Lignin depolymerization and carbohydrate preservation by linking selective fractionation to radical mechanisms

Lignocellulosic biomass (LCB) refining is constrained by the trade-off between fractionation efficiency and component preservation. Here, we report a synergistic fractionation approach applicable to chemically diverse feedstocks, including corn stover, bamboo, poplar, and pine. This strategy enables selective enrichment of cellulose, hemicellulose, and lignin, achieving cellulose retention above 88.6% and lignin removal exceeding 91.2%. Mechanistic investigations reveal that the alkaline hydrogen peroxide stage is governed by a radical-driven network, in which ·OH and O 2 − facilitate aromatic ring activation, side-chain oxidation, and selective β -O-4 cleavage while suppressing lignin condensation. The resulting lignin shows enhanced functional groups and structural uniformity. The cellulose fraction reaches a glucan conversion of 91.4%. The recovered lignin, with moderate molecular weight, narrow dispersity, and high phenolic hydroxy content, can be directly used as a pH-responsive emulsifier without modification. This study links macroscopic fractionation performance to microscopic radical mechanisms and provides a unified model for mechanism-guided LCB refining.