Exploring secondary interactions in Metal-Organic Frameworks

金属有机框架（mof）是由无机阳离子、二聚体或簇（节点）和有机桥接配体（连接体）形成的多孔材料。MOF的每个孔都可以看作是为应用而构建的反应室。通过对节点和连接件的合理选择，可以调节孔的孔径、大小和修饰孔的功能基团。排除缺陷/表面效应，mof的多孔性和结晶性导致节点和连接体存在于孤立的、定义良好的环境中，客体分子可以访问这些环境。对于吸附/催化，将活性位点构建到MOF中可以消除聚集等失活途径。研究人员通过构建具有强吸附/活性位点的连接器/节点的mof来探索这一点。二级相互作用是改善或改变现有吸附/催化过程的相互作用。它们可以与客体、催化剂相互作用，或改变活性位点周围的立体/电子结构。这些二级相互作用可以改善吸附、稳定过渡态或解吸。尽管如此，在mof中引入二级站点的研究却很少。该提案将探索使用三种连接系统的mof中的次级相互作用。每个系统使我们能够研究次要相互作用的不同方面。连接体系统A是基于已知的卟啉连接体。连接体在卟啉上包含两个位置，在那里二级相互作用将以这样一种方式结合，以参与卟啉金属核心周围的化学反应。这将使我们有机会尽早探索次级相互作用。连接体系统B是一种新型的卟啉连接体，其中四个中间碳将被二级相互作用基团修饰。有了连接器，活性部位就可以充血来检查立体位。此外，将探讨互补的次级相互作用（例如，供体和受体）。连接剂系统C是酞菁连接剂。由于酞菁和相关异构体的对称性，对这些连接体的研究很少。我们已经确定了一种方法来制备酞菁连接器，它没有对称限制，同时也允许多达八个位置引入二次相互作用。我们将探讨两种类型的次级相互作用。刚性的二级相互作用迫使官能团保持在活性位点周围的相同环境中。灵活的二次交互是动态的，功能组可以进入/退出活动站点。新的MOFs将通过单组分气体吸附来确定热力学，以及单/多组分突破性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次级相互作用的作用模式。我们将利用这些信息来探索血红蛋白模拟物、甲烷到甲醇转化、手性催化和探索单线态氧化学的应用。

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.