXF300-T3) was used as the light source and no external heat source was applied. The light intensity of Xenon lamp was measured by automatic strong light power meter (CEL-NP2000-2A, Beijing China Education Au-light Co., Ltd.). Throughout the reaction, the system was stirred at 800 rpm. After reaction, the reactor was cooled to room temperature in an ice bath, and the liquid and gas phase products were gathered. Gas products were analyzed by a gas chromatography (GC) equipped with FID and TCD detectors, while liquid products were analyzed by nuclear magnetic resonance spectroscopy (NMR, JEOL) with dimethyl sulfoxide (DMSO) as the internal standard, respectively. HCHO was determined via the colorimetric method using a U-T3C type ultraviolet-visible spectrophotometer. In detail, a 0.25% (v/v) acetylacetone solution was first prepared by mixing 20 g of ammonium acetate, 6 mL of acetic acid, and 0.5 mL of acetylacetone in 100 mL of distilled water. Subsequently, 1.5 mL of the solution was mixed with 1.0 mL of as-prepared acetylacetone solution. The HCHO content was then determined by measuring the absorbance at 413 nm. The experimental data variability for the activity tests was <±5%.

Photoelectrochemical measurement
Electrochemical tests were conducted on a Chenhua CHI760E electrochemical workstation configured with a standard three-electrode system. Fluorine-doped tin oxide (FTO) glass slides served as the substrates for photoelectrodes48. A catalyst ink was prepared by mixing 10 mg of the as-prepared samples with of 200 μL ethanol, 800 μL deionized water, and 10 μL Nafion (5 wt.%). This ink was then uniformly coated onto the conductive side of the FTO substrate. The prepared electrode, Pt wire, and Ag/AgCl electrode were used as the working, counter, and reference electrodes, respectively. Na2SO4 aqueous solution (0.5 M, PH=7±0.1) was employed as the electrolyte. The pH value of the electrolyte was measured using a pH meter (PHS-3E, Shanghai INESA Scientific Instrument Co., Ltd.). Electrochemical impedance spectroscopy (EIS) was measured with the frequency range of 100,000–0.1 Hz at different conditions. Zview software was used to fit the Nyquist plots to model the process of electrode-electrolyte interface. The data collected by EIS were fitted by an appropriate equivalent circuit, and the values of the parameters were changed until the mathematical function matched the experimental data. All electrochemical tests were conducted in the absence of iR compensation. The applied potential was corrected by converted to the RHE using the equation:
ERHE = E vs:Ag=AgCl + 0:0591 × pH + E0(Ag=AgCl) (1)

The calculation formulas for product yield (mmol·h−1), and selectivity of C1 oxygenated compounds are as follows:
Product yield = n(total oxidation products) / h (2)
C1 oxygenated compounds selectivity (%) = n(C1 oxygenated compounds) / n(total oxidation products) * 100% (3)

In the equation, n(total oxidation products) is the total molecular mole of CH4 oxidation products, n(C1 oxygenated compounds) is the molecular mole of C1 oxygenated compounds. The experimental data variability for the activity tests was <±5%.

The apparent turnover frequency (TOF) of C1 formation was calculated according to:
TOF(h−1) = The mole of C1 (mol) / (The moles of supported metal (mol) × unit time (h)) (4)

In the equation, the mole of C1 is the molecular mole of C1 oxygenated compounds, the moles of supported metal are the sum of the moles of Fe and Pd. The experimental data variability for the activity tests was <±5%.

The apparent Quantum Yield (AQY) of the photothermal catalytic system was measured under the illumination of 100 W LED light (450 nm) at 63 °C, which can be calculated by the following formula:
AQY = Ne × 100% = (v × NA × K × (h × c) / λ) / (I × A × λ) × 100% = 3:34% (5)

where v(HCOOH, CH3OH, CH3OOH) = 3.93889×10−8 mol s−1, 9.99861×10−9 mol s−1, 1.28375×10−7 mol s−1; K(HCOOH, CH3OH, CH3OOH) = 4, 2, 6; NA = 6.022×1023 mol−1; T = 2 h, A = 12.56 cm2; λ = 450 nm, I = 600×10−3 W m−2, h = 6.62×10−34 J s−1, c = 3.0×108 m s−1. For Fe-Pd1-Pd1 OMNC: AQY% = [(4×3.93889×10−8 + 2×9.99861×10−9 + 6×1.28375×10−7)×6.022×1023]×(6.62×10−34×3.0×108) / (600×10−3×12.566×450×10−9) = 3.3410%.

The conversion of CH4 was determined by using Argon as the internal standard, which can be calculated by the following formula:
Con(CH4%) = (n0(CH4) - nt(CH4)) / n0(CH4) × 100% (6)

where n(CH4) and n0(CH4) represent the moles of CH4 after and before the reaction, respectively.

The carbon balance (%) in the photothermal catalytic system can be calculated by the following formula:
carbon balance (%) = n(C1) / n0(CH4) × 100% (7)

where n(C1) and n0(CH4) represent the moles of products and reactant gas, respectively.

Computational details for calculations
The details of DFT calculations. The DFT calculations were performed by Vienna Abinitio Simulation Package (VASP) using the projector augmented wave (PAW) method49,50. The valence electron configurations applied in this work were 2s22p2 (C), 2s22p3 (N), 2s22p4 (O), and 4s² 3d6 (Fe), 4d10 (Pd), respectively. Planar wave cut-off energy (ENCUT) was set to 400 Ev51. A 4×4×1 Monkhorst–Pack k-point mesh sampling for Brillouin-zone integration was used to optimize all surface structures52. To prevent interaction between two neighboring surfaces, the vacuum layer spacing was set to 15 Å. The transition state (TS) searches on CH4 activation process slab were carried out with the climbing-image nudged elastic band method (CI-NEB). All of the calculations were continued until the force has converged to less than 0.02 eV Å−1, and energies have converged within 10−5 eV. Data analysis and visualization were carried out by VASPKIT53 code and VESTA54. The ΔG of ECRR steps were calculated by:
ΔG = ΔEDFT + ΔEZPE - TΔS (8)

where ΔEDFT, ΔEZPE and ΔS were the energy from DFT optimization, correction of zero-point energy and the variation of entropy, respectively. T was the temperature (T = 298.15 K).

LOBSTER 4.1.0 package55 was employed for Crystal orbital Hamilton population (COHP) analysis to investigate local orbital interactions. This package works by projecting the plane-wave functions onto atomic orbital basis sets, thereby reconstructing the wave functions for specific local orbitals. Integrated crystal orbital Hamilton population (ICOHP) was further calculated to provide a quantitative measure of the bonding strength and the orbital-specific contributions to chemical bonds56.

The AIMD simulations were performed using the CP2K package and the QUICKSTEP module57. For the investigation of the structural stability of Fe-Pd-N6C1 model, simulation temperature was set at 873.15 K using Nose–Hoover thermostat. AIMD simulation was lasted for 10 ps with a timestep of 1 fs. For the investigation of the activation of H2O2 and CH4, the simulation temperature was controlled at 335 K through a Nose–Hoover thermostat.

