Steering charge transfer in CuInS2/BiOCl composites to enable sunlight-driven C–F bond cleavage of PFAS in water

Abstract

Per- and polyfluoroalkyl substances (PFAS) resist most remediation technologies because of their exceptionally inert carbon–fluorine bonds. Here we report a visible-light Z-scheme photocatalyst composed of CuInS2 quantum dots anchored on BiOCl nanoplates (CuInS2/BiOCl) that overcomes this barrier. Femtosecond transient absorption, steady-state spectroscopy and theoretical calculations show that an internal electric field steers photo-generated electrons (e−) migrating to CuInS2 and holes (h+) to BiOCl, maximizing their redox potentials for simultaneous carbon–fluorine scission and carbon chain breakage, respectively. Computations revealed that benzene sulfonic acid and carbon fluoride groups on sodium p-perfluorous nonenoxybenzenesulfonate (OBS) are susceptible to electrophilic attack by h+ and nucleophilic attack by e−, respectively. Under ultraviolet irradiation, the heterojunction achieves 75.8% defluorination and 76.8% total organic carbon removal of OBS within 8 h, with universal applicability for efficient degradation of 17 representative PFAS mixtures. Continuous-flow tests driven by natural sunlight achieve >96% OBS removal in 10 h, confirming system scalability. Toxicity assays indicate negligible hazardous effects of the residual. The work reports a sunlight-powered and flow-compatible photocatalytic platform for sustained PFAS decontamination, opening a sustainable route for ‘forever chemical’ abatement in water.