Remote Tuning of Single-Atom Fe-N5 Sites via High-Coordination Defects for Enhanced Fenton-Like Water Decontamination

FeN5 single-atom catalysts (SACs) hold great promise for water decontamination, however, the fundamental relationship between their high coordination shell environment and catalytic performance in Fenton-like reactions remains poorly understood. Here, we precisely regulate the high coordination shell defects of a model SAC with well-defined axial FeN5 configurations to elucidate the impact of remote interactions on peroxymonosulfate (PMS) activation. Experimental and theoretical studies confirm that remote modulation of FeN5 sites through high coordination shell defects profoundly enhance Fenton-like catalytic activity, enabling FeN5-SD2 to achieve a turnover frequency (TOF) value of 0.338 min⁻1, surpassing state-of-the-art SACs. Our findings reveal a critical volcano-type correlation between defect content and catalytic efficiency, where coordinated modulation of Fe d-band center positioning and PMS adsorption energetics governs reaction dynamics. Only the FeN5-SD2 configuration with an optimal level of defects density and moderate adsorption energy enables sufficient O-O bond elongation in PMS to lower the energy barrier for selective singlet oxygen (1O2) evolution. This study unveils the mechanistic role of higher coordination shell defects in regulating FeN5 active sites and introduces a well-defined model to investigate the structure–property correlations of higher coordination shells in SACs for Fenton-like reactions.