Amphiphilic covalent organic framework mixed-mode chromatography stationary phase, method of making and use thereof

Abstract

The application belongs to the technical field of chromatographic separation, and particularly relates to an amphiphilic covalent organic framework mixed mode chromatographic stationary phase, a preparation method thereof and application. The application is characterized in that: silica gel is used as a carrier, and a covalent organic framework is in-situ immobilized on the surface of the silica gel through a chemical bond; then, an ionic liquid with a hydrophilic group is polymerized in the covalent organic framework by using an in-situ polymerization method, and the stationary phase is obtained. The stationary phase provided by the application can generate multiple interactions such as hydrophobic interaction, pi-pi interaction, hydrophilic interaction and hydrogen bond interaction between the stationary phase and an analyte, can provide high separation selectivity for components with similar structures, and is expected to be widely applied in the field of complex system separation and analysis.

Description

Technical Field

[0001] This invention belongs to the field of chromatographic separation technology, specifically relating to amphiphilic covalent organic framework mixed-mode chromatographic stationary phases, their preparation methods, and applications. Background Technology

[0002] The accurate determination of biomolecules, pesticides, drugs, and other substances is crucial in clinical, environmental, and food safety fields. However, these complex samples are diverse in type and chemical composition, significantly affecting the accuracy and reliability of the results, posing a significant challenge to separation and analysis techniques. To achieve high separation capabilities for complex samples using high-performance liquid chromatography (HPLC), the selectivity of the stationary phase is paramount. However, conventional stationary phases suffer from drawbacks such as limited separation modes, low selectivity, long separation times, and high consumption of organic reagents, restricting their further application in complex systems in clinical, environmental, and food applications. Therefore, developing novel, highly efficient chromatographic stationary phases to meet the separation requirements of complex systems has become a research hotspot in the field of chromatography.

[0003] Covalent organic frameworks (COFs) are a novel type of porous crystalline network polymer, constructed from covalently bonded light elements through dynamic covalent chemistry. Benefiting from their interconnected porosity, ultra-low density, large surface area, and high chemical stability, COFs have shown great promise since their inception, exhibiting significant potential applications in adsorption and separation, heterogeneous catalysis, biochemical sensors, and energy storage. In chromatographic separation, immobilizing different COFs on spherical SiO2 surfaces is a common method for preparing COF-based stationary phases. These COF@SiO2 stationary phases, relying on the hydrophobic properties of the aromatic frameworks of COFs, demonstrate good application potential for hydrophobic compounds such as alkylbenzenes, polycyclic aromatic hydrocarbons, and organohalides, but their selectivity for polar compounds is limited. Furthermore, it has been reported that COFs experience a decrease in porosity and crystallinity after solvent exchange, which contradicts the fact that HPLC requires frequent changes in the mobile phase composition to improve separation performance. When using different mobile phases, structural defects in COFs can lead to low separation selectivity, low column efficiency, and high column pressure, which will severely limit their application potential in HPLC.

[0004] Therefore, it is particularly urgent to develop a simple and effective method to control the hydrophilic sites of the SiO2@COFs stationary phase and maintain its structural stability. Summary of the Invention

[0005] This invention overcomes the limitations in selectivity and stability of COFs-modified silica gel (COFs@SiO2) stationary phases for separating polar compounds. It provides a highly stable amphiphilic covalent organic framework mixed-mode chromatographic stationary phase by in-situ polymerization of ionic liquids with hydrophilic groups on the surface of the COFs@SiO2 stationary phase. This stationary phase has a stable structure, enabling effective separation of polar compounds, and exhibits high column efficiency and low column pressure when applied to high-performance liquid chromatography (HPLC) columns.

[0006] To achieve the above technical objectives, the present invention is implemented through the following technical solution:

[0007] This invention provides a mixed-mode amphiphilic covalent organic framework chromatographic stationary phase. The stationary phase uses silica gel as a carrier, with the covalent organic framework in situ immobilized on the silica gel surface through chemical bonds. Then, an ionic liquid with hydrophilic groups is polymerized into the covalent organic framework using an in-situ polymerization method, yielding polymerized ionic liquid-modified covalent organic framework-based silica gel microspheres, which constitute the amphiphilic mixed-mode amphiphilic covalent organic framework chromatographic stationary phase and can be used as a high-performance liquid chromatography (HPLC) stationary phase. The polymerization of the hydrophilic ionic liquid stabilizes the covalent organic framework, and the hydrophilic groups of the ionic liquid improve the strong hydrophobicity of the covalent organic framework, giving it hydrophilic properties for the separation of polar compounds.

