基于联吡啶基多羧酸配体的多功能金属有机框架的变色现象、后修饰及荧光传感性质研究

At present, the construction and development of multifunctional metal-organic frameworks (MOFs) is still a challenge for scientists. The project selects crystalline multifunctional MOFs materials as the research object. The research work contains the function-oriented structure design, material preparation and property characterization of MOFs with photochromic properties, as well as selective fluorescence sensing of small organic molecules. By using the self-assembly of bipyridl-based (N,N-disubstituted 4,4'-dipyridyl (viologen) or 2,2'-bipyridyl) multicarboxylate with the rare earth metal ions or transition metal ions to obtain the MOFs. For the first part, owing to the characteristics of photochromic and the electron deficiency of viologen-based multicarboxylate ligands, the MOFs constructed by the viologen-based multicarboxylate ligands also own the characteristics of photochromic, and the MOFs can also sense some elctron-rich small organic molecules. For the second part, the MOFs based on the 2,2'-bipyridyl multicarboxylate ligands (the pyridine N atom as the potential functional sites) can be directly used for the research of fluorescence sensing of the electron-withdrawing-containing compounds, and based on this, the MOFs with strong structural stability can be selected to conduct the postmodification based on the nitrogen atoms of pyridine of MOFs, and then realize the selective fluorescence sensing for specific molecules. The implementation of this project lays the foundation for the development from the single function MOFs to the multi-functional MOFs, which has certain academic value and potential application.

目前，多功能金属有机框架(MOFs)的构筑和性能开发对科学家而言仍然颇具挑战性。本项目以晶态多功能金属有机框架为研究对象，以光致变色性、以及对有机小分子的选择性荧光传感为功能导向来进行结构设计、材料制备和性质表征：选取联吡啶基(N,N-双取代的4,4′-联吡啶基(紫精基)或2,2′-联吡啶基)多羧酸为配体与稀土/过渡金属离子自组装合成MOFs晶态材料。基于紫精基多羧酸配体具有的光致变色以及缺电子特点，由其构筑的金属有机框架也具有光致变色性，并且还可实现MOFs对富电子小分子的选择性荧光传感；而基于含潜在功能位点吡啶N原子的2,2′-联吡啶基羧酸类配体构筑的部分金属有机框架可直接用来进行荧光传感研究，在此基础上，对得到的结构稳定的MOFs进行原位后修饰，进而实现对特定分子的选择性荧光传感。本项目的实施为单一功能的MOFs向多功能MOFs的开发奠定基础，有一定的学术价值和潜在应用前景。

本项目开展了三部分研究：1. 基于稀土离子Eu(III)、Tb(III)、Gd(III)以及过渡金属离子Zn(II)、Cd(II)等的荧光MOFs的合成及荧光传感性质研究，得到9例MOFs基荧光传感器，其可实现高选择性、高敏感性、可循环性检测模拟人体尿液中的马尿酸、对氨基酚、1-萘酚；水溶液中叶酸、阴阳离子(Cr(VI)、MnO4ˉ、Fe3+)；农药2,6-二氯-4-硝基苯胺等。其检测具有高效、快速、检测限低的特点，检测机理大多为检测物对MOFs激发和/或发射光的吸收导致的荧光猝灭。这些荧光传感器对环境污染物及与人体相关生命物质的检测有潜在的应用价值。2. 基于紫精配体的配合物光致变色性质及其用于挥发性胺检测的研究，得到3例光致变色配合物，其中Co-MOF-1可实现对各种挥发性烷胺的肉眼可识别检测，其检测机理为从胺到紫精的电子转移伴随颜色变化导致的。将Co-MOF-1涂覆在方便携带的试纸上用于检测挥发性氨，可作为一种无墨可擦除印刷媒介。3. 配合物磁性研究，共得到了5个磁性配合物，其中对配合物[Co3(L2)4(OH)2(H2O)2]n的磁性研究表明其一维链内传递铁磁相互作用，呈现出类单链磁体性质和大的磁滞环。对配合物{[Co3(L)6(C8N2H6)(H2O)]∙(H2O)4}n的磁性研究表明四唑桥在Co(II)离子之间传递反铁磁相互作用。对整个温度范围的χT/T的曲线进行了最小二乘法拟合，得出了一套最佳参数值J = -2.77 cm-1、λ = -149 cm-1、α = 1.5 和 ∆ = -805 cm-1。对Dy-MOF的磁性研究表明其呈现出零直流场下的慢磁弛豫性质。