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

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 efficient solid acid catalyst for the alcoholysis of furfuryl alcohol (FA) and esterification 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 Bronsted acidity and therefore exhibits excellent catalytic activity towards production of ALs. The highest Bronsted acidity in UiO-66(Hf)-SO(3)His the result of the covalently bound sulfonic acid groups present inorganic linkers along with the ligated hydroxyl groups (Hf-mu(3)-OH) to the Hf metal clusters.