Peer review rounds
[{"round": 1, "reviewer_comments": {"reviewer_1": "In this study, the authors make an important conceptual contribution by proposing a novel mechanism of C-H bond activation using asymmetric charge distribution dual-sites. Firstly, the manuscript presents a novel strategy for incorporating the dual atomic Fe1-Pd1 sites within the periodical macropore (Fe1-Pd1 OMNC), which enables the efficient CH4 conversion under ambient conditions. The Fe1-Pd1 OMNC catalyst demonstrates exceptional photothermal catalytic performance, achieving a production rate of 16.2 mol gmetal-1 h-1 for C1 oxygenated products. Further mechanistic insights reveal that the asymmetric charge distribution on dual metal sites is able to stabilize the Hδ+ and CH3δ- fragments. This study represents a significant advancement given the systematic methodology and thorough theoretical investigation. Nevertheless, several specific issues require attention prior to publication, as outlined below:\n1) The authors need to expand the discussion on the role of the macroporous skeleton in the photothermal catalytic CH4 conversion reaction.\n2) The monodispersed PS template with a diameter of 270 nm was synthesized, but the aperture size of Fe1-Pd1 OMNC was measured as 200 nm (Fig. 1e). The authors are suggested to provide a proper explanation for the pore size shrinkage observed during the synthesis process.\n3) The synthesized catalyst exhibits a regular tetradecahedral morphology, which appears to differ from the conventional dodecahedral structure of ZIF materials. The authors are recommended to add relevant discussion regarding this morphological distinction in the manuscript.\n4) The authors mentioned in Fig. S16 the detection of formaldehyde products using a UV spectrophotometer, but the experimental methodology was not described. It is recommended to elaborate the analytical procedures in the Methods section.\n5) The quantum efficiency of the photocatalytic system should be provided.\n6) HCHO is a prevalent product that can be derived from the oxidation of CH3OH or the decomposition of CH3OOH. Can the authors explain why there is no HCHO produced in the methane oxidation reaction?\nMinor point:\nThe authors are suggested to thoroughly check the format in the main text, supporting information and the figure axis labels.", "reviewer_2": "In this manuscript, Chen et al. developed a template-oriented encapsulation-pyrolysis protocol to integrate asymmetrically atomic sites on ordered macroporous N-doped carbon for photothermal catalytic selective oxidation of CH4. The catalysts were well characterized. The as-prepared Fe1-Pd1 OMNC demonstrates exceptional photothermal catalytic performance with high C1 oxygenate production rate with O2 serve as oxidant. The authors proposed a unique CH4 activation mechanism, in which a charge polarization region induced by the axial *O is able to break the first C-H bond, which is meaningful for the design of advanced catalytic system. This manuscript is well written with convincing experimental data. The findings are of great interest and may offer inspiring insights into the the in-depth understanding of heterogeneous interfacial catalysis. I recommend this manuscript for publication in Nature Communications after minor revision.\n1. In Figure 3c, the photothermal catalytic performance of the Fe1-Pd1 DOMNC is significantly lower than that of Fe1-Pd1 OMNC, highlighting the crucial role of the orderliness of macropores in photothermal catalytic systems. Thus, a detailed discussion is required.\n2. It is recommended to supplement the error bars for the catalytic performance data in Figure 3.\n3. Photocurrent response test is an effective mean to investigate the migration behavior of photo-induced carrier. So, it is suggested to supplement the relevant experimental data.\n4. Electrochemical impedance spectroscopy and a brief analysis can be given to study the electrical properties of Fe1-Pd1 OMNC.\n5. The selectivity of products should be mentioned in the abstract.\n6. In Figure 5, it is recommended to provide the isosurface values of the differential density plots.\n7. The reaction conditions of AIMD simulations should be provided in the caption.\n8. It is recommended to mark the bonding and antibonding states in COHP.\n9. The subscripts of H2O2/O2 on page 22 and the Zn (NO3)2·6(H2O) on page 23 should be corrected.", "reviewer_3": "This paper reported a dual atomic Fe and Pd catalyst with periodic macroporous structure (Fe1-Pd1 OMNC) for photocatalytic CH4 conversion. Methane conversion has emerged as a topic of significant interest in recent years, driven by its dual implications for sustainable energy production and environmental mitigation. This manuscript addresses a relevant subject aligned with the journal’s scope and could generate broad interest among readers. However, due to the lack of sufficient innovation in the research and the experimental data presented fail to robustly substantiate the central claims, this manuscript cannot be recommended for publication in Nature Communications.\nCritical concerns:\n1. The primary innovation of this work lies in the activation of C-H bonds in CH4 via the charge-polarized region induced by on dual-single-atomic sites. However, the authors failed to identify the active sites and provide detailed mechanistic analysis and experimental validation of the C-H bond activation process. For example, the authors emphasize in the abstract and introduction that two mechanisms coexist during CH4 activation over Fe1-Pd1 OMNC: (1) electron transfer between the d orbitals of the catalyst and the σ orbitals of the C-H bond, leading to C-H bond cleavage, and (2) activation of the C-H bond through a local electrostatic field on the catalyst surface, inducing electrostatic CH3δ-–H δ+ polarization. While these mechanisms are individually similar to those reported in prior studies, the novelty of this work lies in their combined application. However, the results section does not explicitly demonstrate how these two mechanisms synergistically cooperate to activate the C-H bond in CH4.\n2. Furthermore, the authors claim to manipulate C-H bond cleavage by engineering the electronic configuration of the catalyst surface. However, their proposed strategy of generating charge-polarized regions through charge transfer from Fe to active oxygen species to influence C-H bond polarization has already been reported (J. Am. Chem. Soc. 2022, 144, 12357-12366). Furthermore, while they emphasize the impact of these charge-polarized regions and the role of orbital overlap on the reaction process, their conclusions rely solely on theoretical calculations and lack sufficient experimental validation, rendering the findings inadequately substantiated.\n3. The experimental design for photocatalytic performance evaluation is not proper. For example, due to its high cost, H2O2 has been rarely selected as the oxidant in current catalytic systems, and its use typically does not involve pressurized conditions. Furthermore, the reported yield of methanol is predicated on minimal levels of the utilized catalyst (1-5 mg). It is a generally accepted principle that photocatalytic activity does not increase linearly with the mass of the catalyst. Given the minimal use of the catalyst, the quantity of methanol generated is, in comparison, relatively low.\n4. Several critical data are notably absent from the manuscript. For example, quantum efficiency, carbon balance and CH4 conversion rate are all very important in evaluating the catalytic performance of CH4 conversion, but they are not given in this manuscript. The evaluation criteria for the products and the description of the product detection module are unclear. For example, it does not specify whether C2 products are detected and how a UV-visible spectrophotometer is used to measure HCHO. Additionally, key experiments should be repeated, and error bars should be included.\nOther concerns:\n1. The intensity ratio of the D band to the G band (ID/IG) in the Raman spectrum was not explicitly mentioned. This ratio needs to be supplemented to quantify the graphitization degree of the carbon matrix and to discuss its influence on the electron transport performance and the construction of the charge polarization region.\n2. How were the loading amounts of Fe and Pd (0.58 and 0.35 wt%) in the text obtained and were they verified by ICP-OES? Quantitative data need to be provided and compared with the theoretical values.\n3. In the direct comparison of the XANES spectra of the oxidation states of Fe and Pd with standard samples (such as FeO, Fe₂O₃, PdO), the author indicates whether \"No metal-oxygen bonds (i.e., Fe-O and Pd-O) are observed in the FT-EXAFS spectra of Fe1-Pd1 OMNC\" is reasonable? List the corresponding literature support.\n4. The original pictures and selected area for Fig. 1j are suggested to be provided in the manuscript. Moreover, is the colored plots of Fig. 1j three-dimensional? If it is, why are there only two coordinate axises?\n5. XPS fitting should follow important principles (in Fig. S10), such as: the peak width at half height of 2p and 3d doubles peaks should be equal; the peak area radio of 3d 5/2 to 3d 3/2 is 3:2 etc. Please check the XPS results and exclude the irrational fitting parameters.\n6. Some informal English expressions can still be detected in the manuscript, for examples, “As shown in Fig. 4a-b and Supplementary Fig. S27a-b, the distinct six prominent characteristic signals (4 of strong and 2 of relatively weak peaks) and 1:1:1:1 quartet pattern are observed when the Fe1-Pd1 OMNC photothermal reaction is performed”, and additional efforts are required to optimize them.\n7. The catalytic performance-related experiments in the Supporting Information should specify the detailed experimental conditions. Additionally, the conclusions drawn from the comparative experiments should be clearly stated in the main text.\n8. The original text \"Moreover, an obvious photocurrent signal was observed when Fe1-Pd1 OMNC was exposed in the light environment, implying the existence of excited electrons\" lacks supporting data."}, "author_response": "Response to Reviewers’ comments:\nReviewer 1: In this study, the authors make an important conceptual contribution by proposing a\nnovel mechanism of C-H bond activation using asymmetric charge distribution dual-sites. Firstly,\nthe manuscript presents a novel strategy for incorporating the dual atomic Fe -Pd sites within the\n1 1\nperiodical macropore (Fe -Pd OMNC), which enables the efficient CH conversion under ambient\n1 1 4\nconditions. The Fe -Pd OMNC catalyst demonstrates exceptional photothermal catalytic\n1 1\nperformance, achieving a production rate of 16.2 mol gmetal-1 h-1 for C1 oxygenated products.\nFurther mechanistic insights reveal that the asymmetric charge distribution on dual metal sites is\nable to stabilize the Hδ+ and CH δ- fragments. This study represents a significant advancement given\n3\nthe systematic methodology and thorough theoretical investigation. Nevertheless, several specific\nissues require attention prior to publication, as outlined below:\nResponse: We thank the reviewer very much for the constructive comments and suggestions which\nhave helped us to improve the quality of this work significantly.\nComment 1: The authors need to expand the discussion on the role of the macroporous skeleton in\nthe photothermal catalytic CH conversion reaction.\nof Fe -Pd OMNC with large external surface area can efficiently improve the accessibility of Fe -\n1 1 1\nPd dual single-atom sites and enhance the mass transfer efficiency toward substrates and products.\nlight effects and the band-stop reflection generated by coherent Bragg diffraction (e.g., Adv. Mater.\n33, 2102690 (2021); Adv. Mater. 29, 1605349 (2017)). In the revised manuscript, we have added\nthe discussion on the role of the macroporous skeleton in the second paragraph of page 25 in the\nmain text.\nComment 2: The monodispersed PS template with a diameter of 270 nm was synthesized, but the\naperture size of Fe -Pd OMNC was measured as 200 nm (Fig. 1e). The authors are suggested to\n1 1\nprovide a proper explanation for the pore size shrinkage observed during the synthesis process.\nResponse: Thanks for the good suggestion. The size of the macropore is reduced from 270 to 200\nnm after calcination, which may be ascribed to the overall structural shrinkage caused by the the\nrelease of gases during the transformation of organic ligands into carbon and the densification of\nthe inorganic framework (J. Am. Chem. Soc. 141, 14764-14771 (2019)). In the revised manuscript,\nwe have added the discussion on the pore size shrinkage on page 8 of the supporting information.\nappears to differ from the conventional dodecahedral structure of ZIF materials. The authors are\nrecommended to add relevant discussion regarding this morphological distinction in the manuscript.\nResponse: We appreciate the reviewer’s valuable comment and suggestion. The crystal growth of\nZIF-8 is known to start with the formation of cubes composed of six (100) facets, which can\nsubsequently grow into truncated rhombic dodecahedra composed of twelve (110) and six (100)\nfacets (Chem. Mater. 25, 1761-1768 (2013)). In our study, the shaping and templating effects of the\n3D-ordered PS template could directly guide the morphological evolution of ZIF-8 into a\ntetrakaidecahedron morphology and match its crystal face to the oriented 3D-ordered macroporous\narrangement (Science 359, 206-210 (2018)). In the revised manuscript, we have added the\ndiscussion regarding the formation of regular tetradecahedral morphology on page 8 of the\nsupporting information.\nComment 4: The authors mentioned in Fig. S16 the detection of formaldehyde products using a UV\nspectrophotometer, but the experimental methodology was not described. It is recommended to\nelaborate the analytical procedures in the Methods section.