Emerging Mo4/3B2 MBene promoted high-valent iron-oxo species generation in the FeⅢ/PMS system:The role of ordered metal vacancies.

Regulating the electronic structure of Fe active sites is an effective strategy to enhance peroxymonosulfate (PMS)-triggered high-valent iron-oxo (FeIV=O) systems for environmental remediation. In this study, we designed the emerging two-dimensional Mo4/3B2 MBene with ordered metal vacancies as ideal anchoring sites for FeⅢ to boost PMS activation and regulate FeIV=O generation. The Mo4/3B2 MBene/FeⅢ/PMS system exhibits outstanding catalytic performance: the pseudo-first-order rate constant (kobs) of bisphenol A (BPA) degradation is 200-fold higher than that of the pristine FeⅢ/PMS system, and over 90% of BPA can be removed within 5 min. PMSO probe experiments and density functional theory (DFT) calculations confirm that surface-anchored FeⅢ acts as the active center to activate PMS via direct electron transfer for FeIV=O formation, and verify the critical role of ordered metal vacancies. Quenching experiments and electron paramagnetic resonance (EPR) spectroscopy reveal that sulfate radicals and hydroxyl radicals serve as supplementary reactive oxygen species in the Mo4/3B2 MBene/FeⅢ/PMS system. This work provides a new Fe site design strategy to promote FeIV=O generation for water purification.