Abstract
Precise modulation of spin states of single-atom catalysts (SACs) offers a promising route to fine-tune peroxide activation behaviors and selectivity toward different oxidation pathways. Here, we report a spin-tunable Fe SAC composed of iron phthalocyanine (FePc) axially coordinated via oxygen bridges (-O-) onto annealed nanodiamond (AND), denoted as FePc-O-AND. The axial oxygen coordination induces a spin transition from high-spin (t2g5eg3) to an intermediate-spin (t2g4eg2) state. This transition generates an unoccupied Fe 3dz2 orbital that enables oriented electron transfer to peracetic acid (PAA) via hydroxyl oxygen coordination. In situ synchrotron-based Fourier-transform infrared spectroscopy (SR-FTIR) reveals a distinct PAA activation pathway involving inner-sphere complexation and a non-radical electron-transfer mechanism. As a result, the FePc-O-AND/PAA system drives a non-radical electron-transfer pathway with a high reaction rate (2.11 min−1), selectively converting phenolic pollutants into high-molecular-weight polyphenolic products (n ≥ 5). Density functional theory (DFT) calculations reveal that axial oxygen coordination in FePc-O-AND enhances PAA adsorption energy (−0.89 eV) and induces a favorable inner-sphere interaction with the hydroxyl oxygen, thereby facilitating effective PAA activation. The FePc-O-AND/PAA system exhibits strong resistance to water matrix interferences and maintains high performance over 130 h of continuous-flow operation. These findings establish axial coordination-mediated spin-state regulation as a powerful strategy for engineering SACs for sustainable water purification and recycling of micropollutants.
Similar content being viewed by others
Data availability
The data supporting the findings of the study are included in the main text and Supplementary Information files. Raw data can be obtained from the corresponding authors upon request. Source data are provided with this paper.
References
Zhang, J., Shan, C., Zhang, W. & Pan, B. In situ ligand-modulated activation of inert Ce(III/IV) into ozonation catalyst for efficient water treatment. Proc. Natl. Acad. Sci. USA. 120, e2305255120 (2023).
Zhang, Y. J. et al. Distinguishing homogeneous advanced oxidation processes in bulk water from heterogeneous surface reactions in organic oxidation. Proc. Natl. Acad. Sci. USA. 120, e2302407120 (2023).
Su, R. et al. Utilizing the oxygen-atom trapping effect of Co3O4 with oxygen vacancies to promote chlorite activation for water decontamination. Proc. Natl. Acad. Sci. USA. 121, e2319427121 (2024).
Miao, F. et al. Carbon-based peracetic acid activation towards advanced water purification. Appl. Catal. B: Environ. 363, 124807 (2025).
Chen, X. J. et al. pH-driven efficacy of the ferrate(VI)-peracetic acid system in swift sulfonamide antibiotic degradation: A deep dive into active species evolution and mechanistic insights. Environ. Sci. Technol. 57, 20206–20218 (2023).
Cheng, C. et al. Generation of Fe(IV) =O and its contribution to Fenton-like reactions on a single-atom iron-N-C Catalyst. Angew. Chem. Int. Ed. Engl. 62, e202218510 (2023).
Liang, X., Fu, N., Yao, S., Li, Z. & Li, Y. The progress and outlook of metal single-atom-site catalysis. J. Am. Chem. Soc. 144, 18155–18174 (2022).
Zhu, Z. S. et al. Atomic-level engineered cobalt catalysts for Fenton-like reactions: Synergy of single atom metal sites and nonmetal-bonded functionalities. Adv. Mater. 36, e2401454 (2024).
Huang, F. et al. Insight into the activity of atomically dispersed Cu catalysts for semihydrogenation of acetylene: Impact of coordination environments. ACS Catal. 12, 48–57 (2021).
Yang, Y. et al. Boosting electrochemical nitrogen reduction via axial coordination engineering on single-iron-atom catalysts. Adv. Funct. Mater. 34, 2403535 (2024).
Li, P. et al. Coordination environment and architecture engineering over Co4N-based nanocomposite for accelerating advanced oxidation processes. Appl. Catal. B: Environ. 302, 120850 (2022).