\nResponse: Thanks for the good suggestion. As suggested, we have provided the detailed analytical\nprocedure and the relevant standard curve for formaldehyde product in the revised manuscript (the\nfirst paragraph of page 29 in the revised main text, and supplementary Figs. S17, S19 of the revised\nsupporting information).\nComment 5: The quantum efficiency of the photocatalytic system should be provided.\nResponse: We would like to sincerely thanks for this professional suggestion. As suggested, we\nhave measured the apparent quantum yield (AQY) of the photothermal catalytic system under the\nillumination of a 100 W LED light (450 nm) at 63 °C. Upon irradiation at 450 nm and under\nconditions of 63°C, the AQY is measured to be 3.34% (Equation R1). In the revised manuscript, we\nhave included the above results in the first paragragh of page 10 and the third paragragh of page 30\nin the revised main text.\nN 109(v×N ×K)×(h×c)\ne A\nAQY= ×100%= ×100%=3.34% (R1)\nN (I×A×λ)\nP\nwhere v(HCOOH, CH3OH, CH3OOH) = 3.93889 × 10-8 mol s-1, 9.99861 × 10-9 mol s-1, 1.28375 × 10-7 mol s-1;\nK(HCOOH, CH3OH, CH3OOH) = 4, 2, 6; NA = 6.022 × 1023 mol-1; T = 2 h, A = 12.56 cm2; λ = 450 nm, I = 600 ×\n10-3 W m-2, h = 6.62 × 10-34 J s-1, c = 3.0 × 108 m s-1. For Fe1-Pd1 OMNC: AQY% = [(4 × 3.93889 × 10-8 + 2 ×9.99861\n× 10-9 + 6 × 1.28375 × 10-7 ) × 6.022 × 1023] × (6.62 × 10-34 × 3.0 × 108)/(600 × 10-3 × 12.566 × 450 ×10-9) = 3.3410%\n3\ndecomposition of CH OOH. Can the authors explain why there is no HCHO produced in the\n3\nmethane oxidation reaction?\nResponse: We appreciate the reviewer’s valuable comment. We fully agree with the reviewer’s\ncomment that HCHO is a prevalent product that can be derived from the oxidation of CH OH or the\n3\ndecomposition of CH OOH. In this regard, we have established the standard curve for the detection\n3\nof HCHO and found that the concentration of HCHO in the reaction solution is much lower than\nthe the detection limit of the equipment (0.01 mmol L-1) (Fig. R1). The trace amount of HCHO in\nthe reaction solution may be due to its instability nature in the H O environment with strong\n2 2\noxidized capacity (J. Am. Chem. Soc. 146, 16039-16051 (2024)). In the revised manuscript, we have\nincluded the above results in supplementary Figs. S17 and S19 and added the related discussions in\nthe first paragraph of page 29 in the revised main text and page 22 in the revised supporting\ninformation.\nFig. R1 (a) Uv-vis spectra of chromogenic solution; (b) the calibration curve; (c) Uv-vis spectra and optical\nphotographs (inset) of the reaction solution and 0.01 mmol L-1 of HCHO solution.\nComment 7: The authors are suggested to thoroughly check the format in the main text, supporting\ninformation and the figure axis labels.\nResponse: Thanks for your valuable suggestion. As suggested, we have double-checked the whole\nmanuscript and supporting information thoroughly and corrected the errores in the revised\nmanuscript and supporting information.\nprotocol to integrate asymmetrically atomic sites on ordered macroporous N-doped carbon for\nphotothermal catalytic selective oxidation of CH . The catalysts were well characterized. The as-\n4\nprepared Fe -Pd OMNC demonstrates exceptional photothermal catalytic performance with high\n1 1\nC1 oxygenate production rate with O serve as oxidant. The authors proposed a unique CH\n2 4\nactivation mechanism, in which a charge polarization region induced by the axial *O is able to\nbreak the first C-H bond, which is meaningful for the design of advanced catalytic system. This\nmanuscript is well written with convincing experimental data. The findings are of great interest and\nmay offer inspiring insights into the the in-depth understanding of heterogeneous interfacial\ncatalysis. I recommend this manuscript for publication in Nature Communications after minor\nrevision.\nResponse: We greatly appreciate the reviewer‘s constructive and insightful comments and\nsuggestions which have helped us to improve the quality of of this work significantly.\nComment 1: In Figure 3c, the photothermal catalytic performance of the Fe -Pd DOMNC is\n1 1\nsignificantly lower than that of Fe -Pd OMNC, highlighting the crucial role of the orderliness of\n1 1\nmacropores in photothermal catalytic systems. Thus, a detailed discussion is required.\nResponse: We appreciate the reviewer’s valuable comment and suggestion. The macroporous\nstructure of Fe -Pd OMNC with large external surface area can efficiently improve the accessibility\n1 1\nof Fe -Pd dual atomic sites and enhance the mass transfer efficiency toward substrates and products.\n1 1\nIn addition, the macroporous stucture can also enhance the light absorption due to the slow light\neffects and the band-stop reflection generated by coherent Bragg diffraction (Adv. Mater. 33,\n2102690 (2021); Adv. Mater. 29, 1605349 (2017)). Particularly, both the light absorption capability\nand mass transfer efficiency can be significantly amplified if the macropores are periodically\narranged into the three-dimensional ordered array (Matter 3, 1-20 (2020); Angew. Chem. Int. Ed.\n58, 4587-4591 (2019)). In the revised manuscript, we have added the discussion on the role of the\norderliness of macropores macroporous skeleton in the second paragraph of page 25 in the revised\nmain text.\nComment 2: It is recommended to supplement the error bars for the catalytic performance data in\nFigure 3.\nResponse: Thanks for your good suggestion. In the revised manuscript, we have provided the error\nbars for the catalytic performance data of all the studied samples and included the related description\nin the captions of the relevant figures and the first paragraph of page 29 in the revised main text.\nof photo-induced carrier. So, it is suggested to supplement the relevant experimental data.\nResponse: We appreciate the reviewer’s valuable suggestion. As suggested, we have conducted the\nphotocurrent response test to investigate the migration behavior of photo-induced carrier. As shown\nin Fig. R2, an obvious photocurrent signal is observed when Fe -Pd OMNC was exposed in the\n1 1\nlight environment, implying the existence of excited electrons. In addition, Fe -Pd OMNC exhibits\n1 1\na higher current density than OMNC, suggesting that the presence of Fe -Pd dual metals sites can\n1 1\npromote the fomation of photo-induced electron. In the revised manuscript, we have included the\nresults in supplementary Fig. S31 and added the related discussions in the first paragraph of page\n14 in the revised main text and page 34 in the revised supporting information.\nFig. R2 Photocurrent signals of Fe1-Pd1 OMNC and OMNC.\nComment 4: Electrochemical impedance spectroscopy and a brief analysis can be given to study\nthe electrical properties of Fe -Pd OMNC.\n1 1\nResponse: We appreciate the reviewer’s valuable suggestion. Accordingly, we have conducted the\nelectrochemical impedance spectroscopy to study the electrical properties of Fe -Pd OMNC.\n1 1\nAs\nshown in Fig. R3, Fe -Pd OMNC exhibits smaller semicircle diameter than OMNC, pointing out\n1 1\nits smaller charge-transfer resistance for charge-transfer. In addition, both Fe ONNC and Pd\n1 1\nOMNC display the semicircle diameter similar to that of Fe -Pd OMNC, indicating their similar\n1 1\nelectrochemical properties. In the revised manuscript, we have included the results in supplementary\nFig. S32 and added the related discussions in first paragraph of page 14 in the revised main text and\npage 35 in the revised supporting information.\namplification and equivalent circuit: solution resistance (Rs), double-layer capacitance at the electrode surface (Cdl),\ncharge transfer resistance (R1), and Warburg impedance (W)).\nComment 5: The selectivity of products should be mentioned in the abstract.\nResponse: Thanks for the valuable suggestion. In the revised manuscript, we have provided the\nselectivity of products in the abstract.\nComment 6: In Figure 5, it is recommended to provide the isosurface values of the differential\ndensity plots.\nResponse: Thanks for the valuable suggestion. In the revised manuscript, we have provided the\nisosurface values of the differential density plots in supplementary Figs. S45 and S50.\nComment 7: The reaction conditions of AIMD simulations should be provided in the caption.\nResponse: Thanks for the good suggestion. We have supplemented the detailed calculation method\nof AIMD simulations in the caption of Fig. 4 and the second paragraph of page 32 in the revised\nmain text.\nComment 8: It is recommended to mark the bonding and antibonding states in COHP.\nResponse: Thanks for the valuable suggestion. As suggested, we have labeled the bonding and\nantibonding states in COHP diagrams. Please also see the revisions in Fig. 5c and supplementary\nFig. S55 of the revised manuscript.\n2 2 2 3 2 2\nbe corrected.\nResponse: Thanks for pointing out this mistake. We have carefully checked and polished the whole\narticle, and the spelling errors were corrected in the revised manuscript.\nstructure (Fe -Pd OMNC) for photocatalytic CH conversion. Methane conversion has emerged as\n1 1 4\na topic of significant interest in recent years, driven by its dual implications for sustainable energy\nproduction and environmental mitigation. This manuscript addresses a relevant subject aligned\nwith the journal’s scope and could generate broad interest among readers. However, due to the\nlack of sufficient innovation in the research and the experimental data presented fail to robustly\nsubstantiate the central claims, this manuscript cannot be recommended for publication in Nature\nCommunications.\nResponse: We would like to extend our deepest gratitude to the reviewer for her/his detailed and\nthorough feedback, which plays an essential role in maintaining the high standards of articles\npublished in Nature Communications. In this work, we designed an asymmetric Fe-Pd diatomic\nactive sites and found that the oxidant prefers to be activated on Fe site to an axial *O, forming\na Oδ--Fe-Pdδ+ charge polarization region. Such in-situ formed\npolarization region contribute to the activation of C-H bond, where the electron-rich Oδ- region is\nable to capture the Hδ+ fragment in CH and the remaining CH δ- species tends to be stabilized by\n4 3\nthe Pdδ+ site. We believe that our work is original, as we have successfully demonstrated the\nfollowing inovative points:\n1. A novel strategy to boost the activation of inert C-H bond.\nDirect conversion of CH into liquid oxygenates under mild conditions is of critical importance\n4\nconsidering the present energy-intensive protocols. Unfortunately, the non-polar tetrahedral\nstructure of CH with extremely high dissociation energy of C-H bond (439.3 kJ mol-1) put the CH\n4 4\nactivation in a dilemma, especially under mild conditions (Chem 5, 2296-2325 (2019); Chem. Rev.\n124, 1288-1320 (2024)). Generally, C-H bond can be activated in the form of electrostatic CH δ--\nthat the transfer of electrons from ZnO to Fe O can induce the charge accumulation on Fe sites,\n2 3\nthus reducing the CH adsorption energy and facilitating the activation of C-H bond (J. Am. Chem.\nthe active sites with high local charge accumulation, we have demonstrated a unique example of\nmanipulating the cleavage behavior of C-H bond via in-situ constrution of charge polarization\nregion on asymmetric atomic sites during the CH oxidation process. That is, we found that the\n4\noxidant prefers to be activated on Fe site to in-situ form a Oδ--Fe-Pdδ+ charge polarization region,\nwhere the electron-rich Oδ- region and the electron-deficient Pdδ+ region are able to capture the Hδ+\nand CH δ-species in CH , respectively, thus jointly participating in the activation of C-H bond.\n3 4\nIn order to verify the above claims, we have proposed a combination of the ab initio molecular\ndynamics simulations and in-situ spectra to gain atomic-level insights into the dynamic process of\nin-depth understanding of heterogeneous interfacial catalysis.\nIn order to gain more understanding in the reaction process, we have additionally conducted a\nseries of in-situ spectra (i.e., in-situ FTIR, quasi in-situ XPS, in-situ EPR spectra), Zeta potential,\nKelvin probe force microscopy (KPFM) and control experiments to reveal the activation of C-H\nbond on Oδ--Fe-Pdδ+ charge polarization regions (Please also see the detailed results in Respond to\nComment #1). Therefore, beyond a novel strategy to boost the activation of inert C-H bond,\nour work also delves into the conversion behavior of oxidants at the catalytic interface and\ntheir impact mechanism on molecular activation.\n2. Exceptional catalytic performance toward CH oxidation.\n1 1\nperformance toward the selective oxidation of CH with an evolution rate of C1 oxygenates as high\n4\nas 0.754 mmol h-1 when using H O as the oxidant. Considering the safety issue of H O during the\n2 2 2 2\nphotothermal catalytic process, we first pre-treated the Fe -Pd OMNC with H O at room\n1 1 2 2\ntemperature (denoted as O/Fe -Pd OMNC) to construct a charge polarization region on catalyst\n1 1\nsurface (i.e., O-Fe-Pd sites). We found that the pre-catalyst O/Fe -Pd OMNC exhibits an\n1 1\nexceptional photothermal catalytic activity toward CH oxidation using O as the oxidant, delivering\n4 2\na methanol production rate of 0.787 mmol h-1 (see Fig. R12). The yield of oxygenates is significantly\nhigher than the previously reported catalysts for CH conversion under comparable conditions (see\ntowards the efficient conversion of CH under mild conditions.\n4\n3. The elaborate design of catalyst.\nWe have developed a template-oriented encapsulation-pyrolysis protocol to integrate\nasymmetrically atomic sites on ordered macroporous N-doped carbon. The well-defined atomic\nstructure enables us to reveal the activation mechanism of C-H bond at the atomic/molecular levels.\nIn addition, the constructed periodic pores may ensure the maximum accessibility of active sites,\nthus reinforcing the fundemental understanding of the structure-performance relationships.