Nano silica extracted from horsetail plant as a natural silica support for the synthesis of H3PW12O40 immobilized on aminated magnetic nanoparticles (Fe3O4@SiO2-EP-NH-HPA): a novel and efficient heterogeneous nanocatalyst for the green one-pot synthesis of pyrano[2,3-c]pyrazole derivatives

Abstract

In this work, nanomesoporous silica has been prepared from horsetail (Equisetum arvense), which is a medicinal plant, with high surface area. This natural silica has been applied as a support to prepare H3PW12O40 immobilized on aminated epibromohydrin-functionalized Fe3O4@SiO2 nanoparticles (Fe3O4@SiO2-EP-NH-HPA) as a highly powerful magnetically solid acid catalyst. Characterization of this nanocatalyst has been investigated by a variety of techniques such as FTIR, XRD, N2 adsorption–desorption, TEM, SEM–EDX, TGA, VSM, ICP-OES and elemental analysis. This magnetically solid acid nanocatalyst has been successfully used for the one-pot green synthesis of pyrano[2,3-c]pyrazole derivatives in an aqueous medium at room temperature. The procedure resulted in structurally different pyrano[2,3-c]pyrazoles in excellent yields in very low reaction times. Moreover, this magnetically solid acid nanocatalyst can be simply recovered by an external magnetic field and reused for seven consecutive reaction cycles without significant loss of activity. In this work, Fe3O4@SiO2-EP-NH-HPA as a highly powerful magnetically solid acid nanocatalyst based on natural silica which was extracted from a medicinal plant was prepared and characterized using various techniques. The activity of the new catalyst was tested for the synthesis of pyrano[2,3-c]pyrazole derivatives.