Axial pyridine coordination-induced Co d-orbital rearrangement boosts peroxymonosulfate activation for singlet oxygen evolution in water remediation

In this work, a cobalt phthalocyanine catalyst with axial pyridine coordination anchored on carbon nanotubes (CoPc-Py-CNT) was developed for enhanced peroxymonosulfate (PMS) activation toward singlet oxygen ( 1 O 2 ) evolution. Axial pyridine coordination induces Co 3 d -N 2 p rehybridization, elevating the Co d z 2 orbital energy level to strengthens d-p orbital hybridization with the oxygen atom in PMS, thereby lowering the activation energy barrier for O-O bond cleavage. The CoPc-Py-CNT/PMS system exhibits an 8.3-fold increase in ciprofloxacin degradation rate and nearly quantitative selectivity in aromatic alcohol oxidation to corresponding aldehydes compared to axially unmodified CoPc-CNT. CoPc-Py-CNT maintains excellent performance in both continuous-flow and 50 L pilot-scale water treatment systems, with minimal cobalt leaching (<20 μg L −1 ) and negligible ecotoxicity. This work proposes a tailored symmetry-breaking strategy via axial coordination to modulate the electronic structure of SACs, offering a robust platform for 1 O 2 -mediated water remediation and selective oxidation reactions in green chemistry applications.