Benzothiadiazoles incorporated in a metal–organic framework for improved photocatalysis in azacycle synthesis

Abstract

Visible-light-responsive metal–organic frameworks (MOFs) are an emerging class of photocatalysts, able to capture and activate substrates. Herein, we report the design and synthesis of a series of benzothiadiazole-based photosensitizers through atom-bridged meso-substituent annulation (ATDB, BTDB, IBTDB, and TBTDB). The incorporation of these sensitizers in UiO-66 yielded heterogeneous photocatalysts, denoted as UiO-66-L (where L = ATDB, BTDB, IBTDB, and TBTDB), active under visible light. The modulation significantly enhances the efficiency of charge separation and transfer within the resulting UiO-66-L composites upon visible-light excitation. Notably, the catalyst featuring a benzo(triazole-thiadiazole) moiety (UiO-66-TBTDB) exhibits the best photocatalytic activity. It efficiently drives the synthesis of valuable azacyclic compounds, specifically 1-substituted benzimidazoles, benzothiazoles, and quinazolinones, via photoinduced condensation reactions between anilines and diverse aldehydes, achieving yields up to 97%.