多孔有机笼(POCs)是一种新型的分子材料。定义明确的空洞,丰富的主客识别能力,和良好的溶解性POCs使它们有吸引力的使用在各个领域,如分子识别,气体吸附,分子容器,传感,催化作用,色谱分离。在这项研究中,通过4,4\'的席夫碱缩合合成了手性POC(CPOC),4″,4“\'-(乙烯-1,1,2,2-四烷基)四苯甲醛与(R,R)-1,2-环己二胺。CPOC使用核磁共振(NMR)光谱进行表征,傅里叶变换红外(FT-IR)光谱,质谱(MS),和热重分析(TGA)。CPOC的FT-IR光谱在1638cm-1处显示出强峰,这归因于亚胺(-C=N-)吸收,以及2928和2856cm-1处的吸收峰,这归因于-CH2-和-CH-的拉伸振动,分别。CPOC的MS分析显示在m/z=1801.9797、m/z=901.9914和m/z=601.6631处的峰,对应于[M+H]+,[M+2H]2+,和[M+3H]3+,分别,并表示CPOC的分子式(C126H120N12)。CPOC的TGA曲线表明高达360℃的热稳定性高;因此,该材料适合用作气相色谱(GC)的固定相。使用静态涂覆方法将CPOC涂覆在毛细管柱的内壁上以制备GC柱。扫描电子显微镜(SEM)用于表征所制造的色谱柱的涂层条件。SEM图像显示该柱具有厚度为约200nm的均匀涂层。在120°C下,使用正十二烷作为目标确定柱效率为3500板/m。使用McReynolds常数评估CPOC固定相的极性,它们是用苯测量的,1-硝基丙烷,2-戊酮,吡啶,和1-丁醇作为探针分子在120℃。平均McReynolds常数为152,表明CPOC是中等极性固定相。色谱柱分离有机混合物的能力,异构体,随后研究了手性化合物。四种有机混合物的所有成分(正烷烃,芳烃,n-醇,和Grob混合物)测试在色谱柱上实现基线分离。此外,二取代苯的九种位置异构体被很好地分离,和七(o,m,对硝基甲苯,a,m,对硝基氯苯,a,m,对硝基溴苯,a,m,对溴甲苯,a,m,对二氯苯,a,m,对氯苯胺,o,m,对溴苯胺)实现基线分离。一些极性和非极性结构异构体,如戊醇,二甲基苯酚,二甲基苯胺,丁醇,和C9芳烃异构体,在柱子上也很好地分离。五种顺式/反式异构体(神经醇/香叶醇,顺式/反式-1,3-二氯丙烯,顺式/反式-1,2,3-三氯丙烯,顺式/反式柠檬醛,和顺式/反式十氢萘)在色谱柱上进行基线分离。更重要的是,色谱柱成功分离出12个手性化合物,良好的手性分离能力。在这些手性化合物中,五(3-羟基丁酸乙酯,缬氨酸衍生物,谷氨酸衍生物,1,2-丁二醇二乙酸酯,和1,2-环氧丁烷)实现了基线分离。这些手性化合物中的六种(3-羟基丁酸乙酯,缬氨酸衍生物,谷氨酸衍生物,1,2-环氧丁烷,表氯醇,和表溴醇)无法在β-DEX120色谱柱上分离,但在开发的色谱柱上分离良好。此外,1,2-丁二醇二乙酸酯和异亮氨酸衍生物在该色谱柱上的分离效率优于β-DEX120色谱柱。谷氨酸衍生物和o的分离,m,在柱用于重复注射之前和之后进行对硝基甲苯以探索其可重复性。80、160和500次进样后观察到的保留时间和选择性与首次使用色谱柱获得的保留时间和选择性相比几乎没有变化。表明该色谱柱具有良好的重复性。将柱在280℃下调节一定时间以检查其热稳定性。3-羟基丁酸酯和邻,m,柱在280℃下调节2、4或8小时后,对硝基氯苯与首次使用柱相比没有明显变化,表明该柱具有良好的热稳定性。因此,CPOC是GC的固定相,具有良好的应用潜力。
Porous organic cages (POCs) are a new type of molecular material. The well-defined cavities, abundant host-guest recognition ability, and good solubility of POCs render them attractive for use in various fields such as molecular recognition, gas adsorption, molecular containers, sensing, catalysis, chromatographic separation. In this study, a chiral POC (CPOC) was synthesized via the Schiff base condensation of 4,4\',4″,4″\'-(ethene-1,1,2,2-tetrayl)tetrabenzaldehyde with (R,R)-1,2-cyclohexanediamine. CPOC was characterized using nuclear magnetic resonance (NMR) spectroscopy, Fourier transform-infrared (FT-IR) spectroscopy, mass spectroscopy (MS), and thermogravimetric analysis (TGA). The FT-IR spectrum of CPOC showed a strong peak at 1638 cm-1, which was attributed to imine (-C=N-) absorption, as well as absorption peaks at 2928 and 2856 cm-1, which were attributed to the stretching vibrations of -CH2- and -CH-, respectively. MS analysis of CPOC revealed peaks at m/z=1801.9797, m/z=901.9914, and m/z=601.6631, corresponding to [M+H]+, [M+2H]2+, and [M+3H]3+, respectively, and indicating a molecular formula of CPOC (C126H120N12). The TGA curve of CPOC indicated high thermal stability up to 360 ℃; thus, the material is suitable for use as a stationary phase for gas chromatography (GC). CPOC was coated on the inner wall of a capillary column using the static coating method to prepare a GC column. Scanning electron microscopy (SEM) was used to characterize the coating condition