In situ bifunctional solid acids bearing B–OH and –COOH groups for efficient hydrolysis of cellulose to sugar in a pure aqueous phase

Pyruvaldehyde as a carbon source is synthesized together with boric acid to produce a carbon-based solid catalyst with in situ bifunctional groups of adsorptive boron hydroxyls and carboxyls in a single-step hydrothermal carbonization process, which is mainly utilized to induce the hydrolysis of cellulose to sugar in pure water. The obtained catalyst exhibits a strong adsorption capacity of 532 mg g−1 with cotton cellulose and possesses good water dispersibility. It can effectively break the aggregated structure of cellulose through the strong interfacial adsorption interaction to induce the hydrolysis of cellulose to sugar with high efficiency in the pure aqueous system. The cellulose conversion and the glucose yield reach 97.3% and 40.0%, respectively. Additionally, the catalyst demonstrates excellent hydrothermal stability and reusability. As a result, a high-yield, acid-free, green, and environmentally friendly hydrolytic process of cellulose to sugar in pure water is successfully established.