【作者】 付艳艳；

【导师】 严秀平；

【作者基本信息】 南开大学 ， 分析化学， 2013， 博士

【摘要】 金属-有机骨架(metal-organic frameworks, MOFs),也称多孔配位聚合物(porous coordination polymers, PCPs),是由金属与有机配体通过配位作用自组装形成的网状骨架结构。因具有比表面积大、结构多样性、孔道尺寸可调、骨架可修饰、热稳定性和化学稳定性良好等优点而广泛应用于分离分析等领域。目前MOFs作为固定相用于气相色谱分离的研究较多,但是作为液相色谱分离介质的研究相对滞后。鉴于高效液相色谱强有力的分离分析能力,本文旨在拓展MOFs在高效液相色谱中的应用种类及分析范围,探索MOFs复合材料作为液相色谱分离介质的潜能。主要研究内容如下：(1)开展了通过调控固定相MIL-101(Cr)空配位点的配位状态,实现高效液相色谱分离极性化合物的工作。利用甲醇和MIL-101(Cr)中Cr空配位点的可逆配位能力,在高压匀浆法填充的MIL-101(Cr)色谱柱上,以含有甲醇调控分子的二氯甲烷作为流动相,实现了硝基苯胺、氨基苯酚、萘酚异构体以及磺胺和磺胺二甲基嘧啶的高效分离。将甲醇与具有调控能力的异丙醇及不具备调控能力的乙腈进行对比,证明了流动中甲醇在分离过程中的极性调节作用及配位点修饰作用；通过红外光谱和X-射线电子能谱表征,进一步证明了甲醇和Cr空配位点之间的配位作用。计算了硝基苯胺异构体在分离过程中的吉布斯自由能变化、焓变及熵变,从能量角度说明了流动相中甲醇含量对MIL-101(Cr)色谱柱分离分析物的影响。MIL-101(Cr)色谱柱具有较高的重现性,11次重复分离极性化合物的保留时间、峰高和峰面积的相对标准偏差分别是0.08-0.61%、0.65-2.4%和0.33-2.4%。此外,详细考察了流动相中甲醇含量对分离的影响,并将动态调控分离的模式拓展至另一含有空配位点MOF:MIL-100(Fe)的分离应用。(2)开展了MIL-100(Fe)作为色谱固定相,同时用于反相和正相高效液相色谱分离的研究。中性化合物：苯、甲苯、乙苯、萘和1-氯萘以及碱性化合物：苯胺、乙酰苯胺、2-硝基苯胺和1-萘胺作为分析物用于考察MIL-100(Fe)色谱柱的反相色谱分离能力；氯苯胺和甲苯胺异构体作为分析物用于考察MIL-100(Fe)色谱柱的正相色谱分离能力。所有分析物在MIL-100(Fe)色谱柱上都实现了高效和高选择性分离。MIL-100(Fe)色谱柱具有较高的重现性,11次重复进样分离分析物的保留时间、峰面积、峰高和半峰宽的相对标准偏差分别是0.2-0.7%、0.5-3.6%、0.6-2.3%和0.8-1.7%。此外,我们考察了流动相组成、进样量和温度对分离的影响。结果表明,MIL-100(Fe)是一种非常有应用前景并可同时用于反相和正相色谱分离的色谱固定相。(3)开展了MOF复合材料作为色谱固定相,用于反相高效液相色谱分离内分泌干扰物和杀虫剂的研究。以羧基修饰的硅球作核,ZIF-8纳米晶作壳,采用层层原位生长的方式制备了具有核-壳结构的SiO2@ZIF-8复合微球。通过控制ZIF-8生长的次数,可控的调节复合微球中ZIF-8的密度。FI-IR、XRD和SEM表征证明了单分散SiO2@ZIF-8复合微球的成功合成。进而考察了SiO2@ZIF-8复合微球作为色谱固定相的分离能力,结果表明SiO2@ZIF-8色谱柱具有较低的背压并能够快速、高效分离内分泌干扰物和杀虫剂。此外,还对比了硅球分离目标物的能力,考察了ZIF-8纳米晶的密度、流动相组成、进样量和温度对分离的影响。结果表明,SiO2@ZIF-8核-壳微球同时具备硅球良好的填充性能以及ZIF-8良好的分离能力,是一种稳定的、有应用前景的复合材料。(4)开展了有机聚合物整体柱中掺杂Ui0-66纳米颗粒,用于改善反相高效液相色谱等度分离小分子的研究。以经典甲基丙烯酸整体柱的前驱溶液作为基质,制备了不同Ui0-66掺杂量的整体柱。利用乙腈／水作流动相,在Ui0-66掺杂整体柱上实现了四组小分子分析物：中性多环芳烃(苯、萘、芴、芘、屈)；碱性芳香胺类(乙酰苯胺、对氟苯胺、邻硝基苯胺、1-萘胺)；酸性苯酚类(间苯二酚、间甲苯酚、2,6-二甲基苯酚、2,6-二氯苯酚)和萘取代物(1-萘酚、1-甲基萘、1-氯萘)的基线分离。通过和未掺杂Ui0-66的整体柱对比,体现了UiO-66的掺杂对小分子分离的改善。UiO-66掺杂整体柱具有较高的重现性,11次重复进样分离化合物的保留时间、峰面积、峰高和半峰宽的相对标准偏差分别是0.02-0.27%,0.33-1.49%,0.35-1.85%和0.19-1.09%。此外,考察了流动相组成、进样量和温度对分离的影响,并对比了Ui0-66掺杂整体柱和甲基丙烯酸整体柱的压力曲线。结果表明,UiO-66掺杂整体柱不仅显著改善了小分子的分离而且具有良好的渗透性,在分离分析领域有潜在的应用价值。更多还原

【Abstract】 Metal-organic frameworks (MOFs), also called porous coordination polymers (PCPs), are a new class of hybrid inorganic-organic microporous crystalline materials self-assembled from metal ions with organic linkers via coordination bonds. Owing to their fascinating structures and unusual properties, such as large surface area, structural diversity, good thermal and chemical stability, uniform and regulatory pore size, and the availability of framework functionality, MOFs have great potential for separation applications. In the past decade, MOFs have been widely used as stationary phase for gas chromatography. However, researches on the application of MOFs as stationary phase for high performance liquid chromatography (HPLC) have lagged behind. This dissertation focused on the expanding