Efficient Catalytic Upgradation of Bio-Based Furfuryl Alcohol to Ethyl Levulinate Using Mesoporous Acidic MIL-101(Cr)

Enlarging the dispersed micropores of metal-organic frameworks to the well-ordered mesostructure can enhance the accessibility of acidic sites for reactants resulting in the improvement of selectivity. With the regulation of cetyltrimethylammonium bromide/Cr³⁺ and ClSO₃H sulfonation, a series of mesoporous MIL-101(Cr)-SO₃H (MMSs) with multiple pore sizes and acidic properties were synthesized and explored to further facilitate the furfuryl alcohol (FA) ethanolization to ethyl levulinate (EL) for the first time. The optimal catalytic activity of 83.8% EL yield at full FA conversion demonstrated that the appropriate mesopore size, acidic density, and accessible -SO₃H sites contributed to the superior performance of the MMS(0.3)-0.15. The turnover frequency value (14.8 h^-1) obtained with MMS(0.3)-0.15 was comparable to the commercial Nafion NR50 (18.3 h^-1) and much higher than the classical Amberlyst-15 (1.9 h^-1), confirming the predominant catalytic performance. Furthermore, two coexistent reaction paths with 2-ethoxymethylfuran and 4,5,5-triethoxy-pentan-2-one as intermediates indicated the possibility of producing EL from FA.