Equisetum arvense As an abundant source of silica nanoparticles. SiO2/H3PW12O40 nanohybrid material as an efficient and environmental benign catalyst in the synthesis of 2-amino-4H-chromenes under solvent-free conditions

Uniform SiO₂ nanoparticles were successfully prepared from Equisetum arvense obtained from the north-east of Iran. Then, surface modification of the extracted nanoparticles was performed with a methanol solution of H₃PW₁₂O₄₀ via wet impregnation method. The prepared nanocatalyst was characterized by XRD, FESEM, ICP, UV-Vis, and FT-IR spectroscopy. The supported heterogeneous nanocatalyst was successfully applied as a Lewis/Bronsted acid catalyst in the synthesis of a series of substituted 4H-chromenes via condensation of aromatic aldehydes, malononitrile, and 4-hydroxycoumarin under solventless conditions with fine yields in appropriately short times. [ABSTRACT FROM AUTHOR]