Tailored Metal–Oxygen Interface Engineering of Self-Assembled CoMn Spinel Nanocatalysts for Singlet Oxygen-Mediated Peroxymonosulfate Activation and Pollutant Degradation

Cobalt-based heterogeneous catalysts have emerged as high-performance activators of peroxymonosulfate (PMS) for advanced oxidation processes targeting pharmaceutical contaminants. This work presents a morphology-engineered spinelloid phase (g-CoMn₂O₄) synthesized through a glycerol-modulated crystallization strategy, exhibiting a 3D hierarchical nanofloral architecture with enhanced interfacial active sites. Remarkable tetracycline (TC) degradation efficiency of 98.90% was achieved within 10 min (k = 1.19 min^-1), representing a 3.6-fold enhancement in degradation capacity and a 21.5-fold acceleration in reaction kinetics compared with pristine PMS systems. Atomic-level characterization revealed that Mn³⁺/Mn⁴⁺ doping optimizes electron transfer networks and promotes Co²⁺/Co³⁺ redox cycling, thereby boosting PMS utilization efficiency (η_PMS = 82.7%). Multipathway activation mechanisms were quantitatively decoupled through spin-trapping EPR and chemical quenching studies, identifying 1O²-dominated nonradical oxidation with supplementary contributions from SO₄ ^- and ·OH. LC-MS analysis mapped three primary degradation pathways involving demethylation, hydroxylation, and ring-opening reactions, with TEST predictions confirming detoxification of transformation products. This structure-activity relationship study provides molecular-level insights for the rational design of transition metal catalysts in emerging contaminant remediation.