Rationally modulating thiophene- and porphyrin-based donor-acceptor type covalent organic framework for effective photocatalytic organic reactions

In order to specifically demonstrate the improvement of photocatalytic activity attributed to the donor-acceptor (D-A) structure rather than other contributing factors, two highly comparable COFs incorporating porphyrin and thiophene species are synthesized in this work. The first COF, named BTDA-Por, is composed of porphyrin (Por) as the donor unit and 2,2′-bithiophene (BTDA) as the acceptor moiety. The second COF, referred to as TT-Por, is constructed using Por and thieno[3,2-b]thiophene (TT) units while lacking a D-A structure. These synthesized COFs serve as effective models for investigating the role of D-A structures in improving photocatalytic activity. Photoelectronic property studies and density function theory calculations indicate that the D-A configuration can significantly enhance the efficiency of charge carrier generation, separation, and migration. Consequently, the D-A type BTDA-Por exhibits superior performance in photochemical reactions such as oxidative homocoupling of aromatic amine and reversible complexation-mediated radical polymerization when compared to the non-D-A type TT-Por.