Donor-Acceptor-π-Acceptor-Donor-Type Photosensitive Covalent Organic Framework for Effective Photocatalytic Aerobic Oxidation

Developing effective photocatalysts for the oxidation reaction is of great significance in chemical synthesis but is still challenging. Herein, linking photochromic triphenylamine with pyrene units by the in situ formed robust imidazole moieties, a covalent organic framework (COF), PyNTB-COF, containing a rare donor-acceptor-pi-acceptor-donor (D-A-pi-A-D) fragment, was successfully synthesized for photocatalytic aerobic oxidation. Structure characterizations confirm its crystalline framework, high porosity, and good stability. Property studies reveal its photoelectric semiconductor feature with high photoresponsive charge separation and migration activity derived from the D-A-pi-A-D fragments, proven by the experimental results and theoretical calculations. Photocatalytic experiments not only display its highly effective photoresponsive activity in triggering the generation of <middle dot>O2 - under visible light irradiation but also exhibit its high photocatalytic efficiency in the aerobic oxidations of toluene and the amidation of aldehydes. This work demonstrates that the integration of photochromic units into framework materials to construct pi-conjugated D-A moieties could enhance photocatalytic charge separation and migration efficiency, achieving promising photocatalysts for photocatalytic aerobic oxidation.