ChemInform Abstract: Synthesis of Magnetically Recyclable ZIF‐8@SiO₂@Fe₃O₄ Catalysts and Their Catalytic Performance for Knoevenagel Reaction.

Abstract

The title catalyst is prepared by addition of aqueous 2-methyl imidazole solution containing NEt 3 to an aqueous suspension of Zn(NO3)2 and SiO2@Fe3O4. The SiO2@Fe3O4 support is obtained from a mixture of NaOAc, polyvinylpyrrolidone, FeCl 3, and ethylene glycol (autoclave, 200 C, 12 h) followed by dispersion of the obtained magnetic particles in a mixture of EtOH and aqueous ammonia, and addition of tetraethoxysilane (ultrasonication, 30 min). The catalyst samples are characterized by XRD, SEM, TEM, FTIR spectroscopy, and magnetic measurements. ZIF-8@SiO 2@Fe3O4 samples exhibit superparamagnetism and good catalytic activity for the Knoevenagel reaction. The conversion of p-chlorobenzaldehyde and the selectivity of the production reaches about 98% at 25 C for 4 h. After reaction, the catalyst is easily separated from the reaction mixture by an external magnet, and can be reused five times. -(LI, Q.; JIANG, S.; JI*, S.; AMMAR, M.; ZHANG, Q.; YAN, J.; J. Solid State Chem. 223 (2015) 65-72, http://dx.