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Magnetism of Cu(II)-MOF-74 and its three mixed analogous compounds with Zn(II)

Metal-organic frameworks (MOFs) are the subject of intensive study due to their potential applications in ion exchange, drug delivery, hydrogen storage, gas separation, etc. These porous coordination polymers are comprised of metal ions/clusters that represent framework nodes and organic ligands as bonds between them. [1] M(II)-MOF-74 materials, where M(II) is a transition metal center, are widely researched for applications related to open metal sites, well-defined large channels in their honeycomb structure and also for their interesting magnetic properties arising from the complex connectivity of metal ions. Furthermore, it was shown that adsorption, stability and catalytic activity of M1(II)-MOF-74 were increased by the partial incorporation of a second metal center M2(II) in its structure, i.e. the existence of heterometal nodes.[2] We investigated magnetic properties of copper(II)-MOF-74 (Cu-MOF-74) and its three mixed analogous compounds with zinc(II). CuZn-MOF-74 and ZnCu-MOF-74 were obtained through different intermediate complexes, from magnetic Cu-INT and non-magnetic Zn-INT, respectively. The Alloyed-MOF-74 was obtained by mechanical alloying, growing the MOF-74 structure from mechanically amorphized Cu-MOF-74 and Zn-MOF-74 mixture by accelerated aging process.[3, 4] Magnetic properties of these compounds were studied by static magnetization measurements, X-band electron paramagnetic resonance (EPR) spectroscopy, multifrequency high-field high-frequency EPR (HF-EPR) spectroscopy as well as theoretical models.

copper(II) ; magnetism ; EPR spectroscopy ; MOF-74

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