Exploring secondary interactions in Metal-Organic Frameworks

金属有机骨架(MOF)是由无机阳离子、二聚体或簇合物(节点)和有机桥联配体(连接体)形成的多孔材料。MOF的每个孔都可以被视为一个为应用而建造的反应室。通过合理地选择节点和连接物，可以调整孔的孔径、大小和装饰孔的官能团。除了缺陷/表面效应，MOF的多孔性和结晶性导致节点和连接体存在于隔离和明确定义的环境中，客体分子可以访问这些环境。对于吸附/催化，将活性中心构建到MOF中可以移除聚集等失活途径。研究人员通过构建具有强吸附/反应位点的连接体/节点的MOF来探索这一点。二次相互作用是指改善或修改现有的吸附/催化过程的相互作用。它们可以与客体、催化剂相互作用，或修饰活性中心周围的立体结构/电子结构。这些二次相互作用可以改善吸附、过渡态稳定或解吸。尽管如此，将二级站点引入MOF的探索一直很少。该提案将探索使用三个连接系统的MOF中的二次相互作用。每个系统都使我们能够研究二次互动的不同方面。接头系统A以已知的卟啉接头为基础。连接体在卟啉上包含两个位置，二级相互作用将以这种方式结合，以参与围绕卟啉的金属核心的化学。这将使我们有机会在早期探索二次互动。连接物系统B是一种新型的卟啉连接物，其中的四个中间碳将被二次相互作用基团修饰。有了连接子，活性部位就会被挤满，无法检测立体结构。此外，还将探讨互惠的二次互动(例如，捐赠者和接受者)。连接物系统C是一种酞菁连接物。由于酞菁和相关异构体的对称性，这些连接体的研究很少。我们已经确定了一种制备没有对称性限制的酞菁连接体的方法，同时还允许多达八个位置引入二级相互作用。本课程将探讨两种类型的二次互动。刚性的二次相互作用迫使官能团保持在活性部位周围的相同环境中。灵活的二次互动是动态的，功能群可以进入/退出活动站点。新的MOF将通过单组分气体吸附来确定热力学，并通过单组分/多组分突破实验来研究动力学和竞争结合。我们将结合原位红外实验来确定二次相互作用的作用模式。我们将利用这些信息来探索在血红蛋白模拟、甲烷到甲醇转化、手性催化以及探索单线态氧化学方面的应用。

Metal-organic frameworks (MOFs) are porous materials formed from inorganic cations, dimers, or clusters (nodes), and organic bridging ligands (linkers). Each pore of the MOF can be viewed as a reaction chamber built for an application. With judicious choice of node and linker, the pore aperture, size, and functional group decorating the pore can be tuned. Barring defects/surface effects, the porous and crystalline nature of MOFs results in nodes and linkers existing in isolated and well-defined environments that can be accessed by guest molecules. For adsorption/catalysis, building an active site into a MOF removes deactivation pathways such as aggregation. Researchers have explored this by building MOFs with linkers/nodes that have strongly adsorbing/reactive sites. Secondary interactions are interactions that improve or modify the existing adsorption/catalysis process. They can interact with the guest, the catalyst, or modify the sterics/electronics around the active site. These secondary interactions can improve adsorption, transition state stabilization, or desorption. Despite this, introducing secondary sites into MOFs has been poorly explored. The proposal will explore secondary interactions in MOFs using three linker systems. Each system enables us to study a different aspect of secondary interactions. Linker System A is based on a known porphyrin linker. The linker contains two locations on the porphyrin where secondary interactions will be incorporated in such a way as to participate with chemistry around the metal core of the porphyrin. This will give us the opportunity to explore secondary interactions early on. Linker System B is a new porphyrin linker where the four meso carbons will be modified with secondary interaction groups. With the linker, the active site can be congested to examine sterics. Additionally, complimentary secondary interactions (e.g., donor and acceptor) will be explored. Linker System C is a phthalocyanine linker. These linkers are poorly explored due to the symmetry of the phthalocyanine and the associated isomers. We have identified a method to prepare a phthalocyanine linker that doesn't have the symmetry limitation while also enabling up to eight locations to introduce secondary interactions. Two types of secondary interactions will be explored. Rigid secondary interactions force functional groups to remain in the same environment around the active site. Flexible secondary interactions are dynamic and functional groups can enter/exit the active site. The new MOFs will be explored using single component gas adsorption to determine thermodynamics, and single/multicomponent breakthrough experiments to study kinetics and competitive binding. We will couple this with in-situ IR experiments to determine the mode of action of secondary interactions. We will utilize this information to explore applications in hemoglobin mimics, methane to methanol conversion, chiral catalysis, and explore singlet oxygen chemistry.