TpBD COF@ZnIn2S4 nanosheets: A novel S-scheme heterojunction with enhanced photoreactivity for hydrogen production

Covalent-organic frameworks (COFs) are emerging photocatalysts with porous structures and excellent light-harvesting abilities. However, their photoreactivity still needs further improvement before they can be used in practical applications. Herein, we report, for the first time, on the construction of a heterojunction consisting of core-shell structured 1,3,5-triformylphloroglucinol (Tp) and 4,4′-biphenylenediamine (BD) COF at ZnIn2S4 (ZIS) nanosheets, using a microwave-hydrothermal method. The best performing sample, TpBD COF@ZIS-10 (with a ZIS:TpBD COF mass ratio of 10:1), in the absence of a co-catalyst, achieves a visible-light-driven H2 production rate of 2304 μmol g−1 h−1 with an AQE of 5.02% at 420 nm, and exhibits excellent stability. The improved photocatalytic performance of TpBD COF@ZIS was attributed to the strong interaction at the interface and the S-scheme charge transfer mechanism, which not only stimulates efficient charge separation and migration, suppressing recombination, but also preserves the higher redox potentials of photo-generated electrons and holes.