Heterogeneous Photocatalytic Recycling of FeX₂/FeX₃ for Efficient Halogenation of C−H Bonds Using NaX

Abstract

Environmental-friendly halogenation of CÀ H bonds using abundant, non-toxic halogen salts is in high demand in various chemical industries, yet the efficiency and selectivity of laboratory available protocols are far behind the conventional photolytic halogenation process which uses hazardous halogen sources. Here we report an FeX 2 (X = Br, Cl) coupled semiconductor system for efficient, selective, and continuous photocatalytic halogenation using NaX as halogen source under mild conditions. Herein, FeX 2 catalyzes the reduction of molecular oxygen and the consumption of generated oxygen radicals, thus boosting the generation of halogen radicals and elemental halogen for direct halogenation and indirect halogenation via the formation of FeX 3 . Recycling of FeX 2 and FeX 3 during the photocatalytic process enables the halogenation of a wide range of hydrocarbons in a continuous flow, rendering it a promising method for applications.