Surface Engineered Carbon Microspheres with Tunable Brønsted/Lewis Acidity for Cellulose Conversion to Glucose, Combining Mechanochemical and Hydrothermal Treatments

A series of functionalized carbon catalysts were synthesized via a bottom-up hydrothermal carbonization of glucose in the presence of inorganic precursors, such as Keggin-type heteropolyacids (HPAs: H3PMo12O40 and H3PW12O40) and transition metals (M: Co and Ni), or both. These materials were evaluated in cellulose conversion using a stepwise process that combined mechanochemical and hydrothermal assistance. The influence of reaction parameters─temperature, milling speed and duration, reaction time, and catalyst loading─on conversion and selectivity was systematically studied. The catalysts exhibited activity in cellulose hydrolysis to glucose, achieving moderate yields under mild conditions: (MoO2/C (38.5%); Co,Ni,HPW/C (38.3%); Co,HPW/C (37.3%); Co/C (34.4%); Co,Ni,MoO2/C (33.4%); Co,MoO2/C (31.8%); CS-COOH (29.8%), and HPW/C (22.5%)). Conversion values indicated a correlation between mechanocatalytic activity and the surface acidity. These findings highlight the potential of such composites as promising heterogeneous acid catalysts. Moreover, their catalytic activity can be enhanced through surface engineering of carbon supports to tailor Brønsted and Lewis acidity, offering distinctive acid site strengths. This integrative strategy provides a cost-effective and safe alternative to conventional acid catalysts, enabling synergistic interactions between Brønsted and Lewis sites for biomass valorization. Ultimately, this approach facilitates the selective production of value-added chemicals, advancing sustainable practices and supporting a circular economy.