Non-radical pathway dominated peroxymonosulfate activation using MOF-derived Co3Fe7@CN: Regulation of pore structure and active sites for efficient oxytetracycline degradation

The increasing complexity and concentration of refractory organic pollutants in industrial wastewater necessitate the development of efficient and stable advanced oxidation processes (AOPs). Herein, metal–organic framework (MOF)-derived Co₃Fe₇@CN carbon composites were successfully fabricated and evaluated as peroxymonosulfate (PMS) activators for the degradation of oxytetracycline (OTC). Among the as-prepared catalysts, Co₃Fe₇@CN-1 exhibited superior catalytic performance, achieving 90% OTC removal within 10 min with an apparent rate constant ( k obs ) of 0.158 min −1 , which represents a 1.7- and 1.5-fold enhancements over Co₃Fe₇@CN-2 and Co₃Fe₇@CN-3, respectively. The outstanding activity of Co₃Fe₇@CN-1 is primarily attributed to its favorable pore structure and pronounced adsorption–catalysis synergy. Specifically, Co₃Fe₇@CN-1 and Co₃Fe₇@CN-3 achieved 23% and 21% of OTC removal via adsorption, respectively, whereas the dense structure of Co₃Fe₇@CN-2 significantly impeded pollutant uptake (<5%). Mechanistic investigations revealed that PMS activation is driven by the synergistic redox cycling of Co (Co 0 /Co(II)/Co(III)) and Fe (Fe 0 /Fe(II)/Fe(III)) species. Electrons transferred from zero-valent and low-valent metals promote O O bond cleavage in PMS, triggering the generation of SO₄• − and •OH radicals. Crucially, the Fe species acts as an electron reservoir to accelerate the reduction of Co(III) to Co(II), thereby effectively circumventing the rate-limiting step of the Co redox cycle. Simultaneously, high-valent Fe(III)/Co(III) species interact with PMS to form high-valent metal-oxo intermediates ( Fe(IV) O and Co(IV) O), which serve as the predominant reactive species responsible for OTC degradation. The coexistence of radical and non-radical pathways ensures efficient OTC degradation. This work establishes a controllable strategy for constructing MOF-derived carbon catalysts and elucidates the structure–activity relationship between pore architectures and redox centers.