Impact of imine bond orientations on photocatalytic hydrogen generation of benzothiadiazole-based covalent organic frameworks constructed using “two-in-one” monomers

Abstract

Covalent organic frameworks (COFs) have received great attention for their promising application as photocatalysts for photocatalytic hydrogen generation. However, constructing COFs with excellent photocatalytic performances and building the structure–property-relationship is still a great challenge. Herein, two benzothiadiazole-based COFs, HIAM-0026 and HIAM-0026v, were designed and prepared with different imine bond orientations via a “two-in-one” strategy. Under visible-light illumination, HIAM-0026 shows much higher photocatalytic performance (14.10 mmol g⁻¹ h⁻¹) than that of HIAM-0026v (8.70 mmol g⁻¹ h⁻¹) with the amine groups close to the benzothiadiazole core in the organic building unit. The transient photocurrent responses and the electrochemical impedance spectroscopy indicate that HIAM-0026 exhibits higher charge separation and immigration rates. This work demonstrates that imine bond orientations significantly affect photocatalytic hydrogen generation and sheds light on the rational design and synthesis of benzothiadiazole-based COFs for efficient hydrogen generation.