Oxygen vacancy–rich spinel oxide drives phenol polymerization via direct oxidative transfer

Advanced oxidation processes are widely deployed in water purification to eliminate persistent organic pollutants. However, conventional systems relying on free radicals require high energy and massive oxidant inputs, inevitably producing toxic intermediates and increasing carbon emissions. The direct oxidation transfer process (DOTP) offers a non-radical alternative for efficient pollutant removal with minimal oxidant demand, yet designing catalysts that selectively drive this pathway remains a formidable challenge. Here we show that oxygen vacancy (V_O)-enriched manganese ferrite spinel (MnFe₂O₄) triggers phenol polymerization via a surface-confined DOTP. By engineering V_O concentrations on a carbon cloth support, we establish a quantitative structure-activity relationship demonstrating that higher vacancy densities suppress radical generation and drive a two-electron oxidative transfer. The vacancies promote electron delocalization and an upward shift of the d-band center from −1.10 to −0.95 eV, simultaneously optimizing the chemisorption of both the oxidant and the pollutant. This mechanism yields 97.5% phenol removal and 73.2% total organic carbon elimination in continuous flow over 240 h, utilizing an ultralow oxidant-to-pollutant ratio. Crucially, this V_O-dependent polymerization pathway is highly generalizable to other oxide systems, such as Mn₃O₄ and α-FeOOH. Our findings highlight a robust defect-engineering strategy to precisely dictate organic reaction pathways on catalytic surfaces. This targeted polymer-forming approach establishes a sustainable, low-carbon paradigm for advanced water purification.