Haigis Volker, Coudert François-Xavier, Vuilleumier Rodolphe, Boutin Anne, Fuchs Alain H
École Normale Supérieure, PSL Research University, Département de Chimie, Sorbonne Universités - UPMC Univ Paris 06, CNRS UMR 8640 PASTEUR, 24 rue Lhomond, 75005 Paris, France.
PSL Research University, Chimie ParisTech - CNRS, Institut de Recherche de Chimie Paris, 75005 Paris, France.
J Phys Chem Lett. 2015 Nov 5;6(21):4365-70. doi: 10.1021/acs.jpclett.5b01926. Epub 2015 Oct 20.
Flexible metal-organic frameworks, also known as soft porous crystals, have been proposed for a vast number of technological applications, because they respond by large changes in structure and properties to small external stimuli, such as adsorption of guest molecules and changes in temperature or pressure. While this behavior is highly desirable in applications such as sensing and actuation, their extreme flexibility can also be synonymous with decreased stability. In particular, their performance in industrial environments is limited by a lack of stability at elevated temperatures and in the presence of water. Here, we use first-principles molecular dynamics to study the hydrothermal breakdown of soft porous crystals. Focusing on the material MIL-53(Ga), we show that the weak point of the structure is the bond between the metal center and the organic linker and elucidate the mechanism by which water lowers the activation free energy for the breakdown. This allows us to propose strategies for the synthesis of MOFs with increased heat and water stability.
柔性金属有机框架材料，也被称为软多孔晶体，已被提出用于大量技术应用中，因为它们会因诸如客体分子吸附以及温度或压力变化等微小外部刺激而在结构和性质上发生巨大变化。虽然这种行为在传感和驱动等应用中非常理想，但它们的极端柔性也可能意味着稳定性降低。特别是，它们在工业环境中的性能受到高温和有水存在时稳定性不足的限制。在此，我们使用第一性原理分子动力学来研究软多孔晶体的水热分解。以材料MIL-53(Ga)为重点，我们表明结构的弱点在于金属中心与有机连接体之间的键，并阐明了水降低分解活化自由能的机制。这使我们能够提出合成具有更高热稳定性和水稳定性的金属有机框架材料的策略。
