Design of mesoporous sulfated zirconia nanocrystals with dual Brønsted acid and Lewis acid

Abstract

Sulfated ZrO₂ (S-ZrO₂) nanocrystals with a pure tetragonal phase and mesopores were designed by calcination of sulfated UiO-66. Benefiting from the inhibitory effect of organic linkers and sulfate ions on the growth of crystals during the pyrolysis process, S-ZrO₂, derived from sulfated UiO-66, is composed of nano-sized crystals with a size of about 5 nm. In addition, the released gases from the decomposition of organic linkers enable S-ZrO₂ with mesopores, avoiding the severe agglomeration of ZrO₂ nanocrystals. As a result, the as-synthesized S-ZrO₂ nanocrystals can function as the promising catalysts containing dual Brønsted acidic and Lewis acidic sites to display a good catalytic activity in the esterification reaction of propanoic acid with methanol. In particular, a good conversion of 96.8 % for propanoic acid was achieved at 7 h, higher than that of commercial ZrO₂-based sulfated ZrO₂ (74 %) and pristine UiO-66 (24 %).