Construction of two-dimensional porous polymers with crystalline or amorphous forms for near-infrared electrochromism

Two electrochromic porous polymers with two-dimensional (2D) conjugated structures are synthesized by Schiff base condensation reaction. One polymer named TPA-BTT-COF is a covalent organic framework (COF) with the regular crystal structure composed of triphenylamine (TPA) and benzo[1,2-b:3,4-b':5,6-b"]trithiophene (BTT) units, while the other polymer named TPPA-BTT-CPP is a conjugated porous polymer (CPP) with the amorphous defect structure composed of N,N,N',N'-tetraphenyl-1,4-phenylenediamine (TPPA) and BTT units. Both TPABTT-COF and TPPA-BTT-CPP exhibit multiple and reversible color transitions containing orange/yellow/bluegray and orange/brown-yellow/gray respectively in the p-type doping/dedoping processes. They also present satisfactory near-infrared (NIR) electrochromic behaviors, with TPA-BTT-COF showing more stable NIR electrochromic switching due to the more ordered 7C-7C stacking system and porous structure, and TPPA-BTT-CPP showing higher NIR optical contrast owing to the stronger intervalence charge transfer (IVCT) interaction. The two polymers enrich the species of COF and CPP with favorable electrochromic properties, and their remarkable properties including NIR electrochromic activity and multichromism are deserved attention.