Mechanism exploration of Cu-SnS2-sv@GO during the process of converting cellulose hydrolysate to lactic acid under mild reaction conditions

Valorization of cellulose-based materials requires overcoming the energy barrier of glucose isomerization to fructose. However, the process is often reliant on high temperatures and harsh thermal-catalytic conditions. In this study, 6 %Cu-SnS_2-sv@GO aerogels were developed as catalysts to produce lactic acid (LA) from enzyme-pretreated microcrystalline cellulose. These aerogels demonstrated remarkable thermo-catalytic and photocatalytic performances. The participation of Cu significantly enhanced the Lewis acidity and the total acidity of the catalyst, thereby boosting thermo-catalytic efficiency. Notably, the catalyst facilitated glucose isomerization to fructose at relatively low temperatures, with the reaction launching around 40 °C. Furthermore, Cu doping modulates the band structure of the catalyst, enhancing its light absorbability and improving the separation efficiency of photoinduced electron-hole pairs. Fructose produced during the single thermo-catalysis process accumulates due to its slow conversion rate. In contrast, the accumulated fructose is effectively depleted during thermo-photocatalysis, significantly enhancing both the selectivity and yield of levulinic acid (LA). Among the synthesized catalysts, 6 %Cu-SnS_2-sv@GO demonstrated the highest performance, achieving an optimal LA yield of 83.6 % (based on the enzymatic hydrolysate) at 80 °C under 2 hours of visible-light irradiation. These findings present a novel and efficient strategy for the high-value utilization of cellulose-based materials.