Preparation of chiral ionic organic crystal material and application as gas chromatography stationary phase

Abstract

The application discloses a preparation method of chiral ionic organic crystal material, and mainly is used for separation of position isomers and chiral compounds, and belongs to the technical field of novel chromatographic stationary phase. The CIL-Py and BDA are respectively dissolved into a toluene-methanol mixed solution, are fully mixed, and are incubated at 15-35 DEG C for 5-7 days, so that the chiral ionic organic crystal material CIOC is obtained; the CIOC is ultrasonically peeled in methanol for 14-16 h, so that the organic crystal material two-dimensional nanosheet 2D-NSs is obtained. The unique bonding mode of the chiral ionic organic crystal material enhances the stability thereof, the order of the single crystal is improved, and the performance of the material is improved. The chiral ionic organic crystal material has good separation effect on isomers such as nitrotoluene, nitroaniline and dimethylphenol. In addition, the preparation condition is simple, the process is mild, and the chiral ionic organic crystal material has wide application prospect.

Description

Technical Field

[0001] This invention relates to a gas chromatography stationary phase material, and more particularly to a method for preparing a chiral ionic organic crystal gas chromatography stationary phase, which is mainly used for the separation of positional isomers and chiral compounds, and belongs to the field of novel chromatographic stationary phase technology. Background Technology

[0002] Stationary phase-based chromatography is widely used in separation and analysis, and the stationary phase is crucial in determining chromatographic separation performance. In recent years, organic framework materials with controllable structure and tunable porosity have become a research hotspot. Materials such as chiral metal-organic frameworks (MOFs) and chiral covalent organic frameworks (CFOs) have wide applications in chiral chromatographic separation. However, these materials still have some significant drawbacks, such as the poor stability of chiral MOFs and the demanding preparation conditions and high costs of chiral CFOs. Therefore, the research and development of stable and low-cost gas chromatography stationary phase materials is of great importance. Summary of the Invention

[0003] The purpose of this invention is to provide a method for preparing chiral ionic organic crystal materials;

[0004] Another object of the present invention is to provide the chiral ionic organic crystal material prepared above as a chromatographic stationary phase for use in chromatographic separation.

[0005] I. Preparation of chiral ionic organic crystal materials

[0006] The method for preparing the chiral ionic organic crystal material of the present invention involves dissolving pyridine-type ionic liquid (CIL-Py) and biphenyl disulfonic acid (BDA) into a toluene-methanol mixed solution, mixing thoroughly, and then incubating at 15-35°C for 5-7 days to obtain CIOC.

[0007] The structure of the pyridine-type ionic liquid CIL-Py is as follows:

[0008]

[0009] Where X is Cl - , Br - or I - .

[0010] In the toluene-methanol mixed solution, the volume percentage of toluene is 5-18%; the molar ratio of pyridine ionic liquid (CIL-Py) and biphenyl disulfonic acid (BDA) is 1:1.

[0011] The obtained chiral ionic organic crystal CIOC was dispersed in methanol, ultrasonically exfoliated for 14–16 h, and dried to obtain two-dimensional nanosheet-like chiral ionic organic crystal material 2D-NSs. The concentration of CIOC dispersed in methanol was 1–2 mg / mL.

[0012] II. Characterization of 2D-NSs, CIOC, and the prepared capillary column

[0013] 1. Single-crystal X-ray diffraction

[0014] Figure 1 The ellipsoid diagram for the CIOC asymmetric element. Figure 2 This is the unit cell packing diagram of CIOC. Figure 1 This indicates that CIOC is formed by CIL-Py and BDA through ionic bonds, mainly relying on the bonding between the positively charged N atoms of the CIL-Py unit and the negatively charged O atoms of the BDA unit. Figure 2 This indicates that CIOC is formed through intralayer ionic bonds and interlayer π-π interactions.

[0015] Table 1 presents the relevant crystallographic data for chiral ionic organic crystals. Based on the crystallographic data and unit cell packing diagrams, the molecular formula of CIOC is C1. 46 H 58 N2O 10 S2 has unit cell parameters a=9.0954, b=28.981, c=20.898(3); α=90, β=90, γ=90, and belongs to the orthorhombic crystal system with space group C2221.

[0016]

[0017] 2. Atomic force microscope (AFM) images

[0018] Atomic force microscopy (AFM) images are primarily used to determine the thickness of 2D-NSs. AFM images of 2D-NSs and related thickness analysis plots are shown below. Figure 3 As shown, the thickness of the 2D-NSs prepared in this invention is approximately 10 nm.

