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

Abstract

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.