Chemoselective hydrogenation of biomass derived 5-hydroxymethylfurfural to diols: Key intermediates for sustainable chemicals, materials and fuels

Biomass-derived 5-hydroxymethylfurfural (HMF) is hailed as an all-purposed platform molecule that holds great promise to address a number of high volume markets for chemicals, polymeric materials, and transportation fuels. HMF-derived diols, including 2,5-bishydroxymethylfuran (BHMF), 2,5-bishydroxymethyltetrahydrofuran (BHMTF), and 1,6-hexanediol (1,6-HD), are key intermediates for the catalytic upgrading of HMF in a biorefinery. These diols can be employed as renewable polymeric monomers, and among them BHMF and BHMTF are also attractive precursors for biofuels, such as 2,5-dimethylfuran (DMF), 2,5-bis(alkoxymethyl)furans (BAMFs), and 2,5-dimethyltetrahydrofuran (DMTHF). Hence, gaining more insights into the chemoseletive hydrogenation of HMF to these diols is of particular importance. In this review, we comprehensively summarize the advances in the selective hydrogenation of HMF into these diols in terms of the diversity of hydrogen sources, mainly including molecular H2, alcohols, formic acid and water, over homogeneous or heterogeneous catalysts. Assessment of the relative merits of different hydrogen sources for the hydrogenation of HMF is performed as well. We also discuss challenges and opportunities in employing these HMF-derived diols for the production of polymeric materials and biofuels.