Silica-coated magnetic NiFe2O4 nanoparticlessupported H3PW12O40; synthesis, preparation, and application as an efficient, magnetic, green catalyst for one-pot synthesis of tetrahydrobenzo[b]pyran and pyrano[2,3-c]pyrazole derivatives

Abstract

A powerful, magnetic, supported, acid catalyst, NiFe2O4@SiO2–H3PW12O40, was prepared by chemical support of Keggin (H3PW12O40) heteropolyacid (HPA) on silica-coated NiFe2O4 magnetic nanoparticles. XRD, TEM, SEM, VSM, and FTIR confirmed that the keggin HPA is well dispersed on the surface of silica-coated NiFe2O4 magnetic nanoparticles. The magnetically recoverable catalyst could be easily recycled at least six times without significant loss of catalytic activity. After full characterization, its catalytic activity was investigated in the synthesis of tetrahydrobenzo[ b]pyran and pyrano[2,3-c]pyrazole derivatives.