固体核磁共振研究金属有机框架体系内在主客体相互作用机制

Metal–organic frameworks (MOFs) are a class of porous materials that have attracted enormous attention due to their extraordinarily high surface areas, controllable structures and tunable pore sizes, and advantageous for contact with guest molecules. MOFs have shown great potential to be widely applied in various fields such as green energy storage, membrane separation, chemical sensors, and heterogeneous catalysis. It is well recognized that the application performance of MOFs is strongly subject to their structure property as well as the presence of host-guest interactions. Therefore, it is of great significance to unravel the detailed interaction between MOFs and guest molecule at atomic level, which might facilitate the understanding of their intrinsic structure-property relationship. This project intends to develop multi-nuclear and multi-dimensional solid-state NMR methods to investigate the host-guest interaction present in disordered MOFs system. The project focuses on the elucidation of host-guest interaction mechanism between adsorbates and metal ions/organic ligands and extraction of primary adsorption sites confined inside the MOFs pores utilizing feasible solid-state NMR techniques. Meanwhile, solid-state NMR is further employed to monitor the NMR parameters variation to address the host-guest interactions influence on the chemical environments and dynamic behavior of MOFs. Moreover, the structure-property relationship is reasonably established on the basis of experimental observations as well as the proposed host-guest interaction and adsorption-separation mechanism. The project might provide some basis and insights for the rational design of new types of functional MOFs.

金属有机框架材料(MOFs)作为一种新型多孔材料，因其具有较大的比表面积和可调控的孔道结构且易于与客体分子充分接触，在绿色能源存储、膜分离、传感器、多相催化等方面具有良好的应用前景。金属有机框架材料的应用性能直接与其结构特性以及存在的主客体相互作用模式密切相关。因此，从原子分子水平观测MOFs与客体分子相互作用机制对理解其内在的构效关系有着非常重要的意义。本项目旨在发展适用于研究MOFs材料体系主客体相互作用的多核、多维固体核磁共振技术方法，应用其研究客体分子在MOFs孔道内与金属中心或有机配体相互作用的强弱，并借助实验数据分析来推断相互作用模式及其优先吸附位点。通过对比吸附前后相关NMR参数的变化，揭示相互作用对MOFs材料微观化学环境和分子动力学行为的影响，以此建立相互作用机制与吸附分离特性之间的内在关联。本项目的开展实施将会为设计合成新型功能化的MOFs材料提供一些参考性依据。

本项目通过发展和应用固体核磁共振方法来研究金属有机框架材料体系内在主客体相互作用机制，建立其在吸附分离等应用领域中的内在构效关系。本项目我们提出了一种测量ZIFs内乙烷乙烯吸附分离选择性的NMR实验方法，并从微观视角观测吸附物与吸附剂骨架主客体相互作用的强弱。同时，我们也提出了用一维自旋扩散演化曲线来测定低碳烷烃在多组分MOFs上优先吸附位点的技术方案。此外，我们也提出了用高速魔角旋转NMR测量多组分MOFs配体的成分组成和空间分布的实验方法。借用固体NMR实验结合理论计算，我们研究了溶剂化呼吸效应对官能团化MIL-53配体转动速率的影响，研究了甲醇与顺磁性Cu3-xZnx(btc)2的主客体相互作用模式，表征了多组分官能团修饰的UiO-66的酸性性质。另外，我们运用多核、多维固体NMR研究MIL-53与乙基苯及苯乙烯的相互作用及分离机制。同时，我们还围绕固体核磁共振研究MOFs的结构性质、动力学行为、内在主客体相互作用机制攥写了相关综述论文。该项目研究的开展和实施，能为理解吸附分离过程中MOFs与小分子相互作用提供一些参考性的依据。本项目代表性的研究成果包括以下: (1) Adv. Mater. 2020, 32, 2002879 (2) Solid State Nucl. Magn. Reson. 2018, 90，1 (3) Magn. Reson. Chem. 2020, 59, 1091 (4) J. Phys. Chem. C 2019, 123, 24062 (5) Chem. J. Chinese. U. 2020, 41, 204 (6) J. Phys. Chem. C 2020, 124, 17640 (7) J. Phys. Chem. C 2020, 124, 3738 (8) Chem. Eur. J. 2021, 27, 14711 (9) Chem. Eur. J. 2021, 27, 11303 (10) Solid State Nucl. Magn. Reson. 2022, 341, 101772