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Elucidating the Formation and Transformation Mechanisms of the Switchable Metal-Organic Framework ELM-11 by Powder and Single-Crystal EPR Study

Kultaeva A, Bon V, Weiss MS, Poeppl A, Kaskel S (2018)

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Publication Type: Journal article

Publication year: 2018

Journal

Book Volume: 57

Pages Range: 11920-11929

Journal Issue: 19

DOI: 10.1021/acs.inorgchem.8b01241

Abstract

The effect of the synthesis conditions on the structure and guest-responsive properties of a "gate pressure" metal-organic framework (MOF) with composition [Cu(4,4′-bipy)2(BF4)2]n (4,4′-bipy = 4,4′-bipyridine), also known as ELM-11 (ELM = elastic layer material) was investigated. Two different batches of ELM-11, synthesized from water-methanol and water-acetonitrile solutions, have been entirely characterized by PXRD, nitrogen (77 K) and carbon dioxide (195 K) physisorption, elemental analysis, DRIFT, TG, and SEM. Both ELM-11 samples were studied by electron paramagnetic resonance (EPR) spectroscopy in order to follow the change in the local structure of the copper ion during the activation and resolvation. Continuous wave X-band EPR measurements on powder samples provided an elongated octahedral coordination symmetry of the cupric ions and revealed different axial ligands in the as-synthesized and activated forms in both bulk samples of ELM-11. One of the procedures was amended in order to slow down the crystallization that allows isolation of single crystals of two polymorphic modifications of Cu-4,4′-bipyridine coordination polymers, namely [Cu(4,4′-bipy)2(CH3CN)2](BF4)2 and [Cu2O(4,4′-bipy)3(CH3CN)4](BF4)2, one of which shows a crystal structure similar to that of ELM-11. Further single-crystal EPR experiments on the as-synthesized material [Cu(4,4′-bipy)2(CH3CN)2](BF4)2 revealed the orientation of the g tensor of the cupric ions and proved that layers of acetonitrile-synthesized ELM-11 are arranged perpendicularly to the crystallographic c axis.

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How to cite

APA:

Kultaeva, A., Bon, V., Weiss, M.S., Poeppl, A., & Kaskel, S. (2018). Elucidating the Formation and Transformation Mechanisms of the Switchable Metal-Organic Framework ELM-11 by Powder and Single-Crystal EPR Study. Inorganic Chemistry, 57(19), 11920-11929. https://doi.org/10.1021/acs.inorgchem.8b01241

MLA:

Kultaeva, Anastasiia, et al. "Elucidating the Formation and Transformation Mechanisms of the Switchable Metal-Organic Framework ELM-11 by Powder and Single-Crystal EPR Study." Inorganic Chemistry 57.19 (2018): 11920-11929.

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