Sustained Fe³⁺/Fe²⁺ Cycling Enables Photochemical Defluorination of Perfluoroalkyl Carboxylic Acids via Ligand-to-Metal Charge Transfer

Although Fe³⁺-mediated ligand-to-metal charge transfer (LMCT) has been shown to promote PFAS photochemical defluorination, existing systems rely predominantly on high-energy UV irradiation, often achieve incomplete defluorination, and generally exhibit poor performance toward short-chain and ultrashort-chain PFASs.

Herein, we report a near-UV- to visible-light-driven photodefluorination strategy for perfluoroalkyl carboxylic acids (PFCAs) using commercial Fe³⁺ salts in acetonitrile under 405 nm irradiation, which achieved complete defluorination of long-chain perfluorooctanoic acid (PFOA) within 420 min and ultrashort-chain trifluoroacetic acid (TFA) within 240 min. Mechanistic studies combining density functional theory calculations and experimental evidence revealed that LMCT initiated decarboxylation, generating perfluoroalkyl radicals that subsequently degraded through oxidative chain-shortening reactions.