Engineered nickel phyllosilicate for selective 5-HMF C–O bond hydrogenation under benign conditions

Abstract

The selective transformation of biomass-derived 5-hydroxymethylfurfural (5-HMF) into value-added chemicals is of significant interest to both academia and industry. In this study, we report on the direct hydrogenation of 5-HMF to 2,5-bis(hydroxymethyl)tetrahydrofuran (BHMTHF) instead of 2,5-dimethylfuran, achieving an impressive yield of 90.4% in 7 runs using a nickel phyllosilicate catalyst (Ni-PSL) under optimized conditions. The choice of solvent is crucial for minimizing side reactions, with tetrahydrofuran identified as an optimal solvent for reducing the formation of acetal by-products, which are typically promoted by protic organic solvents such as methanol or n-butanol. Pyridine–FTIR results reveal that the surface of Ni-PSL is enriched with Lewis acid sites, originating from coordinatively unsaturated Ni species, which are effectively generated through proper thermal treatment. Moreover, the total amount of acid sites in Ni-PSL can be modulated by adjusting the calcination temperature, without affecting the size of the Ni nanoparticles. These Lewis acid sites play pivotal roles in promoting the adsorption of the furan ring, thereby favoring the formation of BHMTHF under mild reaction conditions. However, an excess of Lewis acid sites promotes the cleavage of the C−OH bond, reducing the selectivity towards DMTHF.