Geometric switching of linear to area negative thermal expansion in uniaxial metal-organic frameworks
Geometric switching of linear to area negative thermal expansion in uniaxial metal-organic frameworks
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DOI：
10.1039/c3ce42165a
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发表时间：
2014-01-01
期刊：
影响因子：
3.1
通讯作者：
Goodwin, Andrew L.
中科院分区：
文献类型：
--
作者：
Collings, Ines E.;Tucker, Matthew G.;Goodwin, Andrew L.
使用变温中子粉末衍射测量，我们表明，这两个石英类金属有机框架（MOFs）氘铟（III）对苯二甲酸和锌（II）异烟酸表现出各向异性的积极和消极的热膨胀（PTE/NTE）的行为。而在前者的NTE响应是单轴发生沿着六方晶轴，这种行为是在后者颠倒，PTE发生沿着六方轴和NTE是在整个平面的垂直方向。我们表明，这种机械响应的倒置可以单独用几何理由来解释;具体来说，我们确定了一个关键的框架几何形状，该几何形状划分了从线性到区域NTE响应的切换。扩展到其他常见的MOF拓扑结构的分析，我们建立了一个通用的预测方法，建立在大范围的不同的框架系统的NTE（或，通过扩展，负压缩性）响应的维度。我们的分析表明，框架的几何形状起着至关重要的作用，在确定力学响应的框架材料，通过铰链显示各向异性的响应。
Using variable-temperature neutron powder diffraction measurements, we show that the two quartz-like metal-organic frameworks (MOFs) deuterium indium(III) terephthalate and zinc(II) isonicotinate exhibit anisotropic positive and negative thermal expansion (PTE/NTE) behaviour. Whereas in the former the NTE response is uniaxial-occurring along the hexagonal crystal axis-this behaviour is inverted in the latter such that PTE occurs along the hexagonal axis and NTE is found in the entire plane of perpendicular directions. We show that this inversion of mechanical response can be explained on geometric grounds alone; specifically, we identify a critical framework geometry that demarcates a switch from linear to area NTE response. Extending this analysis to other common MOF topologies, we establish a generic predictive approach for establishing the dimensionality of NTE (or, by extension, negative compressibility) responses in a large range of different framework systems. Our analysis suggests that framework geometry plays a crucial role in determining the mechanical response of framework materials which show anisotropic responses via hinging.