[0019] 3. Infrared spectroscopy (FT-IR)

[0020] Figure 4 Infrared spectra of BDA, CIL-Py, CIOC, and 2D-NSs. 1190 -1 1077 -1 604 and 556 cm -1 The peak at 1733 cm⁻¹ is the characteristic absorption peak of sulfonic acid in BDA; in CIL-Py, the peak at 1733 cm⁻¹ is also present. -1 The absorption peak is at C=O, 1645 cm⁻¹. -1 1578cm-1 and 1456cm -1 Indicates the bipyridine skeleton, 1123 cm -1 and 1056 cm -1 The characteristic peaks indicate antisymmetric stretching of COC. All of these characteristic peaks can be found in the infrared spectra of CIOC and 2D-NSs, proving the successful synthesis of CIOC and 2D-NSs.

[0021] 4. Scanning electron microscope (SEM)

[0022] Figure 5 Cross-sectional scanning electron microscope (SEM) images of capillary columns coated with CIL-Py (a), CIOC (b), and 2D-NSs (c). Figure (a) shows that CIL-Py was successfully deposited on the inner wall of the capillary with a thickness of 3.2 μm. In Figure (b), the inner wall of the capillary column is coated with CIOC, with a thickness of 2.4 μm, appearing as blocks of varying sizes. Figure (c) shows protrusions of 4.4 μm on the surface of the gel layer, confirming the successful preparation of the 2D-NSs-coated capillary column.

[0023] III. Chromatographic performance of 2D-NSs, CIOC, and precursor molecule CIL-Py coated capillary columns

[0024] 1. Separation effect diagram of the three positional isomers (nitrotoluene, nitroaniline, and dimethylphenol)

[0025] The separation conditions used for the CIL-Py coated capillary column are as follows: (a) The temperature program for nitrotoluene is: 100 °C as the initial temperature, and 30 °C min at a time. -1 The temperature was increased to 170℃, and the N2 flow rate was 3.0 mL / min. -1 (b) The heating program for nitroaniline is as follows: starting at 50°C, and increasing by 30°C min... -1 The temperature was increased to 150℃, and the N2 flow rate was 3.0 mL / min. -1 (c) The heating program for dimethylphenol is as follows: starting at 70°C, increasing by 20°C min... -1 Heat to 150℃, N2 flow rate 2.0 mL / min -1 .

[0026] The separation conditions used for the CIOC-coated capillary column are as follows: (a) The temperature program for nitrotoluene is: 120 °C as the initial temperature, and 50 °C min at a time. -1 The temperature was increased to 180℃, and the N2 flow rate was 4.0 mL / min. -1 (b) The heating program for nitroaniline is as follows: starting at 80°C, and increasing by 40°C min. -1 The temperature was increased to 140℃, and the N2 flow rate was 2.0 mL / min.-1 (c) The heating program for dimethylphenol is as follows: starting at 100℃, increasing by 20℃ min... -1 Heat to 150℃, N2 flow rate 1.5 mL / min -1 .

[0027] The separation conditions used for the 2D-NSs-coated capillary column are as follows: (a) The temperature program for nitrotoluene is: 100 °C as the initial temperature, and 20 °C min at a rate of 20 °C. -1 Heat to 150℃, N2 flow rate 2.0 mL / min -1 (b) The heating program for nitroaniline is as follows: starting at 90°C, and increasing by 20°C min. -1 The temperature was increased to 160℃, and the N2 flow rate was 2.0 mL / min. -1 (c) The heating program for dimethylphenol is as follows: starting at 120°C, and increasing by 20°C min. -1 Heat to 150℃, N2 flow rate 1.0 mL / min -1 .

[0028] Figure 6 Figure (a) shows the separation effect of three capillary columns coated with CIL-Py, CIOC, and 2D-NSs on positional isomers. In Figure (a), (1) o- Nitrotoluene, (2) m- Nitrotoluene, (3) p- Nitrotoluene; in Figure (b), (1) o- Nitroaniline, (2) m- Nitroaniline, (3) p- Nitroaniline; in Figure (c), (1) 2,6- Dimethylphenol, (2) 2,5- Dimethylphenol, (3) 3,5- Dimethylphenol. From Figure 6 As can be seen, the CIL-Py, CIOC, and 2D-NSs columns exhibit similar retention capabilities for the three groups of substances, and their elution orders are also consistent. It is worth noting that the 2D-NSs coated column has a larger separation factor, indicating that the 2D-NSs column has stronger chromatographic separation capabilities.

