Design of a novel tribromide ionic liquid covalent triazine framework for green synthesis of benzimidazoles

Ionic covalent triazine frameworks are a class of porous materials that integrate ionic liquid moieties into the backbone or pores of CTF. This combination imparts unique properties such as high ionic conductivity, enhanced catalytic activity, and improved affinity for polar or charged species. A novel tribromide ionic liquid covalent triazine framework catalyst was synthesized through the combination of 4,4'-(butane-1,4-diylbis(oxy))dibenzaldehyde and N ¹,N ¹'-(6-(2-aminobenzyl)-1,3,5-triazine-2,4-diyl)bis(benzene-1,2-diamine), denoted as [IL-BD-AT]⁺Br₃ ^-. Its elevated nitrogen content provides abundant anchoring sites for bromine species, thereby enhancing catalytic performance. This rational design significantly reduces the intrinsic toxicity of bromine and minimizes associated environmental hazards. Furthermore, the catalyst exhibits excellent thermal stability, ensuring robust performance under diverse reaction conditions. The catalyst demonstrated exceptional catalytic activity, achieving high yields of benzimidazole derivatives from the reaction of various aldehydes and 1,2-phenylenediamine (up to 98%) under mild conditions within short reaction times (5-20 min). Notably, the catalyst was easily recovered by centrifugation and reused for six consecutive cycles without significant loss of activity. Owing to its insolubility, the catalyst can be readily separated via centrifugation, thereby improving its applicability in sustainable catalytic processes. This study underscores the potential of covalent triazine frameworks in developing efficient, thermally stable, and environmentally benign catalytic systems for organic synthesis. The structural and physicochemical characteristics of the catalyst were comprehensively elucidated using a range of analytical techniques.