Pyrene-based conjugated microporous polymers for red light-powered oxidation of amines to imines

Abstract

Conjugated microporous polymers (CMPs) are highly operative photocatalysts. To harvest red light, pyrene and dithieno(3,2-b:2′,3′-d)thiophene 4,4-dioxide (DTDO) were adopted as the donor and the acceptor for CMPs. Two pyrene-based CMPs, namely Py–DTDO–2 and Py–DTDO–4, were assembled from 1,6-dibromopyrene or 1,3,6,8-tetrabromopyrene and DTDO by direct C−H arylation polymerization. As designed, both Py–DTDO–2 and Py–DTDO–4 are n-type semiconductors with band gaps of 2.01 and 1.98 eV, respectively, which perfectly match the emitted red light (623 ± 8 nm) of light-emitting diodes (LEDs). Besides, the redox potentials of Py–DTDO–2 and Py–DTDO–4 are well aligned to activate O2. With O2 as the oxidant, imines were formed by the red light-powered oxidation of amines over both Py–DTDO–2 and Py–DTDO–4. The optoelectronic virtues of Py–DTDO–4 imparted its better photocatalytic performance than Py–DTDO–2. The oxidation of a plethora of amines was achieved swiftly in forming imines. This work underlines the versatility of pyrene-based CMPs in conducting visible light-powered reactions.