Engineering Co-N4 active sites in heptazine-porphyrin organic polymer to boost non-radical singlet oxygen generation in peroxymonosulfate activation

Precisely designing catalyst structures through chemical strategies to achieve non-radical-mediated Fenton-like catalysis for the efficient removal of organic contaminants is of great significance. Herein, a heptazine-porphyrin organic polymer (HPOP) was synthesized via a nucleophilic substitution reaction. Subsequently, a heptazine-porphyrin organic polymer catalyst featuring Co-N 4 sites (HPOP-Co 20 ) was fabricated through a solvothermal method for efficient peroxymonosulfate (PMS) activation. The porphyrin core effectively anchored the Co-N 4 active sites, inducing the generation of singlet oxygen from PMS. The high conjugation of porphyrin and heptazine effectively enhances the charge transport capability of the catalyst. Upon coordination with Co single atoms, the charge distribution of the polymer was reconstructed, facilitating rapid electron transfer to PMS. Compared with the original HPOP, the reaction rate constant of HPOP-Co 20 activating PMS for degrading sulfamethoxazole (SMX) could reach 1.7018 min −1 , which is 92.99 times that of the HPOP/PMS system (0.0183 min −1 ). The non-radical-mediated characteristic enabled HPOP-Co 20 /PMS to achieve efficient degradation across various water bodies, pollutants, anions, and initial pH conditions. The results of phytotoxicity and continuous wastewater treatment experiments indicated that SMX toxicity decreased after degradation, highlighting the practical application potential of this system. This study introduces a controllable substrate structure and a Co-N 4 site catalyst that promote non-radical pathways and enhance its stability and environmental adaptability.