【作者】 郑成成；

【导师】 仲崇立；

【作者基本信息】 北京化工大学 ， 化学工程与技术， 2012， 博士

【摘要】 金属-有机骨架材料和共价有机骨架材料是新型的纳米多孔材料，由于其高的比表面积、大的孔隙率、结构的多样性与可调控以及可设计性等诸多优势，已经成为目前材料领域研究的前沿和热点。其在气体存储、多组分气体分离、催化以及传感器等方面均有潜在的应用价值，正得到越来越多的科研人员的关注。但是，由于材料的多样性以及孔道结构的复杂性，单纯用实验的手段很难对其进行系统的研究，特别是针对吸附机理，扩散特性的研究更是十分困难。随着计算机水平的提高，计算化学得到了长足的发展，并且逐渐被应用于材料的结构和性质的研究。利用量子化学的方法，可优化材料的结构和客体分子与材料的相互位置关系，计算能量以获得材料中各原子的电荷分布和电子云轨道分布；利用分子动力学方法研究客体分子在材料中的扩散路径以及扩散行为；利用蒙特卡罗方法模拟流体分子在材料中的吸附以及分离等性质，并且进一步探索其中具体的优先吸附位置，探索其机理。本论文主要是综合利用以上方法，研究金属-有机骨架材料中的CO₂储存、CO₂相关工业气体的分离以及探索性地研究共价有机骨架材料的催化特性。主要内容和创新点如下：1、选取沸石咪唑酯骨架材料（ZIFs）中有代表性的ZIF-68和ZIF-69两种材料，用蒙特卡罗和分子动力学相结合的方法，研究了其中CO₂吸附和扩散性质。研究发现CO₂优先吸附在由nIM围成的小孔中。压力不断增加，小孔中的CO₂几乎饱合，CO₂则趋于吸附在大孔中的苯环角落处，最后CO₂分布在整个大孔中，整个吸附也接近饱合。对比ZIF-68和ZIF-69的吸附过程，我们还发现，ZIF-69中的有机部分由Cl取代了苯环上的H,使得ZIF-69的吸附能变大。但同时，由扩散速度我们也可以发现，这在一定程度上阻碍了ZIF-69中的分子扩散。2、发现CO₂的强四偶极距在含CO₂的体系吸附和分离中起重要作用。本文研究了不同离子交换(Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, Mg²⁺, Ca²⁺, Sr²⁺,Al³⁺)的usf-ZMOF材料，对于三种不同工业体系（CO₂/CH₄, CO₂/N₂,CO₂/H₂）的分离选择性。发现其分离选择性远高于现有的材料，对于不同的离子交换后的usf-ZMOF，吸附选择性随着离子电荷值的增加而增大；对于同一主族的离子，选择性随着原子序数增加而减小。3、在吸附和分离的模拟计算中，量化计算材料的电荷耗时费力，制约着在人们大规模筛选材料。很多研究表明，材料和流体之间的静电贡献随压力的增加而减少，并且在工业应用中都是在中高压力下。因此，本论文中选择了一批有代表性的金属-有机骨架材料，对材料和流体之间的静电贡献进行了系统的研究。发现，对于天然气净化所在的2-3MPa下，材料和流体之间的静电贡献都接近或小于10%。也就是说，在进行大规模材料筛选时，静电贡献可以忽略。4、把针对于金属-有机骨架材料开发的基于原子链接性的电荷估算方法（CBAC）应用于共价有机骨架材料。从结果中发现，对于在两种材料中都存在的原子类型，基于金属-有机骨架材料所得的结果可以很好地应用到共价有机骨架材料中。一方面，进一步证明了基于原子链接的电荷估算方法的可靠性和普适性；另一方面，扩展了原来的电荷库。5、利用量化计算的方法探索了COF-1的催化活性位。利用CO为探针分子，分别优化吸附CO前后的COF-1的最优结构。通过对其频率、电荷转移、键长等进行分析，发现其本身并不具备酸性位。但是，由于其高的比表面积以及低密度，仍具负载催化的潜质。更多还原

【Abstract】 Metal-Organic Frameworks and Covalent Organic Frameworks are newfamilies of nanoporous frameworks materials. Due to their extremely highaccessible areas, porosities, chemical diversities and tailored and designedstructures, they have been recongised as the frontier area and hotspot in thefield of materials. They have show potential applications in many fields, suchas in gas storage, separation, catalyst and sensors. However, their structure iscomplex and thus it is difficult to study the materials just by experiments. Withthe development of computer, computational chemical has been wildly used tostudy the structure and properties of materials..This work mainly studies the CO₂storage, CO₂related industry gasseparation in Metal-Organic Frameworks and Covalent Organic Frameworksusing computational tool. The main findings and contents are followed.1. We have studied two typical Zeolitic Imidazolate Frameworks （ZIFs）,ZIF-68and ZIF-69. Using a combined molecular dynamic and Monto Carlomethod, we studied the adsorption and diffusion of CO₂in ZIF-68and ZIF-69. The results show that the small pores formed by he nIM linkers in ZIF-68andZIF-69are the preferential adsorption sites. The corners formed by phenylrings in the large pores are the second preferential aadsorption sites. We alsofound that the chlorine atoms in cbIM linkers in ZIF-69lead to enhancedbinding energy but reduced diffusivity for CO₂.2. We report a molecular simulation study for the separation of industrialgas mixtures in different ion-exchanged (Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, Mg²⁺, Ca²⁺,Sr²⁺, Al³⁺) usf zeolite-like metal-organic framework （usf-ZMOF）. Theselectivity of the three systems （CO₂/CH4, CO₂/N2, CO₂/H2） is higher thanaverage. For the different ion-exchanged usf-ZMOF, the selectivity enhanceswhen the ion valences go up from positive one to three. In the same maingroup, the selectivity decreased with the increasing of the atom number.3. This work takes a computational study to investigate the influences offramewok charges on CO₂uptake in metal-organic frameworks. The resultsshow that the contribution of framework charges to CO₂uptake dependslargely on pressure. For applications operated at moderate or high pressures,such as in the natural gas purification process, the framework contributionbecomes less important ansd is usually less than10%. In this case, it isreasonable to neglect the framework contribution in the initial materialscreening, which makes it possible to pursue a large-scale computationalscreening of MOF materials for applications operated at moderate or highpressure. 4. An approach named connectivity-based atom contribution method（CBAC） was developed for estimationg framework charges in metal-organicframeworks in our group. This work extends the approach to covalent Organicframeworks. The results show that those framework atoms with the samebonding connectivity in covalent organic frameworks have identical chargesas that in metal-organic frameworks, this further validates the suitability of theCBAC method and makes it possible to apply to other nanoporous materials.We also extend the CBAC charge databank.5. We explored whether there are catalysis sites in Covalent OrganicFrameworks by Quantum Mechanics. We optimized the structures of bothCOF-1and CO-COF-1，and CO is adopted as probe molecule. We find thatthere is no catalysis activity in COF-1, by comparing frequencies, charges andthe length of bonds.更多还原