Trifloaluminate Ionic Liquids Supported UIO-67 as Lewis Acidic Catalyst for Excellent Synthesis of Alkyl Levulinates

Graphical An efficient trifloalumiate supported MOF(UIO-67) catalyst was synthesized to promote the butyl levulinate formation from α-angelica lactone under mild reaction, resulting in remarkable conversion and selectivity. The catalyst was easily separated and could be recycled five times without significant activity loss. Herein, levulinate acid esters (LAEs) were efficiently synthesized from the α-angelica lactone (α-AL) esterification with trifloaluminate ionic liquids supported UIO-67 MOF as Lewis acidic catalyst. A series of UIO-67 catalysts with varied trifloaluminate ionic liquids loading were prepared via the post-modification method and exhibited excellent catalytic activity for α-AL esterification. Remarkable α-AL conversion (100 %) and LAEs selectivity (>99 %) were achieved by UIO-67 catalysts (0.2 mol %) with 12.4 %, trifloaluminate ionic liquids loading (UIO-67-TFA) at 70 °C and 90 min. The UIO-67-TFA catalyst can be reused at least 5 cycles without significant loss of catalytic activity. The UIO-67-TFA catalysts were fully characterized by XRD, SEM, XPS, TGA, IR, N 2 physisorption, etc. The results indicated that the well-distributed active trifloaluminate Lewis acid catalytic sites, high BET surface area, and good thermal stability could contribute to its excellent catalytic activity.