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.

我们报道了由[NaP5W30O110]14–与Mn、Fe、Co、Ni、Cu或Zn桥联金属离子组装得到的金属氧化物骨架的合成方法。X射线衍射（X-ray diffraction）结果显示，无论采用何种桥联金属离子，该类骨架均遵循相同的组装模式。此外，本合成策略可实现混合金属离子桥联的同构骨架组装，或是对簇基结构进行Mo掺杂后组装得到骨架，从而实现高度丰富的组分多样性。这种一致的组装模式，使得我们能够探究结构基元在金属氧化物骨架性能中所发挥的作用。与未桥联的骨架相比，桥联金属离子的存在可提升骨架的导电性，其中以Fe作为桥联金属离子的骨架导电性最优。此外，Mo掺杂可进一步提升该类骨架的导电性。通过将簇中心的Na+替换为Bi3+或Sm3+，也可获得类似的骨架结构。总体而言，通过选择桥联金属离子与簇基结构基元，可调控该类簇基骨架的光电性能，并展现出这类簇基骨架的涌现特性。本研究结果证明，以多金属氧簇（polyoxometalate clusters）作为结构基元，可用于制备具有可调谐性能与涌现特性的复杂金属氧化物材料，展现出良好的应用前景。