Temperature-Induced Structural Transitions in the Gallium-Based MIL-53 Metal-Organic Framework
Temperature-Induced Structural Transitions in the Gallium-Based MIL-53 Metal-Organic Framework
复制标题
DOI：
10.1021/jp312179e
复制
发表时间：
2013-04-25
影响因子：
3.7
通讯作者：
Patarin, Joel
中科院分区：
文献类型：
--
作者：
Boutin, Anne;Bousquet, David;Patarin, Joel
我们报告了 Ga(OH,F)-MIL-53 的相行为的结构和热力学研究，Ga(OH,F)-MIL-53 是一种镓基金属有机骨架 (MOF)，具有 MIL-53 拓扑结构，其中含有 0.7 wt% 的氟键合到金属上。尽管存在一些小的结构差异，尤其是水合形式，但 Ga(OH,F)-MIL-53 的整体物理化学行为与标准无氟 Ga-MIL-53 材料非常相似。结合原位X射线衍射、原位傅里叶变换红外光谱、差示扫描量热法和热容测量，我们确定Ga(OH,F)-MIL-53在真空下（即空材料）表现出两个稳定相：低温下有利的无孔窄孔（np）相和高温下有利的大孔（lp）相，并伴有巨大的滞后效应。还对合成、活化和再水合后获得的水合材料Ga(OH,F)-MIL-53 _np_H2O进行了结构测定。密度泛函理论计算表明，在没有吸附水分子的情况下，Ga(OH,F)-MIL-53不是稳定的结构。相反，这种水合结构是 np 相的膨胀变体，其中柔性框架已膨胀以容纳水分子。
We report a structural and thermodynamic investigation of the phase behavior, of Ga(OH,F)-MIL-53, a gallium-based metal-organic framework (MOF) having the MIL-53 topology containing 0.7 wt % fluorine bonded to the metal. Despite some small structural differences, especially for the hydrated form, the overall physical chemistry behavior of Ga(OH,F)-MIL-53 is very similar to standard fluorine free Ga-MIL-53 material. A combination of in situ X-ray diffraction, in situ Fourier transform infrared spectroscopy, differential scanning calorimetry, and heat capacity measurements allowed us to establish that Ga(OH,F)-MIL-53 under vacuum (i.e., the empty material) exhibits two stable phases: a nonporous narrow-pore (np) phase favored at low temperature and a large-pore (lp) phase favored at high temperature, accompanied by a huge hysteresis effect. Structure determination of the hydrated material Ga(OH,F)-MIL-53 _np_H2O obtained after synthesis, activation, and rehydration was also performed. Density functional theory calculations show that it is not a stable structure of Ga(OH,F)-MIL-53 in the absence of adsorbed water molecules. Instead, this hydrated structure is a swollen variant of the np phase, where the flexible framework has expanded to accommodate water molecules.