Selective hydrogenation of 5-hydroxymethylfurfural over bidentate phosphine protected Pdn nanoclusters

Abstract

The synthesis of high activity atomically precise nanoclusters is crucial to understand structure–property relationships in environmentally friendly reactions. However, Pd nanoclusters have been rarely reported due to their susceptibility to oxidization. In this work, Pd_n nanoclusters protected by bis[2-(diphenylphosphino)phenyl] ether (DPEphos) have been synthesized and fully characterized by electrospray ionization mass spectrometry (ESI-MS) and HAADF-STEM. In the hydrogenation of 5-hydroxymethylfurfural (HMF) to 2,5-dimethylfuran (DMF), which is an important candidate for liquid fuels, the supported Pd_n nanoclusters show great catalytic performance with a yield of 94.1% under mild conditions. The theoretical investigations reveal that, in the phosphate protected Pd_n system, the desorption of DMF is the rate-determining step. And compared with the Pd catalyst coordinated with PPh₃, the Pd_n catalyst protected by DPEphos has a modest desorption ability of DMF, leading to the high yield of DMF. This work presents the synthesis and application of a Pd_n catalyst with bidentate phosphine ligands, which could contribute to the development of rational design of effective catalysts in biomass and energy conversion.