Molecular Interactions of a Cu-Based Metal-Organic Framework with a Confined Imidazolium-Based Ionic Liquid

A Combined Density Functional Theory and Experimental Vibrational Spectroscopy Study

Nilesh R. Dhumal, Manish P. Singh, James A. Anderson, Johannes Kiefer, Hyung J. Kim*

*Corresponding author for this work

Research output: Contribution to journalArticle

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Abstract

The interactions between a Cu-based metal-organic framework (MOF), Cu-BTC, and an ionic liquid (IL), 1-ethyl-3-methylimidazolium ethyl sulfate, were studied by employing density functional theory (DFT) calculations and vibrational spectroscopy. The Fourier transform infrared (FTIR) and Raman spectra show that the confinement of the IL in the MOF has significant impact on the structure of the MOF as well as on the IL. Raman spectra and DFT calculations reveal a perturbation of the symmetry of the MOF structure due to the interaction of the IL anion with the Cu ions. FTIR and Raman spectra show that the molecular interactions in turn influence the structure of the ion pair. Inside the MOF, two different types of structure of IL ion pairs are formed. One ion-pair structure exhibits enhanced interionic interactions by strengthening the hydrogen bonding between cation and anion, whereas the other structure corresponds to weaker interactions between the IL cation and anion. Moreover, it is shown that the IL imidazolium ring can directly interact with either the MOF or the anion. The difference electron density analysis by DFT calculations indicates that molecular interactions of MOF and IL are accompanied by a transfer and redistribution of electron density.

Original languageEnglish
Pages (from-to)3295-3304
Number of pages10
JournalThe Journal of Physical Chemistry C
Volume120
Issue number6
Early online date25 Jan 2016
DOIs
Publication statusPublished - 18 Feb 2016

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Ionic Liquids
Vibrational spectroscopy
Molecular interactions
molecular interactions
Ionic liquids
Density functional theory
Metals
density functional theory
liquids
metals
spectroscopy
Anions
Negative ions
Ions
anions
Raman scattering
Raman spectra
Carrier concentration
Cations
Fourier transforms

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Electronic, Optical and Magnetic Materials
  • Surfaces, Coatings and Films
  • Energy(all)

Cite this

Molecular Interactions of a Cu-Based Metal-Organic Framework with a Confined Imidazolium-Based Ionic Liquid : A Combined Density Functional Theory and Experimental Vibrational Spectroscopy Study. / Dhumal, Nilesh R.; Singh, Manish P.; Anderson, James A.; Kiefer, Johannes; Kim, Hyung J.

In: The Journal of Physical Chemistry C, Vol. 120, No. 6, 18.02.2016, p. 3295-3304.

Research output: Contribution to journalArticle

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title = "Molecular Interactions of a Cu-Based Metal-Organic Framework with a Confined Imidazolium-Based Ionic Liquid: A Combined Density Functional Theory and Experimental Vibrational Spectroscopy Study",
abstract = "The interactions between a Cu-based metal-organic framework (MOF), Cu-BTC, and an ionic liquid (IL), 1-ethyl-3-methylimidazolium ethyl sulfate, were studied by employing density functional theory (DFT) calculations and vibrational spectroscopy. The Fourier transform infrared (FTIR) and Raman spectra show that the confinement of the IL in the MOF has significant impact on the structure of the MOF as well as on the IL. Raman spectra and DFT calculations reveal a perturbation of the symmetry of the MOF structure due to the interaction of the IL anion with the Cu ions. FTIR and Raman spectra show that the molecular interactions in turn influence the structure of the ion pair. Inside the MOF, two different types of structure of IL ion pairs are formed. One ion-pair structure exhibits enhanced interionic interactions by strengthening the hydrogen bonding between cation and anion, whereas the other structure corresponds to weaker interactions between the IL cation and anion. Moreover, it is shown that the IL imidazolium ring can directly interact with either the MOF or the anion. The difference electron density analysis by DFT calculations indicates that molecular interactions of MOF and IL are accompanied by a transfer and redistribution of electron density.",
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AU - Singh, Manish P.

AU - Anderson, James A.

AU - Kiefer, Johannes

AU - Kim, Hyung J.

N1 - This work was supported in part by NSF Grant CHE-1223988 and by EPSRC Grant EP/K00090X/1.

PY - 2016/2/18

Y1 - 2016/2/18

N2 - The interactions between a Cu-based metal-organic framework (MOF), Cu-BTC, and an ionic liquid (IL), 1-ethyl-3-methylimidazolium ethyl sulfate, were studied by employing density functional theory (DFT) calculations and vibrational spectroscopy. The Fourier transform infrared (FTIR) and Raman spectra show that the confinement of the IL in the MOF has significant impact on the structure of the MOF as well as on the IL. Raman spectra and DFT calculations reveal a perturbation of the symmetry of the MOF structure due to the interaction of the IL anion with the Cu ions. FTIR and Raman spectra show that the molecular interactions in turn influence the structure of the ion pair. Inside the MOF, two different types of structure of IL ion pairs are formed. One ion-pair structure exhibits enhanced interionic interactions by strengthening the hydrogen bonding between cation and anion, whereas the other structure corresponds to weaker interactions between the IL cation and anion. Moreover, it is shown that the IL imidazolium ring can directly interact with either the MOF or the anion. The difference electron density analysis by DFT calculations indicates that molecular interactions of MOF and IL are accompanied by a transfer and redistribution of electron density.

AB - The interactions between a Cu-based metal-organic framework (MOF), Cu-BTC, and an ionic liquid (IL), 1-ethyl-3-methylimidazolium ethyl sulfate, were studied by employing density functional theory (DFT) calculations and vibrational spectroscopy. The Fourier transform infrared (FTIR) and Raman spectra show that the confinement of the IL in the MOF has significant impact on the structure of the MOF as well as on the IL. Raman spectra and DFT calculations reveal a perturbation of the symmetry of the MOF structure due to the interaction of the IL anion with the Cu ions. FTIR and Raman spectra show that the molecular interactions in turn influence the structure of the ion pair. Inside the MOF, two different types of structure of IL ion pairs are formed. One ion-pair structure exhibits enhanced interionic interactions by strengthening the hydrogen bonding between cation and anion, whereas the other structure corresponds to weaker interactions between the IL cation and anion. Moreover, it is shown that the IL imidazolium ring can directly interact with either the MOF or the anion. The difference electron density analysis by DFT calculations indicates that molecular interactions of MOF and IL are accompanied by a transfer and redistribution of electron density.

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