A-site defect regulates d-band center in perovskite-type catalysts enhancing photo-assisted peroxymonosulfate activation for levofloxacin removal via high-valent iron-oxo species

The high-valent iron-oxo species (Fe(IV)=O) attracted widespread attention for water cleaning due to its long lifetime, high reductive potential and strong anti-interference ability. However, formation of Fe(IV)=O is challenging because of the low conversion efficiency of Fe(III)/Fe(II) and the high activation barrier of Fe(II)peroxymonosulfate (PMS) complex. Herein, A-site defect and oxygen vacancy (Ov) were ingeniously incorporated into perovskite via the metal-organic framework (MOF) derivation method with the objective of activating PMS for the degradation of levofloxacin (LVX) under visible light conditions. The introduction of dual defects could stretch the Fe-O bond and induce a transformation in the electron spin state of Fe, from low spin (LS) to medium spin state (MS), resulting in an upward shift of the d-band center, which reduces the barrier for Fe(IV)= O formation. Furthermore, MOF-derived La0.8FeO3-delta (Md-La0.8FeO3-delta) exhibited superior reactivity, selectivity and environment robustness. This work proposes a strategy for improving the formation of Fe(IV)=O through regulating the induced oxygen vacancies triggered by the A-site defect in perovskite.