Coordination engineering enables highly selective generation of carbonate radicals for enhanced Fenton-like reactions.

The ubiquitous presence of matrix anions typically suppresses Fenton-like oxidation processes via competitive scavenging of reactive oxygen species; however, bicarbonate (HCO3-) exhibits a distinctive dual role, as it can alternatively act as a precursor for selective oxidants. In this work, we exploit coordination engineering of cobalt single-atom catalytic sites to modulate this competing chemistry and favor the productive pathway. Specifically, the rationally designed CoN6 catalyst directs the H2O2/HCO3- reaction system toward interfacial peroxymonocarbonate (HCO4-) transformation, subsequently generating the carbonate radical anion (CO3•-) as the dominant oxidizing species. This tailored system achieves 96.9% removal of sulfamethoxazole within 60 min, with CO3•- accounting for 98.9% of the overall reactivity. The coordination-controlled pathway exhibits marked selectivity toward electron-rich, amine-bearing antibiotic contaminants, while maintaining robust degradation performance over a broad range of initial pH values and in complex real water matrices containing diverse coexisting substances. These findings demonstrate that coordination engineering offers a viable strategy to repurpose bicarbonate from a conventional radical quenching agent into an effective oxidant precursor, providing a fundamental design rationale for developing selective, matrix-tolerant Fenton-like treatment technologies with enhanced practical applicability.