Spin-State–Engineered Fe–δ-MnO2 Directs Peroxymonosulfate Activation through an Electron-Transfer Pathway

Efficient and selective activation of peroxymonosulfate (PMS) is central to robust oxidative water treatment, yet design rules linking catalyst electronic structure to nonradical PMS activation remain poorly defined. Here, we show that spin-state engineering of layered δ-MnO 2 by Fe incorporation enhances PMS activation by strengthening the electron-transfer process (ETP). The resulting Fe–δ-MnO 2 catalyst rapidly oxidizes structurally diverse contaminants, including tetracycline and dyes, achieving >90% removal within 24 min while retaining high activity across a broad pH window, in the presence of common inorganic ions and natural organic matter, and in real water matrices. Spectroscopy and magnetometry, supported by density functional theory, reveal Fe-induced restructuring of the Mn d-manifold and stabilization of lower-spin metal sites that promote interfacial charge exchange with PMS. Radical quenching and probe tests, electrochemical signatures of electron mediation, and in situ Raman identification of a reactive surface PMS* intermediate collectively support an enhanced nonradical electron-transfer pathway. These results establish spin-state tuning as a general strategy to modulate oxidant activation on transition-metal oxides and to design robust catalysts for water purification.