[0029] 2. Separation effect diagram of chiral compounds

[0030] Figure 7 The separation results of decahydronaphthalene, phenylethanol nitrile, epichlorohydrin, and benzoin on three capillary columns coated with CIL-Py, CIOC, and 2D-NSs are shown. Figure 7Four analytes were involved: (a) decahydronaphthalene, (b) phenylethanol nitrile, (c) epichlorohydrin, and (d) benzoin. The separation conditions used for the CIL-Py coated capillary column were as follows: (a) for decahydronaphthalene: 80°C, N2 flow rate of 2.0 mL / min. -1 (b) The separation conditions for phenylethanol nitrile were: 80℃, N2 flow rate of 2.0 mL / min. -1 (c) The separation conditions for epichlorohydrin were: 120℃, N2 flow rate of 2.0 mL / min. -1 (d) The separation conditions for benzoin were: 180℃, N2 flow rate of 2.0 mL / min. -1 The separation conditions used for the CIOC-coated capillary column are as follows: (a) The separation conditions for decahydronaphthalene are: 105℃, N2 flow rate of 1.0 mL / min. -1 (b) The separation conditions for phenylethanol nitrile were: 80℃, N2 flow rate of 2.0 mL / min. -1 (c) The separation conditions for epichlorohydrin were: 110℃, N2 flow rate of 1.0 mL / min. -1 (d) The separation conditions for benzoin were: 180℃, N2 flow rate of 2.0 mL / min. -1 The separation conditions used for the 2D-NSs-coated capillary column are as follows: (a) The separation conditions for decahydronaphthalene are: 45℃, N2 flow rate of 1.5 mL / min. -1 (b) The separation conditions for phenylethanol nitrile were: 150℃, N2 flow rate of 1.0 mL / min. -1 (c) The separation conditions for epichlorohydrin were: 70℃, N2 flow rate of 1.0 mL / min. -1 (d) The separation conditions for benzoin were: 150℃, N2 flow rate of 1.0 mL / min. -1 .

[0031] from Figure 7 As can be seen, for decahydronaphthalene and phenylethanol nitrile, which can be separated by all three columns, the chromatographic peaks presented by the 2D-NSs-coated capillary column exhibit better symmetry. Based on the separation chromatograms of epichlorohydrin and benzoin, the enantiomeric separation performance can be reasonably determined to be in the order of superiority: 2D-NSs > CIOC > CIL. This performance improvement can be attributed to the enhanced hydrogen bonding, dipole-dipole, and π-π interactions between CIL and BDA, as well as the introduction of a certain steric hindrance effect. Compared with CIOC, 2D-NSs exposes more interaction sites and has stronger interactions with the analytes, thus achieving better selective separation.

[0032] In summary, this invention presents the first preparation of an ionicly bridged chiral ionic organic crystal material. Two-dimensional nanosheets were fabricated via ultrasonic exfoliation and applied to gas chromatography, where the two-dimensional nanosheets exhibited optimal chiral resolution performance. The unique bonding mechanism of the material enhances its stability, while the orderliness of the single crystals improves its performance. The chiral ionic liquid, being a multi-component organic cation, mitigates preparation costs, and the solvent-evaporation preparation method significantly improves the safety of the experimental process. Attached Figure Description

[0033] Figure 1 Ellipsoid diagram of the asymmetric unit cell of a chiral ionic organic crystal.

[0034] Figure 2 This is a unit cell packing diagram of a chiral ionic organic crystal.

[0035] Figure 3 An atomic force microscope image of a two-dimensional nanosheet.

[0036] Figure 4 Infrared spectra of pyridine-type chiral ionic liquids, biphenyl disulfonic acid, chiral ionic organic crystals, and two-dimensional nanosheets.

[0037] Figure 5 Cross-sectional scanning electron microscope images of pyridine-type chiral ionic liquids, chiral ionic organic crystals, and two-dimensional nanosheet-coated capillary columns.

[0038] Figure 6 The separation effect of nitrotoluene (a), nitroaniline (b), and dimethylphenol (c) on capillary columns coated with pyridine-type chiral ionic liquid, chiral ionic organic crystal, and two-dimensional nanosheets is shown in the figure.

[0039] Figure 7 The separation effects of decahydronaphthalene (a), phenylethanol nitrile (b), epichlorohydrin (c), and benzoin (d) on capillary columns coated with pyridine-type chiral ionic liquid, chiral ionic organic crystal, and two-dimensional nanosheets are shown in the figure. Detailed Implementation

[0040] The following specific embodiments further illustrate the preparation method of the chiral ionic organic crystal-based two-dimensional nanosheets of the present invention as a stationary phase for gas chromatography.

