Activated-Carbon-Supported Clusters Consisting of Four Planarly Arranged Palladium Atoms as Highly Active and Alkene-Selective Hydrogenation Catalysts

The development of metal catalysts that require a minimum amount of precious metals is highly desirable due to the high cost and scarcity of noble metals. In this study, we synthesized a heterogeneous catalyst consisting of a cluster of four planarly arranged Pd atoms (Pd4) immobilized onto activated carbon. The obtained catalyst exhibited high catalytic activity in the hydrogenation of various alkenes, whereby the highest TON was 455,556 per Pd atom. This catalyst is characterized by high alkene selectivity, while intramolecular −NO2, −CN, −OCH2Ph, epoxy, ester, ketone, and halogen groups remained intact. An X-ray absorption fine structure analysis revealed that the Pd4 framework was maintained on activated carbon after catalysis. This heterogeneous catalyst structure provides a platform for the development of catalysts that combine good catalytic activity with high chemoselectivity, recyclability, and good substrate compatibility based on a minimum amount of palladium atoms.