Coordination Engineering of Cobalt Single-Atom Catalysts for Periodate Activation with Regulated Reactive-Species Production toward Emerging Contaminants Degradation

Abstract Fenton-like reaction of heterogeneous periodate (PI) activation exhibits high efficiency for emerging contaminants degradation due to the production of iodine-centered radicals, and single-atom metal catalysts demonstrate high activity. However, precisely controlling the radical production pathway during catalysis remains a great challenge. Herein, we design three zeolitic imidazolate framework-derived single-atom catalysts with different cobalt active centers, i.e., symmetric Co–N4 sites (Co–N–C (P)), distorted Co–N2O2 sites (Co–N–C (A)), and highly asymmetric Co–N3O1 sites (Co–N–C (L)). Advanced synchrotron spectroscopy and density functional theory (DFT) calculations collectively reveal the geometric and electronic symmetry of the Co–N4 configuration in Co–N–C (P), which enables π-electron delocalization from the low-spin d7 state of the Co center, maintaining high-energy orbitals partially occupied or vacant for PI activation. The unique electronic structure drives selective PI activation to generate IO3• while effectively suppressing other competing pathways, thereby achieving superior degradation performance for chlortetracycline hydrochloride (CTC). Practical evaluation confirms the consistent performance of Co–N–C (P) in continuous-flow operation with strong resistance to water-matrix interference. These findings elucidate the mechanistic understanding of catalytic PI activation at the molecular level and guide the rational design of efficient catalysts.