Halloysite Nanotubes Functionalized Sulfonic Acid: Synthesis, Spectroscopic Characterization, Computational Studies and Application for the Synthesis of 1,4-Dihydropyridines

In this study, naturally occurring clay halloysite has been used to synthesize novel halloysite functionalized sulfonic acid in two steps, i.e. functionalization followed by oxidation, and its catalytic activity has been estimated for one-pot synthesis of Hantzsch 1,4-dihydropyridines under green solventfree conditions. Spectroscopic studies such as FTIR, TGA, elemental analysis and first-principles-based quantum chemical studies have been employed to characterize the catalyst. Recyclability without significant loss of catalytic activity has been observed for several runs.