[0008] In one specific embodiment, the silica gel is an amino silica gel; the covalent organic framework is obtained by reacting 1,4-dialdehyde-2,5-divinylbenzene (1,4-Benzenedicarboxaldehyd, DVA) and 1,3,5-tris(4-aminophenyl)benzene (TAPB) as raw materials; the aldehyde-containing 1,4-dialdehyde-2,5-divinylbenzene is chemically bonded to the amino groups on the surface of the amino silica gel, thereby achieving in-situ immobilization of the covalent organic framework on the silica gel surface.

[0009] In one specific embodiment, the hydrophilic group in the ionic liquid is a sulfonic acid group. Specifically, the ionic liquid is a 1-sulfopropyl-3-vinylimidazolium chloride-based ionic liquid (sIL).

[0010] The structure formed by the polymerization of the ionic liquid in a covalent organic framework is shown in formula (I):

[0011]

[0012] In addition, this invention provides a method for preparing a mixed-mode chromatographic stationary phase with an amphiphilic covalent organic framework, specifically including the following steps:

[0013] Aminosilicone, 1,4-dialdehyde-2,5-divinylbenzene, 1,3,5-tris(4-aminophenyl)benzene, and acetic acid were dispersed in acetonitrile and reacted at room temperature for 72 h. After washing and drying, COFs-modified silica gel, namely SiO2@COF, was obtained. DVA-TAPB Microspheres. The ratio of aminosilicone, 1,4-dialdehyde-2,5-divinylbenzene, 1,3,5-tris(4-aminophenyl)benzene and acetic acid is 3.0 g: 0.3 g: 0.4 g: 15 mL.

[0014] The COFs-modified silica gel obtained in step 1 above, 1-propylsulfonic acid-3-vinylimidazolium chloride ionic liquid, and azobisisobutyronitrile were added to dimethyl sulfoxide; the reaction was carried out at room temperature under a nitrogen atmosphere for 0.5–2 h, followed by heating to 60–110 °C and reacting for 18–36 h. After washing and drying, SiO2@COFs were obtained. DVA-TAPB / PsIL microspheres. The ratio of COFs-modified silica gel, 1-propylsulfonic acid-3-vinylimidazolium chloride ionic liquid, azobisisobutyronitrile, and dimethyl sulfoxide is 3.0 g: 0.1-3 g: 0.1-0.5 g: 50-200 mL. Preferably, the ratio of COFs-modified silica gel, 1-propylsulfonic acid-3-vinylimidazolium chloride ionic liquid, azobisisobutyronitrile, and dimethyl sulfoxide is 3.0 g: 2.0 g: 0.3 g: 100 mL.

[0015] Furthermore, the present invention also provides the application of amphiphilic covalent organic framework mixed-mode chromatographic stationary phase in the separation of polar compounds, wherein the polar compounds are nucleoside / base compounds, sulfonamide antibiotics, alkylbenzenes, aniline compounds, phenolic compounds, organophosphorus pesticides and / or benzoylurea insecticides.

[0016] Among them, nucleoside / base compounds include 2-amino-4-chloro-6-methoxypyrimidine, 6-chloro-7-azapurine, thymine, β-thymidine, 2'-deoxyuridine, 5-methyluridine, adenosine, 2-aminoadenosine, and cytosine.

[0017] Sulfonamide antibiotics include sulfonamides, sulfaguanidine, sulfapyridine, sulfadimethylpyrimidine, sulfamethoxypyridazine, and sulfamethylpyrimidine;

[0018] Alkylbenzenes include toluene, ethylbenzene, n-propylbenzene, n-butanebenzene, and n-pentanebenzene;

[0019] Aniline compounds include aniline, o-toluidine, N-methylaniline, m-nitroaniline, o-nitroaniline, and 1-naphthylamine;

[0020] Phenolic compounds include 2,6-dichlorophenol, hydroquinone, phenol, o-cresol, 2,5-xylenol, and 3-nitrophenol;

[0021] Organophosphorus pesticides include diazinon, chlorpyrifos, fenthion, and chlorpyrifos;

[0022] Benzoylurea insecticides include fluorourea, chlorfenapyr, fluorourea, and fluorobenzoylurea.

[0023] The chromatographic stationary phase is used in the separation of polar compounds in a high-performance liquid chromatography (HPLC) column, and the preparation method of the HPLC column includes:

[0024] Take 1.7–3.4 g of the chromatographic stationary phase, disperse it in methanol, pack the column at 40 MPa pressure, maintain for 30 min, and finally wash the column with pure methanol at 0.2 mL / min for 10 h to complete the column packing.

[0025] Compared with the prior art, the beneficial effects of the present invention include:

[0026] (1) Polymerized ionic liquids, which are polymerized from ionic liquid monomers, combine the excellent properties of both ionic liquids and polymers. This invention introduces ionic liquids into the pores of COFs for in-situ polymerization. This not only utilizes the hydrophilic properties of ionic liquids to introduce multiple interaction sites, enabling efficient separation of multiple analytes, but also cleverly utilizes the mechanical strength of polymerized ionic liquids to support the pores of COFs, enhancing the applicability of COFs-based stationary phases in different mobile phases.

