PdAg Nanoparticles within Core-Shell Structured Zeolitic Imidazolate Framework as a Dual Catalyst for Formic Acid-based Hydrogen Storage/Production.

Formic acid (FA; HCOOH) is one of the most promising candidates for the storage of hydrogen (H). Herein, we report a H storage/production system based on the hydrogenation of CO and dehydrogenation of FA, using a nanostructured heterogeneous catalyst. PdAg nanoparticles with an average size of 2.8 nm were encapsulated within a zeolitic imidazolate framework (ZIF-8) having a core-shell structure (ZIF-8@PdAg@ZIF-8). This composite displayed high activity and stability during both the hydrogenation of CO to produce FA and the dehydrogenation of FA into H and CO. This improved performance is attributed to the use of ultrafine PdAg nanoparticles as well as the spatial regulation of the nanoparticles within the reaction field. This study suggests a new strategy for controlling the spatial distribution of metal nanoparticles within MOFs so as to fine-tune the catalytic activity and selectivity of ZIF-8@metal nanoparticles@ZIF-8 catalysts.