Designing fluorene-based conjugated microporous polymers for blue light-driven photocatalytic selective oxidation of amines with oxygen

Abstract

Conjugated microporous polymers (CMPs) have been showcased with a brilliant prospect in organic semiconductor photocatalysis, attributing to accessible molecular design, chemical stability and environmental friendliness. Here, two novel fluorene-based CMPs were designed and conveniently synthesized with carbazole as an electron donor. Importantly, subtle variation of substituent at the methylene bridge (9-position) of fluorene precursor results in different performances in which dimethyl substituent was proven to be more efficient than difluoro substituent for blue light photocatalysis. MFC [9,9'-(9,9-dimethyl-9H-fluorene-2,7-diyl)bis(9H-carbazole)]-CMP has a much larger specific surface area, a more favourable redox position, and resultantly a superior photocatalytic performance during blue light-driven selective oxidation of amines into imines with oxygen (O2) in an environmentally benign solvent ethanol (C2H5OH). This work suggests that subtle tweaking in electron acceptors could give rise to superior photocatalytic activity for CMPs in selective chemical conversions.