A novel carbon-based solid-acid nanocatalyst (Sta-SO 3 H) was simply prepared for
the first time by the thermal treatment of sulfuric acid with starch at 180 C in a sealed
autoclave. The catalytic activities of Sta-SO 3 H as an efficient and reusable catalyst were
investigated by the condensation reaction of aldehyde, amine and β-keto ester for the
synthesis of functionalized piperidines under solvent-free conditions at room temperature in
good to high yields. Density functional theory calculations were used to study the structure