Radical and nonradical cocatalysis induced by asymmetric medium-spin cobalt single atom for water decontamination

Decreasing spin state of cobalt to reduce the redox energy barrier of peroxymonosulfate has been challenging. Herein, we constructed asymmetric coordination of Co−BN 3 to decrease spin state of cobalt from high to medium. The developed medium-spin cobalt-mediated Fenton-like system had a carbamazepine degradation rate constant of 0.815   min −1 and removed 58.0% of chemical oxygen demand, 52% of total phosphorus, 69% of total nitrogen and 85% of ammonia nitrogen from the hospital wastewater. This was attributed to that the medium-spin cobalt formed by the construction of asymmetric Co−BN 3 , enhancing the electrons absorption and donation from dz 2 and dx 2 -dy 2 orbitals to PMS, achieving the reduction in redox energy barrier of peroxymonosulfate for the generation of sulfate radical and singlet oxygen. This work provided a new perspective to develop efficient spin-induced synergistic oxidation Fenton-like water treatment technology.