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31
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Seminari: "Modeling the structure and properties of Metal-Organic Frameworks with open metal sites"

Dates:

31-05-2018

Horari:

12:00

Organitza:

Dep. de Química Inorgànica i Orgànica

Lloc:

Aula 202

Conferenciant: Prof. Petko Petkov (Uninversity of Sofia)

Resum: By means of Density Functional Theory a local and periodic structure of Metal-Organic Frameworks (MOF) was studied. Since MOFs are 3D crystalline materials composed of organic linkers and metal or metal-oxide, in addition to the periodic structure calculations, we can study their local properties on an isolated cluster fragments. In this way we have shown by DFT simulations, that using infrared spectroscopy of a probe molecule like CO can be used as a low cost monitoring method for defect concentration in HKUST-1 MOF. Combining DFT calculations with Pulsed Electron Paramagnetic Resonance Spectroscopic of CO, CO2, and methanol adsorption in HKUST-1 MOF, which exhibits an open metal Cu(II) sites , we have shown the potential of EPR spectroscopy for analyzing adsorption complexes in such porous materials and extracting structural information from the g- and A- tensor of the adsorbed complexes.  , The magnetic properties of the SURMOF-2 series of metal-organic frameworks are very interesting. The Cu(II)-ions within these crystalline nanoporous solids are connected via carboxylate-groups in a zipper-like fashion. This unusual coupling of the spin 1⁄2-ions within the resulting one-dimensional chains is found to stabilize a low-temperature, ferromagnetic phase. In contrast to other ordered 1D-systems, no strong magnetic fields are needed to induce the ferromagnetism. The magnetic coupling constants describing the interaction between the individual metal ions have been determined in SQUID experiments and are found to be fully consistent with the results of our periodic DFT electronic structure calculations.

The collective framework motion in a specific class of MOFs called flexible MOFs is a subject of another study. As an example we have studied DUT-8(Ni) MOF with Born-Oppenheimer DFT based molecular dynamics. In this computational experiment we have shown that the rotational isomerism in the linkers in MOFs is important for their framework flexibility and also, that the berating modes of the pore channels could be visualized by orientation dependent Raman spectroscopy experiment.


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