How Can a Hydrophobic MOF be Water-Unstable? Insight into the Hydration Mechanism of IRMOFs
How Can a Hydrophobic MOF be Water-Unstable? Insight into the Hydration Mechanism of IRMOFs
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DOI：
10.1002/cphc.201200455
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发表时间：
2012-10-22
期刊：
影响因子：
2.9
通讯作者：
Fuchs, Alain H.
中科院分区：
文献类型：
--
作者：
De Toni, Marta;Jonchiere, Romain;Fuchs, Alain H.
我们报告了一个模型IRMOF材料的水化过程的从头算分子动力学研究。在低水含量（每单位细胞一个分子），水的物理吸附上观察到的锌阳离子，但自由？束缚平衡强烈地倾向于自由态。这与在经典的Monte Carlo模拟中观察到的基质的疏水性质及其V型等温线是一致的。在较高的负载，水簇可以形成在Zn4O网站，这是稳定的水结合状态。这种结构迅速转变为连接体置换状态，其中水完全置换了连接体的一个臂，这对应于材料完全有序结构的丧失。因此，整体疏水的MOF材料也可能变得对水不稳定，这是一个迄今为止尚未完全理解的特征。
We report an ab initio molecular dynamics study of the hydration process in a model IRMOF material. At low water content (one molecule per unit cell), water physisorption is observed on the zinc cation but the free?bound equilibrium strongly favors the free state. This is consistent with the hydrophobic nature of the host matrix and its type-V isotherm observed in a classical Monte Carlo simulation. At higher loading, a water cluster can be formed at the Zn4O site and this is shown to stabilize the water-bound state. This structure rapidly transforms into a linker-displaced state, where water has fully displaced one arm of a linker and which corresponds to the loss of the materials fully ordered structure. Thus an overall hydrophobic MOF material can also become water unstable, a feature that has not been fully understood until now.