In Situ Synthesis of Trimeric Ruthenium Cluster-Encapsulated ZIF-11 and Its Carbon Derivatives for Simultaneous Conversion of Glycerol and CO2

Stable, high-performance noble-metal catalysts have proven effective for obtaining lactate (LA) and formate (FA) from simultaneous conversion of glycerol and carbonate as a CO2 source. For this purpose, we developed a novel method reported herein for the synthesis of Ru nanoparticles (NPs) supported on graphitic nanoporous carbon (Ru/NCT, T = pyrolysis temperature). The Ru/NCT catalysts were prepared by in situ encapsulation of trimeric ruthenium clusters in ZIF-11 pores, with a subsequent pyrolysis process. The pyrolysis temperature affected the size and crystallinity of Ru NPs and the textural properties of the ZIF-11-derived carbon. Optimization of reaction parameters such as CO2 source, reaction temperature, reaction time, and glycerol/carbonate ratio resulted in Ru/NCTs with significantly higher turnover number (TON) and space-time yield (STY) of the desired products (LA and FA). Moreover, these Ru/NCTs were stable even after three consecutive recycle tests without leaching of active metal or notable structural change. The correlation of reaction performance and detailed characterization revealed that large Ru NPs with high crystallinity exhibit superior catalytic activity for the combined dehydrogenation-hydrogenation reactions that yield the desired products.