Synthesis of Noble Metal-oxo Cluster-based Metal-Organic Frameworks and their Use in Heterogeneous Catalysis and Magnetism

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This project aims at the systematic design, synthesis and characterization of a series of fundamentally novel polyoxo-noble-metalate (PONM)-based metal-organic frameworks (MOFs) and the investigation of their catalytic and magnetic properties. The entire class of discrete polyoxopalladates (POPs) and polyoxoaurates (POAs) of different shape, size and composition will be utilized to construct noble-metal and mixed noble-metal-based PONM-MOFs. The stability and composition of such framework materials will be tuned by suitable modification of the organic linkers, or by employing a dual secondary-building-unit (SBU) strategy, wherein the POP/POA SBUs will be linked to other types of SBUs such as conventional POMs, noble-metal complexes or single metal-ions. This project is expected to result in a library of PONM-MOF-based heterogeneous catalysts with either single or dual catalytic centers, which will be utilized as catalysts for organic oxidation, reduction, and C-C coupling reactions. The obtained PONM-MOFs can also be used as sacrificial templates to synthesize noble-metal- or mixed-noble-metal-based nanoparticles@porous-carbon composites, which will be tested as catalysts for photo- and electrocatalytic reactions. The formation of noble-metal-based nanoparticles from PONM-MOFs is highly attractive, because the composition and size of the nanoparticles can be tuned by simply using PONMs of different shape, size and composition as SBUs. We also aim to utilize lanthanide-centered POPs as SBUs to isolate Ln-POP-MOFs and to study them as molecular spin qubits, because the individual lanthanide ions inside the POP cavities exhibit highly symmetrical coordination environments (8-coordinated cubic in the LnPd12 nanocube or 10-coordinated pentagonal-prismatic in the LnPd15 nanostar). The Ln-POPs are well-oriented in the rigid framework of the Ln-POP-MOFs and the interactions of the individual spin qubits with each other can be fine-tuned by increasing/decreasing the length of the organic linkers or by using flexible organic linkers. The proof of principle for the synthesis, structure and catalysis of POP-MOFs was demonstrated recently (J. Am. Chem. Soc. 2019, 141, 3385−3389).