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 (FeIV=O) is expected to break the activity-selectivity trade-off of traditional reactive oxygen species, while attempts to regulate the oxidation behaviors of heterogeneous FeIV=O remain unexplored. Here, by coordination engineering of Fe-Nx single-atom catalysts (Fe-Nx SACs), we propose a feasible approach to regulate the oxidation behaviors of heterogeneous FeIV=O. The developed Fe-N₂ SACs/peroxymonosulfate (PMS) system delivers boosted performance for FeIV=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-Nx SACs favor the generation of FeIV=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 FeIV=O (FeIVN₂=O) oxidize SMX to small molecules with less toxicity, while FeIVN₄=O produces series of more toxic azo compounds through N-N coupling with more complex oxidation pathways.