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Isolating the Role of the Node-Linker Bond in the Compression of UiO-66 Metal–Organic Frameworks
Chemistry of Materials ( IF 7.2 ) Pub Date : 2020-06-17 , DOI: 10.1021/acs.chemmater.0c01922 Louis R. Redfern 1 , Maxime Ducamp 2 , Megan C. Wasson 1 , Lee Robison 1 , Florencia A. Son 1 , François-Xavier Coudert 2 , Omar K. Farha 1
Chemistry of Materials ( IF 7.2 ) Pub Date : 2020-06-17 , DOI: 10.1021/acs.chemmater.0c01922 Louis R. Redfern 1 , Maxime Ducamp 2 , Megan C. Wasson 1 , Lee Robison 1 , Florencia A. Son 1 , François-Xavier Coudert 2 , Omar K. Farha 1
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Understanding the mechanical properties of metal–organic frameworks (MOFs) is essential to the fundamental advancement and practical implementations of porous materials. Recent computational and experimental efforts have revealed correlations between mechanical properties and pore size, topology, and defect density. These results demonstrate the important role of the organic linker in the response of these materials to physical stresses. However, the impact of the coordination bond between the inorganic node and organic linker on the mechanical stability of MOFs has not been thoroughly studied. Here, we isolate the role of this node–linker coordination bond to systematically study the effect it plays in the compression of a series of isostructural MOFs, M-UiO-66 (M = Zr, Hf, or Ce). The bulk modulus (i.e., the resistance to compression under hydrostatic pressure) of each MOF is determined by in situ diamond anvil cell (DAC) powder X-ray diffraction measurements and density functional theory (DFT) simulations. These experiments reveal the distinctive behavior of Ce-UiO-66 in response to pressures under 1 GPa. In situ DAC Raman spectroscopy and DFT calculations support the observed differences in compressibility between Zr-UiO-66 and the Ce analogue. Monitoring changes in bond lengths as a function of pressure through DFT simulations provides a clear picture of those which shorten more drastically under pressure and those which resist compression. We hypothesize that the presence of ∼10% Ce3+ in the nodes of Ce-UiO-66 may contribute to the weakening of the node–linker coordination, manifesting in the distinct behavior under pressure. This study demonstrates that changes to the node–linker bond can have significant ramifications on the mechanical properties of MOFs.
中文翻译：
分离节点链接器键在UiO-66金属有机框架压缩中的作用
了解金属有机框架（MOF）的机械性能对于多孔材料的基础发展和实际实施至关重要。最近的计算和实验工作已经揭示了机械性能与孔径，拓扑和缺陷密度之间的相关性。这些结果证明了有机接头在这些材料对物理应力的响应中的重要作用。但是，尚未深入研究无机节点和有机连接基之间的配位键对MOFs机械稳定性的影响。在这里，我们分离了该节点-接头配位键的作用，以系统地研究它在一系列同构MOF M-UiO-66（M = Zr，Hf或Ce）的压缩中所起的作用。体积模量（即原位金刚石砧室（DAC）粉末X射线衍射测量和密度泛函理论（DFT）模拟。这些实验揭示了Ce-UiO-66在1 GPa以下压力下的独特行为。原位DAC拉曼光谱和DFT计算支持Zr-UiO-66和Ce类似物之间可观察到的压缩性差异。通过DFT模拟监测键长变化随压力的变化，可以清楚地看到在压力下急剧缩短的粘结长度和抵抗压缩的粘结长度。我们假设存在〜10％Ce 3+Ce-UiO-66节点中的碳原子可能会减弱节点-连接子的协调性，表现为在压力下的独特行为。这项研究表明，节点-接头键的变化可能对MOF的机械性能产生重大影响。
更新日期：2020-07-14
中文翻译：
分离节点链接器键在UiO-66金属有机框架压缩中的作用
了解金属有机框架（MOF）的机械性能对于多孔材料的基础发展和实际实施至关重要。最近的计算和实验工作已经揭示了机械性能与孔径，拓扑和缺陷密度之间的相关性。这些结果证明了有机接头在这些材料对物理应力的响应中的重要作用。但是，尚未深入研究无机节点和有机连接基之间的配位键对MOFs机械稳定性的影响。在这里，我们分离了该节点-接头配位键的作用，以系统地研究它在一系列同构MOF M-UiO-66（M = Zr，Hf或Ce）的压缩中所起的作用。体积模量（即原位金刚石砧室（DAC）粉末X射线衍射测量和密度泛函理论（DFT）模拟。这些实验揭示了Ce-UiO-66在1 GPa以下压力下的独特行为。原位DAC拉曼光谱和DFT计算支持Zr-UiO-66和Ce类似物之间可观察到的压缩性差异。通过DFT模拟监测键长变化随压力的变化，可以清楚地看到在压力下急剧缩短的粘结长度和抵抗压缩的粘结长度。我们假设存在〜10％Ce 3+Ce-UiO-66节点中的碳原子可能会减弱节点-连接子的协调性，表现为在压力下的独特行为。这项研究表明，节点-接头键的变化可能对MOF的机械性能产生重大影响。
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