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 H-2 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.