Ultrasonic‐assisted preparation of Co<sub>3</sub>O<sub>4</sub> and Eu‐doped Co<sub>3</sub>O<sub>4</sub> nanocatalysts and their application for solvent‐free synthesis of 2‐amino‐4<i>H</i>‐benzochromenes under microwave irradiation
Leila Kafi‐Ahmadi, Ahmad Poursattar Marjani, Ehsan Nozad
Abstract
Co 3 O 4 and Eu‐doped Co 3 O 4 nanocatalysts were synthesized through an ultrasonic‐assisted solvothermal method and were characterized with X‐ray diffraction (XRD), Fourier transform infrared (FT‐IR), energy‐dispersive X‐ray (EDX), and field‐emission scanning electron microscopy (FESEM) methods. Spinel cubic crystalline system for synthesized nanocatalysts was confirmed with XRD, whereas the spherical morphology of Co 3 O 4 changed to nanorods after Eu 3+ doping, which was affirmed with FESEM micrographs. Catalytic performance of the nanomaterials was examined through the synthesis of 2‐amino‐4 H ‐benzochromenes using aromatic aldehydes, malononitrile, and β‐naphthol condensation under solvent‐free conditions and microwave irradiation. Mild reaction conditions, short reaction times, simple setup, using an affordable catalyst, and high‐quality products were some of the advantages of this procedure. The efficiency for Eu‐doped nanocatalyst was achieved by about 96%.