the scope of MOF-based stationary phase and the analytes, and exploring the potential of MOFs composites as separation media for HPLC. The main contents are summarized as follows:(1) Metal-organic frameworks (MOFs) with open metal sites have great potential for enhancing adsorption separation of the molecules with different polarities. However, the elution and separation of polar compounds on such MOFs packed columns using nonpolar solvents is difficult due to too strong interaction between polar compounds and the open metal sites. Therefore, the coordination status of the open metal sites in MOFs was controlled by adjusting the content of methanol (MeOH) in the mobile phase for fast and high-resolution separation of polar compounds. To this end, HPLC separation of nitroaniline, aminophenol and naphthol isomers, sulfadimidine, and sulfanilamide on the column packed with MIL-101(Cr) possessing open metal sites was performed. The interaction between the open metal sites of MIL-101(Cr) and the polar analytes was adjusted by adding an appropriate amount of MeOH to the mobile phase to achieve the effective separation of the polar analytes due to the competition of MeOH with the analytes for the open metal sites. Fourier transform infrared spectra and X-ray photoelectron spectra confirmed the interaction between MeOH and the open metal sites of MIL-101(Cr). Thermodynamic parameters were measured to evaluate the effect of the content of MeOH in the mobile phase on the separation of polar analytes on MIL-101(Cr) packed column. The universality of the present approach for the control of the open metal sites of MOFs with MeOH was demonstrated using another MOF containing open metal sites, MIL-100(Fe). This approach provides reproducible and high performance separation of polar compounds on the open metal sites-containing MOFs.(2) Metal-organic framework MIL-100(Fe) was explored as a novel stationary phase for both normal-phase and reverse-phase HPLC. Two groups of analytes (benzene, toluene, ethylbenzene, naphthalene and1-chloronaphthalene; aniline, acetanilide,2-nitroaniline and1-naphthylamine) were used to test the separation performance of MIL-100(Fe) in the reverse-phase mode, while the isomers of chloroaniline or toluidine were employed to evaluate its performance in the normal-phase mode. The MIL-100(Fe) packed column gave a baseline separation of all the tested analytes with good precision. The separation was controlled by negative enthalpy change and entropy change in the reverse-phase mode, but positive enthalpy change and entropy change in the normal-phase mode. The relative standard deviations of retention time, peak area, peak height, and half peak width for eleven replicate separations of the tested analytes were0.2-0.7%,0.5-3.6%,0.6-2.3%and0.8-1.7%, respectively. The mesoporous cages, accessible windows, excellent chemical and solvent stability, metal active sites and aromatic pore walls make MIL-100(Fe) a good candidate as novel stationary phase for’both normal-phase and reverse-phase high performance liquid chromatography.