Sulfonic acid-functionalized MIL-101(Cr): An efficient catalyst for esterification of oleic acid and vapor-phase dehydration of butanol

A highly porous and acidic metal-organic framework (MOF), MIL-101(Cr)-SO₃H, was hydrothermally synthesized in one step using sulfonic acid-functionalized ligands. The prepared catalysts were systematically characterized with X-ray diffraction, FTIR, nitrogen adsorption, and thermogravimetric analysis. MIL-101(Cr)-SO₃H was successfully used in the liquid-phase reaction (esterification of oleic acid), and also applied for the first time in the vapor-phase (2-butanol dehydration) reaction. The esterification is catalyzed in the heterogeneous mode, as confirmed by a negligible increase in the esterification yield after the filtration of the catalyst. The esterification was performed under both microwave (MW) and conventional heating (CE), and a beneficial effect of the MW reaction for rapid reactions was observed. The vapor-phase dehydration of 2-butanol to olefins (BTO) over MIL-101(Cr)-SO₃H was very stable in conversion, which is different from the results obtained using the SAPO-34 molecular sieve, which has been widely used in the dehydration of simple alcohols. The obtained results demonstrated the versatile applicability of the sulfonic acid-functionalized MOFs both in the liquid- and vapor-phase reactions.