Enhanced donor–acceptor synergy in covalent organic frameworks enabling broad light harvesting for efficient photocatalytic hydrogen production

Abstract

Covalent organic frameworks (COFs) have demonstrated significant potential in visible-light-driven photocatalysis due to their tunable structures and adjustable bandgaps. However, most COFs exhibit a limited light absorption range and poor solar energy utilization, leading to low catalytic efficiency. Developing COFs with a broad absorption range is therefore crucial for enhancing solar utilization and photocatalytic reaction rates. This study constructed three benzothiadiazole-based donor–acceptor (D–A) COFs (HIAM-0032 to HIAM-0034) with fes topology, extending the light-absorption range into the near-infrared region. Among the three COFs, HIAM-0033 exhibited a remarkable photocatalytic hydrogen production rate of 7.8 mmol g⁻¹ h⁻¹ under visible light irradiation, which is 4.1 and 11.4 times higher than those of HIAM-0034 (1.9 mmol g⁻¹ h⁻¹) and HIAM-0032 (0.7 mmol g⁻¹ h⁻¹). Photoelectrochemical analyses revealed that the superior performance of HIAM-0033 originates from enhanced donor–acceptor interactions, which reduce the exciton binding energy, accelerate charge separation and migration, and increase carrier concentration. This work sheds light on the design and synthesis of COFs with broad light-harvesting capability to realize efficient photocatalysis.