Synthesis and characterization of reusable nano-order SO3H-KIT-5 as a heterogeneous catalyst for eco-friendly synthesis of 1,4-dihydropyridines

A novel nanocatalyst silica-bonded sulfuric acid supported on KIT-5 as an organic–inorganic hybrid with high activity was prepared successfully. The KIT-5 with high surface area was reacted with chlorosulfonic acid via simple and rapid method. This efficient and reusable heterogeneous catalyst sulfuric acid nanocatalyst catalyzed one-pot synthesis of β-dicarbonyl compounds, aldehyde and ammonium acetate in the presence of 0.05 g of nanocatalyst at room temperature via solvent-free conditions to afford excellent yields of 1,4-dihydropyridines. This nanocatalyst was fully characterized by XRD, SEM–EDXS and Map analyses. The morphology of the catalyst surface by SEM images shows all porous of KIT-5 after the reaction was filled with the SO3H groups. The average size determines around 22–24 nm. This catalyst can be reused five times without any significant loss of activity, too. The ease of separation, high activity, high surface area and reaction under open air condition are the main advantages of this catalyst.