Jin Eunji, Lee In Seong, Kim Dongwook, Lee Hosoowi, Jang Woo-Dong, Lah Myung Soo, Min Seung Kyu, Choe Wonyoung
Department of Chemistry, Ulsan National Institute of Science and Technology, 50 UNIST, Ulsan 44919, Republic of Korea.
Department of Chemistry, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 03722, Republic of Korea.
Sci Adv. 2019 May 10;5(5):eaav4119. doi: 10.1126/sciadv.aav4119. eCollection 2019 May.
Mechanical metamaterials exhibit unusual properties, such as negative Poisson's ratio, which are difficult to achieve in conventional materials. Rational design of mechanical metamaterials at the microscale is becoming popular partly because of the advance in three-dimensional printing technologies. However, incorporating movable building blocks inside solids, thereby enabling us to manipulate mechanical movement at the molecular scale, has been a difficult task. Here, we report a metal-organic framework, self-assembled from a porphyrin linker and a new type of Zn-based secondary building unit, serving as a joint in a hinged cube tessellation. Detailed structural analysis and theoretical calculation show that this material is a mechanical metamaterial exhibiting auxetic behavior. This work demonstrates that the topology of the framework and flexible hinges inside the structure are intimately related to the mechanical properties of the material, providing a guideline for the rational design of mechanically responsive metal-organic frameworks.
机械超材料具有诸如负泊松比等常规材料难以实现的特殊性能。由于三维打印技术的进步，在微观尺度上对机械超材料进行合理设计正变得越来越流行。然而，在固体内部纳入可移动的构建单元，从而使我们能够在分子尺度上操纵机械运动，一直是一项艰巨的任务。在此，我们报道了一种由卟啉连接体和新型锌基二级构建单元自组装而成的金属有机框架，它在铰接立方体镶嵌中充当接头。详细的结构分析和理论计算表明，这种材料是一种表现出负泊松比行为的机械超材料。这项工作表明，框架的拓扑结构和结构内部的柔性铰链与材料的机械性能密切相关，为合理设计机械响应性金属有机框架提供了指导。
