Titanium(III)-Oxo Clusters in a Metal-Organic Framework Support Single-Site Co(II)-Hydride Catalysts for Arene Hydrogenation.

Titania (TiO) is widely used in the chemical industry as an efficacious catalyst support, benefiting from its unique strong metal-support interaction. Many proposals have been made to rationalize this effect at the macroscopic level, yet the underlying molecular mechanism is not understood due to the presence of multiple catalytic species on the TiO surface. This challenge can be addressed with metal-organic frameworks (MOFs) featuring well-defined metal oxo/hydroxo clusters for supporting single-site catalysts. Herein we report that the Ti(μ-O)(μ-OH) node of the Ti-BDC MOF (MIL-125) provides a single-site model of the classical TiO support to enable Co-hydride-catalyzed arene hydrogenation. The catalytic activity of the supported Co-hydride is strongly dependent on the reduction of the Ti-oxo cluster, definitively proving the pivotal role of Ti in the performance of the supported catalyst. This work thus provides a molecularly precise model of Ti-oxo clusters for understating the strong metal-support interaction of TiO-supported heterogeneous catalysts.