(3) The unique features of high porosity, shape selectivity and multiple active sites make MOFs promising as novel stationary phases for HPLC. However, the wide particle size distribution and irregular shape of conventional MOFs lead to lower column efficiency of such MOFs-packed columns. Monodisperse SiO2@MOF core-shell microspheres were fabricated as the stationary phase for HPLC to overcome the above-mentioned problems. Zeolitic imidazolate framework-8(ZIF-8) was used as an example of MOFs due to its permanent porosity, uniform pore size, exceptional chemical stability. The unique carboxyl modified silica spheres were used as the support to grow ZIF-8shell. The fabricated monodisperse SiO2@ZIF-8packed columns (5cm long×4.6mm i.d.) show high column efficiency (23000plates m-1for bisphenol A) for the HPLC separation of the endocrine-disrupting chemicals (bisphenol A,β-estradiol and p-(tert-octyl)phenol) and the pesticides (thiamethoxam, hexaflumuron, chlorantraniliprole and pymetrozine) within7min with good relative standard deviations for eleven replicate separations of the analytes (0.01-0.39%,0.65-1.7%,0.70-1.3%and0.17-0.91%for retention time, peak area, peak height, and half peak width, respectively). The SiO2@ZIF-8microspheres combine the advantages of the good column packing properties of the uniform monodisperse silica microspheres and the separation ability of the ZIF-8crystals.(4) Metal-organic framework UiO-66has been incorporated into porous poly methylarylic acid-co-ethylene dimetharylate (MAA-co-EDMA) monolith to enhance HPLC separation of small molecules in an isocratic mode. Four groups of small molecules:neutral polycyclic aromatic hydrocarbons (benzene, naphthalene, fluorene, pyrene, chrysene), basic aniline series (acetanilide,4-fluoroaniline,2-nitroaniline,1-naphthylamine), acid phenol series (resorcinol, m-cresol,2,6-dimethylphenol,2,6-dichlorophenol) and naphthyl substitutes (1-naphthol,1-methylnaphthalene,1-chloronaphthalene) were used to test the chromatography separation enhancement on the prepared monolith. Baseline separations of all the tested analytes on UiO-66incorporated monolith were achieved with improved column efficiency compared with the parent monolith. The relative standard deviations of retention time, peak area, peak height, and half peak width for eleven replicate separations of the tested analytes were0.02-0.27%,0.33-1.49%,0.35-1.85%, and0.19-1.09%, respectively. The intrinsic characteristics such as aromatic rings-based structures, carboxylate functional groups and Zr active sites make UiO-66a good candidate as a novel nanomaterial to afford monolithic column for enhancing chromatographic separation of small molecules.更多还原