Cross-linked conjugated polymers based on triazine and polybranched polycyclic thiophene for improved photocatalytic hydrogen evolution

Abstract

Conjugated porous polymers (CPPs) incorporating donor–acceptor (D–A) structures are gaining significant interest for their potential in photocatalytic hydrogen evolution reaction (HER). The microstructure and electronic properties of the polymer frameworks are crucial for optimizing their photocatalytic efficiency. Here, we design two D–A type CPP photocatalysts using 4,8-di(thiophen-2-yl)benzo[1,2-b:4,5-b′]dithiophene (DBD) and triazine units to investigate the impact of different bridging units on HER activity. Compared with PhDBD–CPP using benzene as the bridging unit, ThDBD–CPP with a thiophene linking unit achieves an expansion of the HOMO orbital distribution and an enlarged molecular dipole moment, which is conducive to the efficient separation and migration of photogenerated carriers. Consequently, ThDBD–CPP with thiophene as the bridging unit exhibits a remarkable photocatalytic hydrogen evolution rate of 20.75 mmol h⁻¹ g⁻¹ under full arc light. After loading 1 wt% Pt cocatalyst, the HER activity is further improved to 30.36 mmol h⁻¹ g⁻¹. This study suggests that modulating bridging units provides a new viable approach to designing efficient polymer photocatalysts.