Designing Organic–Inorganic Semiconductor Heterojunctions Based on COFs for Efficient Photocatalytic Hydrogen Evolution

Covalent organic frameworks have attracted widespread attention in the field of photocatalytic hydrogen evolution, but their limited light capture ability and charge transfer efficiency still limit their photocatalytic performance. Catalysts based on single-crystal semiconductors have unique crystal faces and show great potential for applications in the fields of energy and environment. Here, an organic-inorganic semiconductor heterojunction based on donor-acceptor covalent organic framework (COF) has been developed, utilizing intramolecular and interfacial built-in electric fields to enhance the mobility of photo-generated carriers. Specifically, a COF containing thiophene groups is synthesized through a Schiff base reaction, which activates the (002) crystal plane of CdS by reacting with snowflake-shaped CdS. COF with strong π conjugated structures and unevenly distributed electrons on the surface provide a large number of photo-generated electrons for the reaction system. The synergistic effect of intramolecular and interfacial built-in electric fields in CdS/COF heterostructures significantly improves the migration ability of photo-generated carriers, allowing more photo-generated electrons to migrate to the active sites on the CdS surface for photocatalytic hydrogen evolution reaction. This work introduces an organic-inorganic semiconductor heterojunction photocatalyst based on covalent organic frameworks, opening up a new path for efficient clean energy conversion.