\nTo sum up, the present work provides a rational approach to manipulate the charge polarization\nin catalyst interface for promoting the the activation of inert C-H bond and offer valuable insights\ninto the design of highly efficient catalystic system towards alkanesconversion. We believe this\nrevised version contains novel and important findings that will be of great interest to wide research\nfields of the general scientific community.\nTo address the reviewer’s comments, we have included the above new results in Figs. 3i, 4b-\nc, 4h-i, 5e-h, supplementary Figs. S34, S48, S53-54, S59, Tables S5-6 and S8 and added the related\ndiscussions in the revised main text (the first and last paragraphs of page 15, the second paragraph\n9\nof page 20, the first paragraph of page 22, the first paragraph of page 23, the second and third\nparagraphs of page 24 and the first and second paragraphs of page 25) and revised supporting\ninformation (page 37). In addition, the introduction section have also been revised (the second and\nthird paragraphs of page 3; the first paragraph of page 4).\nComment 1: The primary innovation of this work lies in the activation of C-H bonds in CH via the\n4\ncharge-polarized region induced by on dual-single-atomic sites. However, the authors failed to\nidentify the active sites and provide detailed mechanistic analysis and experimental validation of\nthe C-H bond activation process. For example, the authors emphasize in the abstract and\nintroduction that two mechanisms coexist during CH activation over Fe -Pd OMNC: (1) electron\n4 1 1\ntransfer between the d orbitals of the catalyst and the σ orbitals of the C-H bond, leading to C-H\nbond cleavage, and (2) activation of the C-H bond through a local electrostatic field on the catalyst\nsurface, inducing electrostatic CH δ--Hδ+ polarization. While these mechanisms are individually\n3\nsimilar to those reported in prior studies, the novelty of this work lies in their combined application.\nHowever, the results section does not explicitly demonstrate how these two mechanisms\nsynergistically cooperate to activate the C-H bond in CH .\nuncover a principal fact that the in-situ construction of charge-polarized regions on diatomic active\nsites can induce the polarization and cleavage of C-H bond in CH . In\n4\ndetail, we designed the Fe-\nPd diatomic active sites and found that the oxidant (i.e., H O ) prefers to be activated on Fe site to\n2 2\nan axial *O, forming an Oδ--Fe-Pdδ+ charge polarization region. Such in-situ formed polarization\nregions jointly participate in the activation of C-H bond, among which the electron-rich Oδ- region\nis able to capture the Hδ+ fragment in CH and the remaining CH δ- species tends to be stabilized by\n4 3\nthe Pdδ+ site. Thus, the activation of C-H bond mainly depends on the in-situ generation of local\nelectrostatic fields on the catalyst surface, while the orbital interactions of σ/d-p represent the\nbonding behavior between the fragments (i.e., *H and *CH ) and active sites after C-H bond\n3\nactivation. Such orbital interactions are more likely the consequence of CH activation, rather than\n4\nthe dominant factor in the initial C-H bond activation. We sincerely apologize for any ambiguity in\nexplaining the innovative aspects of our work. We have revised our manuscript to highlight the C-\nH bond activation process and removed the relevant statements regarding the orbital interactions.\nRegarding the concern about the lack of sufficient experimental validation, we have conducted\nadditional in-situ spectra (i.e., in-situ FTIR, quasi in-situ XPS and in-situ EPR spectra), Zeta\npotential, KPFM and control experiments to streghthen the central claims.\nFirstly, we treated the catalysts with H O or H O and conducted the Zeta potential\n2 2 2\nmeasurements to probe the O-Fe-Pd asymmetry charge stucture. As shown in Fig. R4, the charges\n10\non Fe OMNC and Fe -Pd OMNC are reduced significantly by 13.0 and 30.9 mV, respectively upon\n1 1\nthe treatment of H O . In contrast, H O treatment displays negligible change on the charge of Pd\n2 2 2 2\nOMNC and OMNC. The variation in the surface charge of Fe -Pd OMNC by O implanting is also\n1 1\nobserved by KPFM images, which show that the surface potential increases significantly upon the\ntreatment of H O (Fig. R5). These results suggest that the Fe sites in Fe -Pd OMNC should be the\n2 2 1 1\nactive center for H O activation and an electron-rich region (Fe-O) may be generated after H O\n2 2 2 2\ntreatment. Actually, the formation of O species on Fe -Pd OMNC has been confirmed by XPS\n1 1\nspectra, which show that the proportion of Fe-O bond (529.5 eV) in O 1s increases significantly\nafter the treatment of H O (Fig. R6).\n2 2\nSecondly, in order to well disclose the mechanism of CH oxidation on Fe -Pd OMNC, we\n4 1 1\nhave re-conducted the in-situ FTIR tests by using another FTIR equipment (i.e., Thermofisher\nNicolet IS50) with higher resolution and sensitivity and increased the scan numbers and resolution\nwhen acquiring the spectra. The time-resolved FTIR spectra of Fe -Pd OMNC show that a set of\n1 1\npeaks emerge and strengthen along with the prolongation of light irradiation times (Fig. R7a).\nAmong these peaks, peaks emerged at 1354, 1435, and 1470 cm-1 are assigned to the methyl species\n(*CH ) (e.g., Nat. Commun. 15, 10451 (2024); Angew. Chem. Int. Ed. 62, e202302196 (2023); Nat.\n4\nmolecules. In addition, we also supplemented additional time-resolved FTIR spectra over Fe\n1\ncatalytic CH oxidation process (Fig. R7b-c). We found that the intensity of the *CH signals on\n4 3\nPd OMNC is significantly higher than that on Fe OMNC. Additionally, the FTIR band of *CH\n1 1 3\non Pd OMNC exhibits a blue shift from 1417 to 1435 cm-1 compared with that on Fe OMNC (Fig.\n1 1\nR8 and Table R1). The intense signals of *CH and the blue shift of the FTIR bands indicates a\n3\nstronger intreaction of Pd-CH than Fe-CH (Nat. Commun. 9, 3250-3259 (2018); J. Am. Chem. Soc.\n3 3\n147, 18, 15490-15498 (2025); Nat. Commun. 15, 564-574 (2024)). Additionally, we also found that\nthe FTIR band of *CH on Fe -Pd OMNC is closer to that on Pd OMNC but farther away from\n3 1 1 1\nthat on Fe OMNC, suggesting that the generated *CH intermediate during the CH activation\n1 3 4\nprocess is more readily captured by Pd sites. Further, we have performed the quasi in-situ XPS to\nmonitor the variation of chemical states and surface electrons during the CH activation process,\n4\nwhere Fe -Pd OMNC was first treated with H O and then subjected to CH and light treatment in\n1 1 2 2 4\nan in-situ chamber. As shown in Fig. R9, the surface OH species (531.5 eV) in the O 1s spectra\nincrease significantly upon light irradiation under CH atmosphere, signifying that the H species in\n4 1 1\nC-H bond activation process. Moreover, the binding energy of Pd 3d significantly shifts towards a\nlower binding energy by 0.4 eV after CH and light treatment, suggesting that Pd sites tend to gain\n4\n11\nelectrons during the CH activation process (Sci. Adv. 11, eadu1602 (2025); Angew. Chem. Int. Ed.\n4\n64, e202425622(2025)). Considering that negative electrons nature of the carbon center in *CH ,\n3\nwe speculate that electrons obtained by the Pd sites during CH activation are likely to come from\n4\nthe *CH fragment. In fact, these experimental data are consistent with the density functional theory\n3\n(DFT) calculations and the AIMD simulations (see Figs. 4d-g and 5a, 5c-d in the revised main text\nand supplementary Figs. S36-40, S42-47, S50-52, S55-58, Tables R7 and R9 in revised supporting\ninformation).\nFinally, to prove the feasibility of in-situ formed O-Fe-Pd sites for C-H bond activation, we\npre-treated the Fe -Pd OMNC with H O to obtain a precatalyst with O-Fe-Pd sites on surface\n1 1 2 2\n(denoted as O/Fe -Pd OMNC). Then, in-situ EPR and in-situ FTIR spectra have been conducted\n1 1\non O/Fe -Pd OMNC to explore the activation of CH under H O free conditions. As shown in Fig.\n1 1 4 2 2\nR10a, a stable ·CH radical signal is detected over O/Fe -Pd OMNC without externally added H O .\n3 1 1 2 2\nMoreover, the intensity of ·CH signals in the O/Fe -Pd OMNC system is closer to that in Fe -Pd\n3 1 1 1 1\nOMNC with the assistant of H O (Fig. R10b). In addition, in-situ FTIR spectra exhibit the distinct\n2 2\nFTIR bands of *CH and *OH on O/Fe -Pd OMNC upon CH and light treatment, while\n3 1 1 4\nneglectable signals are observed on the surface of Fe -Pd OMNC without the assistant of H O\n1 1 2 2\n(Fig. R11). These results demonstrate that the in-situ formed O-Fe-Pd site on Fe -Pd OMNC is able\n1 1\nto drive the activation of C-H bond in CH under illumination. Thereafter, we have conducted the\n4\nphotothermal catalytic CH oxidation by using O/Fe -Pd OMNC as the catalyst without the addition\n4 1 1\nof H O (Fig. R12). We found that the pre-catalyst O/Fe -Pd OMNC exhibits surpassingly higher\n2 2 1 1\nmethanol production (0.787 mmol h-1) compared with the pristine Fe -Pd OMNC (0.035 mmol h-\n1 1\n1) under O condition, further highlighting the significant role of O-Fe-Pd sites in CH conversion.\n2 4\nIn the revised manuscript, we have included the above new results in Figs. 3i, 4b-c, 4h-i, 5e-h,\nsupplementary Figs. S34, S48, S53-54, S59, Table S8 and added the related discussions in the\nrevised main text (the first and last paragraphs of page 15, the second paragraph of page 20, the first\nparagraph of page 22, the first paragraph of page 23, the second and last paragraphs of page 24, the\nfirst paragraph of page 25) and revised supporting information (page 37). In addition, the\nintroduction section have also been revised (the first and second paragraphs of page 3, the first\nparagraph of page 4). Moreover, the relevant statements regarding the orbital interaction have been\nremoved (Fig. 5g and supplementary Figs. S46, S47 in the original manuscript and the abstract\nsection, the first paragraph of page 4 in revised main text).\ntreatment.\nFig. R5 (a, d) AFM, (b, e) KPFM images and (c, f) corresponding potential profile of Fe1-Pd1 OMNC after the\ntreatment of H2O2 (a-c) and H2O (d-f).\nFig. R7 In-situ FTIR spectra of the photothermal catalytic CH4 oxidation system over (a) Fe1-Pd1 OMNC, (b) Fe1\nOMNC, and (c) Pd1 OMNC.\nFig. R8 In-situ FTIR spectra of the photothermal catalytic CH4 oxidation system over (a) Fe1-Pd1 OMNC, (b) Fe1\nOMNC, and (c) Pd1 OMNC.\nSamples *CH3 (cm-1)\nFe1-Pd1 OMNC 1435 1470\nFe1 OMNC 1417 1446\nPd1 OMNC 1433 1472\nFig. R9 Quasi in-situ XPS spectra of O/Fe1-Pd1 OMNC before, and after CH4 and light treatment.\nFig. R10 In-situ EPR spectra of the photothermal catalytic CH4 oxidation system over (a) O/Fe1-Pd1 OMNC without\nthe addition of H2O2 and (b) Fe1-Pd1 OMNC, Fe1 OMNC and Pd1 OMNC with the addition of H2O2.\n(c) Fe1-Pd1 OMNC in the absence of H2O2.\nFig. R12 Photothermal catalytic CH4 oxidation over O/Fe1-Pd1 OMNC. Reaction conditions: Wcat. = 5 mg, VH2O =\n5 mL, PCH4 = 1.8 MPa, PO2 = 0.2 MPa, t = 2 h, light source: 300 W Xe lamp.\nComment 2: Furthermore, the authors claim to manipulate C-H bond cleavage by engineering the\nelectronic configuration of the catalyst surface. However, their proposed strategy of generating\ncharge-polarized regions through charge transfer from Fe to active oxygen species to influence C-\nH bond polarization has already been reported (J. Am. Chem. Soc. 2022, 144, 12357-12366).\nFurthermore, while they emphasize the impact of these charge-polarized regions and the role of\norbital overlap on the reaction process, their conclusions rely solely on theoretical calculations and\nlack sufficient experimental validation, rendering the findings inadequately substantiated.\nmanuscript. As the reviewer pointed out, previous report has demonstrated that the charge-\naccumulated Fe sites in ZnO/Fe O heterojunction prefer to adsorb CH molecules and influence C-\n2 3 4\nH bond polarization (J. Am. Chem. Soc. 144, 12357-12366 (2022)). Nevertheless, we firmly believe\nthat this report does not diminish the innovation of our study. We are deeply grateful for your\ninsightful recommendation of this exceptional literature, which has provided us with valuable\nguidance and inspiration. We have carefully cited this reference (see Ref. 18 in the revised main\ntext), and added a detailed comparative discussion in the revised manuscript, clearly highlighting\nthe unique aspects of our study. Here, we would like to respectfully emphasize the distinctive\ncontributions of our work compared to previous studies:\n1. Distinct activation mechanism toward C-H bond. Zheng et al. fabricated a ZnO/Fe O\n2 3\ncomposite and found that the photo-generated electrons in ZnO can transfer to Fe O during the\n2 3\nphotocatalytic process (J. Am. Chem. Soc. 144, 12357-12366 (2022)). DFT calculation\ndemonstrated that the high local charge accumulation on Fe sites reduced the CH adsorption energy\n4\nand facilitated the activation of C-H bond. Thus, the C-H activation process mainly occurred on\nindividual charged Fe site (Feδ-). In contrast, our work designed an asymmetric Fe-Pd diatomic\nactive site and demonstrated that oxidant prefers to be activated on Fe site to an axial *O, forming\na Oδ--Fe-Pdδ+ charge polarization region. Such in-situ formed polarization region jointly participates\nin the activation of C-H, among which the electron-rich Oδ- region is able to capture the Hδ+ fragment\nin CH and the remaining CH δ- species tends to be stabilized by the Pdδ+ site. Thus, beyond\n4 3\nproposing a novel strategy to boost the activation of inert C-H bond, our work also delves into the\nconversion behavior of oxidants on catalytic interface and their impact mechanism on inert\nmolecular activation. In order to clarify the proposed mechanism, we have conducted\ncomprehensive characterizations, in-situ spectra, DFT calculation as well as AIMD simulation to\nreveal the C-H bond activation in the original version (see Figs. 4a-b, 4d-g, 4j and 5a-d in the revised\nrevised main text, supplementary Figs. S35-47, S49-52, S55-58, Tables S7 and S9 in revised\nsupporting information). Following your insightful suggestion, we have also provided additional in-\nsitu spectra (e.g., in-situ FTIR and quasi in-situ XPS, in-situ EPR spectra), Zeta potential,\nKPFM\nand control experiments to robustly substantiate the central claims (see Figs. 4c, 4h-i, 5e-h in the\nrevised main text, supplementary Figs. S48, S53-54, S59 and Table S8 in revised supporting\ninformation).