[0041] Example 1

[0042] (1) 6.2 mg (0.01 mmol) of pyridine-type chiral ionic liquid (CIL-Py, X=Cl) -Solution A was obtained by dissolving 3.1 mg (0.01 mmol) of biphenyl disulfonic acid (BDA) in 1 mL of methanol containing 8% toluene. Solution B was obtained by dissolving BDA in 1 mL of methanol containing 8% toluene. Solution A and solution B were mixed in a sample vial, the cap was tightened, and the vial was incubated at 25°C. The crystals that initially formed in a short time were heated to dissolve and then allowed to cool naturally for recrystallization. After 5 days, pale yellow transparent crystals were obtained, which are chiral ionic organic crystals (CIOC).

[0043] (2) CIOC was ultrasonically exfoliated in methanol (1.0 mg / mL) for 10 h to obtain two-dimensional nanosheets (2D-NPs).

[0044] (3) The separation performance of capillary columns coated with CIOC and 2D-NSs was analyzed under the aforementioned conditions and methods. The results showed that the separation performance of 2D-NSs and CIOC coated capillary columns was comparable.

[0045] Example 2

[0046] (1) 7.1 mg (0.01 mmol) of pyridine-type chiral ionic liquid (CIL-Py, X=Br) - Solution A was obtained by dissolving 3.1 mg (0.01 mmol) of biphenyl disulfonic acid (BDA) in 1 mL of methanol containing 8% toluene. Solution B was obtained by dissolving BDA in 1 mL of methanol containing 8% toluene. Solution A and solution B were mixed in a sample vial, the cap was tightened, and the vial was incubated at 25°C. The crystals that initially formed in a short time were heated to dissolve and then allowed to cool naturally for recrystallization. After 7 days, pale yellow transparent crystals were obtained, which are chiral ionic organic crystals (CIOC).

[0047] (2) CIOC was ultrasonically exfoliated in methanol (1.0 mg / mL) for 14 h to obtain two-dimensional nanosheets (2D-NPs).

[0048] (3) The separation performance of CIOC and 2D-NSs coated capillary columns was analyzed under the aforementioned conditions and methods. The results showed that the chromatographic separation performance of the 2D-NSs coated capillary column was significantly better than that of the CIOC coated capillary column.

[0049] Example 3

[0050] (1) 7.1 mg (0.01 mmol) of pyridine-type chiral ionic liquid (CIL-Py, X=I) -Solution A was obtained by dissolving 3.1 mg (0.01 mmol) of biphenyl disulfonic acid (BDA) in 1 mL of methanol containing 8% toluene. Solution B was obtained by dissolving BDA in 1 mL of methanol containing 8% toluene. Solution A and solution B were mixed in a sample vial, the cap was tightened, and the vial was incubated at 25°C. The crystals that initially formed in a short time were heated to dissolve and then allowed to cool naturally for recrystallization. After 7 days, pale yellow transparent crystals were obtained, which are chiral ionic organic crystals (CIOC).

[0051] (2) CIOC was ultrasonically exfoliated in methanol (1.0 mg / mL) for 16 h to obtain two-dimensional nanosheets (2D-NPs).

[0052] (3) The separation performance of capillary columns coated with CIOC and 2D-NSs was analyzed under the aforementioned conditions and methods. The results showed that the separation performance of 2D-NSs and CIOC coated capillary columns was comparable.

[0053] Example 4

[0054] (1) 7.1 mg (0.01 mmol) of pyridine-type chiral ionic liquid (CIL-Py, X=Br) - Solution A was obtained by dissolving 3.1 mg (0.01 mmol) of biphenyl disulfonic acid (BDA) in 1 mL of methanol containing 5% toluene; Solution B was obtained by dissolving BDA in 1 mL of methanol containing 5% toluene; Solution A and Solution B were mixed in a sample vial, the cap was tightened, and the vial was incubated at 15°C. The crystals initially formed in a short time were heated to dissolve and then allowed to cool naturally before recrystallization. After 5 days, pale yellow transparent crystals were obtained, which are chiral ionic organic crystals (CIOC).

[0055] (2) CIOC was ultrasonically exfoliated in methanol (2.0 mg / mL) for 10 h and dried to obtain two-dimensional nanosheets (2D-NPs).

