Plasmon-driven carbon–fluorine (C(sp3)–F) bond activation with mechanistic insights into hot-carrier-mediated pathways

Abstract

The activation of carbon–fluorine bonds is an industrially and environmentally critical, but energetically challenging, transformation. Here we demonstrate a plasmonic photocatalysis approach to visible-light-driven hydrodefluorination that utilizes aluminium–palladium antenna–reactor heterostructures. Photocatalytic hydrodefluorination of aliphatic carbon–fluorine (C(sp3)–F) bonds in fluoromethane as a model molecule, in the presence of deuterium, results in the selective production of monodeuterated methane with a remarkable photocatalytic efficiency and stability. Analysis of the reaction kinetics reveals a reduction in the apparent reaction barrier and changes to the deuterium reaction order under illumination, which suggests a non-thermal contribution from photogenerated hot carriers to the reaction pathway. Using embedded correlated wavefunction methods, the ground- and excited-state energetics and the role of plasmon excitation in lowering the reaction barrier and modifying the kinetics under illumination are determined. Plasmon-mediated carbon–fluorine bond activation represents a promising potential for applications in high-value chemical transformations, as well as in abatement technologies for the mitigation of anthropogenic polyfluoroorganic compounds. The cleavage of C–F bonds through hydrodefluorination is challenging and has been traditionally limited to unsaturated fluorocarbons. Now, a simple plasmonic approach based on the use of aluminium nanocrystal-supported palladium nanoparticles is introduced to effectively upgrade fluoromethane under visible light.