Tunable hydrated deep eutectic solvents for efficient lignocellulose fractionation towards sustainable biorefineries

Abstract

Lignin valorization is pivotal for sustainable biorefineries; however, conventional extraction techniques invariably cause structural degradation and repolymerization, thereby limiting lignin's functional utility. Here, we present a water-tunable hydrated deep eutectic solvent (HDES) system that overcomes this limitation by strategically modulating hydrogen-bonding networks. Mechanistic studies reveal that water serves as a molecular regulator, attenuating hydrogen-bond acidity (α) to suppress lignin condensation while concurrently reducing viscosity by 68%, thereby enhancing mass transfer. Under optimized hydration conditions, the system achieves 95.41% lignin extraction efficiency while preserving 37% higher β-O-4 linkages than anhydrous DES; the resulting lignin exhibits low molecular weight, narrow dispersity, and high phenolic hydroxyl content. It demonstrates exceptional colloidal stability, thermal stability, and marked antioxidant/anti-UV properties. Notably, the “lignin-first” strategy simultaneously boosts saccharification efficiency, achieving glucose and xylose yields of 92.67% and 98.29%, respectively, from cellulose-rich residues. This study establishes a rational framework for balancing fractionation efficiency with structural preservation, offering a scalable route for integrated lignocellulosic biorefining.