\n2. Different design concept of catalysts. In the mentioned reference, Zheng et al. elaborately\ndesigned a Z-scheme heterostructure composed of two different metal oxides (i.e., ZnO/Fe O ) to\n2 3\npromote the separation of photogenerated carriers. In our work, we have developed a template-\noriented encapsulation-pyrolysis protocol to integrate asymmetrically atomic sites on ordered\n17\nmacroporous N-doped carbon. The well-defined atomic structure enables fundemental\nunderstanding of the structure-performance relationships as well as the activation mechanism of C-\nH bond at the atomic/molecular levels. In addition, the constructed periodic pores may ensure the\nmaximum accessibility of active sites.\n3. Exceptional catalytic performance toward CH oxidation.\ncatalystic system over Fe -Pd OMNC affords an excellent photothermal performance toward the\n1 1\nselective oxidation of CH with an evolution rate of C1 oxygenates as high as 0.754 mmol h-1 when\n4\nusing H O as the oxidant. Considering the safety issue of H O during the photothermal catalytic\n2 2 2 2\nprocess, we first pre-treated the Fe -Pd OMNC with H O at room temperature (denoted as O/Fe -\n1 1 2 2 1\nPd OMNC) to construct a charge polarization region on catalyst surface (i.e., O-Fe-Pd sites).\n1 1\nactivity toward CH oxidation using O as the oxidant, delivering a methanol production rate of\n4 2\n0.787 mmol h-1 (Table R2). The yield of oxygenates is significantly higher than the previously\nreported catalysts for CH conversion under comparable conditions. Thus, this achievement might\n4\noffer a design principle of advanced catalytic system towards the efficient conversion of CH under\n4\nmild conditions.\nRegarding the concern about the lack of sufficient experimental validation, we have conducted\nadditional in-situ spectra analysis (e.g., in-situ FTIR and quasi in-situ XPS, in-situ EPR spectra),\nZeta potential, KPFM and control experiments to streghthen the central claims. Firstly, we have\nconducted the Zeta potential measurements, KPFM and XPS spectra to probe the O-Fe-Pd\nasymmetry charge stucture (Figs. R4-6). Secondly, we have supplemented additional in-situ FTIR\nspectra and quasi in-situ XPS analysis to further reveal the activation of C-H bond during the\nphotothermal CH oxidation process (Figs. R7-9 and Table R1). Finally, we have performed in-situ\nformed O-Fe-Pd sites for C-H activation (Figs. R10-11). Moreover, we have pre-treated the Fe -Pd\n1 1\nOMNC with H O to obtain a precatalyst with O-Fe-Pd sites on surface (denoted as O/Fe -Pd\n2 2 1 1\nOMNC) and found that the O/Fe -Pd OMNC exhibits surpassingly higher methanol production\n1 1\n(0.787 mmol h-1) compared with the pristine Fe -Pd OMNC (0.035 mmol h-1) under O condition,\n1 1 2\nfurther highlighting the significant role of O-Fe-Pd sites in CH conversion (Fig. R12). Please also\n4\nsee the detailed results in Respond to Comment #1.\nIn the revised manuscript, we have included the above new results in Figs. 3i, 4b-c, 4h-i, 5e-h,\nsupplementary Figs. S34, S48, S53-54, S59, Tables S6 and S8 and added the related discussions in\nthe revised main text (the first and last paragraphs of page 15; the second paragraph of page 20; the\nfirst paragraph of page 22; the first paragraph of page 23; the second and last paragraphs of page\n24; the first paragraph of page 25) and revised supporting information (page 37). In addition, the\n18\nintroduction section have also been revised (the first and second paragraphs of page 3; the first\nparagraph of page 4).\nWe sincerely appreciate your valuable feedback and constructive suggestions, and the\ncorresponding revisions have been carefully implemented to address all key points raised.\nComment 3: The experimental design for photocatalytic performance evaluation is not proper.\nFor\nexample, due to its high cost, H O has been rarely selected as the oxidant in current catalytic\n2 2\nsystems, and its use typically does not involve pressurized conditions. Furthermore, the reported\nyield of methanol is predicated on minimal levels of the utilized catalyst (1-5 mg). It is a generally\naccepted principle that photocatalytic activity does not increase linearly with the mass of the\ncatalyst. Given the minimal use of the catalyst, the quantity of methanol generated is, in comparison,\nrelatively low.\nResponse: We sincerely appreciate your insightful comments, which have been instrumental in\nstrengthening the rigor of our work. For the concern raised by the high cost of H O , we have\n2 2\nconducted the photothermal catalytic CH oxidation using O instead of H O as the oxidant. As\n4 2 2 2\nshown in Fig. R13, Fe -Pd OMNC demonstrates good catalytic performance in the selective\n1 1\noxidation of CH with a methanol production rate of 35.7 μmol·h-1 and a selectivity of nearly 100%\n4\nin the presence of O . We also performed the 13C isotope labeling experiment using 13CH as the\n2 4\nfeedstock to confirm the source of the product. As shown in Fig. R14, the 13C NMR spectra reveal\nthe featured peak matchs well with the 13C-labeled methanol (13CH OH), confirming that the\n3\nmethanol product truly came from the oxidation of 13CH . Considering the safety issue of H O\n4 2 2\nduring the photothermal catalytic process, we first pre-treated the Fe -Pd OMNC with H O at\n1 1 2 2\nroom temperature (denoted as O/Fe -Pd OMNC) to construct a charge polarization region on\n1 1\ncatalyst surface (i.e., O-Fe-Pd site). Unexpectedly, the as-prepared O/Fe -Pd OMNC exhibits an\n1 1\nexceptional photothermal catalytic activity toward CH oxidation using O as the oxidant, delivering\n4 2\na methanol production rate of 0.787 mmol h-1. The obtained methanol yield is significantly higher\nthan the previously reported catalysts in CH conversion under comparable conditions (Table R2).\nthe mass of the catalyst. In this case, we firstly investigated the effect of catalyst dosages on the\nphotothermal catalytic activity of CH oxidation. As shown in Fig. R15, the yield of C1 oxygenated\n4\nproducts significantly increases as the dosage of Fe -Pd OMNC changes from 1 to 5 mg. However,\n1 1\nfurther increase in the amount of catalyst will slow down the trend of performance improvement.\nAccording to the suggestion, we have revised the unit of C1 oxygenated products from mmol g-1 h-\n1 into mmol h-1 to avoid the misleading interpretation of catalytic activity induced by the catalyst\n19\ndosages. As shown in Table R3, the yield of C1 oxygenates is significantly higher than the\npreviously reported catalysts for CH conversion under comparable conditions.\nconditions of the Fe -Pd OMNC photothermal catalytic system. Firstly, we have lifted the light\n1 1\nintensity of catalytic system to accelerate the CH OOH-to-CH OH process (Nat. Commun. 16,\n3 3\n2831-2545 (2025); Sci. Adv. 10, eado9664 (2024)). As shown in Fig. R16a, the CH OH yield\n3\nincreases from 0.096 to 0.319 mmol h-1 with the light intensity increases from 600 to 1000 mW cm-\n2. Secondly, we have conducted the photothermal catalytic CH oxidation by using both O and\n4 2\nH O as the oxidants in order to promote the CH OOH-to-CH OH process (Nat. Commun. 13, 1375-\n2 2 3 3\n1385 (2022); Adv. Sci. 11, 2305471 (2024)). As shown in Fig. R16b, the introduction of O\n2\nsignificantly increases the methanol yield from 0.096 to 0.515 mmol h-1. Finally, we pre-treated the\nFe -Pd OMNC with H O at room temperature and performed the photothermal catalytic CH\n1 1 2 2 4\noxidation under O condition to avoid the fomation of deep-oxidized product (i.e., HCOOH). We\n2\nfound that the as-prepared O/Fe -Pd OMNC exhibits excellent methanol production rate of 0.787\n1 1\nmmol h-1 (Fig. R16c). Actually, the methanol yield of these photothermal catalytic systems over\nFe -Pd OMNC are significantly superior to that of previous reports under comparable conditions,\n1 1\nhighlighting the structural virtue of Fe -Pd OMNC in CH oxidation.\n1 1 4\nWe have included the above results in Figs. 3f-i and supplementary Figs. S27, S34, Tables S5-\n6 and added the related discussions in the revised main text (the last paragraph of page 11, the\nsecond paragraph of page 13, the last paragraph of page 14; the first paragraph of page 15) and page\n37 of the revised supplementary information.\nFig. R13 Photothermal catalytic CH4 oxidation over Fe1-Pd1 OMNC with O2 as the oxidant. Reaction conditions:\nWcat. = 5 mg, VH2O = 5 mL, PCH4 = 1.8 MPa, PO2 = 0.2 MPa, light source: 300 W Xe lamp.\nas the oxidant.\nFig. R15 Effect of catalst amounts on the CH4 catalytic conversion over Fe1-Pd1 OMNC. Reaction conditions: VH2O\n= 5 mL, PCH4 = 2 MPa, MH2O2 = 5 mol/L, t = 2 h, light source: 300 W Xe lamp.\nTable R2. Catalytic performance comparison of Fe1-Pd1 OMNC with previously reported representative catalysts\nfor the conversion of CH4 (O2 as oxidant).\nSamples Oxidant Catalyst Methanol performance Ref.\namounts (mmol h-1)\n(mg)\nO/Fe1-Pd1 OMNC O2 5 0.787 This Work\nO/Fe1-Pd1 OMNC O2 10 1.197 This Work\ne202505267 (2025)\nPt/WO3 O2 10 0.021 J. Phy. Chem. Lett. 12, 7459-\n7465 (2021).\nAu0.75/ZnO O2 10 0.006 J. Mater. Chem. A 8, 13277-\n13284 (2020).\n0.1 wt.% Pd/ZnO O2 10 0.030 J. Am. Chem. Soc. 141,\n20507-20515 (2019).\nAu9Pd1/ZnO O2 10 0.063 Adv.Energy Mater. 14,\n2303642 (2024).\n10 wt%N- O2 10 0.042 Appl. Catal. B Environ 365,\nFe2Ti3O9/TiO2 124934 (2025).\nCu–Pd/anatase O2 20 0.636 Energy Environ. Sci. 17,\n9122-9133 (2024).\nZnO/Fe2O3 O2 10 0.001 J. Am. Chem. Soc. 144,\n12357-12366 (2022).\nAu0.2Cu0.15-ZnO O2 20 0.224 J. Am. Chem. Soc. 144,\n740-750 (2022).\n0.1wt% Au/ZnO O2 10 0.125 J. Am. Chem. Soc. 141,\n20507 (2019).\nAu0.75/ZnO O2 10 0.007 J. Mater. Chem. A 8,\n13277 (2020).\nAu-CoOx/TiO2 O2 10 0.025 ACS Catal. 10, 14318\n(2020).\n5.3%WTiO2 O2 10 0.061 ChemSusChem 15,\ne202200548 (2022).\nAuNPs/In2O3 O2 10 0.021 J. Am. Chem. Soc. 145,\n2698-2707 (2023).\n0.5Pd-ZnTiLDHA200 O2 20 0.049 Adv. Energy Mater.\n13, 2301118 (2023).\nfor the conversion of CH4 (H2O2 as oxidant).\nCatalyst\nOxygenates Yield Selectiv TOF\nCatalyst Additives amounts Ref.\n(mmol·h-1) ity (%) (h-1)\n(mg)\n5 0.754 ~100 1106.4 This work\nFe1-Pd1 OMNC H2O2 10 0.968 ~100 710.2 This work\n20 1.209 ~100 443.5 This work\nNano Lett. 21, 10368-\n0.75FeCA800-4 H2O2 10 0.132 ~100 -\n10376 (2021).\nPNAS 120,\nCu-BTC-P-235 H2O2 25 0.042 99.6 -\ne2206619120 (2023).\nAngew. Chem. Int. Ed.\nCu-Fe (2/0.1)/ZSM-5 H2O2 27 0.051 80 70\n51, 5129-5133 (2012).\nAngew. Chem. Int. Ed.\nUiO-66(2.5TFA)-Fe H2O2 25 0.018 97.9 -\n60, 5811-5815 (2021).\nAngew. Chem. Int. Ed.\n1 wt%Cr1/TiO2 H2O2 10 0.043 93 57.9\n59, 1216-1219 (2020).\nAngew. Chem. Int. Ed.\nPd1O4/ZSM-\nH2O2 28 0.027 86.5 3.2 55, 13441-13445\n5+2wt%CuO\n(2016).\nJ. Am. Chem. Soc.\nRu1/UiO-66 H2O2 5 0.074 ~ 100 185.4 145, 13169-13180\n(2023).\nChemcatchem. 15,\n0.28Fe1/ZIF-8 H2O2 30 0.074 96.8 45\ne202201234 (2023).\nScience 358, 223-226\nAuPd colloid H2O2 100 0.029 92 8.6\n(2017).\nChem 4, 1902-1910\nFeN4/GN-2.7 H2O2 50 0.001 94 0.4\n(2018).\nAngew. Chem. Int. Ed.\n0.68CNT@PNC/Ni1 H2O2 5 0.020 94.2 - 58, 18388-18393\n(2019).\n0.5Rh1/TiO2+CuCl2 H2O2 16 0.007 99 - 61, e202201540\n(2022).\nJ. Am. Chem. Soc.\nFe-HZ5-TF H2O2 27 0.040 ~ 91.1 451.0 145, 5888-5898\n(2023).\nAngew. Chem. Int. Ed.\n1AuPd/TiO2 H2O2 28 0.006 88.4 25.7\n52, 1280-1284 (2013).\nJ. Am. Chem. Soc.\n0.01 wt%Pd/ZSM-5+2\nH2O2 30 0.030 98.6 3.2 139, 17694-17699\nwt%CuO\n(2017).\nACS Catal. 8, 5542-\n0.3 wt%Rh/ZrO2 H2O2 10 0.001 78.4 1.3\n5548 (2018).\nAngew. Chem. Int. Ed.\n2.5 wt%CuFe/ZSM-5 H2O2 27 0.005 85 31.4\n51, 5129-5133 (2012).\nACS Catal. 8, 5542-\nMIL-53(Fe, Al) H2O2 10 0.050 80 90\n5548 (2018).\nChem. Commun. 56,\nCu-SAs/C3N4 H2O2 30 0.005 95 11\n14677-14680 (2020).\nAppl. Catal. B-\nCu1/ZSM-5 H2O2 28 0.034 99 157 Environ. 285, 119827\n(2021).\nChem. Eng. J. 450,\nCu1/ZiF-7 H2O2 20 0.001 - 1.6\n138472 (2022).\nEES Catal. 1, 153-\nCr1/ZSM-5 H2O2 10 0.211 99.9 99.8\n161(2023).\nAppl. Catal. B-\n0.38wt%Cu2@C3N4-D H2O2 10 0.048 - 83 Environ. 299, 120682\n(2021).\nNat. Commun. 13,\n0.35wt%Cu2@C3N4 H2O2 10 0.056 99 8.3\n1375-1385 (2022).\nACS Catal. 14, 10689-\nFe1/Cu1-C3Nx H2O2 10 0.188 ~100 534.1\n10700 (2024).\npresence of 0.2 MPa O2. (c) Different pressures. Reaction conditions in (a)-(b): Wcat. = 5 mg, VH2O = 5 mL, PCH4 =\nWcat. = 5 mg, VH2O = 5 mL, PCH4 = 1.8 MPa, PO2 = 0.2 MPa, t = 2 h, light source: 300 W Xe lamp.\nComment 4: Several critical data are notably absent from the manuscript. For example, quantum\nefficiency, carbon balance and CH conversion rate are all very important in evaluating the\n4\ncatalytic performance of CH conversion, but they are not given in this manuscript. The evaluation\n4\ncriteria for the products and the description of the product detection module are unclear. For\nexample, it does not specify whether C products are detected and how a UV-visible\n2\nspectrophotometer is used to measure HCHO. Additionally, key experiments should be repeated,\nand error bars should be included.\nResponse: We appreciate the reviewer’s insightful comments and suggestions. Following the\nsuggestion, we have firstly measured the apparent quantum yield (AQY) of the photothermal\ncatalytic system under the illumination of 100 W LED light (450 nm) at 63 °C. As shown in\nEquation R2, upon irradiation at 450 nm and 63 °C, the AQY of the Fe -Pd OMNC photothermal\n1 1\ncatalytic system is estimated to be 3.34%. Secondly, we have determined the CH conversion rate\n4\nin the photothermal catalytic system by using Argon as the internal standard (Fig. R17 and Equation\nR3). Thereafter, we have evaluated the carbon balance of the photothermal catalytic system over\nFe -Pd OMNC (Equation R4). The result shows that the carbon balance of the present photothermal\n1 1\ncatalytic system is higher than 97%, suggesting that the C1 oxygenated products came from the\ntransformation of CH . To confirm the source of the product, we further conducted the 13C isotope\n4\nlabeling experiment using 13CH as the feedstock. As shown in Fig. R18, the 13C NMR spectra\n4\nreveal the featured peaks match well with the 13C-labeled formic acid (H13COOH),\nmethyl\nhydroperoxide (13CH OOH), and methanol (13CH OH), indicating that C1 oxygenated products\n3 3\nindeed came from the oxidation of 13CH rather than from the catalyst itself.