Abstract

In this study, we synthesized hybrid materials using well-Dawson polyoxometalates (POMs), K₇[H₄PW₁₈O₆₂]·18H₂O or K₆[P₂W₁₈O₆₂]·13H₂O and a room temperature ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF₄]). K, W, P and CHN elemental analysis showed that one mole of [H₄PW₁₈O₆₂]⁷⁻ reacts with 6 moles of BMIM⁺ and one mole of [P₂W₁₈O₆₂]⁶⁻ reacts with 4 moles of BMIM⁺ to form, respectively, K[BMIM]₆H₄PW₁₈O₆₂ and K₂[BMIM]₄P₂W₁₈O₆₂. X-ray diffraction illustrated amorphous structure of the hybrid materials. FT-IR spectra showed the presence of both 1-butyl-3-methylimidazolium cation and the Dawson anion. TG analysis displayed a relative thermal stability of the hybrid materials compared to the parents Dawson POMs. Cyclic voltammetry showed that the reduction peak potentials of the Dawson anion in the hybrid materials shift towards negative values and the shift is more pronounced for K[BMIM]₆H₄PW₁₈O₆₂ compared to K₂[BMIM]₄P₂W₁₈O₆₂. This was attributed to a decrease in the acidity of the Dawson POM anion in the hybrid material.

Graphical abstract

Powder XRD patterns of (a) PW₁₈, (b) K[BMIM]₆H₄PW₁₈O₆₂, (c) P₂W₁₈, and (d) K₂[BMIM]₄P₂W₁₈O₆₂.

Research highlights

► 1-butyl-3-methylimidazolium tetrafluoroborate([BMIM][BF₄]) reacts with K₇[H₄PW₁₈O₆₂]·18H₂O to form K[BMIM]₆H₄PW₁₈O₆₂. ► [BMIM][BF₄] reacts with K₆[P₂W₁₈O₆₂]·13H₂O to form K₂[BMIM]₄P₂W₁₈O₆₂. ► K[BMIM]₆H₄PW₁₈O₆₂ and K₂[BMIM]₄P₂W₁₈O₆₂ displayed amorphous structures. ► K[BMIM]₆H₄PW₁₈O₆₂ and K₂[BMIM]₄P₂W₁₈O₆₂ illustrated low water content. ► K[BMIM]₆H₄PW₁₈O₆₂ and K₂[BMIM]₄P₂W₁₈O₆₂ showed improved thermal stability.