Nanostructure of Polyoxometalate-Ionic Liquids: Effects of Anion Geometry and Cation Chain Length
Polyoxometalate-ionic liquids (POM-ILs) show promise for catalysis and energy storage, but how molecular structure controls nanostructure remains unclear. This study uses small-angle X-ray scattering to examine how POM geometry and cation chain length affect self-assembly in four systems combining Keggin ([SiW<sub>11</sub>O<sub>39</sub>]<sup>8-</sup>) or Dawson ([P<sub>2</sub>W<sub>18</sub>O<sub>62</sub>]<sup>6-</sup>) polyoxometalates with tetraoctylammonium (Q<sub>8</sub><sup>+</sup>) or hexadecyltributylphosphonium (Q<sub>16</sub><sup>+</sup>) cations. Keggin-Q<sub>8</sub> remained solid because the high POM charge density (-8) overwhelms the limited disorder imparted by the octyl chains. Dawson-Q<sub>8</sub> formed a liquid with a 22.1 Å spacing, matching simple volume-fraction packing. Both Q<sub>16</sub> systems produced liquids with an amphiphilic nanostructure. The repeat spacings of Dawson-Q<sub>16</sub> (34.5 Å) and Keggin-Q<sub>16</sub> (28.5 Å) exceed volume-fraction predictions by 75% and 45%, respectively, due to solvophobic self-assembly into polar/apolar domains. These results demonstrate that the POM charge density and cation chain length control liquid formation and the nanostructure.
Authors
- Zahra Nazar
- Zahra Mohammadizadeh Tahroudi
- Rob Atkin
- Muhammad Sajid
- Gregory G. Warr
Institutions
- Bahauddin Zakariya University (PK)
- The University of Sydney (AU)
- The University of Western Australia (AU)
Publication Details
- Journal
- The Journal of Physical Chemistry Letters
- Published
- 2026-02-14
- DOI
- https://doi.org/10.1021/acs.jpclett.5c03715
- Primary Topic
- Polyoxometalates: Synthesis and Applications
- Type
- article
- Field-Weighted Citation Impact
- 0.00