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

Abstract

Graphdiyne (GDY) alone as a photocatalyst is unsatisfactory because of its low crystallinity, limited regulation of the band gap, weak photogenerated charge separation, <i>etc.</i>, 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 employed to construct a 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 the photocatalytic hydrogen evolution reaction (HER). By theoretical prediction on the donor-acceptor (D-A) pair, two other 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). A joint experimental-theoretical study suggests that the appropriate D-A structure for photogenerated charge separation and diacetylene motif as the adsorption site are the key reasons for the boosted HER. This work opens a new avenue for the rational design of COFs as GDY mimics for photocatalytic application.