Diacetylene-bridged covalent organic framework as crystalline graphdiyne analogue for photocatalytic hydrogen evolution

Graphdiyne (GDY) alone as photocatalyst is unsatisfactory because of low crystallinity, limited regulation of band gap, weak photogenerated charge separation, etc., and heterojunctioning with other materials is necessary to activate the photocatalytic activity of GDY. Through elaborate design, a diacetylene-rich linker (S2) was prepared and allowed to construct crystalline and structurally well-defined GDY-like covalent organic framework (COF, namely S2-TP COF) which merges the merits of both COF and GDY to boost photocatalytic hydrogen evolution reaction (HER). By theoretical prediction on the donor-acceptor (D-A) pair, other two monoacetylene-bridged COFs (S1-TP COF and S3-TP COF) were prepared for comparison. Exhibiting enhanced separation and suppressed recombination of photogenerated excitons, Pt-photodeposited S2-TP COF showed a higher HER rate (10.16 mmol g−1 h−1) than the other two non-GDY-like COFs (3.71 and 1.13 mmol g−1 h−1). The joint experimental-theoretical study suggests appropriate D-A structure for photogenerated charge separation and diacetylene motif as adsorption site to be key accounts for boosted HER. This work opens a new opportunity for the rational design of COF as GDY mimic for photocatalytic application.