A Preyssler-type polyoxometalate-based coordination supramolecule with proton conducting property.

A novel polyoxometalate-based coordination supramolecule was synthesized via a hydrothermal method. The compound exhibited high proton conductivity with good stability. Polyoxometalate skeleton, 2-methylimidazole ligands and water molecules provided continuous hydrogen bonds for the proton conduction. Kinetic studies indicated that the proton conduction mechanism of the compound followed the vehicle mechanism. Developing new low-cost and efficient proton-conducting materials remains an attractive and challenging task. Herein, a Preyssler-type polyoxometalate derived coordination compound had been synthesized with a hydrothermal method, namely, H 4.5 NaCo 5 (2-MI) 15.5 (2-MI) 3 [NaP 5 W 30 O 110 ]·5H 2 O (1) (where 2-methylimidazole is abbreviated as 2-MI, and partial 2-MI was deprotonated). The structure was characterized by single crystal X-ray diffraction, PXRD, FT-IR, TG, CHN and ICP-OES elemental analyses. We studied the relationship between the crystal structure and proton conduction of compound 1 and found that the presence of 2-MI reduced the leakage of polyoxometalate under high relative humidity. Meanwhile, the strong interaction of the counter cation Na+ with water is beneficial to form more hydrogen bonds. Compound 1 showed the maximum proton conductivity with a value of 4.42 × 10−3 S cm−1 at 367 K and 97% RH. Kinetic investigation indicates that the proton conduction mechanism of compound 1 follows the vehicle mechanism. [ABSTRACT FROM AUTHOR]