Deep eutectic solvent (DES) as novel and green solvents can efficiently promote the fractionation of high-purity lignin from lignocellulosic biomass pretreatment. Revealing the fundamental chemistry of lignin during DES pretreatment will improve methodology to optimize the pretreatment in an integrated biorefinery. Herein, an acidic biomass-derived DES (choline chloride/oxalic acid) pretreatment was developed to deconstruct the recalcitrance of bamboo for enhanced lignin fractionation and valorization. The structure transformation of the regenerated lignin samples obtained at different pretreatment temperatures has been investigated in comparison with enzymatic mild acidolysis lignin (EMAL) by state-of-the-art NMR (2D HSQC, quantitative ¹³C, ³¹P), GPC, and TGA analysis. The results revealed that acidic DES assisted bamboo delignification and promoted the cleavage of β-O-4′ linkages at elevated reaction temperature, leading to an increase in the sustained rise of phenolic OH groups and lower molecular weights. Those lignin samples exhibited higher thermal stability and excellent antioxidant activity, suggesting great potential applications in lignin-based chemicals and material. Lignin condensation with unsaturated reactive intermediates which is accompanied by the depolymerization process during this acidic DES system. The results also highlight the utilization of acidic DES as a low-cost, high performance with a long delignification durability and thermal stability. Overall, the insights gained here could shed new light on the design and fabrication of efficient and durable DES-based pretreatment for the production of bio-fuel, bio-based materials and bio-chemicals.

深共熔溶剂（DES）作为新型绿色溶剂可以有效促进木质纤维素生物质预处理中高纯度木质素的分离。在 DES 预处理过程中揭示木质素的基本化学性质将改进优化集成生物精炼厂预处理的方法。在此，开发了一种酸性生物质衍生的 DES（氯化胆碱/草酸）预处理，以解构竹子的顽固性，以增强木质素的分离和价值化。通过最先进的 NMR（2D HSQC，定量¹³ C，³¹P)、GPC 和 TGA 分析。结果表明酸性DES有助于竹子脱木素并促进β- O的裂解-4' 键在升高的反应温度下，导致酚类 OH 基团的持续上升和较低的分子量增加。这些木质素样品表现出更高的热稳定性和优异的抗氧化活性，表明在基于木质素的化学品和材料中具有巨大的应用潜力。木质素与不饱和反应中间体的缩合，伴随着该酸性 DES 系统中的解聚过程。结果还突出了酸性DES作为低成本、高性能、脱木素耐久性和热稳定性长的利用。总的来说，这里获得的见解可以为用于生产生物燃料、生物基材料和生物化学品的高效耐用的基于 DES 的预处理的设计和制造提供新的思路。