Surfactant-Templated Synthesis of Mg-Stabilized High-Loading Co Single Atoms in Mesoporous Silica Featuring Robust Co–O Bonds for Efficient Peroxymonosulfate Activation

Cobalt single-atom catalysts (SACs) hold significant promise for water decontamination. However, the simultaneous achievement of both high Co loading and stability continues to pose challenges. Herein, we report a surfactant-templated (CTAB/TMB) synthesis of Mg-stabilized Co single atoms anchored in mesoporous silica (600CoMg/MS). This facile strategy yields a high Co loading of 5.97 wt % while preserving a high specific surface area of 457.359 m 2 /g. Multiple characterizations (FT-IR, XPS, XAFS, TEM and BET) confirm that magnesium silicate plays a pivotal role in stabilizing the Co–O bonds and enhancing the specific surface area. When applied to activate peroxymonosulfate (PMS) for 5-fluorouracil (5-FLU) degradation, 600CoMg/MS achieves >97% removal in 30 min and maintains 95% removal after four cycles. Comparable performance is retained even after fabricating the powder into a ceramic monolith. EIS, LSV and i–t confirm Mg-enhanced charge transfer: smaller arc radius, higher current upon PMS addition, and current rise/fall upon sequential PMS/5-FLU, evidencing electron transfer to PMS to generate ROS for 5-FLU degradation. Moreover, the catalyst exhibits stable performance in real water matrices (e.g., lake water, river water) and shows low biotoxicity toward seed germination. Radical quenching and EPR confirm SO 4 •-, O 2 •-, and 1 O 2 as the dominant reactive species, with • OH playing a minor role. By employing a simple extrusion forming strategy, catalysts were flexibly designed with varying lengths and shapes. This work thus establishes a new paradigm for Co SACs confined in mesoporous structures toward sustainable environmental catalysis.