State Key Laboratory of Materials-Oriented Chemical Engineering and College of Chemistry and Molecular Engineering, Nanjing Tech University, Nanjing 211816, P. R. China.
Dalton Trans. 2019 Nov 26;48(46):17210-17216. doi: 10.1039/c9dt03960k.
As a class of anionic oxoclusters of early transition metals in their highest oxidation states, polyoxometalates (POMs) show considerable structural versatility and unique chemical and physical properties, making them promising multifunctional materials. In this study, a Keggin-type POM has been achieved, with a formula of [(H2O)0.3@K6(H2O)12]H4.45[PV7.45Mo4.55O40]·11H2O (1), and its microcrystals and nanocrystals have been obtained, respectively. This POM was characterized by elemental analysis for C, H and N, ICP-MS, TG, PXRD, SEM, X-band EPR and XPS techniques. Single crystal X-ray diffraction analysis demonstrated that 1 shows a rare extended structure with a high-connected three-dimensional (3D) all inorganic network of a Keggin-type POM, built from {Mo4.55V7.45PO40}10.45- polyoxoanions and {(H2O)0.3@K6(H2O)12}6+ clusters with CsCl-type crystal structure. In addition, to the best of our knowledge, 1 shows the highest ratio of vanadium to molybdenum among Keggin-type POMs reported thus far. Most interestingly, 1 exhibits intrinsic proton conduction below the freezing point of water, with a proton conductivity of 6.90 × 10-7 S cm-1 at 249 K and further reaching 3.36 × 10-6 S cm-1 at 272 K and Ea = 0.44 eV at 249-272 K.
作为早期过渡金属最高氧化态的一类阴离子氧簇合物，多金属氧酸盐（POMs）表现出相当大的结构多样性和独特的化学和物理性质，使其成为有前途的多功能材料。在本研究中，实现了一种 Keggin 型 POM，其化学式为[(H2O)0.3@K6(H2O)12]H4.45[PV7.45Mo4.55O40]·11H2O（1），并分别得到了其微晶和纳米晶。该 POM 通过 C、H 和 N 的元素分析、ICP-MS、TG、PXRD、SEM、X 波段 EPR 和 XPS 技术进行了表征。单晶 X 射线衍射分析表明，1 呈现出罕见的扩展结构，具有由{Mo4.55V7.45PO40}10.45-多氧阴离子和{(H2O)0.3@K6(H2O)12}6+簇构建的高连接三维（3D）全无机 Keggin 型 POM 网络，具有 CsCl 型晶体结构。此外，据我们所知，1 显示了迄今为止报道的 Keggin 型 POM 中钒与钼的最高比例。最有趣的是，1 在水的冰点以下表现出内在的质子传导，在 249 K 时质子电导率为 6.90×10-7 S cm-1，在 272 K 时进一步达到 3.36×10-6 S cm-1，Ea=0.44 eV 在 249-272 K 之间。
