Christensen Rasmus, Bokor Bleile Yossi, Sørensen Søren S, Biscio Christophe A N, Fajstrup Lisbeth, Smedskjaer Morten M
Department of Chemistry and Bioscience, Aalborg University, Aalborg 9220, Denmark.
Department of Mathematical Sciences, Aalborg University, Aalborg 9220, Denmark.
J Phys Chem Lett. 2023 Aug 24;14(33):7469-7476. doi: 10.1021/acs.jpclett.3c00962. Epub 2023 Aug 14.
Metal-organic framework (MOF) glasses have multiple potential applications, as they combine advantages of traditional glasses with those of MOFs. The melt-quenching process used to form MOF glasses typically leads to a significant decrease in porosity, but the structural origin of this thermally induced pore collapse remains largely unknown. Here, we study the melting process of three zeolitic imidazolate frameworks (ZIFs), namely ZIF-4, ZIF-62, and ZIF-76, using molecular dynamics (MD) simulations. By analyzing the MD data using topological data analysis, we show that while the three ZIF systems exhibit similar short-range order structural changes upon heating, they exhibit significant differences in their medium-range order structure. Specifically, ZIF-76 retains more of its medium-range order structures in the liquid state compared to the other glass-forming ZIF systems, which allows it to remain more porous than ZIF-4 and ZIF-62. As such, our results may aid in understanding the structural features that govern the ability to maintain porosity in the melt-quenched glassy state.
金属有机框架（MOF）玻璃具有多种潜在应用，因为它们结合了传统玻璃和MOF的优点。用于形成MOF玻璃的熔体淬火过程通常会导致孔隙率显著降低，但这种热诱导孔隙坍塌的结构起源在很大程度上仍然未知。在这里，我们使用分子动力学（MD）模拟研究了三种沸石咪唑酯框架（ZIF），即ZIF-4、ZIF-62和ZIF-76的熔化过程。通过使用拓扑数据分析MD数据，我们表明，虽然这三个ZIF系统在加热时表现出相似的短程有序结构变化，但它们在中程有序结构上存在显著差异。具体而言，与其他玻璃形成ZIF系统相比，ZIF-76在液态时保留了更多的中程有序结构，这使其比ZIF-4和ZIF-62保持更多的孔隙率。因此，我们的结果可能有助于理解在熔体淬火玻璃态中控制保持孔隙率能力的结构特征。
