Molecular transition metal catalysts for the epoxidation of olefins are very efficient; yet, they are largely neglected in industrial applications since recycling proves to be difficult. The immobilization of molecular epoxidation catalysts on classic silica supports is, however, intricate and usually associated with a dramatic loss of activity compared to homogeneous congeners mainly due to limited diffusion. The host material must be robust towards oxidative conditions and exhibit large pores to avoid diffusion problems.Four different metal-organic frameworks of the very stable UiO series were prepared using solvothermal synthesis as described in literature, including the fully amino-functionalized UiOsand mixed UiOs where only 1/6 of the linkers contain �NH2 groups. The structure of UiO-67-NH2 was determined by single crystal X-ray diffraction.The frameworks were subjected to post-synthetic modification using salicylaldehyde to create a Schiff base like moiety at which MoO2(acac)2 can bind via ligand exchange. All Mo@UiO materials were tested for epoxidation of cyclooctene with neat tert-butyl hydroperoxide. While in all cases the selectivity of cyclooctene oxide is very high, the conversion and recyclability show a strong dependence on the pore size. Stability and recyclability of the materials was investigated and confirmed for ten cycles.

UiO-type MOFs for catalyst immobilization

248th National Meeting (2014)

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