Highly Selective Aldol Condensation of Furfural and Acetone Over Defective-Engineered MIL-88B Metal–Organic Frameworks

Abstract

Furfural (FUR), a valuable platform molecule derived from lignocellulosic biomass, is a promising feedstock for producing furfural acetone (FAc) through aldol condensation reactions, offering pathways to various chemical products. However, identifying efficient and sustainable catalysts for FAc production remains challenging. Here, we introduce a novel strategy employing Fe-MIL-88B and Fe-MIL-88B-NH₂ metal–organic frameworks (MOFs) composed of nonnoble metals designed to enhance catalytic efficiency in FUR conversion. In contrast to conventional synthesis methods, our approach integrates magnetic stirring during solvothermal synthesis, promoting defect formation that improves the structural and catalytic properties of the MOFs without requiring additional reagents. Extensive characterization confirmed these structural improvements, while a statistical design of experiments guided the optimization of catalytic parameters for the FUR-acetone reaction. Thermal pretreatment emerged as a critical factor in driving high FAc selectivity. Catalytic tests showed that MOFs synthesized with stirring exhibited significantly greater selectivity than those synthesized without stirring. Furthermore, functionalization with amino groups (-NH₂) reduced FUR conversion. The optimized catalyst, Fe-MIL-88B-s, achieved a remarkable 99.4% conversion and 99.9% selectivity for FAc, demonstrating stability across three cycles. This work provides a sustainable approach to catalyzing furanic conversions using defect-engineered, nonnoble metal MOFs. It underscores the potential of simplified, scalable methods for defect induction to expand MOF applications in sustainable chemical transformations.