Olefin Epoxidation over Metal-Organic Frameworks Modified with Transition Metals

Abstract: Mixed aluminum-containing metal-organic frameworks (MOF) modified with Fe, V, and Ti are synthesized in two steps. At the first step, the amorphous precursors of metal-organic frameworks containing various amounts of transition metals are obtained by the electrochemical method. At the second step, the precursors are crystallized under solvothermal conditions. Study of the effect of synthesis conditions shows that Fe-containing metal-organic frameworks crystallize in the presence of dimethylformamide; V- and Ti-containing counterparts crystallize in the presence of water. The time and temperature of crystallization are varied in the range from 150 to 200°С and 24 to 72 h depending on the concentration of the transition metals. The resulting samples are investigated by low-temperature nitrogen adsorption, scanning electron microscopy, X-ray powder diffraction, X-ray photoelectron spectroscopy, and thermogravimetric and differential thermal analysis (TGA-DTA). Research into the influence of catalyst composition on its activity in 1-octene epoxidation by tert-butyl hydroperoxide suggests that that the titanium-containing samples are catalytically inactive, while the vanadium-containing samples are more active than the iron-containing ones. Testing of the vanadium-containing samples in propylene epoxidation demonstrates that their activity is comparable with the activity of a commercial titanium silicate catalyst.