Narrowing the bandgaps of thiazolo[5,4-d]thiazole-bridged conjugated microporous polymers to capture green light for selective oxidation of amines

Abstract

Conjugated microporous polymers (CMPs) have evloved into versatile visible light photocatalysts. Narrowing the bandgaps of CMPs could capture more visible light without shifting the suitable position with an established electron acceptor like thiazolo[5,4-d]thiazole (TzTz). Here, benzene-1,3,5-tricarbaldehyde (Bz-CHO) and benzo[1,2-b:3,4-b':5,6-b'']trithiophene-2,5,8-tricarbaldehyde (BTT-CHO) are adopted to undergo condensation with dithiooxamide, preparing two TzTz-bridged CMPs, namely TzTz-Bz and TzTz-BTT. Thereby, TzTz-BTT could capture visible light more substantially than TzTz-Bz due to narrowing the bandgap. Endowed by TzTz, both TzTz-BTT and TzTz-Bz possess similar positions for the activation of O2 and can drive the subsequent formation of imines. However, TzTz-BTT, with a narrower bandgap, could capture more green light to drive the electron and proton transfer for the selective formation of imines with higher conversions than TzTz-Bz. This work suggests that CMPs can be equipped with extensive visible light absorption for photocatalytic selective oxidations.