Oxalate-tailored microenvironment engineering of zero-valent copper for enhanced molecular oxygen activation

Dark-generated reactive oxygen species (ROS) derived from molecular oxygen (O₂) hold great potential for removing emerging organic contaminants. However, the spin-forbidden nature of triplet O₂ (³O₂) requires highly efficient catalysts to overcome kinetic limitations in ROS generation. In this study, oxalate-modified zero-valent copper (Ox-ZVC) was synthesized via a mechanochemical method. This novel Ox-ZVC significantly enhanced O₂ activation, achieving a 236% increase in oxytetracycline (OTC) removal efficiency compared to pristine zero-valent copper (ZVC). Combined experimental and density functional theory calculations revealed that oxalate modification increased surface Cu charge density and the Cu⁺^/⁰ ratio, weakened O-O bonds in adsorbed O₂, accelerated O₂ activation to generate reactive ROS (^•OH, ^•O₂⁻, and ¹O₂), and altered the ¹O₂ generation pathway-collectively boosting OTC degradation. Life cycle assessment and long-term operation tests highlighted its strong potential for industrial wastewater treatment with sustainable performance. This work establishes an eco-friendly strategy for contaminant elimination and provides new mechanistic insights for designing rational Cu-based materials in sustainable environmental remediation.