ClO4-/Al-MCM-41 as a novel nanostructured solid acid catalyst for the synthesis of 4H-benzo[b]pyrans

A one-pot three-component reaction of various types of aldehydes, cyclic 1,3-diketones and malononitrile was studied in the presence of perchlorated Al-MCM-41 nanoparticles for the synthesis of 4 H -benzo[ b ]pyrans. Mesoporous Al-MCM-41 molecular sieves with the Si/Al mole ratios of 30, 40 and 50 were synthesized by the sol–gel method and ClO 4 - /Al-MCM-41 with different calcination temperatures were prepared and characterized by scanning electron microscopy, XRD, FT-IR and potentiometric titration techniques. The characterization results show that 8 wt% ClO 4 - /Al-MCM-41 with calcination temperature of 300 °C has the best catalytic activity. The catalyst is reusable many times with moderate loss in its activity.