The preparation of polyvinyl imidazole-functionalized magnetic biochar decorated by silver nanoparticles as an efficient catalyst for the synthesis of spiro-2-Amino-4H-pyran compounds.

The silver nanoparticle was synthesized by developing poly (1-vinylimidazole) on the surface of magnetized biochar (the stem and roots of Spear Thistle) (biochar/Fe3O4/PVIm/Ag). This nanocomposite was characterized by Fourier-transformed infrared spectroscopy (FTIR), powder X-ray diffraction (XRD), vibrating sample magnetometer (VSM), scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS), and transmission electron microscopy (TEM). The SEM and TEM images of the nanocatalyst, biochar/Fe3O4/PVIm/Ag-NPs, confirmed the observation of microscopic sheets of biochar. The catalytic activity of these Ag NPs was tested via multicomponent reaction plus reusing to successful formation of 2-amino-4H-pyran and functionalized spirochromen derivatives. The prepared nanocatalyst was easily separated by an external magnet and reused in repeating coupling reaction cycles four times without remarkable activity loss. The catalyst showed great efficiency and reusability, thus making it an ideal candidate for catalytic purposes in several organic transformations.