In situ iodine generation enables solution-phase polymerization of organic pollutants for continuous resource recovery from water

Oxidation-driven polymerization of organic pollutants offers a route to convert contaminants into value-added products and enable continuous resource recovery from water, but conventional heterogeneous processes are plagued by polymeric overlayers that foul catalyst surfaces and hinder long-term operation. Here, we realize solution-phase polymerization of 4-chlorophenol (4-CP) by relocating key bond-forming steps from catalyst interfaces into the bulk aqueous phase. In a facet-engineered bismuth oxyiodide/hydrogen peroxide (BiOI/H2O2) system, BiOI directs H2O2 activation toward in situ generation of freely diffusing, moderately oxidizing iodine (I2) as the dominant reactive species. Accordingly, I2 drives 4-CP polymerization predominantly in solution rather than on the solid surface, delivering a record 73% retention of polymeric products in the aqueous phase. In situ scanning electrochemical cell microscopy (SECCM) directly visualizes the spatial generation of I2 and its subsequent reaction with 4-CP. Complementary spectroscopy and density functional theory reveal that the (110) facet of BiOI stabilizes H2O2 adsorption via a hydrogen-bond bridging configuration that promote O–O bond cleavage and I2 formation, whereas other favors radical pathway. This “facet–species–phase” strategy, in which catalyst facets govern the dominant reactive species and thus direct solution-phase polymerization, enables fouling-resistant advanced oxidation that couples water purification with continuous resource recovery. Catalyst fouling hinders oxidation-driven polymerization of organic pollutants. This study shows a facet-programmed BiOI/H2O2 system generating I2 in situ to drive solution-phase polymerization, eliminating fouling while enabling resource recovery.