Red light photocatalysis of conjugated microporous polymers based on fused thiophenes for selective oxidation of amines

Abstract

By virtue of tailorable building blocks, the band gaps and electronic structures of conjugated microporous polymers (CMPs) can be readily adjusted at the molecular level. Generally, the building blocks possessing extended π-conjugations result in exceptional photocatalytic performances. In this work, the direct CH arylation of fused thiophenes, thieno[3,2-b]thiophene (TT) and dithieno[3,2-b:2′,3′-d]thiophene (DTT), with 1,3,6,8-tetrabromopyrene affords two CMPs, namely TT-Py-CMP and DTT-Py-CMP. The expansion of π-conjugations of the fused thiophenes from TT to DTT gives rise to a bathochromic shift about 30 nm from TT-Py-CMP to DTT-Py-CMP. Besides, systematic characterizations suggest the optoelectronic properties of DTT-Py-CMP are better than that of TT-Py-CMP. Furthermore, DTT-Py-CMP drives better red light photocatalysis than TT-Py-CMP for the selective oxidation of amines with molecular oxygen. The selective oxidation of benzyl amines by red light photocatalysis of DTT-Py-CMP progresses via an electron transfer pathway with high selectivities for imines. This work provides new insights that fused thiophenes could be the stepping stone in designing CMPs for expansive visible light photocatalysis.