Upcycling Water Pollutants Into Long‐Chain Polymers via Synergistic Interfacial Dechlorination and Organic Radical Stabilization

High-entropy oxides (HEOs) offer unusual electronic structures arising from lattice distortion, multimetal synergy, and high chemical stability. Here we report nitrogen-doped carbon-encapsulated HEOs catalysts (HEO@NC) synthesized by in situ carbothermal reduction for efficient pollutant removal and upcycling through selective oxidative polymerization. HEO@NC activates periodate via an electron-transfer pathway coupled with surface-adsorbed hydroxyl radicals, enabling the selective conversion of phenolic contaminants into polymeric products under extreme pH and strong ionic interference. Relative to metal-free nitrogen-doped carbon, HEO@NC markedly enhances periodate activation through interfacial electronic coupling and achieves a periodate utilization efficiency of 449.2%, far exceeding that of conventional mineralization. Density functional theory and experimental analyses reveal complementary roles of the HEOs components: Co/Ni provide periodate-binding sites, Pt lowers the barrier for electron transport, Bi/Pb promote charge delocalization to stabilize polymeric intermediates, and oxygen orbitals strengthen periodate coordination and surface charge transfer via p-d hybridization. This synergy drives dechlorination-coupled polymerization with sustained 4-chlorophenol removal at ultralow oxidant consumption. HEO@NC further maintained > 95% efficiency with negligible metal leaching during 20-day treatment of real coal chemical wastewater, demonstrating the potential for sustainable and low-chemical-consumption remediation of industrial-relevant wastewater.