The synthesis of materials possessing enzyme-like active sites is one of the long standing dream of any chemist. Exploiting a synthetic procedure developed at the University of Minnesota for Co-Co and Co-Al species, single bimetallic units constituted by earth abundant metals (Co-Mn and Fe-Mn) were installed on the Zr6O8 nodes of NU-1000 metal organic framework by grafting and calcination of CoMnOPh(py3tren) and FeMnOPh(py3tren) precursors. The structure of the CoMn- and FeMn- hydroxy species on the NU-1000 nodes was investigated by DFT methods and by X-ray absorption spectroscopy. The position of the Mn-based species before and after calcination in the MOF pores was determined through indirect (N2 volumetry) and direct techniques (difference envelope density analysis, DED), providing the same description of the complex position. Electron dispersion spectroscopy associated with TEM imaging allows to evidence a uniform distribution of the metallic species along the MOF crystals. The effective loading per MOF node was evaluated by means of 1H NMR of digested MOF and Inductively Coupled Plasma (ICP-OES). These materials were then tested for their ability to perform heterogenous catalysis such as olefin epoxidation, benzene to phenol oxidation and oxidative dehydrogenation of N-heterocycles. The larger activity of these species with respect to previously reported metallo-organic catalysts suggests their potentiality also for more challenging reactions as dehydrogenation of propane or the oxidation of methane in analogy with their Cu and Co-Co analogues. A theoretical investigation was conducted in this sense and extended to generic Fe-based bimetallic systems to direct the synthetic efforts on optimal catalysts for ODH of propane.

Immobilization of earth abundant metals coordinated in heterobimetallic ligand scaffolds on metal organic frameworks (MOFs)

255th National Meeting (2018)

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