One-pot mild acidic triethylene glycol fractionation with dual functions: in situ lignin stabilization and controllable self-assembly light-colored nanoparticles production.

This study proposed a strategy for the efficient fractionation of sugarcane bagasse under mild conditions (100°C) using acidic triethylene glycol (TEG), which is achieved by elucidating a dual mechanism that facilitates the high-value utilization of lignin. Under the optimized conditions (0.1 M H2SO4, TEG, 100°C, 40 min), a delignification rate of 82.10% and a cellulose retention rate of 90.46% were achieved, while the enzymatic hydrolysis sugar yield of the solid residue increased significantly from 9.3% to 80.63%. This study elucidated two key mechanisms involved in this process. The first mechanism involves the chemical stabilization of lignin. 2D HSQC NMR analysis confirmed that TEG forms covalent bonds with the α-carbon of the lignin side chain, resulting in the formation of a novel α-TEG-β-O-4 structure. This in situ capping strategy effectively suppressed lignin condensation during acidic pretreatment, thereby enabling the production of high-quality, uncondensed lignin. The second mechanism involves the physical self-assembly of lignin particles. By dropwise addition of the pretreatment liquor into water as an anti-solvent, the self-assembly of lignin was controllably induced, yielding spherical lignin nanoparticles with high purity (89.72%), light color, and uniform morphology. In summary, by elucidating and leveraging these synergistic mechanisms spanning chemical structure and physical morphology, this study offered a novel green and efficient approach for the mild valorization of lignocellulose, while also facilitating the precise fabrication of functionalized, uncondensed lignin nanomaterials.