Carbon–Iodine Coordination Activates Co–N ₄ Sites for Efficient Peroxymonosulfate Activation toward Mass-Transfer-Accelerated Singlet Oxygen Oxidation of Electron-Rich Pollutants

Mass transfer limitations and inefficient nonradical oxidant generation often constrain the practical performance of Fenton-like catalysts for micropollutant removal. Here, we develop a synergistic architectural strategy to construct carbon-supported cobalt single-atom catalysts (Co-INC) via ammonium iodide-assisted chemical vapor deposition, integrating atomically dispersed Co–N 4 sites with carbon–iodine (C–I) coordination motifs to simultaneously enhance reactant transport and singlet oxygen ( 1 O 2 ) production. Benefiting from in situ NH 3 -mediated etching, the architecture enhances active-site accessibility while achieving a high Co density of 0.165 mmol g –1, facilitating peroxymonosulfate (PMS) diffusion. Additionally, iodine incorporation creates an asymmetric Co–N 4 /C–I coordination environment that upshifts Co d -band center to −0.54 eV, strengthening PMS adsorption (−2.54 eV). This configuration promotes interfacial electron transfer and reduces the rate-determining energy barrier to −0.84 eV, substantially boosting 1 O 2 generation and achieving a steady-state concentration of 0.295 mM. Furthermore, the optimized pore architecture alleviates mass-transfer constraints, enabling efficient 1 O 2 utilization and a 2.3-fold increase in the ciprofloxacin mass-transfer coefficient. Consequently, Co-INC exhibits an exceptional normalized rate constant of 507 min –1 ·M –1 for ciprofloxacin degradation, outperforming pristine Co-NC by 10.3 times and surpassing most PMS-based catalysts. This study demonstrates that coupling active-site coordination with mass-transfer enhancement is pivotal for maximizing nonradical oxidation pathways in water treatment.