Hexagonal Mesoporous Silica Supported Ultrasmall Copper Oxides for Oxidative Amidation of Carboxylic Acids

Hexagonal mesoporous silica (HMS) supported copper oxide nanoparticles were prepared by a one-pot sol–gel synthesis, and their physicochemical properties were determined by XRD, ICP-MS, SEM, TEM, and N 2 physisorption, HR-TEM, and elemental mapping. A series of CuO/HMS catalysts was prepared with different Cu loadings (1, 1.5, 2, 2.5, 3, and 5 wt %). The catalytic performance of the prepared catalysts was investigated for the oxidative amidation of carboxylic acids. Notably, under mild reaction conditions the CuO/HMS catalysts exhibited excellent activity in terms of conversions (70–95%) and selectivity (80–86%). The improved catalytic performance of CuO/HMS catalysts may be attributed to the homogeneous dispersion and uniformity of the active copper species on the HMS support with a large surface area. Having investigated the functional group tolerance, the developed protocol can also be extended for the synthesis of insect repellent molecules such as N,N -diethyl phenylacetamide (DEPA), N,N -diethylbenzamide (DEB), and N,N -Diethyl-3-methylbenzamide (DEET) in good to excellent conversions with a better TON and E factor. The reaction protocol is sustainable due to its mild reaction conditions, high conversions, and selectivities superior to reported protocols. Importantly, the catalysts can be separated by simple centrifugation and can be recycled for several reaction cycles.