Cockayne Eric
Materials Measurement Science Division, Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899 USA.
Powder Diffr. 2019;34(3). doi: 10.1017/s0885715619000587.
We use density functional theory meta-GGA TPSS+D3(BJ)+U+J calculations to investigate the energetics and geometry of water molecules in the flexible metal-organic framework material MIL-53(Cr) as a function of cell volume. The critical concentration of water to cause the transition from the large pore () to the narrow pore () structure is estimated to be about 0.13 water molecule per Cr. At a concentration = 1 water molecule per Cr, the zero-temperature np and lp configurations each have a hydrogen bond between the H of each framework hydroxyl group and a water oxygen (O ). At intermediate volumes, water dimer-like configurations are observed. A concentration = 1.25 leads to hydrogen bonding between water molecules in the np phase that is absent for = 1. Our results suggest possible mechanisms for pore closing in hydrated MIL-53(Cr).
我们使用密度泛函理论的meta-GGA TPSS+D3(BJ)+U+J计算方法，研究了柔性金属有机骨架材料MIL-53(Cr)中水分子的能量学和几何结构随晶胞体积的变化。估计导致从大孔（）向窄孔（）结构转变的临界水浓度约为每Cr原子0.13个水分子。在每Cr原子有1个水分子的浓度下，零温度下的np和lp构型在每个骨架羟基的H与水氧（O ）之间都有一个氢键。在中间体积时，观察到类似水二聚体的构型。浓度 = 1.25时，np相中水分子之间会形成氢键，而浓度 = 1时则不存在这种氢键。我们的结果表明了水合MIL-53(Cr)中孔闭合的可能机制。
