Design and Synthesis of Trithiophene‐Based Donor‐Acceptor Covalent Organic Framework for Cocatalyst‐Free Photocatalytic Hydrogen Evolution

The development of high-performance, noble-metal-free photocatalysts for the hydrogen evolution reaction (HER) is meaningful for sustainable development. While it remains a significant challenge. Herein, a novel covalent organic framework (COF), named BN-COF, was designed by the imine condensation between the (N4, N4-bis(4'-amino-[1,1'-biphenyl]-4-yl)-[1,1'-biphenyl]-4,4'-diamine) (NBD/N) and benzo[1,2-b:3,4-b': 5,6-b″]trithiophene-2,5,8-tricarbaldehyde (BTT/B) monomers, as electron donor and acceptor, respectively. The BN-COF is synthesized facilely via a liquid-liquid interfacial (LLI) strategy. The BN-COF shows photocatalytic HER activity of 7.8 mmol g^-1 h^-1 under AM 1.5 G irradiation without any cocatalysts and maintains the activity over 5 recycling reactions. This remarkable activity stems from the enhanced charge separation, driven by a stronger built-in electric field within the donor-acceptor structure, coupled with enhanced hydrophilicity imparted by the thiophene group. This work highlights the significant potential of rationally engineered D-A structure and LLI synthetic strategy for developing effective noble-metal cocatalyst-free photocatalysts for efficient solar-to-chemical energy conversion.