论文标题
弹性异质性控制软多孔晶体中的不对称吸附解吸
Elastic heterogeneity governs asymmetric adsorption-desorption in a soft porous crystal
论文作者
论文摘要
金属 - 有机框架（MOF）具有高度的结晶度和具有可调的无机节点和有机接头的大表面积，具有较高的刺激反应性和分子吸附选择性，可实现各种应用。 MOF的吸附改变了晶体结构和弹性模量。因此，吸附/解吸位点的共存使宿主矩阵弹性异质。然而，弹性异质性在吸附 - 解吸转变中的作用已被忽略。在这里，我们显示了弹性异质性在吸附 - 解测转变中的不对称作用。我们构建了一个最小模型，其中包含吸附诱导的晶格膨胀/收缩，并增加/减少弹性模量。我们发现，熵和能量效应在吸附过程和解吸过程中变得不对称，从而妨碍了过渡，从而导致过渡的强滞后性质。此外，吸附/解吸的位点在空间上表现出空间异质的结构域的形成，这意味着吸附/解吸位点之间的域形态和界面区域可以通过弹性异质性来控制。我们的结果提供了一种理论指南，用于设计具有可调的吸附滞后式柔软的多孔晶体以及使用弹性异质性的吸附物的分散和结构域形态。
Metal--organic frameworks (MOFs), which possess a high degree of crystallinity and a large surface area with tunable inorganic nodes and organic linkers, exhibit high stimuli-responsiveness and molecular adsorption selectivity that enable various applications. The adsorption in MOFs changes the crystalline structure and elastic moduli. Thus, the coexistence of adsorbed/desorbed sites makes the host matrices elastically heterogeneous. However, the role of elastic heterogeneity in the adsorption--desorption transition has been overlooked. Here we show the asymmetric role of elastic heterogeneity in the adsorption--desorption transition. We construct a minimal model incorporating adsorption-induced lattice expansion/contraction and an increase/decrease in the elastic moduli. We discover that the transition is hindered by the entropic and energetic effects which become asymmetric in adsorption process and desorption process, leading to the strong hysteretic nature of the transition. Furthermore, the adsorbed/desorbed sites exhibit spatially heterogeneous domain formation, implying that the domain morphology and interfacial area between adsorbed/desorbed sites can be controlled by elastic heterogeneity. Our results provide a theoretical guideline for designing soft porous crystals with tunable adsorption hysteresis and the dispersion and domain morphology of adsorbates using elastic heterogeneity.
