Nitrogen vacancy optimizes adjacent asymmetric coordination in VN-CoN3O1 affording to selectively generate 1O2 for sewage purification

The development of efficient and sustainable environmentally functional material is a crucial approach to global water pollution control. Single-atom catalysts (SACs) Fenton technology, as a promising means of water treatment, still suffers from problems such as the single active site and secondary pollution caused by metal ion leaching. In this study, trace Co single atoms (SAs) are chelated by tannic acid to reduce metal ion leaching and anchored to g-C 3 N 4 containing nitrogen vacancy (V N ). DFT calculation results reveal that the d-band structure of Co SAs is regulated by orbital hybridization with the electronic states of coordinating atoms in V N -CoN 3 O 1 , which further improves the intrinsic activity of Co SAs in asymmetric coordination. In addition, V N acts as the charge transfer bridge of the V N -CoN 3 O 1 /PMS/BPS system, transferring the electrons captured from BPS to the adjacent asymmetric Co SAs, further enhancing the activation ability of the Co SAs sites. Benefiting from the tuning between the dual active sites, V N -CoN 3 O 1 with asymmetric coordination and nitrogen vacancies in the PMS system exhibits a high degradation rate (99%) and high mineralization (75.1%) for bisphenol S (BPS) in 30 min. After multi-factor experiments and five consecutive cycles, the system maintained high efficiency in degrading electron-rich BPS. In addition, BPS as the electron provider transporting to V N -CoN 3 O 1 and was effectively degraded by a non-radical dominated 1 O 2 conversion pathway of (PMS → PMS* → OH* + SO 4 * → O* + H* → OO* → 1 O 2 ) with OO* as the rate-determining step. This study highlights the feasibility of dual-active site structural engineering-nitrogen vacancy and asymmetric coordination tuning for single-atom Fenton chemistry and inspires rational SACs design in water purification.