<p>Novel, green, and reusable heteropoly acid-supported aluminum-exchanged Indian clay catalytic materials have been prepared and utilized for producing several tetrasubstituted imidazoles by reacting various substituted aromatic aldehydes with a primary amine, benzil, and ammonium formate in an ethanol medium. It was found that a heteropoly acid-supported aluminum-exchanged Indian clay catalyst (PWA/Al³⁺-ExIC) showed better activity compared to other catalysts tested. The reaction parameters were optimized for the product, 1,2,4,5-tetraphenyl-1H-imidazole, and the catalyst’s physicochemical properties were analyzed using XRD, SEM, TGA, BET surface area, and FTIR. The optimized reaction parameter conditions were selection of the nitrogen source, catalyst, amount of the catalyst, solvent, and time. Several substituted imidazoles were prepared in 68 to 93% yield. Additionally, the acidity of Al³⁺-ExIC and its supported clays were explored by the DRIFTS method using pyridine as a probe molecule. A reaction pathway for the substituted imidazoles was provided. The substituted imidazoles were characterized by their proton NMR spectra, FTIR, and melting points. After the reaction, the heterogeneous solid acid catalyst, PWA/Al³⁺-ExIC, can be easily retrieved. The catalyst was found to lose activity gradually in the reusability test.</p>