Precise fractionation of hemicellulose from bamboo biomass achieved with renewable bifunctional 4-hydroxybenzoic acid stabilizing lignin βO4 bonds

The precise fractionation of hemicellulose from lignocellulosic biomass remains a challenging task, complicated by the incorporation of lignin into the reaction liquor due to cleavage of β O 4 bonds, especially via a green strategy. The bifunctional 4-hydroxybenzoic acid (4-HA), a renewable plant phenolic acid, achieved selective and efficient separation of bamboo hemicellulose. Compared to conventional p-toluenesulfonic acid (p-TsOH) treatment, the separation yield of hemicellulose via 4-HA was up to 93.83 % while retaining ∼98 % of cellulose and ∼91 % of lignin in residual bamboo. The nucleophilic reaction of phenolic hydroxyls stabilized β O 4 bonds and prevented lignin degradation, ensuring that carboxyl groups in 4-HA selectively cleaved glycosidic bonds. That was proven by more β O 4 bonds (25.56/ 100 C 9 ), aliphatic hydroxyl groups (1.53 mmol·g −1 ), and fewer condensed structures in resultant bamboo lignin. This study provided a novel green strategy for the highly- selective and efficient separation of hemicellulose from lignocellulosic biomass preserving lignin structural integrity.