Xie, X., Peng, H., Ma, G., Lei, Z. & Xu, Y. Recent progress in heteroatom doping to modulate the coordination environment of M–N–C catalysts for the oxygen reduction reaction. Mater. Chem. Front. 7, 2595–2619 (2023).
Li, L. et al. Longitudinally grafting of graphene with iron phthalocyanine-based porous organic polymer to boost oxygen electroreduction. Angew. Chem. Int. Ed. Engl. 62, e202301642 (2023).
Qiao, Z., Jiang, R., Xu, H., Cao, D. & Zeng, X. C. A general descriptor for single-atom catalysts with axial ligands. Angew. Chem. Int. Ed. Engl. 63, e202407812 (2024).
Wu, Q. Y., Yang, Z. W., Wang, Z. W. & Wang, W. L. Oxygen doping of cobalt-single-atom coordination enhances peroxymonosulfate activation and high-valent cobalt-oxo species formation. Proc. Natl. Acad. Sci. USA. 120, e2219923120 (2023).
Ren, S. et al. Transforming plastics to single atom catalysts for peroxymonosulfate activation: Axial chloride coordination intensified electron transfer pathway. Adv. Mater. 37, e2415339 (2025).
Yuan, L. J. et al. d-orbital electron delocalization realized by axial Fe4C atomic clusters delivers high-performance Fe-N-C catalysts for oxygen reduction reaction. Adv. Mater. 35, e2305945 (2023).
Chen, K. et al. Iron phthalocyanine with coordination induced electronic localization to boost oxygen reduction reaction. Nat. Commun. 11, 4173 (2020).
Cao, P. et al. Metal single-site catalyst design for electrocatalytic production of hydrogen peroxide at industrial-relevant currents. Nat. Commun. 14, 172 (2023).
Li, Z. et al. The marriage of the FeN4 moiety and MXene boosts oxygen reduction catalysis: Fe 3d electron delocalization matters. Adv. Mater. 30, e1803220 (2018).
Zhu, W. et al. by strengthening Fe-CO π-backbonding to enhance two-carbon products formation toward CO2 electroreduction on Fe–N4 sites. Adv. Funct. Mater. 34, 2402537 (2024).
Zhong, H. et al. Boosting the electrocatalytic conversion of nitrogen to ammonia on metal-phthalocyanine-based two-dimensional conjugated covalent organic frameworks. J. Am. Chem. Soc. 143, 19992–20000 (2021).
Chen, Z. et al. Iron-single sites confined by graphene lattice for ammonia synthesis under mild conditions. ACS Catal. 13, 14385–14394 (2023).
Liu, L. et al. Spectroscopic identification of active sites of oxygen-doped carbon for selective oxygen reduction to hydrogen peroxide. Angew. Chem., Int. Ed. Engl. 62, e202303525 (2023).
Li, M. et al. Atomically-dispersed NiN4–Cl active sites with axial Ni–Cl coordination for accelerating electrocatalytic hydrogen evolution. J. Mater. Chem. A 10, 6007–6015 (2022).
Zhang, L. et al. Stabilization of palladium nanoparticles on nanodiamond-graphene core-shell supports for CO oxidation. Angew. Chem. Int. Ed. Engl. 54, 15823–15826 (2015).
Guo, J. et al. Fenton-like activity and pathway modulation via single-atom sites and pollutants comediates the electron transfer process. Proc. Natl. Acad. Sci. USA. 121, e2313387121 (2024).
Guo, J. et al. Size-dependent catalysis in Fenton-like chemistry: From nanoparticles to single atoms. Adv. Mater. 36, e2403965 (2024).
Pan, Q. et al. Electrochemical activation of peracetic acid with activated carbon fiber cathode for sulfamethoxazole elimination: Long-lasting catalytic performance and mechanism. Chem. Eng. J. 481, 148507 (2024).
Chen, J. H. et al. Proton-coupled electron transfer controls peroxide activation initiated by a solid-water interface. Nat. Commun. 16, 3789 (2025).
Zhong, S. et al. Hierarchically ordered porous carbon crystals for nanoconfined and sustainable Fenton oxidation of water pollutants. Appl. Catal. B: Environ. 361, 124665 (2025).
