Nanoconfined Catalysts Enable Tunable Radical and Nonradical Ozonation for Selective Treatment of Saline Industrial Wastewaters.

Selective control of ozone activation pathways remains challenging, particularly in saline industrial wastewaters, where chloride-rich matrices suppress radical oxidation and reduce mineralization efficiency. Here, we show that carbon-shell nanoconfinement of FeCo alloy nanoparticles enables material-defined tuning between radical and nonradical catalytic ozonation pathways. By controlling carbon-shell thickness and nitrogen speciation, we modulate interfacial electron transfer, ozone activation, and oxidation selectivity. Thin carbon shells create electron-rich metal-carbon interfaces that promote radical-driven ozonation and enhance TOC mineralization. In contrast, thicker shells enriched in pyridinic N favor the formation of surface oxygenated intermediates and promote a surface-mediated nonradical oxidation pathway that resists chloride quenching, delivering more than 3-fold higher COD removal in high-salinity real wastewater than the radical-dominant catalyst. Scavenger experiments, electron paramagnetic resonance spectroscopy, electrochemical measurements, in situ FTIR and Raman spectroscopy, and density functional theory calculations collectively show how metal-carbon interactions and N speciation govern ozone adsorption, electron-transfer kinetics, and pathway selection. These results establish carbon-shell nanoconfinement as a general material strategy for tuning catalytic ozonation selectivity in complex industrial wastewaters.