Photoexcited LMCT of Cu2+ perfluorocarboxylate for initiating efficient defluorination

Per- and polyfluoroalkyl substances are widely distributed persistent pollutants in water resources that pose serious environmental and health threats. Current per- and polyfluoroalkyl substance destruction strategies are energy-intensive, nonselective, and often generate recalcitrant short-chain fluorinated byproducts. Herein, we report a near-ultraviolet to visible light-driven complete defluorination approach of per- and polyfluoroalkyl substance based on ligand-to-metal charge transfer, wherein commercially available Cu²⁺ salts serves as the electron acceptor from per- and polyfluoroalkyl substance to initiate the defluorination reaction. The feasibility of the degradation reaction is explored under controlled conditions, in which perfluorooctanoic acid is completely degraded and defluorinated within 300 min. Spectroscopic analyses, intermediates identification, and density functional theory calculations confirm that electron transfer from perfluorooctanoic acid to Cu²⁺ selectively initiates a single-pathway chain-shortening degradation mechanism. The degradation rate of perfluoroalkyl acids increases as chain length decreased. Ultrashort-chain trifluoroacetic acid achieves more than 99% degradation and defluorination within 60 min. This degradation approach is also effective for perfluoroalkyl ether carboxylic acids and is potentially adaptable to a broader range of per- and polyfluoroalkyl substance classes, offering opportunities for extension to other homogeneous or heterogeneous Cu²⁺-based remediation systems, as the reactivity pattern has been substantiated.