Bipyridine-Fe (III)–Based Covalent Organic Frameworks for Efficient Photocatalytic Synthesis of Benzimidazoles

Abstract

Covalent organic frameworks (COFs) with structural versatility, tunable photophysical properties, and excellent chemical stability and recyclability have been widely used as heterogeneous photocatalysts. Developing metal-based COFs for structural designability and unprecedented properties is highly desirable. In this paper, a new COFs-supported photocatalyst BD_Fe-COF embedded with metallic iron (III) was successfully synthesized by the metalation reaction of FeCl₃·6H₂O and bipyridine-based BD-COF, which was prepared by the aldehyde-amine condensation of 2,2′-bipyridine-5,5′-dicarboxaldehyde and 4,4′,4″,4‴-(pyrene-1,3,6,8-tetrayl) tetraaniline via a solvothermal method. The as-synthesized BD_Fe-COF exhibited high crystalline, excellent chemical stability, and good photophysical properties. Moreover, the photoactive BD_Fe-COF was employed as a cost-effective catalyst in the cyclocondensation of o-phenylenediamine with aldehydes. The advantages of the current photocatalytic system included high to excellent yields, easy work-up process, and short reaction time, together with high recyclability.