Solar driven catalytic conversion of cellulose biomass into lactic acid over copper reconstructed natural mineral

Development of new technologies for conversion of biomass-based compounds into energy sources and basic chemicals is important for a circular economy. In this study, a unique solar driven catalysis system is developed to convert cellulose into lactic acid (LA) using Cu modified natural palygorskite (Pal) catalyst. Adequate Cu incorporation reframes Pal with a reduced band gap. As the mass ratio of Cu goes beyond 6 wt%, extra Cu2O quantum dots (QDs) assemble in situ on the Cu-Pal surface and form Cu2O/Cu-Pal heterostructure, which effectively promotes the charge transfer and exposes abundant Lewis acid sites for synergistic adsorption and conversion of intermediates. Notably, the colloidal character of the Cu-Pal substrate enables intimate adsorption of catenulate cellulose. The 10 wt% Cu2O QDs/Cu-Pal nanocomposite exhibits remarkable photocatalytic LA selectivity under visible light. Time-resolved in-situ attenuated total reflectance infrared (ATR-IR) spectros-copy and the density functional theory calculation (DFT) are employed to help elucidate the photocatalytic mechanism. Both theoretical and experimental studies demonstrate that such a Cu-modified mineral catalyzes a series of tandem reactions for LA formation, including the precise cleavage of beta-1,4-glycosidic bonds of cellulose into glucose, selective cleavage of the C3-C4 bond of glucose to C3 intermediates via photogenerated holes, and the selective conversion of C3 into LA. Our findings provide a new potential sustainable alternative for biomass valorization.

Automated summary

This study develops a unique solar driven catalysis system for converting cellulose into lactic acid using Cu modified natural palygorskite catalyst. The incorporation of Cu reframes the properties of palygorskite and reduces the band gap. Cu2O quantum dots assemble on the Cu-Pal surface to form a heterostructure, enhancing charge transfer and providing abundant adsorption sites. The 10 wt% Cu2O QDs/Cu-Pal nanocomposite exhibits remarkable photocatalytic selectivity for lactic acid production under visible light.