Tailoring and exploring the basicity of magnesium oxide nanostructures in ionic liquids for Claisen-Schmidt condensation reaction

Abstract

Solid basic catalysts are extremely useful for green catalytic processes because of their high activity, easy separation, and minimal corrosion. Herein, we report the development and effect of the basicity of five various MgO nanostructures developed by microwave (MW) irradiation in different ionic liquids (ILs) on the Claisen-Schmidt Condensation Reaction. The growth of the shape-controlled MgO nanostructures in the presence of the synergetic effect of the ILs with the MW irradiation developed various basic sites on the surface of the MgO nanocrystals. Due to the synergetic effect (formation of hydrogen bonding and π-π interactions between the ILs and the MgO precursor in the presence of MW irradiation) produced active basic sites in the final nanostructure. The TPD & XPS results show that the synergetic effect strongly altered the percentages of high, low, and moderate basic sites of the catalysts. To determine their catalytic activity based on the obtained different basicity in the MgO nanostructures, prepared all nano structures were tested in the reaction. The altered basicity of the MgO catalysts strongly affected on reaction results and demonstrated better activity than pure MgO. Particularly, hexagonal MgO nanostructures with exposed crystal facets (110) and (111) having high surface area and basicity showed an outstanding activity. In addition, effect or reaction parameters such as temperature, catalyst amount, solvent effect, and reaction time were determine and obtained optimized reaction condition for outstanding results. To determine the diversity of prepared MgO nanostructures, various substituted chalcones were prepared in optimized reaction condition in good to efficient yield. Recyclability of prepared catalyst was also determined up-to 6 cycles and physicochemical changes before and after recyclability test was determined. The proper correlation of obtained basicity & basic sites with the catalytic activity was established with this protocol.