Confinement of controllable oxygen vacancy Fe3O4 in S-doped mesoporous carbon for efficient nonradical peroxymonosulfate activation: Nonradical pathway transition steered by oxygen vacancy in confined space

Seeking efficient and facile methods for precise oxygen vacancy (Ov)-content regulation is challenging for practical application. Herein, we propose a confinement-based Ov optimization strategy, and construct Fe 3 O 4 with controllable Ov confined in S-doped mesoporous carbon (Fe 3 O 4 @SMC) catalyst to enhance nonradical oxidation of PMS. The confinement effect induced the O 2p orbitals p-band-center shift in Fe 3 O 4 @SMC, which promoted Ov formation, thus achieving 100 % BPA degradation within 9 min via an electron-transfer process (ETP) dominated nonradical pathway with a 125.8-fold higher k obs value than unconfinement catalyst. Ov content variation under confinement, triggered by tuning confined support defect level, steered nonradical transition from single-electron-activated singlet oxygen route to two-electron-transferred ETP pathway, which improved selectivity (> 95 % of electron-rich pollutants removal), adaptability and durability (10 h continuous-flow operation) of catalyst. This work paves the way for modulating Ov in iron-oxides via confinement engineering and offers new insights into the Ov-induced mechanism in confined environments.