Quantifying diffusion of organic liquids in a MOF component of MOF/Polymer mixed-matrix membranes by high field NMR
Quantifying diffusion of organic liquids in a MOF component of MOF/Polymer mixed-matrix membranes by high field NMR
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DOI：
10.1016/j.memsci.2021.119786
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发表时间：
2021-09
影响因子：
9.5
通讯作者：
Amineh Baniani;Matthew P. Rivera;Ryan P. Lively;S. Vasenkov
中科院分区：
文献类型：
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作者：
Amineh Baniani;Matthew P. Rivera;Ryan P. Lively;S. Vasenkov
将金属有机骨架（MOF）晶体限制在聚合物中以形成MOF/聚合物混合基质膜（MMM）可导致MOF内扩散的变化。这种MOF内扩散的变化先前已在轻质气体中得到证实，并归因于MOF框架灵活性的降低。然而，据我们所知，对于有机液体，还没有直接测量MMM中的MOF内扩散以及相关的MOF限制对扩散的影响的报道。在这项工作中，13 C脉冲场梯度（PFG）NMR被用来量化自扩散的甲醇，乙醇，对二甲苯，和对二甲苯内的MOF晶体的类型ZIF-71，分散在Torlon聚合物形成MMM。将MMM中的ZIF内自扩散系数与在ZIF-71晶体床中测量的相应自扩散系数进行比较。所观察到的自扩散系数对扩散时间的依赖性解释了晶界效应。在MMM和ZIF-71床中，未受此类影响扰动的ZIF内自扩散率的相应值在不确定性范围内相同。所观察到的ZIF-71限制在Torlon扩散的影响缺乏解释，并讨论了增加扩散选择性的选择。
Confinement of crystals of metal–organic frameworks (MOFs) in polymers to form MOF/polymer mixed-matrix membranes (MMMs) can lead to changes in intra-MOF diffusion. Such changes in intra-MOF diffusion were previously demonstrated for light gases, and attributed to a reduction in MOF framework flexibility. However, to our knowledge, no direct measurements of intra-MOF diffusion in MMMs and of the related MOF confinement effect on diffusion have been reported for organic liquids. In this work,13C pulsed field gradient (PFG) NMR was used to quantify self-diffusion of methanol, ethanol,p-xylene, ando-xylene inside MOF crystals of the type ZIF-71, which were dispersed in a Torlon polymer to form MMMs. The intra-ZIF self-diffusivities in the MMMs were compared with the corresponding self-diffusivities measured in beds of ZIF-71 crystals. The observed self-diffusivity dependencies on diffusion time were explained by crystal boundary effects. The corresponding values of intra-ZIF self-diffusivities not perturbed by such effects were found to be the same, within uncertainty, in the MMMs and ZIF-71 beds. The observed lack of an influence of the ZIF-71 confinement in Torlon on diffusion is explained, and an option to increase diffusion selectivity is discussed.