Preparation and application of ZnFe2O4@SiO2-SO3H, as a novel heterogeneous acidic magnetic nanocatalyst for the synthesis of tetrahydrobenzo[b]pyran and 2,3-dihydroquinazolin-4(1H)-one derivative

In this work, we report the synthesis and identification of ZnFe2O4@SiO2-SO3H as a novel and green nanomagnetic solid acid catalyst, which is containing the sulfuric acid catalytic sites on the surface of ZnFe2O4 magnetic nanoparticles as the catalytic support. The as-synthesized ZnFe2O4@SiO2-SO3H MNPs were characterized with accuracy by different physicochemical methods; including, X-ray powder diffraction, energy-dispersive spectroscopy, Scanning electron microscopy, Fourier transform infrared, X-ray elemental mapping, Thermogravimetric analysis, and Vibrating Sample Magnetometer analyses. The catalytic activity of this nanomagnetic material is considered for the synthesis of the diversely substituted tetrahydrobenzo[b]pyran and DHQZ (2,3-dihydroquinazolin-4(1H)-ones) in ethanol solvent, which affording excellent yields (86-97%). The heterogeneous nature of the catalyst was confirmed via the hot filtration experiment. Furthermore, the activity of the recycled nanocatalyst was examined for at least five cycles with a negligible loss of its activity (97-92%). Also, the amount of sulfamic acid function in the ZnFe2O4@SiO2-SO3H was calculated from back titration.

Automated summary

In this work, a novel and green nanomagnetic solid acid catalyst, ZnFe2O4@SiO2-SO3H, was synthesized and identified. The catalyst contains sulfuric acid catalytic sites on the surface of ZnFe2O4 magnetic nanoparticles. The synthesized catalyst was accurately characterized by various physicochemical methods. It was found to have excellent catalytic activity for the synthesis of tetrahydrobenzo[b]pyran and DHQZ in ethanol solvent, with yields of 86-97%. The heterogeneous nature of the catalyst was confirmed and its recyclability was demonstrated with negligible loss of activity (97-92%). The amount of sulfamic acid in ZnFe2O4@SiO2-SO3H was determined through back titration.