Molecular Packing-Dependent Thermal Expansion Behaviors in Metal Squarate Frameworks,Chemistry of Materials

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Molecular Packing-Dependent Thermal Expansion Behaviors in Metal Squarate Frameworks
Chemistry of Materials ( IF 7.2 ) Pub Date : 2020-03-19 , DOI: 10.1021/acs.chemmater.9b04981
Zhanning Liu _{1,

2} , Rui Ma ₁ , Jinxia Deng ₁ , Jun Chen ₁ , Xianran Xing ₁

Affiliation

Packing mode of the molecules in materials has a great influence on materials’ physical and chemical properties. Herein, we investigated three metal squarate frameworks (Zn_sq_C, Cd_sq_C, and Cd_sq_R) with similar crystal structures. While owing to the difference in the packing mode of the squarate ligand, two kinds of structures can be achieved (cubic phase and trigonal phase). Synchrotron powder X-ray diffraction analyses show that the three compounds exhibit dramatically different thermal expansion behaviors, including positive thermal expansion (PTE), zero thermal expansion (ZTE), and negative thermal expansion (NTE). By directly structural comparison, it is found that, owing to the unique “eclipsed packing mode”, the trigonal phase (Cd_sq_R) can undergo a “wine-rack” distortion upon heating, which makes a great contribution to the NTE behavior, while this “wine-rack” distortion is forbidden in the “staggered packing” cubic phase. Furthermore, single-crystal X-ray diffraction and synchrotron X-ray total scattering analyses shed light on that the difference in magnitude of rotation of the squarate ligand may be responsible for the different thermal expansion behaviors. The present study shows how the proper alignment of the building blocks can be used to tailor materials’ thermal expansion behavior and can provide guidance for the rational design of novel NTE or ZTE materials.

中文翻译：

在金属正方形框架中依赖于分子堆积的热膨胀行为

材料中分子的堆积方式对材料的物理和化学性质有很大的影响。在这里，我们研究了具有相似晶体结构的三个金属方格框架（Zn_sq_C，Cd_sq_C和Cd_sq_R）。由于方形配体的堆积方式的不同，可以实现两种结构（立方相和三角相）。同步加速器粉末X射线衍射分析表明，这三种化合物表现出显着不同的热膨胀行为，包括正热膨胀（PTE），零热膨胀（ZTE）和负热膨胀（NTE）。通过直接的结构比较发现，由于独特的“黯淡堆积模式”，三角相（Cd_sq_R）在加热时会发生“酒架”变形，这为NTE行为做出了巨大贡献，而在“交错堆积”立方相中则禁止这种“酒架”形变。此外，单晶X射线衍射和同步加速器X射线全散射分析揭示了方晶配体旋转幅度的差异可能是造成不同热膨胀行为的原因。本研究表明如何正确使用构件的对齐方式来调整材料的热膨胀性能，并为合理设计新型NTE或ZTE材料提供指导。单晶X射线衍射和同步加速器X射线全散射分析揭示了方晶配体旋转幅度的差异可能是造成不同热膨胀行为的原因。本研究表明如何正确使用构件的对齐方式来调整材料的热膨胀性能，并为合理设计新型NTE或ZTE材料提供指导。单晶X射线衍射和同步加速器X射线全散射分析揭示了方晶配体旋转幅度的差异可能是造成不同热膨胀行为的原因。本研究表明如何正确使用构件的对齐方式来调整材料的热膨胀性能，并为合理设计新型NTE或ZTE材料提供指导。

更新日期：2020-04-23

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