Efficient synthesis of bio‐based monomer 2,5‐bishydroxymethylfuran by the solvent‐free hydrogenation of 5‐hydroxymethylfurfural‐based deep eutectic mixture

BACKGROUND: Biomass holds the promise to provide a sustainable future for the chemical industry. 2, 5‐Bishydroxymethylfuran (BHMF) is a versatile bio‐based diol with a broad range of potential applications in many polymeric materials, artificial fibers and drugs. However, the controlling of the BHMF selectivity in hydrogenation of biomass‐derived 5‐hydroxymethylfurfural (HMF) with complex transformation pathways is always a great challenge especially under solvent‐free conditions in which many side reactions may occur due to its rich reducible groups. RESULTS: A facile and effective approach was developed for the selective synthesis of BHMF by solvent‐free hydrogenation of a deep eutectic mixture consisting of HMF (75 wt%) and choline chloride (ChCl), by which a BHMF selectivity up to 94.6% was gained at full HMF conversion over Raney Co at 100 °C in 4 h. In addition, the HMF conversion and selectivity toward BHMF can be regulated and controlled through altering the strength of hydrogen‐bonding interactions of HMF‐based deep eutectic mixtures (ChCl–HMF mixtures). CONCLUSION: We developed an effective approach that allows the solvent‐free synthesis of BHMF via hydrogenation of HMF‐based deep eutectic mixtures. The extraordinary BHMF selectivity in the solvent‐free hydrogenation of HMF is reasonably attributed to the hydrogen‐bonding interactions formed between ChCl and HMF/BHMF which greatly suppresses the side reactions of HMF and the over‐reduction of BHMF. © 2020 Society of Chemical Industry