\n2\nspectra to rule out the formation of other products. As shown in Fig. R19, no NMR peaks assigned\nto ethanol (chemical shift of 1.72 ppm (-CH ) and 3.7 ppm (-CH -)) (Nat. Commun. 15,\n3 2\n25\n10451 (2024)) and acetic acid (chemical shift of 2.08 ppm) are detected in the 1H NMR spectra of\nreaction solution. In addition, the GC spectra clearly depict that no C hydrocarbon products (e.g.,\n2\nethane, ethylene, and acetylene) are formed during the photothermal catalytic process. For the\ndetection of HCHO, we have provided the detail measuring method and the standard curve for UV-\nvisible spectrophotometer in the revised manuscript (Fig. R20). The results show that only a trace\namount of HCHO is detected in the CH photothermal catalytic system over Fe -Pd OMNC.\n4 1 1\nFinally, we have provided the error bars for the catalytic performance data of all the studied\nsamples and included related description in the captions of the relevant figures and the first\nparagraph of page 29 in the revised main text.\nIn the revised manuscript, we have included the above results in Fig. 3f, supplementary Figs.\nS16-19, S28, S34 and added the related discussions in the revised main text (the second paragraph\nof page 10, the first paragraph of page 12, the first paragraph of page 13, the first paragraph of page\n29, the third and last paragraphs of page 30, the first paragraph of page 31) and revised supporting\ninformation (pages 22 and 31).\nThe apparent quantum yield (AQY) of the photothermal catalytic system was measured under the illumination\nof 100 W LED light (450 nm) at 63 °C, which can be calculated by the following formula:\nAQY=\nNe×100%= 109(v×NA×K)×(h×c)\n×100%=3.34% (R2)\nNP (I×A×λ)\nwhere v(HCOOH, CH3OH, CH3OOH) = 3.93889 × 10-8 mol s-1, 9.99861 × 10-9 mol s-1, 1.28375 × 10-7 mol s-1;\nK(HCOOH, CH3OH, CH3OOH) = 4, 2, 6; NA = 6.022 × 1023 mol-1; T = 2 h, A = 12.56 cm2; λ = 450 nm, I = 600 ×\n10-3 W m-2, h = 6.62 × 10-34 J s-1, c = 3.0 × 108 m s-1. For Fe1-Pd1 OMNC: AQY% = [(4 × 3.93889 × 10-8 + 2 ×9.99861\n× 10-9 + 6 × 1.28375 × 10-7 ) × 6.022 × 1023] × (6.62 × 10-34 × 3.0 × 108)/(600 × 10-3 × 12.566 × 450 ×10-9) = 3.3410%\nFig. R17 GC chromatograms of the gaseous products (a) before and (b) after photothermal catalytic CH4 oxidation\nwith Ar as an internal standard.\nfollowing formula:\nCon. (CH4 %) =(1−\nnt(CH4)\n)× 100% =0.53% (R3)\nn0(CH4)\nwhere nt(CH4) and n0(CH4) represent the moles of CH4 after and before the reaction, respectively.\nThe carbon balance (%) in the photothermal catalytic system can be calculated by the following formula:\ncarbon balance (%) =\n𝑛𝑡(𝐶1)\n×100% =97.01% (R4)\n𝑛0(𝐶𝐻4)\nwhere nt(C1) and n0(CH4) represent the moles of products and reactant gas, respectively.\nwhere nt(HCOOH, CH3OH, CH3OOH, CO2) = 0.3919 × 10−3 mol, 0.19144 × 10−3 mol, 0.9243 × 10−3 mol, 0.0125\n× 10−3 mol; P = 2 MPa; T=330 K; R = 8.314; V=200 mL; n0(CH4) = 0.1457 mol. Carbon balance (%) = (0.76 × 10-\n3)/(0.7834 × 10-3) × 100 = 97.0130%\nFig. 18 13C NMR spectra obtained from typical reaction products of photothermal catalytic CH4 oxidation with (a)\nH2O2 and (b) O2 as the oxidants.\nFig. R19 1H NMR spectra of (a) a mixture of C2H5OH, CH3OH, CH3COOH and HCOOH and (b) reaction solution.\nphotographs (inset) of the reaction solution and 0.01 mmol L-1 HCHO solution.\nComment 5: The intensity ratio of the D band to the G band (I /I ) in the Raman spectrum was not\nD G\nexplicitly mentioned. This ratio needs to be supplemented to quantify the graphitization degree of\nthe carbon matrix and to discuss its influence on the electron transport performance and the\nconstruction of the charge polarization region.\nResponse: We sincerely appreciate the reviewer’s insightful suggestion. As suggestted, we have\nprovided the intensity ratio of the D band to the G band (I /I ) in the Raman spectra to quantify the\nD G\ngraphitization degree of the carbon matrix. As shown in Fig. R21 and Table R4, Fe -Pd OMNC\n1 1\nexhibits the distinct D band (ca. 1350 cm-1) and G band (ca. 1590 cm-1) of graphitized carbon with\na I /I ratio of 1.0215. Notably, the I /I ratio of Fe -Pd OMNC is slightly greater than that of\nD G D G 1 1\nOMNC, suggesting that the introduction of metal species can induce the formation of defects in the\ncarbon skeleton (Nat. Commun. 14, 7549 (2023); Angew. Chem. Int. Ed. 64, e202502430 (2025)).\nGenerally, the fomation of defects in a phototcatalyst is able to promote the generation of photo-\ninduced carriers (Appl. Catal. B-Environ. 365, 125001 (2025)). Actually, the photocurrent response\ntest demonstrates that Fe -Pd OMNC exhibits a higher current density than OMNC (Fig. R22),\n1 1\nconfirming that the presence of dual Fe -Pd metals sites can promote the fomation of photo-induced\n1 1\nelectron. In the revised manuscript, we have included these results in supplementary Figs. S4, S31\nand Table S1 and added the related discussions in the second paragraph of page 5 and the first\nparagraph of page 14 in the revised main text and pages 7 and 34 of the revised supporting\ninformation.\nTable R4 Comparison of ID/IG values in Raman spectra of different samples.\nSample D:1350 cm⁻¹ G:1590 cm⁻¹ ID/IG\nFe1-Pd1 OMNC 1452.24 1421.67 1.0215\nFe1 OMNC 2095.78 2051.31 1.0217\nPd1 OMNC 1938.98 1898.13 1.0215\nOMNC 517.077 517.36 0.9994\nFig. R22 Photocurrent signals of Fe1-Pd1 OMNC and OMNC.\nand were they verified by ICP-OES? Quantitative data need to be provided and compared with the\ntheoretical values.\nResponse: We sincerely appreciate the reviewer’s insightful comments. The contents of Fe and Pd\nin Fe -Pd OMNC are measured to be 0.58 and 0.35 wt% (Table R5 and Equation R5), respectively\n1 1\nby the inductively coupled plasma atomic emission spectroscopy (ICP-AES). In the revised\nmanuscript, we have provided the quantitative data of ICP-AES in supplementary Table S2 and\nrevised the related discussions in the second paragraph of page 6 and the last paragraph of page 28\nof the revised main text. In addition, we have roughly estimated the theoretical contents of Fe and\nPd in Fe -Pd OMNC according to the mass loss of support during the pyrolysis process (weight\n1 1\nloss percentage of 75%). We first assumed that the metal precursor would not be lost during the\npyrolysis process. Thus, we can estimate the theoretical loadings of Fe and Pd as 8.92 and 6.84 wt%,\nrespectively according to the metals contents in 3DOM FePd-ZIF (Table R5). We found that the\ntheoretical loadings of Fe and Pd are much greater than the measured values, which should be due\nto the volatilization of metal precursors caused by high-temperature treatment. We have included\nthe related discussions on page 64 of the revised supporting information.\nTable R5. Raw data of inductive coupled plasma atomic emission spectroscopy (ICP-AES) tests (weight loss\npercentage of 75%).\nMetered\nMet Weight Concentration Dilution Content of\nSample volume (Vo:\nal (W: mg) (C: mg L-1) factor (I) metal (wt%)\nmL)\nFe1-Pd1 OMNC Fe 20 50 2.31 1 0.58\nPd 20 50 1.40 1 0.35\n3DOM FePd-ZIF Fe 15 50 7.58 1 2.53\nPd 15 50 5.82 1 1.94\nThe matel content is calculated by the following equation:\nw(%)=\nC( m\nL\ng )∗V0 (mL)\n∗100% (R5)\nm(g)∗106\nComment 7: In the direct comparison of the XANES spectra of the oxidation states of Fe and Pd\nwith standard samples (such as FeO, Fe O , PdO), the author indicates whether \"No metal-oxygen\n2 3\nbonds (i.e., Fe-O and Pd-O) are observed in the FT-EXAFS spectra of Fe -Pd OMNC\" is\n1 1\nreasonable? List the corresponding literature support.\ninappropriate analysis and discussion of the FT-EXAFS spectra. In the revised manuscript, we have\nrevised the discussions of the FT-EXAFS spectra of Fe -Pd OMNC to avoid any misleading\n1 1\ninterpretation (Figs. R23-24). The revisions are as follows, please also see the revisions in Fig. 2c-\nd and supplementary Figs. S11-12, and the related discussions in the first paragraph of page 8 in the\nrevised main text.\n“As shown in Fig. R23, the Fe K-edge EXAFS spectrum of Fe1-Pd1 OMNC exhibits a main peak located at 1.51 Å\nthat is similar to that of FePc, corresponding to the Fe-N scattering path. No Fe-Fe scattering peaks of Fe foil (i.e.,\n2.17 Å) FeO (i.e., 2.67 Å) or Fe2O3 (i.e., 2.58 Å) are detected. In addition, the k3χ(k) oscillation curve of Fe1-Pd1\nOMNC differs from that of Fe foil and FeO, ruling out the presence of metalic Fe or Fe oxide nanoparticles. In the\ncase of the Pd K-edge FT-EXAFS, a dominant peak at 1.5 Å is observed, corresponding to the Pd-N scattering path.\nNo Pd-Pd scattering peaks of Pd foil (i.e., 2.50 Å) or PdO (i.e., 2.93 Å) are detected. In addition, two-dimensional\nwavelet transform shows that the Pd–N coordination in Fe1-Pd1 OMNC is different from the Pd-Pd or Pd-O\ncoordinations in Pd foil or PdO. According to the well-matched EXAFS fitting, the coordination numbers of Fe-N\nand Pd-N in Fe1-Pd1 OMNC are calculated to be ca. 4 and 3, respectively.”\nFig. R23 FT-EXAFS spectra of (a) Fe K-edge and (b) Pd K-edge.\nFig. R24 WT k2-weighted EXAFS contour plots of (a) Fe1-Pd1 OMNC, (b) PdO and (c) Pd foil.\nmanuscript. Moreover, is the colored plots of Fig. 1j three-dimensional? If it is, why are there only\ntwo coordinate axises?\nResponse: We sincerely appreciate the reviewer’s valuable suggestion. As suggestted, we have\nmarked the selected area for Fig. 1j with a yellow box in Fig. 1i. In addition, the scale of the z-axis\nhas been added in Fig. 1j.\nFig. R25 (a) AC-HAADF-STEM images of Fe1-Pd1 OMNC. (b) Randomly selected images and the intensity profiles\nof atomically dispersed Fe and Pd dual sites.\nComment 9: XPS fitting should follow important principles (in Fig. S10), such as: the peak width\nat half height of 2p and 3d doubles peaks should be equal; the peak area radio of 3d 5/2 to 3d 3/2\nis 3:2 etc. Please check the XPS results and exclude the irrational fitting parameters.\nResponse: We sincerely appreciate the reviewer’s professional comment and suggestion.\nAccording to the suggestion, we have reconducted and re-fitted the XPS spectra where the peak\nwidth at half height and the peak area radio have been considered. As shown in Fig. R26, the Fe 2p\nand Pd 3d XPS spectra reveal the positively charged centers of Fe and Pd in Fe -Pd OMNC (J. Am.\n1 1\nChem. Soc. 147, 18953-18962 (2025); Nat. Synth. 4, 965-975 (2025)), which is consistent with the\nresults of XANES and EXAFS. In the revised manuscript, we have included the re-fitted result in\nFig. S10 of the revised supporting information.\nComment 10: Some informal English expressions can still be detected in the manuscript, for\nexamples, “As shown in Fig. 4a-b and Supplementary Fig. S27a-b, the distinct six prominent\ncharacteristic signals (4 of strong and 2 of relatively weak peaks) and 1:1:1:1 quartet pattern are\nobserved when the Fe -Pd OMNC photothermal reaction is performed”, and additional efforts are\n1 1\nrequired to optimize them.\nResponse: Thanks for the valuable suggestion. We have carefully checked and polished the whole\narticle, and the informal English expressions were corrected in the revised main text (the second\nparagraph of page 15).\nComment 11: The catalytic performance-related experiments in the Supporting Information should\nspecify the detailed experimental conditions. Additionally, the conclusions drawn from the\ncomparative experiments should be clearly stated in the main text.\nResponse: We appreciate the reviewer’s valuable comment and suggestions. In the revised\nmanuscript, we have provided the complete photothermal catalytic information and condition in the\nexperimental method section and the captions of all figures. In addition, the conclusions drawn from\nthe comparative experiments have been clearly stated in the main text. Please see the revisions in\nthe captions of Figs. 3, S25-27, S34, the second paragraph of page 11, the second paragraph of page\n13, the last paragraph of page 14, the first paragraph of page 15 in the revised main text and pages\n28 and 37 in the revised supporting information.\nComment 12: The original text \"Moreover, an obvious photocurrent signal was observed when\nFe1-Pd1 OMNC was exposed in the light environment, implying the existence of excited electrons\"\nlacks supporting data.\nresponse data in the revised manuscript. As shown in Fig. R27, an obvious photocurrent signal was\nobserved when Fe -Pd OMNC was exposed in the Xe lamp environment, implying the existence\n1 1\nof excited electrons. In addition, Fe -Pd OMNC exhibits a higher current density than OMNC,\n1 1\nsuggesting that the presence of dual Fe -Pd metals sites can promote the fomation of photo-induced\n1 1\nelectron. In the revised manuscript, we have included the results in Fig. S31 and added the related\ndiscussions in the first paragraph of page 14 in the revised main text and page 34 in the supporting\ninformation.\nFig. R27 Photocurrent signals of Fe1-Pd1 OMNC and OMNC.\nReviewer #1: All the points concerned have been addressed and this manuscript can be accepted in\nits current form.\nResponse: We thank the reviewer again for her/his valuable comments and suggestions that have\nhelped us to improve the quality of this manuscript significantly.\nReviewer #2: The present manuscript is suitable for publication.\nResponse: We thank the reviewer again for her/his valuable comments and suggestions that have\nhelped us to improve the quality of this manuscript significantly.