Coordination engineering of heterogeneous high-valent Fe(IV)-oxo for safe removal of pollutants via powerful Fenton-like reactions

Coordination engineering of high-valent Fe(IV)-oxo (Fe^IV=O) is expected to break the activity-selectivity trade-off of traditional reactive oxygen species, while attempts to regulate the oxidation behaviors of heterogeneous Fe^IV=O remain unexplored. Here, by coordination engineering of Fe-N_x single-atom catalysts (Fe-N_x SACs), we propose a feasible approach to regulate the oxidation behaviors of heterogeneous Fe^IV=O. The developed Fe-N₂ SACs/peroxymonosulfate (PMS) system delivers boosted performance for Fe^IV=O generation, and thereby can selectively remove a range of pollutants within tens of seconds. In-situ spectra and theoretical simulations suggest that low-coordination Fe-N_x SACs favor the generation of Fe^IV=O via PMS activation as providing more electrons to facilitate the desorption of the key ^*SO₄H intermediate. Due to their disparate attacking sites to sulfamethoxazole (SMX) molecules, Fe-N₂ SACs mediated Fe^IV=O (Fe^IVN₂=O) oxidize SMX to small molecules with less toxicity, while Fe^IVN₄=O produces series of more toxic azo compounds through N-N coupling with more complex oxidation pathways.