Catalytic conversion of furfuryl alcohol or levulinic acid into alkyl levulinates using a sulfonic acid-functionalized hafnium-based MOF

Abstract

Biomass conversion using reusable solid acid catalysts are highly desirable to comply with the principles of green chemistry. Here, we report a sulfonic acid-functionalized hafnium-based metal-organic framework (MOF), UiO-66(Hf)-SO3H, as an efficientsolid acidcatalyst for the alcoholysis of furfuryl alcohol (FA) andesterification of levulinic acid (LA) affording alkyl levulinates (ALs). Among the as prepared UiO-66 based MOFs(UiO-66(Hf), UiO-66(Hf)-NH2, UiO-66(Hf)-SO3H and UiO-66(Zr)-SO3H), UiO-66(Hf)-SO3H holds highest Brønsted acidity and therefore exhibits excellent catalytic activity towards production of ALs. The highest Brønsted acidity in UiO-66(Hf)-SO3His the result of the covalently bound sulfonic acid groups present inorganic linkers along with the ligated hydroxyl groups (Hf-μ3-OH) to the Hf metal clusters.