Boosting photocatalytic H2 evolution on UIO-66-NH2/covalent triazine-based frameworks composites by constructing a covalent heterojunction

Metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) have been proved as efficient catalysts for photocatalytic hydrogen (H-2) evolution, thanks to their tunable functionalities, permanent porosity, excellent visible light response, and physicochemical stability. Herein, a series of photocatalysts (termed NUBC) was fabricated by loading different amounts of Zr-UiO-66-NH2 (NU) onto a benzoic acid-modified covalent triazine-based framework (BC) based on post-synthetic covalent modification. The resulting NUBC catalysts exhibited a type-II Z-scheme heterojunction structure formed via the amide covalent bonds between the amine groups on NU and carboxyl groups on BC. The optimal loading of NU on BC is 30 wt.% (30NUBC) and the corresponding photocatalytic H-2 evolution rate was 378 mu mol h(-1) g(-1), almost 445 and 2 times than that of NU and BC, respectively. The synergistic effect between the type-II Z-scheme heterojunctions and amide bonds was conducive to boosting visible light harvesting and facilitating charge transportation and separation. Furthermore, the prepared NUBC catalysts show great reusability and stability. Overall, this work sheds light on the design of novel MOF/COF hybrid materials and provides a systematic exploration of their photocatalytic H2 evolution properties.