Du Zijuan, Qiao Ang, Zhou Hemin, Li Zhencai, Winters Wessel M W, Zhu Jiexin, He Guanjie, Parkin Ivan P, Tao Haizheng, Yue Yuanzheng
State Key Laboratory of Silicate Materials for Architectures (Wuhan University of Technology), Wuhan 430070, China.
Christopher Ingold Laboratory, Department of Chemistry, University College London, London WC1H 0AJ, UK.
Chem Commun (Camb). 2023 Oct 4;59(79):11871-11874. doi: 10.1039/d3cc02492j.
The high-density amorphous phases (HDAs) of bimetallic zeolitic imidazolate frameworks (Zn/Co-ZIF-4) were prepared. The temperature dependence of the isobaric heat capacity () of ZIF-4 HDAs was measured to determine the glass transition temperature () of HDAs. The non-linearly decreases with the molar ratio , where is Co/(Co + Zn), indicating the presence of a mixed-metal node effect. This effect arises from the non-linear increase of the degree of configurational freedom in the HDA as increases. The degree of configurational freedom is inversely correlated with the network connectivity, which is, in turn, affected by variations in the MN (M: Zn or Co; N: nitrogen) tetrahedral symmetry in the ZIF-4 HDA. Overall, this work offers valuable insights into the glass transition of metal-organic frameworks.
制备了双金属沸石咪唑酯骨架（Zn/Co-ZIF-4）的高密度非晶相（HDA）。测量了ZIF-4 HDA的等压热容（）随温度的变化，以确定HDA的玻璃化转变温度（）。随着摩尔比的增加，呈非线性下降，其中为Co/(Co + Zn)，表明存在混合金属节点效应。这种效应源于随着的增加，HDA中构型自由度的非线性增加。构型自由度与网络连通性呈负相关，而网络连通性又受ZIF-4 HDA中MN（M：Zn或Co；N：氮）四面体对称性变化的影响。总体而言，这项工作为金属有机骨架的玻璃化转变提供了有价值的见解。
