Simultaneous transformation of sugars and CO2 into sugar derivatives and formate at room temperature: Effect of alcohols and cations

Abstract

Catalytic hydrogenation of CO2 to formate is an attractive pathway for CO2 utilization. In this system, replacing fossil fuel based H2 with a biomass-derived H-2 source and using a recyclable heterogeneous catalyst at mild reaction conditions are advantageous to construct a green and sustainable process. Here, we demonstrate the transfer hydrogenation of biomass-derived sugars to CO2 affording sugar-derivatives and formate using a physical mixture of Pt/C and Pd/C catalysts. In this regard, the effects of various parameters such as the solvent composition, CO2 source, reactant concentrations, and sugar source were systematically investigated. In addition, the glucose dehydrogenation and bicarbonate hydrogenation were separately conducted to understand the effect of the parameters on each reaction. Based on the catalytic results and C-13 NMR study, the reaction mechanism was suggested. The results demonstrated that the hydrogen transferring ability, salt solubility, and water structure breaking as well as pH and H2 solubility were crucial factors that could affect the catalytic activity. The high- concentration reaction was carried out to enhance the productivity, and high turnover numbers of 1018 and 99.8 were obtained for Pt/C and Pd/C, respectively. Moreover, the reaction system heterogeneity was confirmed by retained activity after consecutive cycling tests.