【作者】 景学敏；

【导师】 刘云凌； 霍启升；

【作者基本信息】 吉林大学 ， 无机化学， 2011， 博士

【摘要】 材料、信息和能源是当代高科技产业的三大主要支柱,材料的开发与应用在人类社会的发展过程中极为重要,也是信息与能源技术发展的基础和前提。金属-有机骨架化合物(MOFs)是近二十年来兴起的一种新型孔材料,它们具有超大的比表面积和可控的孔道结构,通常在脱除客体分子后能够保持骨架结构的稳定性,与其它多孔材料如活性炭和沸石分子筛等相比,在气体储存、气体选择性吸附、手性催化、药物储存和传输等领域具有更广泛的应用前景。因而,MOFs材料从诞生之日起就备受国内外专家学者的高度关注,并迅速发展成为材料研究领域的热点之一。然而,目前还没有建立起完善成熟的理论体系,对目标产物的设计合成还难以完全掌控,常出现预想之外的结果,甚至对于最简单的有机配体和金属离子的组装,要准确预测其结构都非常困难。因此,不断积累实验数据,摸索合成规律,进一步探究合成与结构之间的黑匣子,最终实现对金属-有机骨架化合物的定向设计合成。鉴于对金属-有机骨架化合物的最新动态研究,我们从金属-吡啶基咪唑羧酸化合物的结构设计出发,对4,5-咪唑二羧酸进行了修饰,在咪唑环的2-位引入了吡啶基团,得到了两个具有T-型配位模式的吡啶基-4,5-咪唑二羧酸配体。由于吡啶基团的引入,增加了一个新的N原子配位点,同时改变了4,5-咪唑二羧酸配体上的电荷分布,产生了一定的空间效应,能够得到一些结构新颖的金属-有机骨架化合物。本文中,我们分别以两种不同的吡啶基-4,5-咪唑二羧酸与过渡/稀土金属离子组装得到以下三个方面的成果：1.在溶剂热体系下,利用对位吡啶基-4,5-咪唑二羧酸与金属铜离子自组装获得了两个分别具有手性bmn和lcy-a拓扑结构的化合物|(1,3-DAP)(DMF)0.5(H2O)2| [Cu11HPyImDC]1和(;MPL)o.5(H20)8|[CuII2CuI(HPyImDC)2(H2PyImDC)]2o化合物1中的铜离子是正二价的,而化合物2中存在CuⅡ和CuⅠ两种混合价态,它们的比例是2：1。有机配体在两个化合物中的配位方式也不尽相同：化合物1中的H3PyImDC采取T-型配位方式,而在化合物2中,H3PyImDC采取T-型和直线型两种配位方式。相似的是,两个化合物中都存在两种完全相反的手性螺旋孔道,它们分别由螺旋链交叉缠绕而成。从金属源、溶剂、模板剂和手性诱导剂等不同方面对两个化合物的合成体系进行了系统考察,结果证明这些合成条件的改变对手性骨架的生成没有影响。结合对化合物结构分析发现,吡啶基团上的N原子参与配位后产生了一定的T-型扭曲效应,这种扭曲效应发生了传递,使吡啶基与咪唑环形成了一定的二面角,从而促使两个手性结构的生成。从能量的角度来看,这种T-型扭曲产生的传递效应降低了体系的活化能,从而满足了体系能量最小化的要求。对两个化合物的性质研究发现它们可以成功地进行客体分子交换,荧光光谱研究表明两个化合物均表现出一定的荧光性质,这为进一步研究它们的应用奠定了基础。2.在溶剂热体系下,采用分子构筑块的方法,基于沸石分子筛四面体拓扑结构与分子构筑块之间的匹配关系,从沸石分子筛拓扑结构连接方式出发,选择对位呲啶基-4,5-咪唑二羧酸与过渡金属中心组装,通过调控合成条件,获得由过渡金属中心与对位吡啶基-4,5-咪唑二羧酸形成的分子构筑块,它们按一定方式连接形成了具有bbm、dft和gis拓扑结构的化合物3-5b,其中dft和gis为类沸石分子筛拓扑结构,并对3-5b合成条件进行了总结。化合物中的过渡金属离子均以八面体MN303构型出现,通过有机配体与其它四个金属中心连接形成4-连接的四面体次级结构单元(一个金属原子占据四面体的中心位置,其它相邻四个金属原子各占据四面体的四个顶点位置),这种次级结构单元是设计合成类沸石分子筛MOFs的前提条件,而过渡金属离子的八面体配位方式是设计合成4-连接的四面体次级结构单元的重要条件。对位吡啶基-4,5-咪唑二羧酸配体均以T-型配位方式出现,分别提供三个N原子和羧酸基团上的两个O原子与金属中心配位,这种配位方式有效地利用了有机配体上的配位点,且配位后的三个金属中心在一个平面上,更有利于生成四面体次级结构单元,这为类沸石分子筛MOFs的合成创造了条件。化合物的孔道结构对比分析发现这类化合物具有超大的比表面积和空旷的孔道结构,为它们在气体吸附和储存方面的潜在应用提供了基础。化合物的荧光和磁学性质研究表明化合物3和4在室温下一定波长的激发光照射下显示出很强的荧光,化合物5a在10000e下存在反铁磁性质。3.在水热／溶剂热体系下,利用两种不同吡啶基-4,5-咪唑二羧酸与稀土和过渡金属中心组装,通过π-π和氢键等分子间相互作用构筑了一系列结构新颖的三维超分子化合物6a-6d和9；并得到了具有矿物ant拓扑结构和四方锥sqp拓扑结构的稀土系列化合物7a-7d和8a-8d。对比两种有机配体的配位模式发现,当它们与金属配位不充分时就形成了一维链状结构,当充分配位时倾向于生成三维网络结构,随着配位点的增多化合物的维数出现不断增高的趋势。同时预测了两种不同有机配体与金属中心组装将会产生更多类型的分子构筑块,它们相互组装将会产生更多新颖结构。对化合物6-9分别进行了荧光和磁学性质研究,研究发现由于化合物结构的不同导致其荧光性质差异很大,通过实验找出了性质差异的主要原,为这类材料的应用提供了一定的实验数据和理论基础。磁学性质研究表明化合物6和7具有明显的反铁磁性质。本文在对金属-吡啶基咪唑羧酸化合物的合成条件和方法、拓扑结构研究的基础之上,总结了产物结构与合成之间的一般规律,丰富了金属-有机骨架化合物合成化学和结构化学,为金属-有机骨架化合物的定向合成和性质开发积累了有价值的方法和数据。更多还原

【Abstract】 Materials science, information technology and energy are widely recognized as three of the main pillars of modern high-tech industries. The sustainable development and application of functional materials is therefore extremely important for the development of human society. Metal-organic frameworks (MOFs) have recently emerged as a novel class of porous materials that are highly modular, highly crystalline and amenable to design, and exhibit controllable pore structure. Many MOFs have been shown to exhibit permanent porosity with large surface areas whereby the framework maintains the stability after the removal of guest molecules. The unique characteristics of MOFs render them more suitable in a more diverse range of applications as compared to other porous materials such as activated carbon and zeolites. Such applications include gas storage, gas selective