Stable and Water-Tolerant Deep Eutectic Solvent from Biomass-Derived 5-Hydroxymethylfurfural (HMF) and Levulinic Acid

High Resolution Image Download MS PowerPoint Slide The development of greener extraction systems is essential to improving the sustainability of biomass valorization processes. Here we report that 5-hydroxymethylfurfural (HMF) and levulinic acid (LEV)─two bioderived platform molecules often coproduced in biomass processing─spontaneously form a stable liquid phase over a broad compositional range. Differential scanning calorimetry (DSC) and thermodynamic modeling reveal a eutectic composition near x HMF = 0.39 with a melting temperature of 258 K and significant negative deviation from ideal behavior. The mixture remains liquid across a wide compositional range even in the presence of low water content (0.3–1.0 wt %), exhibiting deep eutectic solvent (DES)-like behavior. Structural and dynamic analyses using DSC, NMR spectroscopy, molecular dynamics (MD) and density functional theory (DFT) calculations uncover a nonideal mixing regime driven by the network of HMF-LEV hydrogen bonding. Notably, water does not disrupt the HMF-LEV network but enhances its structuration at the eutectic composition by moderating LEV-LEV interactions and enabling more favorable HMF-LEV hydrogen bonding. This work shows that the liquid HMF-LEV phase can be generated in situ within a heterogeneous biomass surrogate, enabling substantially higher HMF extraction efficiencies than conventional solvents and eliminating the need for additional organic extractants. This provides a proof of concept for a solvent-minimized route to HMF recovery, indicating the HMF-LEV system as a promising, bioderived liquid platform with potential for integration into future resource-efficient biorefinery schemes.