Facile synthesis of high loading and highly electron-delocalized Co single-atom catalyst for PMS activation: An...

Single-atom catalysts (SACs) have attracted significant attention for peroxymonosulfate (PMS) activation in advanced oxidation processes, yet their practical application is limited by the lack of simple synthesis routes that enable high metal loading and controlled electronic environments with broad pH adaptability. Here, we report a one-step strategy to construct Co₃(HITP)₂ (HITP=2,3,6,7,10,11-hexaiminotriphenylene), a Co-N₄ SAC with a Co loading of 9.97 wt%. The π-d conjugated HITP ligands provide a highly delocalized electronic environment that precisely modulates the catalytic centers. The catalyst achieved nearly complete degradation of carbamazepine (CBZ) in a continuous-flow reactor, highlighting its efficiency and stability. Mechanistic investigations showed that PMS activation proceeds via the generation of sulfate radicals (SO₄•^-) and singlet oxygen (¹O₂) in comparable yields. Density functional theory (DFT) calculations revealed that preferential adsorption of the terminal oxygen atom of PMS on Co sites is the key step initiating the formation of SO₄•^-, SO₃•^-, and subsequently ¹O₂. This work provides molecular-level insights into the fabrication of delocalized SACs and offers a promising pathway toward efficient catalytic water purification technologies.