A new nanocomposite catalyst based on clay-supported heteropolyacid for the green synthesis of 2,4,5-trisubstituted imidazoles

Intercalation of cetyltrimethylammonium (CTA⁺) cations within the nanolayers of montmorillonite (MMT) clay followed by reaction with Keggin-type phosphomolybdic acid (PMo) resulted in the synthesis of (CTA)₃PMo-MMT nanocomposite catalyst. The prepared nanocomposite catalyst was characterized using different physicochemical methods such as Fourier-transform infrared and inductively coupled plasma–optical emission spectroscopies, X-ray diffraction, and nitrogen adsorption–desorption (Brunauer–Emmett–Teller method) analyses. Characterization techniques demonstrated the intercalation of (CTA)₃PMo species into the nanolayers of MMT. The resulting (CTA)₃PMo-MMT nanocomposite catalyst efficiently catalyzed the synthesis of 2,4,5-trisubstituted imidazoles under solvent-free conditions. The efficiency is due to the fact that the presence of CTA⁺ species makes the nanocomposite catalyst hydrophobic and facilitates the accessibility of hydrophobic reactants to active sites in the course of the reaction. High activity and selectivity were achieved in the presence of the prepared nanocomposite catalyst. The nanocomposite catalyst was readily isolated from the reaction mixture using simple filtration, washed with ethanol, and recycled five times without a major loss of activity.