Magnetic CNTs-supported Ni(II) complex as an efficient heterogeneous catalyst towards nitroaldol (Henry) reaction

A novel heterogeneous support was developed based on hyperbranched poly(citric acid)-picolinic acid and Fe3O4 nanoparticles modified multi-walled carbon nanotubes (MWCNT/Fe3O4@PCA-Pic). Because of the surface modification of the magnetic carbon nanotubes with PCA-Pic, these hybrid nanomaterials are not only dispersible for a long time in a wide range of solvents but also are able to trap Ni(II) ions via complex formation of Pic functional end groups of the PCA-Pic dendrimer with metal ions. The morphology and structural feature of the catalyst was characterized using different microscopic and spectroscopic techniques such as FT-IR, UV-Vis, TGA, TEM, ICP and VSM. The catalyst was effectively used in the Henry (nitroaldol) reaction between nitroethane and a variety of aldehydes in an aqueous medium. Also, this catalyst can be recycled by applying an external magnetic field without significant loss of activity.