\nReviewer #3: Upon reviewing the feedback, I note that the authors did not directly address the issue\nof orbital interaction raised in the previous comments, but instead opted for the removal of the\nrelated descriptions in the manuscript. Furthermore, although the authors have diligently addressed\nsome of the reviewers' concerns, the following points require further attention.\nResponse: We would like to extend our deepest gratitude to the detailed and thorough feedback,\nwhich has helped us to further imrpove the quality of this manuscript.\nIn this work, we uncovered a principal fact that the in-situ construction of charge-polarized\nregions on diatomic active sites can induce the polarization and cleavage of C-H bond in CH .\ndetail, we designed the Fe-Pd diatomic active sites and found that the oxidant preferred to be\nactivated on Fe site to an axial *O, forming an Oδ--Fe-Pdδ+ charge polarization region. Such in-situ\nformed polarization regions jointly participated in the activation of C-H bond, among which the\nelectron-rich Oδ- region can capture the Hδ+ fragment in CH and the remaining CH δ- species tended\n4 3\nto be stabilized by the Pdδ+ site. During the CH activation process, the orbital interactions of s/d-p\n4\nwere estabished between the fragments (i.e., *H and *CH ) in CH and active sites, which then\n3 4\nserved as the electronic transport bridges to inject electrons from catalyst surface into CH\n4\nmolecules to realize their activation. We sincerely apologize for any ambiguities in our discussion\nof the role of orbital interactions in C-H bond activation. As suggested, we have supplemented the\nfragment orbital analysis to fully elucidate the orbital interactions and the eletron transfer\nmechanism during the activation of C-H bond on Fe -Pd OMNC.\n1 1\nWe first ingvestigated the orbital interactions and the eletron transfer between axial *O and Fe\nsite in Fe -Pd OMNC. It is clear that the 3d orbital (i.e., dz2) of Fe site exhibits a large extent of\n1 1\noverlap with the p orbital of O site, pointing out their strong bonding via d-p interaction (Fig. R1).\nFragment orbital analysis (Fig. R2) displays that the interaction between Fe and O is dominated by\nthe hybridization of Fe dxz, dyz and dz2 orbitals with the O 2p orbitals, giving rise to three bonding\norbitals (i.e., dxz-π*, dz2-π*, dyz-π*) and their corresponding antibonding counterparts [i.e., (dxz-\nπ*)*, (dz2-π*)*, (dyz-π*)*]. This bonding model suggests that the electrons in the d orbitals of Fe\nare partially transferred to the singly occupied p orbitals of O via the dz2-pz interaction, leading to\nthe aggregation of electrons on O site and the formation of Oδ--Fe-Pdδ+ charge polarization region.\nSuch a electron transfer process is consistent with the charge‑density‑difference and bader charge\nanalysis (Fig. R3).\nactivation process of CH on the Oδ--Fe-Pdδ+ charge-polarized region. In this case, four catalyst\n4\nmodels, i.e., with CH before adsorption (denoted as CH /O-Fe -Pd -N C), after adsorption of CH\n4 4 1 1 6 4\n(denoted as CH -O-Fe -Pd -N C), C-H bond cleavage (denoted as CH /OH-Fe -Pd -N C) and\n4 1 1 6 3 1 1 6\ncomplete activation (denoted as OH-Fe -Pd -CH -N C) were constructed. In the case of the model\n1 1 3 6\nwith CH before adsorption (i.e., CH /O-Fe -Pd -N C), the electrons in CH are filled in the bonding\n4 4 1 1 6 4\norbitals, thus maintaining its extremely stable structure (Fig. R4). In addition, the 3d orbitals of Fe\nand the 2p orbitals of O have formed three strong bonding orbitals and corresponding antibonding\norbitals through d-p hybridization, thus enabling the electrons transfer from Fe to the O site.\nSubsequently, the positively charged H atom in CH is readily captured by the negatively charged\nthe partial density of states (PDOS) calculations clearly demonstrate that the p orbitals of O site (i.e.,\n2p ) in O-Fe-Pd exhibit a large extent of overlap with the 1s orbital of H atom in CH , pointing out\nZ 4\ntheir strong bonding via s-p obital interaction (Fig. R6). This orbital interaction can be further\nelucidated through fragment orbital analysis, which shows that the 2p orbitals of O site (primarily\nthe 2px orbital) undergo s-p hybridization with the 1s orbital of H, forming a new O-H bonding\norbital (Figs. R5 and R7). Significantly, the electrons in the 2p orbitals of O site is readily transfered\nto the σ* antibonding orbital in CH through the newly formed s-p obital interaction. Accordingly,\n4\nthe injection of electrons into the σ* antibonding orbital of CH molecule is able to weaken the\n4\nbonding interaction within CH , leading to the breakage of C-H bond (Science 380, 955-960 (2023)).\n3\nfragment far from O atom increases by 0.25 e- after the breakage of C-H bond (Fig. R8). This formed\nelectron-rich region will induce the CH δ- fragment to be landed on the electron-deficient region\n3\n(i.e., Pdδ+ site), thus leading to the complete activation of CH . Fragment orbital analysis exhibits\n4\nthat the 2p orbitals of C in CH undergo p-d orbital interaction with the 4d orbitals of Pd (primarily\n3\nthe dz2 orbital), forming a stable coordination bond with several d-π bonding and antibonding\norbitals (Figs. R9-10). Such p-d orbital interaction can serve as an electronic transport bridge to\ntranfer electrons from the CH fragment with lone pair electrons to the 4d orbitals of Pd, therefore\n3\nrealizing the complete activation of CH and the cyclic transfer of electrons within the catalytic\n4\nsystem.\nIn brief, the constructed Oδ--Fe-Pdδ+ charge polarization region can capture CH , giving rise to\n4\nthe formation of s-p obital interaction between O and H atoms. This s-p orbital interaction then\nserves as an electronic transport bridge to inject electrons from the electron-rich Oδ- sites into the\nσ* antibonding orbital of CH , facilitating the breakage of C-H bond. Meanwhile, the electrons in\n4\nthe remained CH fragment transfer to the electron-deficient Pd site via p-d coordination interactions,\n3\nachieving the complete activation of CH .\nsupplementary Figs. S69, S73-77 and added the related discussions in the revised main text (the\nAbstract section, the first paragraph of page 4, the second paragraph of page 24, the second\nparagraph of page 26 and the computational details section on page 33) and revised supporting\ninformation (pages 72, 76, 78-79).\nFig. R2 Model diagrams and fragment orbital analysis of O-Fe1-Pd1-N6C.\nFig. R3 Charge density differences and the integration of ∆ρ in planes along the Z-direction of O coordinated Fe1-\nPd1-N6C.\nFig. R5 Model diagrams and fragment orbital analysis of CH4-O-Fe1-Pd1-N6C with after adsorption of CH4.\nFig. R6 (a) PDOS and (b) pCOHP analysis of CH4-O-Fe1-Pd1-N6C.\nFig. R8 Charge density differences of CH3/OH-Fe1-Pd1-N6C.\nFig. R9 Model diagrams and fragment orbital analysis of OH-Fe1-Pd1-CH3-N6C with complete activation of CH4.\nFig. R10 PDOS analysis of Pd-CH3 in OH-Fe1-Pd1-CH3-N6C. (b) pCOHP of Pd-C in OH-Fe1-Pd1-CH3-N6C.\n1 1\nunder light irradiation would jointly participate in the oxidation of CH , instead of undergoing a\n4\nsimple photo-derived thermal catalysis,\" but they do not explain the respective roles of\nphotoinduced electrons and photogenerated heat in methane conversion, particularly regarding\ntheir effects on charge polarization. This requires the authors to provide additional experimental\nevidence for clarification.\nResponse: We sincerely appreciate the insightful comments and suggestions. As suggested, we\nhave supplemented a series of controlled experiments to verify the specific effect of the combined\naction of light and heat (Figs. R11-23 and Table R1). The results unambiguously demonstrate that\nlight primarily generates photoexcited electrons, which directly participate in the catalytic steps,\nwhile photo-induced heat accelerates the overall reaction kinetics. Please also see the detailed results\nin the response to Comment 2.\nConsidering that the generation and migration dynamics of photogenerated electrons might be\naffected by the photo-induced heat (e.g., J. Am. Chem. Soc. 147, 35913-35923 (2025)), we further\nmeasured the photocurrent of Fe ‑Pd OMNC at varous temperatures. Significantly, the\n1 1\nphotocurrent of Fe ‑Pd OMNC increases exponentially as the solution temperature is raised from\n1 1\n25 to 63 ℃ (Fig. R11). Moreover, this amplification effect of photocurrent becomes more\nsignificant at higher temperatures. These results reveal that the heat generated by Fe ‑Pd OMNC\n1 1\nunder illumination plays an indispensable role in enhancing the generation of photoinduced\nelectrons. We further explored the electron transfer resistance of Fe ‑Pd OMNC at different\n1 1\ntemperatures using electrochemical impedance spectroscopy (EIS), where the data were fitted by\nequivalent circuit model (Fig. R12 and Table R1). The results reveal that the electron transfer\nresistance of Fe ‑Pd OMNC decreases remarkably upon raising the temperature, suggesting that\n1 1\nthe photo-induced heat is able to reduce the migration resistance of photogenerated electrons. Thus,\nin addition to directly faciliating CH oxidation, photoinduced heat in the Fe ‑Pd OMNC\n4 1 1\nphotothermal catalytic system can also promote the generation and migration dynamics of\nphotoexcited charge carriers, thereby enhancing the efficiency of electron-mediated activation\nprocesses.\nWe fully agree with the reviewer that the photoinduced electrons and photogenerated heat may\naffect the charge polarization of Fe -Pd OMNC. In this case, we have explored the changes in the\n1 1\nsurface charge of Fe -Pd OMNC before and after illumination using kelvin probe force microscopy\n1 1\n(KPFM). As shown in Fig. R13, the contact potential difference (CPD) increases significantly after\nXe lamp irradiation, indicating that the charge polarization within Fe -Pd OMNC can be strengthen\n1 1\nupon illumination.\nIn the revised manuscript, we have included the above new results in Figs. 3f-g and\nsupplementary Figs. S16, S32, S35-40, S44, S66, Table S7 and added the related discussions in the\nrevised main text (the second and third paragraphs of page 14, the first and second paragraphs of\npage 15, and the first paragraph of page 16, the first paragraph of page 24) and revised supporting\ninformation (pages 40-41, 43, 47).\nphotocurrent intensities and solution temperatures.\nFig. R12 Nyquist plots of Fe1-Pd1 OMNC acquired under different temperatures at open circuit potential (OCP).\nTable R1 The fitting results of EIS data obtained at different temperatures.\nTempe-\nSamples Rs (Ω) Rct(Ω) CPE-T CPE-P W-R(Ω) W-T W-P\nrature(℃)\n25 2.51 16.85 3.96E-8 1.07 125.8 1.9 E-3 0.67\n25+Light 2.46 16.12 6.73 E-8 1.03 118.7 1.40 E-2 0.64\nFe1-Pd1 35 2.45 14.11 3.12 E-8 1.06 65.45 3.89 E-2 0.57\nOMNC 45 2.46 12.92 5.46 E-8 1.07 65.35 2.55 E-2 0.53\n55 2.42 10.61 3.68 E-8 1.09 65.18 2.93 E-2 0.55\n65 2.48 9.67 2.20 E-8 1.10 64.94 4.52 E-2 0.53\ndark (a-c) and light (d-f) conditions.\nComment 2: The respective roles of photothermal heating and photoexcited charge carriers in\ndriving the reaction are not definitively decoupled. The authors show that both pure thermal\ncatalysis and pure photocatalysis (with cooling) yield lower activity than the photothermal\ncondition. This correctly suggests a synergy but does not clarify the fundamental role of light beyond\nheating. Does the light primarily generate heat, which then drives a thermal catalytic cycle, or do\nphotoexcited electrons directly participate in the catalytic steps (e.g., H O /O activation, C-H bond\n2 2 2\nscission)? Measuring the reaction rate under identical temperature conditions while varying the\nlight intensity (for a non- absorbing or weakly-absorbing catalyst at the excitation wavelength)\ncould help distinguish between a purely thermal and a photo-assisted thermal process. This thereby\nproves the specific effect of the combined action of light and heat.\nResponse: We appreciate the reviewer’s insightful comments and suggestions. As suggested, we\nhave supplemented a series of controlled experiments using a high-pressure photothermal reactor\n(China Education Au-light CEL-HPR100T+, Fig. R14) to verify the specific effect of the combined\naction of light and heat. We first explored the effect of light irradiation on the photothermal catalytic\nCH oxidation over Fe -Pd OMNC. As shown in Fig. R15, the reaction in the absence of Xe lamp\n4 1 1\nirradiation yields only 0.030 mmol h-1 of C1 oxygenates. In contrast, the generation rate of C1\noxygenates increases gradually from 0.188 to 0.754 mmol h-1 when increasing light intensity from\n100 to 600 mW cm-2, suggesting the essential role of light irradiation. We subsequently monitored\nthe temperature of the reaction solution of the reaction system and found that it reached 63 ℃ under\nirradiation at 600 mW cm-2 (Fig. R16). In this case, we have performed the thermal catalytic CH\n4\noxidation experiments at different temperatures under dark condition. As shown in Fig. R17a, the\ngeneration rate of C1 oxygenates increases gradually from 0.030 to 0.233 mmol h-1 with an increase\nin the temperature from 25 to 63 ℃. However, the yield of C1 oxygenates from the purely thermal\ncatalytic system is significantly lower than that from the photothermal catalytic system. Specifically,\nkinetic analysis demonstrates that the apparent activation energy of CH oxidation reaction over\n4\n1 1\n(48.84 KJ mol-1) under purely thermal conditions (Fig. R17b). The above results unambiguously\nreveal that a synergy of light and heat contributes to the oxidation of CH , rather than a simple\n4\nphoto-derived thermal catalysis.\nGenerally, photo-derived heat and photoinduced electrons generated by a photothermal material\nunder light irradiation can jointly participate in the photothermal catalysis (e.g., Adv. Funct. Mater.