Benzotrithiophene conjugated microporous polymer photocatalysts for selective aerobic sulfoxidation driven by green light

Porous organic materials with permanent skeletons, highly delocalized π–π conjugations, and stable chemical bonds have an excellent potential for visible light photocatalysts. Essentially, the efficiency depends on the building blocks, among which benzotrithiophene, electron-rich and planar, is highly favored. In this work, starting with benzo[1,2-b:3,4-b′:5,6-b′′]trithiophene-2,5,8-tricarbaldehyde (BTT), 1,4-phenylenediacetonitrile (PDAN) and 1,4-phenylenediamine (PDA) are adopted to synthesize two porous organic materials with vinylene and imine linkages, respectively. The lowly reversible vinylene only allows the formation of a conjugated microporous polymer (CMP), BTT-PDAN-CMP. In contrast, the highly reversible imine enables the construction of a covalent organic framework (COF), BTT-PDA-COF. Despite being amorphous, BTT-PDAN-CMP, with robust sp2-carbon skeletons, displays superior photoelectric performance than BTT-PDA-COF due to the enhanced electron transfer of vinylene linkage, which is beneficial to be an efficient photocatalyst. Therefore, it is shown that BTT-DPAN-CMP photocatalyst demonstrates better efficiency than BTT-PDA-COF for selective aerobic sulfoxidation driven by green light. This work underlines the importance of rational design for porous organic materials as selective visible light photocatalysts.