Highly efficient hydrolysis of cellulose to high-concentration glucose using synergistic Brønsted/Lewis acid...

Glucose and 5-hydroxymethylfurfural (5-HMF) are attractive platforms for sustainable biomass valorization, yet cellulose conversion remains limited by substrate concentration, reaction conditions, and complex catalyst designs. Here, we report an acidic bifunctional solvent system (ZnCl₂-H₃PO₄) that can both disrupt cellulose structure and promote rapid in situ cascade hydrolysis to glucose and 5-HMF. In this system, ZnCl₂ (a Lewis acid) facilitates protonation of the β-1,4-glycosidic oxygen, while H₃PO₄ (a Brønsted acid) accelerates Zn²⁺ desolvation, together reducing cellulose crystallinity, activating C-O-C bonds, and lowering the energy barrier for carbocation formation. Under mild conditions (65°C), the process reaches completion within 10 min, achieving 94.8 mol% glucose (with a high concentration ∼ 130 mg/mL). Furthermore, this bifunctional solvent shows promise for converting the released glucose into 5-HMF by leveraging ZnCl₂ for isomerization and H₃PO₄ for dehydration. This approach avoids the high temperatures and elaborates catalyst architectures typical of conventional acid hydrolysis, offering a streamlined route to efficient cellulose conversion.