Tunable Metal Oxide Frameworks via Coordination Assembly of Preyssler-Type Molecular Clusters

We present the synthesis of metal oxide frameworks composed
of
[NaP5W30O110]14– assembled with Mn, Fe, Co, Ni, Cu, or Zn bridging metal ions. X-ray
diffraction shows that the frameworks adopt the same assembly regardless
of bridging metal ion. Furthermore, our synthesis allows for the assembly
of isostructural frameworks with mixed-metal ion bridges, or with
clusters that have been doped with Mo, providing a high degree of
compositional diversity. This consistent assembly enables investigation
into the role of the building blocks in the properties of the metal
oxide frameworks. The presence of bridging metal ions leads to increased
conductivity compared to unbridged frameworks, and frameworks bridged
with Fe have the highest conductivity. Additionally, Mo-doping can
be used to enhance the conductivities of the frameworks. Similar structures
can be obtained from clusters in which the central Na+ has
been replaced with Bi3+ or Sm3+. Overall,
the optical and electronic properties are tunable via choice of bridging
metal ion and cluster building block and reveal emergent properties
in these cluster-based frameworks. These results demonstrate the promise
of using polyoxometalate clusters as building blocks for tunable complex
metal oxide materials with emergent properties.