Origin and Mechanisms of Flexibility in Molecular Framework Materials: A Data-driven, Graph Theoretical Approach

分子框架材料（MFMs）是一种新兴的材料类别，它结合了分子的巨大丰富性和常规固体材料的优点。高表面积，可调孔径和官能团在气体吸附和分离，催化和传感等领域提供了应用。它们是通过将金属簇（节点）与有机连接物连接而合成的。有几十个不同形状的可能节点，几乎任何有机分子都可以用作连接器，从而形成一个巨大的“分子Meccano”，用于创建各种各样的多孔mfm。在这些材料中已经观察到一些有趣的现象。连接体本身的灵活性及其与每个节点的连接导致材料中的呼吸和门控行为，而不会破坏它们的结晶度。例如，框架呼吸可以让原本无法通过孔门的客体分子进入。以类似的方式，连接器的小旋转可以创建/破坏吸收二氧化碳和氢气等气体的理想口袋。而基本的MFMs的行为，这种灵活性提出了一个固有的挑战，这些材料的发展和呼吸现象的基本原子的理解尚未在它可以被用来设计这些材料的阶段。该项目将为mfm创建一个包含所有已知构建块的数据库，然后使用该数据库来确定每个构建块中固有的灵活性的程度和类型。然后，每个构建块的灵活性可以与整体框架结构相关联，并用于设计为特定应用量身定制的柔性MFM材料，例如存储能量（氢气或甲烷）或分离和净化气体混合物（如天然气中的氦气）。

Molecular framework materials (MFMs) are an emerging materials class that combines the immense richness of functionalities of molecules with the advantages of regular solid materials. High surface area, tuneable pore size and functional groups offer applications in fields such as gas adsorption and separation, catalysis and sensing. They are synthesised by joining metal clusters (nodes) with organic linkers. There are several dozen possible nodes of different shapes, and almost any organic molecule can be used as a linker resulting in a huge "Molecular Meccano" set for the creation of a vast variety of porous MFMs. Several interesting phenomena have been observed in these materials. Flexibility in the linkers themselves and their attachment to each node leads to breathing and gating behaviour in the materials, without destroying their crystallinity. Framework breathing, for example, can admit guest molecules that would not otherwise fit through pore gates. In a similar manner, small rotations of linkers can create / destroy ideal pockets for absorption of gases such as CO2 and H2.While fundamental to the behaviour of MFMs, this flexibility poses an inherent challenge to the development of these materials and as yet the fundamental atomistic understanding of the breathing phenomena is not at the stage where it can be employed to design these materials. This project will create a database of all known building blocks for MFMs and then use that database to determine degree and type of flexibility inherent in each building block. The flexibility in each building block can then be related back to the overall framework structures and used to design flexible MFM materials tailored for specific applications - e.g. to store energy (hydrogen or methane) or to separate and purify gas mixtures (such as helium in natural gas).