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Theoretical model estimation of guest diffusion in metal-organic frameworks (MOFs)

机译：金属 - 有机框架访客扩散的理论模型估算（MOFS）

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Characterizing molecule diffusion in nanoporous matrices is critical to understanding the novel chemical and physical properties of metal-organic frameworks (MOFs). In this paper, we developed a theoretical model to rapidly and accurately compute the diffusion rate of guest molecules in a zeolitic imidazolate framework-8 (ZIF-8). The ideal gas or equilibrium solution diffusion model was modified to contain the effect of host framework via introducing the possibility of guests passing through the framework gate. The only input in our model is the energy barrier of guests passing through the MOF's gate. Molecular dynamics (MD) methods were employed to gather the guest density profile, which then was used to deduce the energy barrier values. This produced reliable results that require a simulation time of 5 picoseconds, which is much shorter when using pure MD methods (in the nanosecond scale). Also, we used density functional theory (DFT) methods to obtain the energy profile of guests passing through gates, as this does not require specification of a force field for the MOF degrees of freedom. In the DFT calculation, we only considered one gate of MOFs each time; as this greatly reduced the computational cost. Based on the obtained energy barrier values we computed the diffusion rate of alkane and alcohol in ZIF-8 using our model, which was in good agreement with experimental test results and the calculation values from a standard MD model. Our model shows the advantage of obtaining accurate diffusion rates for guests in MOFs for a lower computational cost and shorter calculation time. Thus, our analytic model calculation is especially attractive for high-throughput computational screening of the dynamic performance of guests in a framework.
机译：纳米多孔基质中的分子扩散的特征对于了解金属 - 有机框架（MOF）的新化学和物理性质至关重要。在本文中，我们开发了一种理论模型，可以快速，准确地计算沸石咪唑酯框架-8（ZIF-8）中的客体分子的扩散速率。修改了理想的气体或平衡溶液扩散模型，以通过引入穿过框架栅极的客人的可能性来遏制主机框架的效果。我们模型中唯一的输入是通过MOF大门的客人的能源屏障。采用分子动力学（MD）方法来收集客体密度曲线，然后用于推导能量阻隔值。这产生了可靠的结果，需要使用5皮秒的模拟时间，这在使用纯MD方法时更短（以纳秒刻度）。此外，我们使用了密度泛函理论（DFT）方法来获得通过栅极的客人的能量轮廓，因为这不需要规范MOF自由度的力场。在DFT计算中，我们每次只考虑一个MOF的一门;由于这大大降低了计算成本。基于所获得的能量阻隔值，我们使用我们的模型计算了ZIF-8中烷烃和醇的扩散速率，这与实验测试结果与标准MD模型的计算值吻合良好。我们的模型显示了为MOFS中获得准确扩散速率的优势，以实现较低的计算成本和更短的计算时间。因此，我们的分析模型计算对于高吞吐量计算筛选框架中的客人的动态性能特别有吸引力。

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  • 来源
    《RSC Advances》 |2015年第86期|共6页
  • 作者

    Zheng B.; Huang K-W; Du H.;

  • 作者单位

    Xian Univ Sci &

    Technol Sch Mat Sci &

    Engn Xian 710054 Peoples R China;

    King Abdullah Univ Sci &

    Technol KAUST Div Phys Sci &

    Engn Thuwal 239556900 Saudi Arabia;

    Xian Univ Sci &

    Technol Sch Mat Sci &

    Engn Xian 710054 Peoples R China;

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  • 正文语种 eng
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