adsorption, and drug storage or delivery. Accordingly, MOFs have attracted great attention, from both academics and industry, and have been developed into one of the hottest topics in materials research. Rational control over the design and synthesis of targeted structures often leads to predisgned structures. However, unprecedented or unexpected results are frequently obtained even for the assembly of the simplest molecular building blocks. It therefore remains an ongoing challenge to absolutely predict the outcome each time. It is therefore critical at this stage to accumulate a large database of synthetic data in order to explore the diverse synthetic conditions that yield specific structures and learn more about the synergy between the synthesis and structure. This will ultimately aid us to better direct the rational design and controllable synthesis of functional MOFs and will have a far-reaching significance.With these principles in mind, we modified an organic linker, i.e. 4,5-imidazoledicarboxylate ligand (HalmDC), by appending a pyridyl moiety at the 2-position of the imidazole ring. The resultant ligand, pyridine-4,5-imidazole dicarboxylic acid (H3PylmDC), permits control of the N atom positions on the pyridyl group and carboxylate atoms on the imidazole ring to yield a ligand capable of T-shape coordination modes. Because of the introduction of pyridine groups, a new coordination point N atom has been added, and the charge distribution of organic ligand also changed, resulting in a certain space effect, which will be favorable for constructing a number of novel MOFs. Therefore, reacting two types of H3PyImDC ligand with transition or lanthanide metal ions,respectively, we get the following three aspects results.1. The assembly of H3PyImDC and copper ions yields two chiral MOFs with bmn and lcy-a topology 1 and 2.The copper ion in compound 1 is divalent; whereas,it exists in two mixed valence states in compound 2,i.e. CuII and CuI, with a ratio of 2:1. The coordination modes of the ligand are not the same in compounds 1 and 2; that is, the former assumes a T-shape coordination mode while the latter exhibits two coordination modes of both T-shape and linear. Two independent and opposite ehiral helical channels also exist and are formed by the cross-winding spiral chains. The source of the metal ion, solvent, template, and chiral induction agent used in the synthesis for 1 and 2 were systematically investigated. It was determined that the synthesis conditions had indeed no effect on the generation of the chiral frameworks. Structural analysis reveals that the N atom on the pyridyl ring coordinates with the metal ions in a flexible manner and therefore it permits a certain amount of distortion in the T-shape coordination mode. This feature facilities the formation of two chiral structures. In the view of energy, the T-shape distortion effect reduces the activation energy of the system so as to meet the minimum of energy requirements. Two compounds can successfully exchange with guest molecules, and they also have fluorescence properties, which will provide a foundation for their applications for further research.2. The molecular building blocks (MBBs) approach was employed in this study to further establish a relationship between targeted MBBs in