Photoswitch Mediated Electron Highway Driving Direct Pollutant-to-Oxidant Electron Transfer in Ultrafast Fenton-Like...

Traditional heterogeneous photocatalytic systems coupled with oxidant activation hold great promise for environmental remediation but are constrained by radical scavenging and nonselective oxidation. Here, we introduce an overlooked photoswitch-mediated electron transfer (PSMET) mechanism that circumvents reactive oxygen species by enabling direct, ultrafast electron transfer from pollutants to oxidants through a photoactive mediator. Using environmentally benign bismuth oxyiodide as a model catalyst under visible-light irradiation, we achieve unprecedented degradation rates for various electron-rich pollutants such as sulfamethoxazole (t_1/2 <2.0 min). This mechanism exhibits pollutant-dependent oxidant utilization mode and selective pollutant degradation characteristics. Mechanistic analyses reveal the formation of a high-potential electron-transfer pathway activated by photoexcitation, directly coupling pollutant oxidation to oxidant reduction within a single electron-transfer cycle. Frontier molecular orbital calculations further demonstrate that the narrow bandgap and p-type semiconductor characteristics selectively facilitate electron extraction from contaminants to oxidants. Remarkably, this PSMET mechanism displays universal applicability with diverse oxidants, maintaining >98% pollutant removals even in complex aqueous matrices and continuous-flow systems. Furthermore, the mechanism allows precise optical control over reaction initiation and termination, offering unparalleled spatiotemporal regulation for sustainable wastewater treatment. Our findings redefine photocatalytic oxidation paradigms and open new pathways toward energy-efficient, optically programmable, and environmentally sustainable remediation technologies.