\ne12566 (2025); Sci. Adv. 10, eado9664 (2024)). To decouple the distinct roles of photothermal\nheating and photoexcited charge carriers in driving the reaction, we further investigated the purely\nphotocatalytic process by maintaining the temperature of reaction solution at ca. 25 ℃. The result\nshows that the yield of C1 oxygenates decreases dramatically from 0.754 to 0.286 mmol h-1 when\nthe solution temperature is decreased from 63 to 25 ℃ under the irradiation of Xe lamp (600 mW\ncm-2) (Fig. R18). Interestingly, the sum of the C1 oxygenates (0.519 mmol h-1) produced by the\npurely photocatalytic system and the purely thermal catalysis is still less than that from the normal\nphotothermal catalytic system (0.754 mmol h-1). These results further confirm a distinct synergistic\neffect between photogenerated electrons and photoinduced heat, beyond a simple additive effect.\nAs suggested, we subsequently measured the reaction rate at a constant temperature (i.e., 63 ℃)\nwhile varying the light intensity, so as to further distinguish between purely thermal and photo-\nassisted thermal processes. As shown in Fig. R19a, the yield of C1 oxygenates in Fe ‑Pd OMNC\n1 1\nsystem increases significantly from 0.416 to 0.798 mmol h-1 as the light power density increases\nfrom 100 to 600 mW cm-2, while the temperatures is maintained at 63 ℃ by external heating (Fig.\nR19b). Interestingly, a product yield equivalent to that of the normal photothermal system at 600\nmW cm-2 can be achieved under a heat-assisted photocatalytic system with lower light power (i.e.,\n475 mW cm-2) at 63 ℃. These results fully demonstrate that light primarily generates photoexcited\nelectrons and directly participates in the catalytic steps, while the photo-driven heat accelerates the\noverall reaction kinetics.\nTo verify the direct involvement of photoelectrons in CH oxidation, we have conducted a\n4\ncontrol experiment by using silver nitrate as an electron scavenger (Adv. Mater. 36, 2405060 (2024)).\nAs shown in Fig. R20a, the catalytic performance of Fe ‑Pd OMNC photothermal system decreases\n1 1\nby 18.29% and 50.36% after adding 10 and 100 mg of AgNO , respectively, suggetting that\n3\nphotoinduced electrons play a key role in initiating CH oxidation. Consistently, an obvious\n4\nphotocurrent signal is observed in Fe -Pd OMNC upon light irradiation, confirming the generation\n1 1\nof excited electrons (Fig. R20b). Considering that the generation and migration dynamics of\nphotogenerated electrons may be affected by heat (J. Am. Chem. Soc. 147, 35913-35923(2025)), we\nmeasured the photocurrents of Fe ‑Pd OMNC at various temperatures. Significantly, the\n1 1\nphotocurrent increases exponentially as the solution temperature rises from 25 to 63 ℃. Moreover,\nsuch an amplification effect of photocurrent becomes more pronounced at higher temperatures (Fig.\nR20c). These results unambiguously demonstrate that the heat generated by Fe ‑Pd OMNC under\n1 1\nillumination plays an indispensable role in promoting the generation of photoinduced electrons. We\nfurther used the EIS to explore the electron transfer resistance of Fe ‑Pd OMNC at different\n1 1\ntemperatures, with data fitted by an equivalent circuit model (Fig. R21 and Table R2). The results\nreveal that the electron transfer resistance decreases remarkably after increasing the solution\ntemperatures, indicating that the photoinduced heat is able to reduce the migration resistance of\nphotogenerated electrons.\n4\ndecomposition of H O to •OH, we performed the photothermal reaction under visible-to-IR light\n2 2\nusing a UV-CUT filter. As shown in Fig. R22, the removal of UV light reduces the yield of C1\noxygenates by 34.44% in the H O -assisted system, highlighting the essential role of UV light in\n2 2\npromoting the photothermal catalytic process. We also performed the CH oxidation without the\n4\naddition of H O (i.e., O -assisted system). Interestingly, the yield of C1 oxygenates decreases by\n2 2 2\n33.91% after removing UV light. These results indicate that UV light may mainly participate in the\nphotothermal catalytic process by exciting Fe ‑Pd OMNC to produce photogenrated carriers, rather\n1 1\nthan directly activating H O . In fact, no C1 oxygenates are observed when the control experiment\n2 2\nwas performed in the absence of Fe ‑Pd OMNC under UV light (365 nm), confirming the\n1 1\nneglectable role of UV-induced H O decomposition in promoting CH oxidation.\n2 2 4\nBased on the above results, we have roughly estimated the distinct contributions of photothermal\nheating and photoexcited charge carriers in driving the reaction (Fig. R23). Under irradiation,\nFe ‑Pd OMNC is excited by photons to produce photoexcited charge carriers. At the same time,\n1 1\nthe non-radiative relaxation of photogenerated electrons and the excitation of thermal energy\nproduce phonons, raising the temperature of the catalytic system to 63 ℃. The formed photoexcited\ncharge carriers (ca. 38.03%) and thermal energy (ca. 31.02%) are able to directly facilitate the\nactivation of CH . Additionally, the photoinduced heat can also promote the generation and\n4\nmigration dynamics of photoexcited charge carriers, thereby enhancing the efficiency of electron-\ninvolved activation process (ca. 31.02%).\nIn the revised manuscript, we have included the above new results in Figs. 3f-g and\nsupplementary Figs. S16, S32, S35-40, S44, Table S7 and added the related discussions in the\nrevised main text (the second and third paragraphs of page 14, the first and second paragraphs of\npage 15, and the first paragraph of page 16) and revised supporting information (pages 40-41, 43,\nand 47).\nFig. R14 Digital photographs of (a) a photo-theraml catalytic reactor with a heater, (b) a photocatalytic reactor with\na cooling condensation, and (c) a high-pressure stainless steel reactor.\ncondition: Wcat. = 5 mg, VH2O = 5 mL, PCH4 = 2 MPa, MH2O2 = 5 mol/L, t = 2 h.\nFig. R16 Thermalgrams of catalyst under the irradiation of Xe lamp with different ligtht intensities.\nFig. R17 (a) Thermal catalytic CH4 oxidation over Fe1-Pd1 OMNC under different temperatures. Reaction condition:\nWcat. = 5 mg, VH2O = 5 mL, PCH4 = 2 MPa, MH2O2 = 5 mol/L, t = 2 h; (b) Arrhenius analysis.\n= 5 mg, VH2O = 5 mL, PCH4 = 2 MPa, MH2O2 = 5 mol/L, t = 2 h, light intensity: 600 mW cm−2.\nFig. R19 (a) CH4 oxidation performances and (b) the temperature variation curves over Fe1-Pd1 OMNC under the\nirradiation of Xe lamp with different ligtht intensities. Reaction condition: Wcat. = 5 mg, VH2O = 5 mL, PCH4 = 2 MPa,\nMH2O2 = 5 mol/L, t = 2 h, solution temperature = 63 ℃.\nFig. R20 (a) Photothermal catalytic CH4 oxidation over Fe1-Pd1 OMNC with the addition of electron scavenger.\nReaction condition: Wcat. = 5 mg, VH2O = 5 mL, PCH4 = 2 MPa, MH2O2 = 5 mol/L, t = 2 h, light intensity: 600 mW\ncm−2; (b) Photocurrent signals of Fe1-Pd1 OMNC tested at different temperatures; (c) The relationship between\nphotocurrent intensities and solution temperatures.\nTable R2 The fitting results of EIS data obtained at different temperatures.\nTempe-\nSamples Rs (Ω) Rct(Ω) CPE-T CPE-P W-R(Ω) W-T W-P\nrature(℃)\n25 2.51 16.85 3.96E-8 1.07 125.8 1.9 E-3 0.67\n25+Light 2.46 16.12 6.73 E-8 1.03 118.7 1.40 E-2 0.64\nFe1-Pd1 35 2.45 14.11 3.12 E-8 1.06 65.45 3.89 E-2 0.57\nOMNC 45 2.46 12.92 5.46 E-8 1.07 65.35 2.55 E-2 0.53\n55 2.42 10.61 3.68 E-8 1.09 65.18 2.93 E-2 0.55\n65 2.48 9.67 2.20 E-8 1.10 64.94 4.52 E-2 0.53\nFig. R22 Photothermal catalytic CH4 oxidation over Fe1-Pd1 OMNC with (a) H2O2 and (b) O2 as the oxidants under\ndifferent light sources. Reaction conditions in (a): Wcat. = 5 mg, VH2O = 5 mL, PCH4 = 2 MPa, MH2O2 = 5 mol/L, t =\n2 h. (b) Reaction conditions: Wcat. = 5 mg, VH2O = 5 mL, PCH4 = 1.8 MPa, PO2 = 0.2 MPa, t = 2 h, light intensity: 600\nmW cm−2.\nphotothermal CH4 oxidation.\nComment 3: The synergy between Fe and Pd is demonstrated by comparing with single-atom\ncatalysts. To rule out effects from simply having both metals present but not necessarily cooperating\nat an atomic level, could the authors prepare and test a physical mixture of Fe OMNC and Pd\n1 1\nOMNC? This control would more conclusively prove that the synergy requires the proximate dual-\natom sites.\nResponse: We sincerely appreciate the insightful suggestion. As suggested, we have conducted the\nphotothermal catalytic CH oxidation by using a physical mixture of Fe OMNC and Pd OMNC as\n4 1 1\nthe catalyst. As shown in Fig. R24, the physical mixture exhibits a yield of C1 oxygenates of 0.552\nmmol h-1, which is significantly lower than that of Fe -Pd OMNC (0.754 mmol h-1). This result\n1 1\ndemonstrates that the enhanced catalytic activity of the bimetallic system stems from the synergistic\neffect between Fe and Pd dual-atom sites, rather than from a simple additive contribution of\nindividual monometallic components. In the revised manuscript, we have included the above new\nresults in supplementary Fig. S26 and added the related discussions in the revised main text (the last\nparagraph of page 10 and the first paragraph of page 11).\nFig. R24 Photothermal catalytic CH4 oxidation over Fe1-Pd1 OMNC and the physical mixture of Fe1 OMNC and\nPd1 OMNC. Reaction condition: WFe1-Pd1 OMNC = 5 mg, WFe1 OMNC = 2.5 mg, WPd1 OMNC = 2.5 mg, VH2O = 5 mL, PCH4\n= 2 MPa, MH2O2 = 5 mol/L, light intensity: 600 mW cm−2, t = 2 h.\non catalytic performance, the specific light intensity value that was selected has not been clearly\nstated. This parameter should be clearly reported in the experimental conditions for other control\nexperiments.\nResponse: We thank the reviewer for pointing out this omission. In the revised manuscript, we have\nsupplemented the light intensity for all the catalytic experiments in the captions of the relevant\nfigures (Fig. 3 and supplementary Figs. S20, S25, S28-30, S45).\nReviewer #3: After carefully evaluating the authors’ revisions and supplementary explanations in\nresponse to the review comments, it is considered that the main scientific issues in the original\nmanuscript have been adequately addressed and resolved. However, some details should be noted.\nFor example, the wavenumber (cm⁻¹) on the horizontal axis of the FTIR spectra in the text is\ncurrently arranged in ascending order. It is recommended to uniformly adjust it to the conventional\ndisplay format of descending order (i.e., from high to low wavenumber). Therefore, acceptance after\nrevision is recommended.\nResponse: We thank the reviewer again for her/his valuable comments and suggestions that have\nhelped us to improve the quality of this manuscript significantly. As suggested, the horizontal axis\nof the Fourier-transform infrared spectra has been revised (Please see the revisions in Figs. 4b, 4c,\n4h, 4i, 5i and supplementary Figs. 59, 78, 79). In addition, we have carefully checked and polished\nthe whole article.\nP\nA\nG\nE\n\\"}, {"round": 2, "reviewer_comments": {"reviewer_1": "all the points concerned have been addressed and this manuscript can be accepted in its current form.", "reviewer_2": "The present manuscript is suitable for publication.", "reviewer_3": "Upon reviewing the feedback, I note that the authors did not directly address the issue of orbital interaction raised in the previous comments, but instead opted for the removal of the related descriptions in the manuscript. Furthermore, although the authors have diligently addressed some of the reviewers' concerns, the following points require further attention.\n1. The authors state that \"heat and photoinduced electrons generated by Fe1-Pd1 OMNC under light irradiation would jointly participate in the oxidation of CH4, instead of undergoing a simple photo-derived thermal catalysis,\" but they do not explain the respective roles of photoinduced electrons and photogenerated heat in methane conversion, particularly regarding their effects on charge polarization. This requires the authors to provide additional experimental evidence for clarification.\n2. The respective roles of photothermal heating and photoexcited charge carriers in driving the reaction are not definitively decoupled. The authors show that both pure thermal catalysis and pure photocatalysis (with cooling) yield lower activity than the photothermal condition. This correctly suggests a synergy but does not clarify the fundamental role of light beyond heating. Does the light primarily generate heat, which then drives a thermal catalytic cycle, or do photoexcited electrons directly participate in the catalytic steps (e.g., H2O2/O2 activation, C-H bond scission)? Measuring the reaction rate under identical temperature conditions while varying the light intensity (for a non- absorbing or weakly-absorbing catalyst at the excitation wavelength) could help distinguish between a purely thermal and a photo-assisted thermal process. This thereby proves the specific effect of the combined action of light and heat.\n3. The synergy between Fe and Pd is demonstrated by comparing with single-atom catalysts. To rule out effects from simply having both metals present but not necessarily cooperating at an atomic level, could the authors prepare and test a physical mixture of Fe1 OMNC and Pd1 OMNC? This control would more conclusively prove that the synergy requires the proximate dual-atom sites.\n4. Although the authors have conducted control experiments on the effect of light intensity on catalytic performance, the specific light intensity value that was selected has not been clearly stated. This parameter should be clearly reported in the experimental conditions for other control experiments."}, "author_response": ""}, {"round": 3, "reviewer_comments": {"reviewer_3": "After carefully evaluating the authors’ revisions and supplementary explanations in response to the review comments, it is considered that the main scientific issues in the original manuscript have been adequately addressed and resolved. However, some details should be noted. For example, the wavenumber (cm⁻¹) on the horizontal axis of the FTIR spectra in the text is currently arranged in ascending order. It is recommended to uniformly adjust it to the conventional display format of descending order (i.e., from high to low wavenumber). Therefore, acceptance after revision is recommended."}, "author_response": ""}]

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