PolyoxoNobleMetalate Chemistry Merged with Metal-Organic Frameworks: A Novel Class of Heterogeneous Catalysts

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The aim of this project is merging the areas of polyoxometalates (POMs) and metal-organic frameworks (MOFs) in a synergistic fashion. POMs are discrete, anionic metal-oxides with a multitude of shapes, sizes, compositions and associated properties. MOFs, on the other hand, are ordered periodic networks of metal ions or clusters connected in three dimensions by organic linkers to form cavities or pores. Here the major focus is on the novel class of polyoxo-noble-metalates (PONMs) such as polyoxopalladates(II) (discovered by the group of Prof. U. Kortz in 2008) and their incorporation into porous MOFs. PONMs are discrete, anionic, solution- and air-stable noble metal-oxides comprising exclusively square-planar coordinated d8 metal centers such as Pd2+ and Au3+ ions, e.g. the Pd13-nanocube [PdII13AsV8O34(OH)6]8- (Pd13As8), the Pd15-nanostar Pd15P10, the lanthanide- and 3d transition metal-centered nanocubes LnPd12 and MPd12, the Pd7V6 nanobowl, as well as the mixed noble metal pallado-aurate cluster Pd8Au4. Incorporation of such PONMs in neutral or cationic MOFs (PONM-MOFs) allows for the construction of materials with unprecedented catalytic properties (e.g. heterogeneous oxidations/reductions). The PONMs residing inside the MOFs could further be chemically reduced to form monodisperse nanoparticles (palladium, gold, core-shell or alloys, depending on the PONMs used) resulting in nanoparticle@MOF materials, which would be highly active heterogeneous catalysts. PONMs could also act as Secondary Building Units (SBUs) which can be linked by suitable organic linkers and/or transition metal ions, leading to the formation of PONM integrated MOF compounds (PONM-OFs). This is a novel and open field of research, which offers spectacular potential to realize multifunctional materials, especially in the area of heterogeneous catalysis.