Preparation of Co-C/N flower-like single-atom catalysts via TCPP coordination confinement for enhanced activation of peroxymonosulfate

The design and preparation of highly efficient advanced oxidation processes (AOPs) catalysts is a crucial research area in the field of water pollution control. Herein, a single-atom AOP catalyst Co-N/C material (TPM-650) has been synthesized through the pyrolysis of the flower-shaped Co-TCPP MOF precursor, which is designed based on coordination confinement with TCPP. HAADF-STEM image analysis confirms the uniform distribution of single Co atoms throughout the TPM-650 material, which served as the highly efficient catalytic centers and can achieve 99.99% catalytic degradation of MG dyes in 24 min with only trace dosage ([TPM-650] = 1 mg/L, pseudo-first-order kinetic model, K _obs=0.302 min ⁻¹ ) and low leaching of Co ions (0.348 μg/L). Under optimal condition, the degradation of MG exhibits a high turnover number (dTON) of 68.5 mmol h ⁻¹ g _cat ⁻¹ and a significant reduction in total organic carbon (TOC) by 58.7%. Radical quenching experiments and EPR measurements demonstrated that various reactive oxygen species (•SO ₄ ⁻, •OH, ¹O ₂, M ^IV(O)/M ^V (O)) contributes to accelerating MG degradation. The enhanced efficiency and stability were attributed to the ultrathin layer supported single-atom Co-N/C structure, high mesopore volume, and synergy between the catalyst and peroxymonsulfate (PMS) with a synergy index of 16.5. This study not only reports a highly efficient and stable advanced oxidation catalyst Co-N/C, but also confirms that the nitrogen-coordinated Co sites are the primary active sites responsible for PMS activation; thus providing valuable insights into designing efficient transition metal-based AOP catalyst via coordination method for environmental remediation.