Benzothiadiazole-Based Donor-Acceptor-Type Covalent Organic Frameworks for Effective Heterogeneous Photocatalytic Aerobic Cycloaddition Reaction

Abstract

The development of efficient heterogeneous photocatalysts for oxidative annulation reactions holds significant importance in chemical synthesis, yet remains a challenging endeavor. Benzothiadiazole-based covalent organic frameworks possess strong light-absorption capacity and tunable electronic structures, making them a promising class of heterogeneous photocatalysts. Herein, pyrene units are linked to benzothiadiazole units via imine bonds, resulting in the synthesis of two COFs (HIAM-0015 and HIAM-0035) with different numbers of benzothiadiazole units. Under visible light irradiation at room temperature, the photocatalytic oxidation of N,N,4-trimethylaniline and N-phenylmaleimide by HIAM-0015 and HIAM-0035 achieved a 99% conversion within 8 and 12 hours, respectively. HIAM-0015 demonstrated high conversion activity for the transformation of various substrates due to its efficient charge separation and migration. These findings shed light on the rational design of metal-free COFs with superior photoelectric/chemical properties as heterogeneous photocatalysts for aerobic cycloaddition reactions.