Multi-stage Transformations of a Cluster-Based Metal-Organic Framework: Perturbing Crystals to Glass-Forming Liquids that Re-Crystallize at High Temperature |
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| Authors: | Ming-Zhu Chen Jian Li Sheng Liao Yi-Hang Guo Tao Liu Rui-Fang Ma Tian-Yi Xie Wei-Dong Liu Dr Si-Xu Peng Prof?Dr Xiaojun Kuang Dr Zheng Yin Dr Yingbo Zhao Prof?Dr Ming-Hua Zeng |
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| Institution: | 1. School of Chemistry and Pharmaceutical Sciences, State Key Laboratory for Chemistry and Molecular Engineering of Medicinal Resources, Guangxi Normal University, Guilin, 541004 P. R. China;2. Hubei Collaborative Innovation Center for Advanced Organic Chemical Materials, Ministry of Education Key Laboratory for the Synthesis and Application of Organic Functional Molecules, College of Chemistry and Chemical Engineering, Hubei University, Wuhan, 430062 P. R. China;3. Guangxi Key Laboratory of Electrochemical and Magneto-Chemical Function Materia, College of Chemistry and Bioengineering, Guilin University of Technology, Guilin, 541004 P. R. China;4. School of Physical Science and Technology, Shanghai Key Laboratory of High-resolution Electron Microscopy, ShanghaiTech University, Shanghai, 201210 P. R. China |
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| Abstract: | Glassy and liquid state metal–organic frameworks (MOFs) are emerging type of materials subjected to intense research for their rich physical and chemical properties. In this report, we obtained the first glassy MOF that involves metal-carboxylate cluster building units via multi-stage structural transformations. This MOF is composed of linear Mn3(COO)6] node and flexible pyridyl-ethenylbenzoic linker. The crystalline MOF was first perturbed by vapor hydration and thermal dehydration to give an amorphous state, which can go through a glass transition at 505 K into a super-cooled liquid. The super-cooled liquid state is stable through a wide temperature range of 40 K and has the largest fragility index of 105, giving a broad processing window. Remarkably, the super-cooled liquid can not only be quenched into glass, but also recrystallize into the initial MOF when heated to a higher temperature above 558 K. The mechanism of the multi-stage structural transformations was studied by systematic characterizations of in situ X-ray diffraction, calorimetry, rheological, spectroscopic and pair-distribution function analysis. These multi-stage transformations not only represent a rare example of high temperature coordinative recognition and self-assembly, but also provide new MOF processing strategy through crystal-amorphous-liquid-crystal transformations. |
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| Keywords: | Cluster-Based MOF Glass-Forming Liquid Recrystallization Sequential Perturbation Structural Transformation |
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