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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]