Tailored coordination of atomically dispersed Co sites on MnO₂ drives synergistic peracetic acid activation for ultrafast sulfamethazine degradation via high-valent cobalt-oxo species and acetylperoxy radicals

Efficient degradation of antibiotic contaminants remains challenging in wastewater treatment. Herein, a single-atom Co catalyst with tailored Mn–O coordination on MnO₂ (Co-MnO₂) was synthesized to activate peracetic acid (PAA) for ultrafast sulfamethazine (SMZ) degradation. The Co-MnO₂/PAA system achieved 96.8 % SMZ removal within 10 min (rate constant: 0.3415 min⁻¹), outperforming pristine MnO₂ by 243.9-fold. A multi-pathway degradation mechanism, which included a radical pathway driven by acetylperoxy radical (CH₃C(O)OO^•) and a non-radical pathway mediated by high-valent cobalt-oxo species (Co(IV) = O) and singlet oxygen (¹O₂). Density functional theory calculations revealed that single-atom Co effectively disrupted the distribution of electrons in the MnO₂ crystal and caused charges to be more concentrated at single-atom sites, reducing the system's total energy and weakening the adsorption energy between the catalysts and PAA. This microenvironment features an asymmetric electron localization around the single-atom Co site, architected by the specific Co-O-Mn coordination that effectively polarizes the PAA molecule and lowers the activation energy barrier for its cleavage. To evaluate industrial application potential, a continuous flow reaction system by immobilizing the Co-MnO₂ on a commercially membrane was developed. This work provides deep mechanistic insights into coordination-dependent PAA activation and advances single-atom catalysts for refractory contaminant remediation. © 2025 Elsevier B.V.