Redox-Active Metal-Organic Frameworks: Novel Entatic State Catalysts?

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Porous, redox-active metal-organic frameworks (MOFs) shall be developed which are constructed from aromatic N-donor ligands (e.g. pyrazolate or triazolate moieties) and openshell 3d transition metal ions. Previous investigations have demonstrated that the use of heterocyclic aromatic N-donors leads to greatly enhanced hydrolytic stability of the MOF compounds, which is a necessary condition for catalytic oxidation processes. Particular attention will be addressed to the specific advantages of embedding a multinuclear transition metal cluster into a rigid 3D coordination framework (“entatic state catalyst”). Thus, the spectroscopic and catalytic properties of solid MOF catalysts shall be compared with special emphasis laid upon gas phase reactions. Quantum chemical investigations will address different oxidation states of the electronically coupled metal sites in multinuclear clusters, and their role in catalytic oxidation or oxygenation cycles. Density functional theory (DFT) based on general gradient approximation (GGA) and hybrid functionals is applied to investigate ground and excited state properties of the MOFs. Special attention will be paid to important properties like vibrational and UV/VIS spectroscopy as well as to the redox behaviour of the envisaged compounds.