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, and o-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.

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。MOF 内扩散的这种变化先前已在轻气体中得到证实，这归因于 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 内扩散和相关的 MOF 限制对扩散的影响。在这项工作中，¹³ C 脉冲场梯度 (PFG) NMR 用于量化甲醇、乙醇、对二甲苯和o-ZIF-71 型 MOF 晶体内的二甲苯，这些晶体分散在 Torlon 聚合物中以形成 MMM。将 MMM 中的内部 ZIF 自扩散率与在 ZIF-71 晶体床中测量的相应自扩散率进行比较。观察到的自扩散率对扩散时间的依赖性可以通过晶界效应来解释。在不确定性范围内，在 MMM 和 ZIF-71 床中，发现不受此类影响干扰的 ZIF 内自扩散率的相应值是相同的。解释了在 Torlon 中观察到的 ZIF-71 限制对扩散没有影响，并讨论了增加扩散选择性的选项。