Halogen‐Driven Electronic Modulation of Single‐Atom Fe Sites for Universal Non‐Radical Catalysis

Abstract

ABSTRACT Selective and matrix‐tolerant advanced oxidation processes (AOPs) are essential for treating real waters. Iodine‐polarized Fe–N 4 single‐atom sites in N‐doped carbon (Fe–NI–C) are engineered to molecularly adsorb peroxymonosulfate (PMS) and lower its activation barrier, enabling ultrafast, non‐radical phenol oxidation. Fe–NI–C/PMS achieves complete removal within 2 min ( k obs   =   4.098 min −1 , 195‐fold over N–C) with 71.2% total organic carbon abatement, maintaining near‐quantitative activity from pH 3–11 and in tap, river, and seawater. Electrochemical, quenching, and EPR assays decipher an electron‐transfer‐to‐singlet‐oxygen cascade (ETP → 1 O 2 ): a surface Fe–PMS* adduct triggers interfacial electron flux, producing 1 O 2 as the selective oxidant while suppressing free‐radical and matrix scavenging. Spin‐polarized density functional theory (DFT) shows iodine upshifts the Fe 3d band toward E_F, strengthens Fe 3d–PMS σ* coupling, stabilizes side‐on O–O adsorption (E ads   =   –1.89 eV), and lowers the transition‐state barrier to 0.35 eV. Activity follows I  >  Br > Cl > F, consistent with dopant polarizability and Bader charge transfer (up to 0.88 e). Intrinsic metrics (turnover frequency, TOF; K ac ) confirm site‐level acceleration beyond textural effects. These results establish soft‐ligand electronic polarization of Fe–N 4 as a programmable route to radical‐free, selective, and matrix‐robust PMS activation for advanced water purification.