Unlocking lignin’s potential with innovative DES technology

Lignin, the only large-volume sustainable source of aromatic biopolymer in nature, is an attractive feedstock for the production of functional materials. However, considering its high reactivity, lignin is difficult to extract without avoiding uncontrolled degradation and condensation, which significantly impedes the upgrading of the extracted lignin into high-valued materials. Deep eutectic solvents (DES), as an emerging solvent choice, have driven innumerable advances in sustainable biorefinery, especially in lignin fractionation and valorization. Due to their property tunability and high lignin solubility, lignin modification with DES is an appealing approach to boost the extracted lignin's reactivity and compatibility with polymers. This review systematically summarizes the latest progress of DES in lignin modification and further upgrading into functional materials.