Mhatre Chinmay V, Wardzala Jacob J, Shukla Priyanka B, Agrawal Mayank, Johnson J Karl
Department of Chemical and Petroleum Engineering, University of Pittsburgh, Pittsburgh, PA 15260, USA.
TCAD, TSMC Technoloy Inc., San Jose, CA 95051, USA.
Nanomaterials (Basel). 2023 Jun 2;13(11):1793. doi: 10.3390/nano13111793.
The UiO-6x family of metal-organic frameworks has been extensively studied for applications in chemical warfare agent (CWA) capture and destruction. An understanding of intrinsic transport phenomena, such as diffusion, is key to understanding experimental results and designing effective materials for CWA capture. However, the relatively large size of CWAs and their simulants makes diffusion in the small-pored pristine UiO-66 very slow and hence impractical to study directly with direct molecular simulations because of the time scales required. We used isopropanol (IPA) as a surrogate for CWAs to investigate the fundamental diffusion mechanisms of a polar molecule within pristine UiO-66. IPA can form hydrogen bonds with the μ3-OH groups bound to the metal oxide clusters in UiO-66, similar to some CWAs, and can be studied by direct molecular dynamics simulations. We report self, corrected, and transport diffusivities of IPA in pristine UiO-66 as a function of loading. Our calculations highlight the importance of the accurate modeling of the hydrogen bonding interactions on diffusivities, with about an order of magnitude decrease in diffusion coefficients when the hydrogen bonding between IPA and the μ3-OH groups is included. We found that a fraction of the IPA molecules have very low mobility during the course of a simulation, while a small fraction are highly mobile, exhibiting mean square displacements far greater than the ensemble average.
金属有机框架材料UiO - 6x家族已被广泛研究用于化学战剂（CWA）的捕获和销毁。理解诸如扩散等内在传输现象是理解实验结果和设计用于CWA捕获的有效材料的关键。然而，由于CWA及其模拟物的尺寸相对较大，使得它们在小孔径的原始UiO - 66中的扩散非常缓慢，因此由于所需的时间尺度，直接用直接分子模拟来研究是不切实际的。我们使用异丙醇（IPA）作为CWA的替代物来研究极性分子在原始UiO - 66中的基本扩散机制。IPA可以与UiO - 66中与金属氧化物簇结合的μ3 - OH基团形成氢键，这与一些CWA类似，并且可以通过直接分子动力学模拟进行研究。我们报告了原始UiO - 66中IPA的自扩散系数、校正扩散系数和传输扩散系数随负载量的变化情况。我们的计算突出了氢键相互作用的精确建模对扩散系数的重要性，当考虑IPA与μ3 - OH基团之间的氢键时，扩散系数大约降低了一个数量级。我们发现，在模拟过程中，一部分IPA分子的迁移率非常低，而一小部分分子具有很高的迁移率，其均方位移远大于总体平均值。
