Nile Red-Based Covalent Organic Framework as a Photocatalyst for C−H Bond Functionalization

Abstract

The search for efficient photocatalysts based on covalent organic frameworks (COFs) is an area of increasing interest. However, the development of these heterogeneous photocatalysts is hindered by the symmetry restrictions of the linkers used to construct these materials. Herein, we report the straightforward synthesis of an imine-based 2D-COF, NR0.17-COF, which incorporates a Nile Red (NR) unit via postmodification with a NR-alkyne scaffold. This framework exhibits remarkable photocatalytic activity across various photoredox-catalyzed C−H functionalization reactions, demonstrating the ability to directly functionalize prevalent bonds in organic molecules under mild conditions and with low-energy light. The NR0.17-COF showcases notable versatility, effectively generating aryl, sulfur, and nitrogen radicals from different radical precursors while maintaining good functional group tolerance. Moreover, our heterogeneous photocatalyst outperforms traditional homogeneous systems by addressing critical challenges such as scalability and recyclability, allowing for a 10-fold increase in the reaction scale and enabling recovery and reuse up to six times. This advancement significantly enhances the potential of COF postsynthetic modification for practical applications in organic synthesis, which marks a substantial step forward in photocatalytic technology.