FeOCo bimetallic bridge-mediated oxygen vacancy formation: Mechanism of synergistic activation of PMS degradation of atrazine

Atrazine (ATZ), a highly persistent triazine herbicide, poses significant environmental risks due to its endocrine-disrupting effects, necessitating efficient remediation technologies. To overcome the limitations of active site availability and electron transfer bottlenecks in single-metal iron-based MOFs (Fe-MIL-101) during peroxymonosulfate (PMS) activation, this study innovatively constructed bimetallic FeM-MIL-101 (M = Co, Zn, Ni, Cu) catalysts. Through hydrothermal synthesis and multi-scale characterization, FeCo-MIL-101 was shown to achieve complete ATZ degradation within 60 min ( k obs  = 0.059 min −1 ), representing a 3.9-fold enhancement in degradation efficiency over the best-performing control. The catalyst maintained >95 % removal efficiency across a broad pH range and under interference from high concentrations of common anions (Cl − , NO 3 − , SO 4 2− , H 2 PO 4 − ), while exhibiting minimal inhibition by HCO 3 − (>82 % removal). Mechanistic studies revealed that Fe O Co bridging bonds induced oxygen vacancy (OV) generation, significantly accelerating the Fe 3+ /Co 3+  ↔ Fe 2+ /Co 2+ redox cycles and synergistically optimizing both radical and non-radical pathways. Sulfate radicals (SO 4 – ) served as the dominant reactive species (contributing 58.3 %), with singlet oxygen ( 1 O 2 ) and superoxide radicals (O 2 – ) playing a synergistic role (collectively 38 %). The catalyst retained >90 % activity over 6 consecutive cycles, with metal leaching below 14 μg/L, and the degradation products exhibited significantly reduced developmental toxicity. Bimetallic synergy and OV-mediated electron transfer were identified as the key factors enhancing PMS activation efficiency. By strengthening HSO 5 − adsorption energy and interfacial charge transfer, FeCo-MIL-101 overcomes the limitations of single-metal systems, providing an atomic-level design strategy for the efficient removal of persistent organic pollutants in complex aqueous environments.