Determination of the real structure of multivariate-MOFs

金属有机骨架材料的主要应用领域是气体分离、储存和催化。在寻找具有特定功能（如选择性CO2吸收）的材料时，所谓的多变量（MTV-）MOFs被证明是有希望的候选者，因为其中一些表现明显优于其单变量同源物的混合物。MTV-M0 F是结晶材料，其由无机簇或配位球构建，所述无机簇或配位球通过不同官能化的有机连接体连接。这种材料的平均结构可以用布拉格散射的评价来阐明。此外，发生漫散射，这是由晶体结构中官能团的不规则排列引起的。漫散射的解释是至关重要的连接器的安排，从而了解潜在的结构-性质的关系。所提出的研究的主要目标是通过漫X射线散射的评价的MTV-MOFs的真实的结构的描述。通过金属盐和不同官能化的有机连接剂的一步溶剂热反应可以获得高质量的MTV-MOF单晶（即具有完整的骨架）。真空下的工作可能是必要的，因为溶剂分子会引起额外的无序。单晶MOFs的许多合成路线使用晶体生长的调制器，理想情况下，这些调制器应该避免用于所提出的研究，因为它们可能被并入晶体结构中，从而中断周期性，这会导致额外的漫散射。对于真实结构的分析，提供高动态范围的探测器收集的同步辐射衍射数据是至关重要的。结构测定然后包括几个步骤，即从布拉格散射测定平均结构，仔细检查存在的无序类型的平均结构，将衍射图案从衍射仪空间转换到倒易空间（重建），以及使用3D-PDF和蒙特卡罗方法分析漫散射。平均结构的解析必须非常小心地进行，因为漫散射的后续分析取决于平均结构测定的结果。虽然3D-PDF适合于得出有关所研究材料中存在的相关性的类型和方向的定性结论，但可以使用3D-PDF和Monte Carlo方法进行细化。该研究将有助于更好地理解和合理化多元MOFs的结构-性能关系。

The main applications of metal-organic frameworks (MOFs) are gas separation and storage as well as catalysis. In the search for materials, which have specific functions like selective CO2 uptake, so-called multivariate (MTV-) MOFs turned out to be promising candidates, as some of them perform significantly better than mixtures of their univariate congeners. MTV-MOFs are crystalline materials, which are built of inorganic clusters or coordination spheres, which are connected by differently functionalized organic linkers. The average structure of such materials can be elucidated with the evaluation of the Bragg scattering. In addition, diffuse scattering occurs, which is caused by the irregular arrangement of the functional groups in the crystal structure. The interpretation of the diffuse scattering is crucial for an understanding of the linker arrangement and thus the underlying structure-property relationship. The main goal of the proposed research is the description of the real structure of MTV-MOFs by means of the evaluation of the diffuse X-ray scattering. High-quality single crystals of MTV-MOFs (i.e. with an intact framework) can be obtained by one-step solvothermal reactions of metal salts and differently functionalized organic linkers. Work under vacuum may be necessary, as solvent molecules cause additional disorder. Many synthesis routes for single-crystalline MOFs use modulators for crystal growth, ideally these should be avoided for the proposed research because they may be incorporated in the crystal structures and thus interrupt the periodicity, which causes additional diffuse scattering. For the analysis of the real-structure, synchrotron diffraction data collected with detectors providing a high dynamic range are crucial. The structure determination then comprises several steps, namely the determination of the average structure from the Bragg scattering, scrutinizing the average structure for the types of disorder present, transformation of the diffraction pattern from diffractometer space to reciprocal space (reconstruction) and analysis of the diffuse scattering using both, 3D-PDF and Monte Carlo methods. The elucidation of the average structure has to be performed with extreme care, as the subsequent analysis of the diffuse scattering depends on the results of the average-structure determination. Whereas the 3D-PDF is suited to derive qualitative conclusions regarding the types and directions of correlations present in the material investigated, refinement can be performed using both, 3D-PDF as well as Monte Carlo methods. The proposed research will lead to a better understanding and aid the rationalization of the structure-property relationships of multivariate MOFs.