Asymmetric Single-Atom Catalysts Govern Diffusible and Non-Diffusible Non-Radical Pathways for Selective Degradation...

To address the global health threat from antibiotic resistance genes (ARGs), non-radical dominated advanced oxidation processes (AOPs) show promise for ARG degradation. To better understand and develop the process, a comparative study on diffusible and non-diffusible non-radical-driven AOP would be of great significance. Herein, asymmetric M-NC (M = Co, Fe) single-atom catalysts were engineered to enable tunable switching between distinct non-radical pathways via peroxymonosulfate (PMS) activation. The non-diffusible electron transfer pathway (ETP)-dominated Fe-NC/PMS system displayed higher intrinsic reactivity toward guanine (G) but lower efficiency for ARGs degradation. Compared with diffusible ¹O₂, non-diffusible ETP exhibited a limited spatial accessibility to ARGs, which significantly reduces the degradation efficiency of the ETP pathway. In contrast, the diffusible ¹O₂-driven Co-NC/PMS system selectively oxidized G, achieving irreversible ARG removal with the highest degradation rate constant (2.0 min^-1) among reported M-NC/PMS-based systems. Highlighting the unique advantage of diffusible ¹O₂ in ARG elimination. Moreover, this system maintained high ARG removal (>5.4 log copies/mL) under high salinity (3000 mg/L), low temperature (4°C), and over 20 consecutive cycles, demonstrating exceptional stability and environmental resilience. This study clarifies the inherent advantage of diffusible ¹O₂ over non-diffusible ETP in elimination and delineates a clear direction for future development.