Sulfonated carbon/nano-metal oxide composites: a novel and recyclable solid acid catalyst for organic synthesis in benign reaction media

Abstract

Novel sulfonated carbon/nano-metal oxide composites were successfully synthesized by the partial carbonization of starch in the presence of different nano-metal oxides (nano-titania, nano-ceria and nano-zirconia) followed by sulfonation. The catalytic activity of the prepared catalysts was evaluated for the one-pot synthesis of gem-bisamides, bis(heterocyclyl)methanes and for the one-pot three component synthesis of β-aminocarbonyl compounds via Mannich reaction. Different nano-metal oxides have been investigated as support materials, with a view to select the most active solid acid catalyst. Among the various catalysts, sulfonated carbon/nano-titania composite (C/TiO₂–SO₃H) was found to be the most active and selective, and could be recycled several times without significant loss of activity. All the catalysts were characterized by FTIR and CHNS analysis, and the most active catalyst was further characterized by XRD, SEM, TEM, HRTEM, EDX and TGA.