Sun, P. et al. Designing oxygen-doped Fe-N-C oxygen reduction catalysts for proton- and anion-exchange-membrane fuel cells. Chem. Catal. 2, 2750–2763 (2022).
Huang, Z. F. et al. Tuning of lattice oxygen reactivity and scaling relation to construct better oxygen evolution electrocatalyst. Nat. Commun. 12, 3992 (2021).
Chen, J., Qi, Y., Lu, M., Niu, Y. & Zhang, B. Identify fine microstructure of multifarious iron oxides via O K-edge EELS spectra. Chin. Chem. Lett. 33, 4375–4379 (2022).
Ye, Y. et al. Strong O 2p-Fe 3d hybridization observed in solution-grown hematite films by soft X-ray spectroscopies. J. Phys. Chem. B 122, 927–932 (2018).
Lin, F., Li, M., Zeng, L., Luo, M. & Guo, S. Intermetallic nanocrystals for fuel-cells-based electrocatalysis. Chem. Rev. 123, 12507–12593 (2023).
Cai, S. et al. Pyrrolic N-rich biochar without exogenous nitrogen doping as a functional material for bisphenol A removal: Performance and mechanism. Appl. Catal. B: Environ. 291, 120093 (2021).
Chen, F. et al. Single-atom iron anchored tubular g-C3N4 catalysts for ultrafast Fenton-like reaction: Roles of high-valency iron-oxo species and organic radicals. Adv. Mater. 34, e2202891 (2022).
Miao, F. et al. Dual non-radical catalytic pathways mediated by nanodiamond-derived sp2/sp3 hybrids for sustainable peracetic acid activation and water decontamination. Environ. Sci. Technol. 58, 8554–8564 (2024).
Wang, Z. et al. Non-radical activation of peracetic acid by powdered activated carbon for the degradation of sulfamethoxazole. Environ. Sci. Technol. 57, 10478–10488 (2023).
Chen, Y. et al. Oxygen vacancies-mediated the peracetic acid activation to selectively generate 1O2 for water decontamination. Water Res. 282, 123765 (2025).
Dong, Y. D. et al. Mechanically treated Mn2O3 triggers peracetic acid activation for superior non-radical oxidation of micropollutants: Identification of reactive complexes. Water Res. 255, 121486 (2024).
Jia, W. et al. Insight into nitrogen-doped biochar prepared from Chinese medicine compound residue for peracetic acid activation in sulfamethoxazole degradation: Electron transfer mechanism. Chin. Chem. Lett. 36, 11 (2025).
Li, M. et al. Surface FeIV=O induced highly selective phenol polymerization via proton-coupled electron transfer. J. Am. Chem. Soc. 147, 31165–31174 (2025).
Yao, Z. et al. High-entropy alloys catalyzing polymeric transformation of water pollutants with remarkably improved electron utilization efficiency. Nat. Commun. 16, 148 (2025).
Liu, H. Z. et al. Tailoring d-band center of high-valent metal-oxo species for pollutant removal via complete polymerization. Nat. Commun. 15, 2327 (2024).
Yin, K. et al. High-loading of well dispersed single-atom catalysts derived from Fe-rich marine algae for boosting Fenton-like reaction: Role identification of iron center and catalytic mechanisms. Appl. Catal. B: Environ. 336, 122951 (2023).
Ban, J. et al. Synergistic effects of phase transition and electron-spin regulation on the electrocatalysis performance of ternary nitride. Adv. Funct. Mater. 33, 2300623 (2023).
Wang, Y. et al. Spatial engineering of single-atom Fe adjacent to Cu-assisted nanozymes for biomimetic O2 activation. Nat. Commun. 15, 2239 (2024).
Jiang, Z., Tong, K., Li, Z., Tao, H. & Zhu, M. Spin state regulation for peroxide activation: Fundamental insights and regulation mechanisms. Angew. Chem. Int. Ed. Engl. 64, e202500791 (2025).
Wei, X. et al. Tuning the spin state of Fe single atoms by Pd nanoclusters enables robust oxygen reduction with dissociative pathway. Chem 9, 181–197 (2023).
