Design of Prussian Blue Analogue-Derived Magnetic Binary Ce–Fe Oxide Catalysts for the Selective Oxidation of Cyclohexane

We report the fabrication of Ce–Fe oxides (CFOs) derived from Prussian blue analogues (PBAs) with different shapes of sphere (CFO-S), bipyramid (CFO-B), and flower (CFO-F), which are prepared by controlling the volume ratio of water and ethanol and the addition of deep eutectic solvents (DESs) to control the solvent environment using a modified coprecipitation method. The structure, morphology, and the surface properties of Ce–Fe oxides were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS). The catalytic performance of PBA-derived Ce–Fe oxides was evaluated for the oxidation of cyclohexane, which positively correlated with surface oxygen vacancy and the amount ratio of Ce/Fe. The conversion for cyclohexane of CFO-S and CFO-B was 9.03 and 9.25%, respectively. However, CFO-S had a higher selectivity for K/A-oil (cyclohexanone and cyclohexanol) of 81.8%, resulting from the exposed crystal plane (100) compared to CFO-B (75%). Besides, CFO-F was rich in the Fe2O3 crystal phase, which is beneficial for KA selectivity. It was found that Ce3+, Fe3+, and OV had an important influence on the activation of C–H bonds, which provides a reference for the design of efficient alkane oxidation catalysts.