[0056] (3) The separation performance of CIOC-coated capillary columns and 2D-NSs-coated capillary columns was analyzed under the aforementioned conditions and methods. The results showed that the chromatographic separation performance of CIOC-coated capillary columns was slightly better than that of 2D-NSs-coated capillary columns.

[0057] Example 5

[0058] (1) 7.1 mg (0.01 mmol) of pyridine-type chiral ionic liquid (CIL-Py, X=Br) -Solution A was obtained by dissolving 3.1 mg (0.01 mmol) of biphenyl disulfonic acid (BDA) in 1 mL of methanol containing 10% toluene; Solution B was obtained by dissolving BDA in 1 mL of methanol containing 10% toluene; Solution A and Solution B were mixed in a sample vial, the cap was tightened, and the vial was incubated at 35°C. The crystals initially formed in a short time were heated to dissolve and then allowed to cool naturally before recrystallization. After 6 days, pale yellow transparent crystals were obtained, which are chiral ionic organic crystals (CIOC).

[0059] (2) CIOC was ultrasonically exfoliated in methanol (1.5 mg / mL) for 16 h and dried to obtain two-dimensional nanosheets (2D-NPs).

[0060] (3) The separation performance of CIOC-coated and 2D-NSs-coated capillary columns was analyzed under the aforementioned conditions and methods. The results showed that the chromatographic separation performance of CIOC-coated and 2D-NSs-coated capillary columns was almost the same.

[0061] Example 6

[0062] (1) 14.2 mg (0.02 mmol) of pyridine-type chiral ionic liquid (CIL-Py, X=Br) - Solution A was obtained by dissolving 6.2 mg (0.02 mmol) of biphenyl disulfonic acid (BDA) in 1 mL of methanol containing 18% toluene. Solution B was obtained by dissolving BDA in 1 mL of methanol containing 18% toluene. Solutions A and B were mixed in a sample vial, the cap was tightened, and the vial was incubated at 25°C. The initially formed crystals were dissolved by heating and then allowed to cool naturally before recrystallization. After 5 days, pale yellow transparent crystals were obtained, which were chiral ionic organic crystals (CIOC).

[0063] (2) CIOC was ultrasonically exfoliated in methanol (2.0 mg / mL) for 16 h to obtain two-dimensional nanosheets (2D-NPs);

[0064] (3) The separation performance of CIOC and 2D-NSs coated capillary columns was analyzed under the aforementioned conditions and methods. The results showed that the chromatographic separation performance of the 2D-NSs coated capillary column was slightly better than that of the CIOC coated capillary column.

Claims

1. A method for preparing a chiral ionic organic crystal material, characterized in that, The pyridine-type ionic liquid CIL-Py and biphenyl disulfonic acid BDA are dissolved in a toluene-methanol mixed solution to obtain solution A and solution B. After thoroughly mixing solution A and solution B, they are incubated at 15~35℃ for 5~7 days to obtain the chiral ionic organic crystal material CIOC. The structure of the pyridine-type ionic liquid CIL-Py is as follows: Where X is Cl - , Br - or I - .

2. The method for preparing a chiral ionic organic crystal material as described in claim 1, characterized in that: The obtained chiral ionic organic crystal CIOC was dispersed in methanol, ultrasonically exfoliated for 14-16 h, and dried to obtain two-dimensional organic crystal nanosheets 2D-NSs.

3. The method for preparing a chiral ionic organic crystal material as described in claim 1 or 2, characterized in that: In the toluene-methanol mixed solution, the volume percentage of toluene is 5-18%.

4. The method for preparing a chiral ionic organic crystal material as described in claim 1 or 2, characterized in that: The concentration of chiral ionic organic crystal CIOC dispersed in methanol is 1~2 mg / mL.

5. The application of chiral ionic organic crystal materials prepared by the method described in claim 1 or 2 as stationary phases in chiral gas chromatography.

6. The application of the chiral ionic organic crystal material as described in claim 5 as a stationary phase in chiral gas chromatography, characterized in that: Used to separate nitrotoluene isomers.

7. The application of the chiral ionic organic crystal material as described in claim 5 as a stationary phase in chiral gas chromatography, characterized in that: Used to separate nitroaniline isomers.

8. The application of the chiral ionic organic crystal material as described in claim 5 as a stationary phase in chiral gas chromatography, characterized in that: Used to separate dimethylphenol isomers.

9. The application of the chiral ionic organic crystal material as described in claim 5 as a stationary phase in chiral gas chromatography, characterized in that: It is used to separate decahydronaphthalene, phenylethanol nitrile, epichlorohydrin and benzoin.

Images