of the fabricated column. The SEM images showed that the column had a uniform coating with a thickness of approximately 200 nm. Column efficiency was determined to be 3500 plates/m using n-dodecane as a target at 120 ℃. The polarity of the CPOC stationary phase was evaluated using McReynolds constants, which were measured using benzene, 1-nitropropane, 2-pentanone, pyridine, and 1-butanol as probe molecules at 120 ℃. The average McReynolds constant was 152, indicating that CPOC is a moderately polar stationary phase. The ability of the column to separate organic mixtures, isomers, and chiral compounds was subsequently investigated. All components of the four organic mixtures (n-alkanes, aromatics, n-alcohols, and Grob mixtures) tested achieved baseline separation on the column. In addition, nine positional isomers of disubstituted benzenes were well separated, and seven (o,m,p-nitrotoluene, o,m,p-nitrochlorobenzene, o,m,p-nitrobromobenzene, o,m,p-bromotoluene, o,m,p-dichlorobenzene, o,m,p-chloroaniline, and o,m,p-bromoaniline) achieved baseline separation. Some polar and apolar structural isomers, such as pentanol, dimethylphenol, dimethylaniline, butanol, and C9 aromatic hydrocarbon isomers, were also well separated on the column. Five cis/trans-isomers (nerol/geraniol, cis/trans-1,3-dichloropropene, cis/trans-1,2,3-trichloropropene, cis/trans-citral, and cis/trans-decahydronaphthalene) were baseline-separated on the column. More importantly, the column successfully separated 12 chiral compounds, indicating good chiral separation ability. Among these chiral compounds, five (ethyl 3-hydroxybutyrate, a valine derivative, a glutamic acid derivative, 1,2-butanediol diacetate, and 1,2-epoxybutane) achieved baseline separation. Six of these chiral compounds (ethyl 3-hydroxybutyrate, the valine derivative, the glutamic acid derivative, 1,2-epoxybutane, epichlorohydrin, and epibromohydrin) could not be separated on a β-DEX 120 column but were well separated on the developed column. Moreover, the separation efficiency of 1,2-butanediol diacetate and the isoleucine derivative on this column was better than that on the β-DEX 120 column. Separation of the glutamic acid derivative and o,m,p-nitrotoluene was performed before and after the column was used for repeated injections to explore its repeatability. The retention times and selectivity observed after 80, 160, and 500 injections were nearly unchanged compared with those obtained following the first use of the column, indicating that the column has good repeatability. The column was conditioned at 280 ℃ for a certain period to examine its thermal stability. Separation of 3-hydroxybutyrate and o,m,p-nitrochlorobenzene after the column was conditioned at 280 ℃ for 2, 4, or 8 h revealed no obvious changes compared with the first use of the column, indicating that the column had good thermal stability. Thus, CPOC is a stationary phase with good application potential for GC.