Core–shell CdS@ZIF-8 structures for improved selectivity in photocatalytic H₂ generation from formic acid

Encapsulating well-defined nanoparticles (NPs) into metal–organic frameworks (MOFs) to form core–shell structures not only combines their properties, but may also provide synergistic functionality. Much research attention has been focused on applying core–shell NP@MOF structures to gas storage and sensing, luminescence, lithium ion batteries, selective catalysis, and cascade reactions; however, their application as photocatalysts has been reported much more rarely. Herein, we report the design of a new core–shell structure composed of semiconductor CdS NPs as the core and ZIF-8 as the shell. Both single-core–shell and multiple-core–shell CdS@ZIF-8 were synthesized by varying the concentrations of the ZIF-8 precursor. Photocatalytic hydrogen generation from formic acid over CdS@ZIF-8 demonstrated that core–shell CdS@ZIF-8 structures exhibit increased photocatalytic selectivity for H₂ generation from formic acid compared with pure CdS NPs. Furthermore, the concentration of CO in the products was significantly decreased, which benefits the application of CdS@ZIF-8 to proton-exchange membrane fuel cells. Our results provide guidance for the development of new photocatalysts based on NP@MOF core–shell materials.