Synergistic structural engineering of donor-acceptor-acceptor type conjugated microporous polymers as photocatalysts for boosting sunlight-driven hydrogen evolution.

Significant progress has recently been made in the design and preparation of conjugated microporous polymers (CMPs) as photocatalysts for hydrogen generation. However, a major challenge remains in developing CMP-based photocatalysts with enhanced photoconversion efficiency. In addition, the fixed chemical composition of the donor-acceptor (D-A) polymers' photocatalysts prohibited their efficiency. Here, a set of D-A1-A2 type polymeric photocatalysts has been statistically copolymerized by adopting pyrene (Py), thiazolo[5,4-d]thiazole (TzTz), and dibenzothiophene-S,S-dioxide (SO) as the D, A1, and A2, respectively, with the SO monomer possessing the higher electron-accepting capacity. Besides photocatalytic characterizations, the influence of D-to-A molar ratios on their efficiency has been studied. The obtained analyses represented that the energy gap of D-A1-A2 CMPs can be adjusted by statistical copolymerization, and the optimized photocatalyst PyTzTzSO-1 with a molar ratio of 1.0:3.0:1.0 achieved an attractive hydrogen evolution rate (HER) of 39.11 mmol h g under UV-visible light and of 38.61 mmol h g under visible light in the presence of 1 wt% of platinum (Pt) cocatalyst. Remarkably, the apparent quantum yield (AQY) at 420 nm stands at 51.18 %, representing the state-of-the-art for organic polymeric photocatalysts. The best photocatalytic efficiency of the PyTzTzSO-1 polymer was primarily due to its higher Brunauer-Emmett-Teller (BET) surface area, enhanced hydrophilicity, broader energy gap, as well as decreased recombination rate of photo-induced holes and electrons. Consequently, the structural design of D-A1-A2 CMPs photocatalysts with tuned components had great potential for improving photocatalytic hydrogen generation.