Organocatalysis by site-isolated N-heterocyclic carbenes doped into the UIO-67 framework

Two imidazolium-tagged biphenyldicarboxylates were synthesized and incorporated into the UiO-67 framework. Post synthetic exchange did not prove a useful route to these materials. Alternatively, mixed-linker synthesis of the solid afforded materials loaded with 6-7% imidazolium linker, corresponding to fewer than one active site per cage. Powder X-ray diffraction patterns for the doped metal-organic frameworks (MOFs) revealed that they were isostructural with UiO-67. Once activated, the N-heterocylic carbene (NHC) containing MOF was found to catalyze the transesterification of vinyl acetate with benzyl alcohol in good yield. The catalyst could be recycled with a modest drop in conversion. This is the first report of a NHC-doped MOF acting as an organocatalyst. (C) 2016 Elsevier Ltd. All rights reserved.