Synergistic Hydrothermal Conversion of Biomass Derivative Carbohydrates and CO2 into Value-Added Organic Acid over an NH2-MIL-53(Fe) Catalyst

During CO2/HCO3– reduction with renewable biomass, achieving high-efficiency production of the target products is vital but challenging. In this study, an NH2– functional-group-modified MIL-53(Fe) catalyst was synthesized using a facile and efficient method. Under the action of the NH2-MIL-53(Fe) catalyst, a clear synergistic effect was exhibited on the transformation of glucose and NaHCO3 into formic acid with a high yield of 50% at a low reaction temperature (190 °C) via a three-pronged route, which mainly involved the decomposition of intermediates of glucose to gradually reduce NaHCO3 to formic acid under hydrothermal conditions. An in-depth analysis of the catalytic mechanism and density functional theory calculations demonstrated that the increased alkalinity of active sites by the NH2– functional group incorporation into the catalytic system enhanced the crucial reaction steps and reduced the activation energy of the crucial reactions, including glucose isomerization, aldehyde intermediate retro-aldol condensation, and redox of aldehyde compounds and NaHCO3 to formic acid, thereby promoting the generation of target products and suppressing side products. This study addresses the challenge of reducing NaHCO3 from renewable biomass to commercial formic acid by constructing multifunctional active sites, thus providing a new strategy for achieving carbon cycling.