Liu, Y. et al. Tuning the spin state of the iron center by bridge-bonded Fe-O-Ti ligands for enhanced oxygen reduction. Angew. Chem. Int. Ed. Engl. 61, e202117617 (2022).
Zhong, W. et al. Electronic spin moment as a catalytic descriptor for Fe single-atom catalysts supported on C2N. J. Am. Chem. Soc. 143, 4405–4413 (2021).
Wang, X. et al. Developing a class of dual atom materials for multifunctional catalytic reactions. Nat. Commun. 14, 7210 (2023).
Kaiser, S. K., Chen, Z., Faust Akl, D., Mitchell, S. & Perez-Ramirez, J. Single-atom catalysts across the periodic table. Chem. Rev. 120, 11703–11809 (2020).
Song, J. et al. Directional formation of reactive oxygen species via a non-redox catalysis strategy that bypasses electron transfer process. Adv. Mater. 36, e2405832 (2024).
Li, J. et al. Identification of durable and non-durable FeNx sites in Fe–N–C materials for proton exchange membrane fuel cells. Nat. Catal. 4, 10–19 (2020).
Yu, Y. et al. Local magnetic effect-induced electron configuration regulation: Spin flipping of iron centers for molecular catalysis. ACS Catal. 14, 7191–7200 (2024).
Zeng, Y. et al. Unraveling the dynamic low-spin state evolution of single-Fe-atom sites for efficient CO2 electroreduction. J. Am. Chem. Soc. 147, 42539–42548 (2025).
Yu, L., Li, Y. & Ruan, Y. Dynamic control of sacrificial bond transformation in the Fe-N-C single-atom catalyst for molecular oxygen reduction. Angew. Chem. Int. Ed. Engl. 60, 25296–25301 (2021).
Duan, P.-J. et al. Polymeric products deactivate carbon-based catalysts in catalytic oxidation reactions. Nat. Water 3, 178–190 (2025).
Ren, W. et al. Catalytic resource recovery for transformation of the wastewater industry. Nat. Water 3, 1228–1242 (2025).
Yang, M. et al. Unprecedented relay catalysis of curved Fe1-N4 single-atom site for remarkably efficient 1O2 generation. ACS Catal. 13, 681–691 (2022).
Acknowledgements
This work was funded by the National Natural Science Foundation of China (No. 52570082), Key Shandong Natural Science Foundation (ZR2025QC1388), the Fundamental Research Funds of the University of Jinan (XRC2533), the Australian Research Council (DP230102406 and FT230100526), and the Young Elite Scientists Sponsorship Program by CAST (No. 2023QNRC001). The authors also thank the Australian Synchrotron for X-ray absorption measurements (Grant No. M20537) and SR-FTIR tests (Grant No. M21947). F.M. gratefully acknowledges the China Scholarship Council (No. 202106270138) for the visiting fellowship at Adelaide University.
Author information
Authors and Affiliations
Contributions
F.M., X.D., and W.R. designed the research. F.M. completed most of the experiments and wrote the paper. X.D., W.R., H.Z., and S.W. supervised the research and further revised the paper. Y.W. finished the DFT calculation section. H.Z., J.V., J.L., W.X., S.Z., and X.Y. assisted in performing characterizations. All authors discussed the results and commented on the paper.
Corresponding authors
Ethics declarations
Competing interests
The authors declare no competing interests.
Peer review
Peer review information
Nature Communications thanks Lin Gu, Wen-Long Wang, and the other anonymous reviewer(s) for their contribution to the peer review of this work. A peer review file is available.
Additional information
Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Source data
Rights and permissions
Open Access This article is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License, which permits any non-commercial use, sharing, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if you modified the licensed material. You do not have permission under this licence to share adapted material derived from this article or parts of it. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by-nc-nd/4.0/.
About this article
Cite this article
Miao, F., Wang, Y., Zhou, H. et al. Axial oxygen coordination drives spin-regulated electron transfer in single-atom Fe catalysts for selective pollutant transformation. Nat Commun (2026). https://doi.org/10.1038/s41467-026-71163-y
Received:
Accepted:
Published:
DOI: https://doi.org/10.1038/s41467-026-71163-y
