Preparation, Characterization, and Application of Preyssler Heteropoly Acid Immobilized on Magnetic Nanoparticles as a Green and Recoverable Catalyst for the Synthesis of Imidazoles

An efficient, magnetically separable catalyst was synthesized by immobilization of Preyssler heteropoly acid (HPA) on Ni0.5Zn0.5Fe2O4 magnetite nanoparticles (MNPs) coated with hydroxyapatite (HA). The catalyst was characterized by scaning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), FT-IR, energy dispersive spectroscopy (EDS), and TGA. Activity of this catalyst was tested in the synthesis of imidazole derivatives via one-pot three-component condensation of [9,10]-phenanthraquinone with aryl aldehydes and ammonium acetate at room temperature under solvent-free conditions.