MOFs and the topologies observed in traditional inorganic zeolites. Accordingly, we chose to react H3PyImDC with transition metal ions, through the fine regulation of the synthesis conditions, to obtain rigid tetrahedral MBBs, whose self-assembly yielded a class of MOFs 3-5b, with 3D netswork bbm, and zeolite-like dft and gis topology, respectively. Each transition metal ion assumes an octahedral MN3O3 coordination mode and connects to four independent metal centers through the organic ligands to form a 4-connected MBB which translates into a tetrahedral (a metal atom occupies the center of the tetrahedron, the other four metal atoms occupy four vertices of tetrahedral) secondary building units (SBUs). The deprotonated HpylmDC2- ligand coordinates to the metal ions in a T-shape mode, with three N atoms and two O atoms of the carboxylic acid groups chelating to the metal centers. Accordingly, this coordination mode fully utilizes coordinating atoms, and makes the three metal ions in a plane, which is more conducive to generate tetrahedral SBUs；and is more convenient for constructing the zeolite-like MOFs as well. Comparison of the pore structure of compounds 3-5b by analyzing the structures in Materials Studio software, found that they all have large surface area and open pore structure, providing a basis for the potential application in gas adsorption and storage. The fluorescent and magnetic experiments conducted on these materials reveal that compounds 3 and 4 exhibit a strong excitation effect at room temperature, while compound 5a has an anti-ferromagnetic property in the 1000Oe field.3. The assembly of two different H3PylmDC ligand with rare earth and transition metal centers, through theπ-πand intermolecular hydrogen bonds interactions to yield a series of novel three-dimensional (3D) supramolecular compounds 6a-6d and 9, and a mineral-like ant and a four cones sqp topology structure MOFs 7a-7d and 8a-8d. Comparison of the coordination modes of two organic ligands show that when not fully coordinated with the metal ions, it is more likely to form ID chain structures; when fully coordinated, it is tending to generate 3D network structures. Therefore, the structures often develop from OD to 3D with the increasing coordination atoms. We also predict that the assembly of two different organic ligands with metal center will produce more types of MBBs, and when they are assembled with metal centers, more new structures will generated. The magnetic and fluorescent properties study on compounds 6-9 were carried out by which we found that the different structures lead to the different fluorescence phenomenon, and the reason for the difference, which provide a certain amount of experimental data and theoretical basis for the potential applications of such materials. Magnetic measurements performed on compounds 6 and 7 reveal they display obvious anti-ferromagnetic properties.The results described herein summarize the synthesis, topological analysis and fluorescence properties of an assortment of MOFs constructed using metal-KbPylmDC as organic linkers. A general relationship between the product and synthesis method has been established and we hope that this accumulation of experimental data will be valuable for the continuous development of functional MOFs.更多还原