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 degrees 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. (c) 2020 Society of Chemical Industry