Potentials and challenges of high-field PFG NMR diffusion studies with sorbates in nanoporous media
Potentials and challenges of high-field PFG NMR diffusion studies with sorbates in nanoporous media
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DOI：
10.1007/s10450-020-00255-y
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发表时间：
2020-08
期刊：
影响因子：
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通讯作者：
Amineh Baniani;Samuel Berens;Matthew P. Rivera;Ryan P. Lively;S. Vasenkov
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文献类型：
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作者：
Amineh Baniani;Samuel Berens;Matthew P. Rivera;Ryan P. Lively;S. Vasenkov
高磁场（高达17.6 T）与大磁场梯度（高达25 T/m）相结合，成功地利用脉冲场梯度（PFG）NMR研究气体和液体在纳米多孔材料中的扩散。在这篇小型综述中，我们选择了一些研究实例，展示了高场PFG NMR获得独特见解和区分各种类型扩散的能力。这些实例包括识别和解释分子大小与沸石咪唑酯骨架（ZIF）中气体的自扩散率之间的异常关系，以及揭示和解释在ZIF中混合不同连接剂对气体自扩散的影响。在通过将ZIF晶体分散在聚合物中形成的杂化膜中，对不同类型的正常和受限自扩散进行了定量。这种膜的高场PFG NMR研究允许观察和解释聚合物中的ZIF晶体限制对气体的ZIF内自扩散的影响。该技术还允许测量和理解混合山梨酸盐的异常单列扩散（SFD）。此外，所提出的实施例表明，高场PFG NMR与单晶红外显微镜相结合，以获得更大的物理洞察所研究的扩散过程的高潜力。
High magnetic fields (up to 17.6 T) in combination with large magnetic field gradients (up to 25 T/m) were successfully utilized in pulsed field gradient (PFG) NMR studies of gas and liquid diffusion in nanoporous materials. In this mini-review, we present selected examples of such studies demonstrating the ability of high field PFG NMR to gain unique insights and differentiate between various types of diffusion. These examples include identifying and explaining an anomalous relationship between molecular size and self-diffusivity of gases in a zeolitic imidazolate framework (ZIF), as well as revealing and explaining an influence of mixing different linkers in a ZIF on gas self-diffusion. Different types of normal and restricted self-diffusion were quantified in hybrid membranes formed by dispersing ZIF crystals in polymers. High field PFG NMR studies of such membranes allowed observing and explaining an influence of the ZIF crystal confinement in a polymer on intra-ZIF self-diffusion of gases. This technique also allowed measuring and understanding anomalous single-file diffusion (SFD) of mixed sorbates. Furthermore, the presented examples demonstrate a high potential of combining high field PFG NMR with single-crystal infrared microscopy (IRM) for obtaining greater physical insights into the studied diffusion processes.