Sulfonated Fe[formula omitted]O[formula omitted]@PVA superparamagnetic nanostructure: Design, in-situ preparation, characterization and application in the synthesis of imidazoles as a highly efficient organic–inorganic Bronsted acid catalyst

Abstract

Polyvinyl alcohol is a suitable substrate for the catalysis of the organic reactions due to the large amount of hydroxyl functional groups. In this research, a new approach for in-situ preparation of Fe3O4@PVA nanostructure as well as its sulfonation was investigated. Then, the functional groups of the prepared nanocatalyst was characterized by Fourier transform infrared (FT-IR) spectroscopy. The size and morphology of the nanoparticles were tested by using scanning electron microscopy (SEM) images. The presence of constructive elements in the nanocomposites was confirmed by energy dispersive X-ray (EDX) analysis. To better insight, the structure and magnetic properties of the prepared nanostructure was studied by X-ray diffraction (XRD) pattern and vibrating sample magnetometer (VSM) analysis. Thermal stability and weight loss for the nanostructure composition at each step of weight change were screened by thermogravimetric analysis (TGA). Finally, the nanocomposite structure prepared was confirmed by transmission electron microscope (TEM) image. Then, for the first time, Fe3O4@PVA sulfonic acid–based superparamagnetic nanocatalyst was studied for the synthesis of 2,4,5-triarylimidazoles derivatives via a one-pot three-component condensation reaction starting from between ammonium acetate, aldehyde derivatives and benzil or benzoin. Due to high magnetic property of the catalyst, it was easily recyclable by a magnet at least for ten runs without any significantly reducing of catalytic activity.