Effects of several ionic liquids on the structures and catalytic properties of double metal cyanides

Abstract

A key challenge in the synthesis of catalyst is how to increase the catalytic property. Here Co(II)Fe(III) double metal cyanide (Co(II)Fe(III) DMC) had been prepared in presence with several typical kinds of ionic liquids(ILs), which were the ionic liquids with fluoroborate, fluorophosphate or -CF3, respectively. It is noteworthy that these ILs have shown significant influence on the catalytic performance of DMC for the epoxidation of styrene, and the Co(II)Fe(III) DMC catalyst modified with 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([BMIM]TF2N) show the highest catalytic efficiency. Then a series of techniques including infrared spectroscopy (IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), elemental analysis (EA), X-ray photoelectron spectroscopy (XPS), Thermogravimetric analysis (TGA), NH3-temperature programmed desorption (NH3-TPD), N2 adsorption–desorption measurement and X-ray absorption fine structure measurements(XAFS) have been used to explore the structures of Co(II)Fe(III) DMC + [BMIM]TF2N, respectively. Additionally, to further understand the influence of ionic liquid modifier, the mechanisms of the epoxidation of styrene with Co(II)Fe(III) DMC and Co(II)Fe(III) DMC + [BMIM]TF2N were probed by the density functional theory (DFT) based on the cluster model, respectively, unraveling the internal reason for the promotion of the catalyst performance. This understanding is critical to pave the way toward the design and preparation for novel catalysts.