Pyrene based crosslinked conjugated microporous polymer catalysts for photocatalytic hydrogen evolution reaction: The neglected influences of cross linking degree

Pyrene based crosslinked conjugated microporous polymers (CMPs) emerged as a type of highly efficient polymer photocatalysts towards water splitting. However, the relationship of coupling functional groups-crosslinking degree-photocatalytic hydrogen evolution reaction (HER) performances was seldom discussed. Herein, boric acid ester coupling agents of 1,4-benzenediboronic acid bis(pinacol) ester, 1,4-phenylenediboronic acid and 1,4-benzenediboronic acid bis(neopentyl glycol) ester were selected to construct the pure carbon skeleton pyrene-CMPs with the typical 1,3,6,8-tetrabromopyrene building block. It was found that the pyrene-CMPs with the same carbon backbone building blocks exhibited unexpectedly varied photocatalytic HER activities. Pyrene-CMP constructed by 1,4-benzenediboronic acid bis(neopentyl glycol) exhibited much higher HER activities (43.2 mmol h−1g−1) than that of CMP constructed by 1,4-phenylenediboronic acid (23.1 mmol h−1g−1) in seawater under UV–Visible light with the assistant of 3 wt% Pt co-catalyst. The disparity in HER activities in the pyrene-CMPs was due to the varied crosslinking degree caused by the crosslinking functional groups, which has been greatly neglected when discussing the HER performances. Our results provided an aspect in the discussion of the photocatalytic performances of the crosslinked pyrene-CMPs.