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 imi...
Highlights
Metal−organic frameworks (MOFs) constitute a new generation of porous crystalline materials, which are composed of metals or small clusters of metal sites connected by organic functional groups as linkers
To find the most likely binding site for the ionic liquid to interact with the MOF, it would be interesting to understand the localization of electron density within the MOF structure
It was found that the confinement of the ionic liquid (IL) in the MOF perturbs the symmetry of the MOF
Summary
Metal−organic frameworks (MOFs) constitute a new generation of porous crystalline materials, which are composed of metals or small clusters of metal sites connected by organic functional groups as linkers. MOFs are of great interest because of their exceptionally large surface areas, large pore volume, remarkable storage capacity, and controlled pore textures. They have recently received much attention because of their excellent properties for gas purification, catalysis, molecular sensing, and hydrogen storage.[1−6] MOFs are promising materials for the separation of gas mixtures, for example in the field of carbon capture and storage (CCS). The use of ionic liquids to replace organic solvents in biocatalytic processes has received much attention.[21,22]
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