The thermal properties of a series of twenty-four ionic liquids (ILs) have been determined by isothermal titration calorimetry (ITC) with the aim of simulating processes involving water sorption. For eleven water-free ILs, the molecular structures have been determined by X-ray crystallography in the solid state, which have been used to derive the molecular volumes of the ionic components of the ILs. Moreover, the structures reveal a high prevalence of hydrogen bonding in these compounds. A relationship between the molecular volumes and the experimentally determined energies of dilution could be established. The highest energies of dilution observed in this series were obtained for the acetate-based ILs, which underlines their potential as working fluids in sorption-based thermal energy storage systems.
Keywords: X-ray diffraction; ionic liquids; isothermal titration calorimetry; molecular volume; water sorption.
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