Aperture-Opening Encapsulation of a Transition Metal Catalyst in a Metal-Organic Framework for CO2 Hydrogenation.

The aperture-opening process resulting from dissociative linker exchange in zirconium-based metal-organic framework (MOF) UiO-66 was used to encapsulate the ruthenium complex (tBuPNP)Ru(CO)HCl in the framework (tBuPNP = 2,6-bis((di- tert-butyl-phosphino)methyl)pyridine). The resulting encapsulated complex, [Ru]@UiO-66, was a very active catalyst for the hydrogenation of CO2 to formate. Unlike the analogous homogeneous catalyst, [Ru]@UiO-66 could be recycled five times, showed no evidence for bimolecular catalyst decomposition, and was less prone to catalyst poisoning. These results demonstrated for the first time how the aperture-opening process in MOFs can be used to synthesize host-guest materials useful for chemical catalysis.