Enhancing Photocatalytic Redox Activity of Polymeric Carbon Nitride for Valuable Fluorinated Heterocycles through Fast-Track Electron Highways

The ionic structure of poly(heptazine imides) has a strong implication in photocatalytic hydrogen generation. From numerous reports, it is evident that these materials are also superior to covalent carbon nitrides in various organic transformations. However, the reason has been remaining vague. Herein, we report the design of a molten-salt carbon nitride (MCN) featuring ionic structure represented by negatively charged organic polymeric scaffold and K⁺ counterions and application of this material as the photocatalyst in synthesis of pharmaceutically relevant fluorinated heterocycles under visible light under the redox neutral conditions. K⁺ ions serve as the sites for sorption of ethyl bromodifluoroacetate, while the electronically excited state of MCN acts as the single electron transfer agent, enabling generation of difluoroalkyl radicals from the substrate. Combination of these two features endows a material that outperforms homogeneous photocatalysts and covalent carbon nitrides. Our protocol expands the application of carbon nitrides in synthesis of organic compounds with complex structure and provides fresh perspectives on the factors contributing to the enhanced photocatalytic efficiency of poly(heptazine imides). © 2024 The Authors. Published by American Chemical Society.