Mesoporous Borated Zirconia: A Solid Acid-Base Bifunctional Catalyst

摘要

The development and use of reusable solid catalysts for the selective organic transformation in solvent-free or environmentally benign solvent media is the key interest of modern frontier science. Herein a facile low temperature aqueous solution based chemical route for the synthesis of mesoporous borated zirconia, an acid-base bifunctional solid catalyst, using aqueous zirconium ammonium carbonate complex and borax in presence of cetyltrimethylammonium bromide is presented. The material has a very high surface area and acidity with weak basicity. The catalytic activity of the material was investigated for the solvent-free Knoevenagel condensation reaction of benzaldehyde/substituted benzaldehyde and malononitrile/cyano ethylacetate to confirm the acid-base bifunctionality. High yield (> 90%) of the corresponding benzylidene was obtained within 15-30 min at room temperature. The evidence that the high catalytic activity is a result of acid-base bifunctionality of the synthesized borated zirconia material was further supported by performing Claisen-Schmidt condensation of benzaldehyde and acetophenone. The methodology was also extended for targeted synthesis of cinnamyl ethyl ester and coumarin or coumarin ester; and resulted in a good yield.