Structure property relationships affecting the proton conductivity in imidazole loaded Al-MOFs†
Abstract
The structures of the imidazole loaded derivatives of Al-MIL-53 [Al(OH)(1,4-BDC-(CH3)x)] (x = 0, 1, 2) and CAU-11 ([Al(OH)(SDBA)]) (1,4-H2BDC = terephthalic acid; H2SDBA = 4,4′-sulfonyldibenzoic acid) were determined from powder X-ray diffraction data. Impedance spectroscopy measurements were carried out to evaluate their proton conductivities under anhydrous conditions at temperatures up to 110 °C. In Al-MIL-53-(CH3)x_HIm (x = 0, 1, 2) the formation of hydrogen bonds between the framework and the guest molecules results in a decrease in proton conductivity (x0 = 1.7 × 10−6, x1 = 1.9 × 10−8 and x2 = 1.7 × 10−9 S cm−1 at 110 °C and Eact = 0.42, 0.41 and 0.46 eV, for 0, 1 and 2 CH3-groups, respectively). The highest conductivity has been measured for CAU-11_HIm with 3.0 × 10−4 S cm−1 at 110 °C (Eact = 0.19 eV), where no host–guest hydrogen bonding interactions are observed.
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