Heterogeneous Catalysis by Polyoxometalates in Metal-Organic Frameworks

The embedding of molecular metal oxides, or polyoxometalates (POMs), in metal-organic frameworks (MOFs) opens new research avenues in catalysis and beyond. This review explores the host-guest chemistry of POMs embedded in MOF hosts and discusses the synergism of the resulting composites for heterogeneous catalysis. The review focuses on well-established and well-studied classes of POMs, such as Keggin and Wells-Dawson anions, and well-researched MOFs, including the MIL, UiO, and NENU families. Outstanding examples of synergistic catalytic activity between the POM and MOF are described, and key performance parameters, including POM localization, pore size and pore structure, as well as particle size effects are described for technologically important catalytic processes. In addition to thermal catalysis, we discuss the use of POM@MOF composites for electro- and photocatalysis with an emphasis on energy conversion systems. Finally, we provide an outlook on emerging areas where POM@MOF composites could lead to new catalytic reactivity.