The cascading anchoring strategy fabrication of high-coordination single-atom catalyst: Efficient peroxymonosulfate activation with high 1O2 selectivity

Single-atom catalysts hold great promise for peroxymonosulfate (PMS)-activated non-radical pathways, yet achieving high singlet oxygen (¹O₂) selectivity remains a significant challenge. In this work, we developed a six-coordinated Fe-N₆ single-atom catalyst via a cascading anchoring strategy, enabling efficient PMS activation. Remarkably, this catalyst achieves 99.18% ¹O₂ generation selectivity and demonstrates outstanding degradation performance for levofloxacin (LEV) with a reaction rate constant of 1.475 min^-1. Experimental and theoretical analyses reveal that the isolated Fe sites enhance the adsorption selectivity of terminal oxygen atoms of PMS, creating an optimal platform for generating metastable Fe intermediates. The highly oxidized metal centers of Fe act as electron acceptors to receive electrons from adsorbed PMS, thereby producing highly reactive ¹O₂ for rapid LEV oxidation. This work elucidates the crucial role of Fe-N₆ coordination in dictating PMS activation pathways, offering mechanistic insights for designing catalysts with high selective ¹O₂ generation.