Design and synthesis of double shell CuO hollow microsphere and its application for preparation of tetrazoles in PEG 200

A reusable and efficient double shell hollow CuO microsphere was synthesized by hydrothermal method. Various techniques such as X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), elemental mapping and BET have been used for characterization of catalyst. The catalyst was used as an efficient and safe catalyst in the [3 + 2] cycloaddition reaction of organic nitriles with sodium azide in PEG 200 as a green solvent under mild condition. A variety of aromatic commercial and non-aromatic synthesized nitriles was used to produce the corresponding tetrazoles in good to excellent yields. The recovery and reusability of catalyst was also investigated. The catalyst was recovered by simple filtration and reused five times. After five recycles, the catalyst still showed a significant activity and gave the desired product in fairly good yield.