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<p>Diffusion is ubiquitous in nature and many technological processes, particularly in catalysis and gas separations using nanoporous materials. Interpreting the loading dependence of the self-diffusion coefficient (<i>D</i><sub>self</sub>) of guest molecules in nanopores is imperative to understanding diffusion mechanisms. Pulse gradient field (PFG) NMR is a powerful technique for measuring the <i>D</i><sub>self</sub> of target molecules under various pressures. However, the maximum pressures of commercial NMR tubes (usually&lt;14.0 bar, 1 bar= 101325 Pa) are not high enough to investigate in realistic conditions or a wider pressure range. Herein, we developed a high-pressure tube (HP tube, up to 120 bar) for accurate <i>D</i><sub>self</sub> measurements, particularly in nanoporous material systems, featuring rapid sample loading and recovery. This HP tube bypasses the pressure-resistant design of diameter reduction and is equipped with a suite of sample fill tools, facilitating quick solids loading and non-destructive recovery. Its application to methane diffusion in DNL-6 (RHO) molecular sieve reveals the specifically confined diffusion, highlighting the confinement effect of the d8r structure. The HP NMR tube was confirmed to be a safe and reliable solution for high-pressure diffusion investigation via PFG NMR. This contribution advances molecular transport understanding and enables researchers to optimize materials for energy and catalysis technologies.</p>

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A High-pressure NMR Tube for PFG Diffusion Studies: Revealing the Specific Confinement in RHO Zeolite

  • 期刊论文

  • 发表日期：

    2025年10月14日

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  • Caiyi Lou,
  • Fangxiu Ye,
  • Shutao Xu,
  • Yingxu Wei,
  • Zhongmin Liu

摘要

Diffusion is ubiquitous in nature and many technological processes, particularly in catalysis and gas separations using nanoporous materials. Interpreting the loading dependence of the self-diffusion coefficient (Dself) of guest molecules in nanopores is imperative to understanding diffusion mechanisms. Pulse gradient field (PFG) NMR is a powerful technique for measuring the Dself of target molecules under various pressures. However, the maximum pressures of commercial NMR tubes (usually<14.0 bar, 1 bar= 101325 Pa) are not high enough to investigate in realistic conditions or a wider pressure range. Herein, we developed a high-pressure tube (HP tube, up to 120 bar) for accurate Dself measurements, particularly in nanoporous material systems, featuring rapid sample loading and recovery. This HP tube bypasses the pressure-resistant design of diameter reduction and is equipped with a suite of sample fill tools, facilitating quick solids loading and non-destructive recovery. Its application to methane diffusion in DNL-6 (RHO) molecular sieve reveals the specifically confined diffusion, highlighting the confinement effect of the d8r structure. The HP NMR tube was confirmed to be a safe and reliable solution for high-pressure diffusion investigation via PFG NMR. This contribution advances molecular transport understanding and enables researchers to optimize materials for energy and catalysis technologies.