Pd@UiO-66-type MOFs prepared by chemical vapor infiltration as shape-selective hydrogenation catalysts
Luz, I., Roesler, C., Epp, K., Llabres i Xamena, F. X., & Fischer, R. A. (2015). Pd@UiO-66-type MOFs prepared by chemical vapor infiltration as shape-selective hydrogenation catalysts. European Journal of Inorganic Chemistry, (23), 3904-3912. DOI: 10.1002/ejic.201500299
Host-guest inclusion properties of UiO-66 and UiO-67 metal-organic frameworks have been studied using ferrocene (FeCp2) as probe molecule. According to variable-temperature solid-state H-1 and C-13 CP-MAS-NMR, two different environments exist for adsorbed FeCp2 inside UiO-66 and UiO-67, which have been assigned to octahedral and tetrahedral cavities. At room temperature, a rapid exchange between these two adsorption sites occurs in UiO-67, while at -80 degrees C the intracrystalline traffic of FeCp2 through the triangular windows is largely hindered. In UiO-66, FeCp2 diffusion is already impeded at room temperature, in agreement with the smaller pore windows. Palladium nanoparticles (Pd NPs) encapsulated inside UiO-66 and UiO-67 have been prepared by chemical vapor infiltration of (allyl)Pd(Cp) followed by UV light irradiation. Infiltration must be carried out at low temperature (-10 degrees C) to avoid uncontrolled decomposition of the organometallic precursor and formation of Pd NPs at the external surface of the MOF. The resulting Pd-MOFs are shape selective catalysts, as shown for the hydrogenation of carbonyl compounds with different steric hindrance.