Building sp carbon-bridged g-C3N4-based electron donor-π-acceptor unit for efficient photocatalytic water splitting

sp hybrid carbon is emerging as a promising unit for covalent modification of organic frameworks and conductive polymers, and has been widely concerned in conjugated polymer catalysts because it can be used to construct pi-electron conjugated system. Herein, we provide a simple and effective post reaction strategy to activate g-C3N4 via coupling reactions. The grafted g-C3N4 exhibits improved light absorption and separation of charges, and better water dispersibility along with increased co-catalyst loading sites, which accelerate photocatalytic hydrogen evolution. Photocatalytic H-2 evolution activity of UCN-BTD and UCN-BF, in which terminal amino groups are grafted with 2,1,3-benzothiadiazole,5-(1-propyn-1-yl) or 2,1,3-benzoxadiazole,5-(1-propyn-1yl), reveals the important role of sp hybrid carbon and electronegativity of the acceptor. The optimized UCN-BTD photocatalyst showed a significant improvement in photocatalytic hydrogen evolution performance (122 mu mol.h(-1)), which is nearly five times of that of the pristine g-C3N4. This work provides insights for the preparation of g-C3N4-based donor-p-acceptor unit constructed with different conjugated structures.