[0027] (2) The stationary phase provided by the present invention can generate multiple interactions with the analytes, such as hydrophobic, π-π, hydrophilic, and hydrogen bonding, which can provide high separation selectivity for components with similar structures and is expected to be widely used in the field of separation and analysis of complex systems.

[0028] (3) This invention has discovered that in-situ polymerized ionic liquids can support COF DVA-TAPB The pores promote mass transfer and improve column efficiency, resulting in a column efficiency of up to 21,626 blocks / meter when applied to high-performance liquid chromatography columns. At the same time, it improves the structural stability, and the stability and reproducibility are good when applied to mobile phases with different organic solvents. After 10 consecutive injections, the relative standard deviation of retention time and peak area is less than 1.47%.

[0029] (4) The SiO2@COF provided by this invention DVA-TAPB The / PsIL stationary phase possesses a high density of multiple interaction sites, exhibiting excellent amphiphilicity. It can achieve complete separation of nonpolar and weakly polar compounds in reversed-phase chromatography, and also effectively separate polar compounds in hydrophilic interaction mode, with a selectivity factor as high as 6.05; it is compatible with SiO2@COF DVA-TAPBCompared to the stationary phase, it exhibits extremely high separation selectivity. Attached Figure Description

[0030] Figure 1 This is a flowchart illustrating the preparation process of the amphiphilic covalent organic framework mixed-mode chromatographic stationary phase of the present invention.

[0031] Figure 2 It is amino silica gel (a), SiO2@COF DVA-TAPB (b) and SiO2@COF DVA-TAPB Scanning electron microscope image of / PsIL(c) and SiO2@COF DVA-TAPB X-ray energy spectrum (dh) of / PsIL.

[0032] Figure 3 It is SiO2@COF DVA-TAPB (a) and SiO2@COF DVA-TAPB / PsIL(b) water contact angle diagram.

[0033] Figure 4 It is amino silica gel, SiO2@COF DVA-TAPB and SiO2@COF DVA-TAPB Infrared spectrum of / PsIL.

[0034] Figure 5 It is amino silica gel, SiO2@COF DVA-TAPB and SiO2@COF DVA-TAPB Nitrogen adsorption-desorption isotherms (a) and pore size distribution diagram (b) of / PsIL.

[0035] Figure 6 It is a nucleoside / base compound in SiO2@COF DVA-TAPB / PsIL column capacity factor k versus water content in the mobile phase graph.

[0036] Figure 7 It is a nucleoside / base compound in SiO2@COF DVA-TAPB / PsIL column (a) and SiO2@COF DVA-TAPB Chromatographic separation diagram on column (b). Figure 7 Chromatographic peaks 1–9 in a and 7b are 2-amino-4-chloro-6-methoxypyrimidine, 6-chloro-7-azapurine, thymine, β-thymidine, 2'-deoxyuridine, 5-methyluridine, adenosine, 2-aminoadenosine, and cytosine, respectively. Figure 8 It is a sulfonamide antibiotic in SiO2@COF DVA-TAPB / PsIL column (a) and SiO2@COF DVA-TAPB Chromatographic separation diagram on column (b). Figure 8In a and 8b, chromatographic peaks 1-6 represent sulfonamide, sulfaguanidine, sulfapyridine, sulfadimethylpyrimidine, sulfamethoxypyridazine, and sulfamethylpyrimidine, respectively.

[0037] Figure 9 It is a sulfonamide antibiotic in SiO2@COF DVA-TAPB / PsIL column capacity factor k versus water content in the mobile phase graph.

[0038] Figure 10 It is an alkylbenzene in SiO2@COF DVA-TAPB / PsIL column capacity factor k and acetonitrile content in the mobile phase.

[0039] Figure 11 It is an alkylbenzene in SiO2@COF DVA-TAPB / PsIL column (a) and SiO2@COF DVA-TAPB Chromatographic separation diagram on column (b). Figure 11 In a and 11b, chromatographic peaks 1-5 represent toluene, ethylbenzene, n-propylbenzene, n-butylbenzene, and n-pentylbenzene, respectively.

[0040] Figure 12 It is aniline in SiO2@COF DVA-TAPB / PsIL column (a) and SiO2@COF DVA-TAPB Chromatographic separation diagram on column (b). Figure 12 In a and 12b, chromatographic peaks 1-6 represent aniline, o-toluidine, N-methylaniline, m-nitroaniline, o-nitroaniline, and 1-naphthylamine, respectively.

[0041] Figure 13 It is phenols in SiO2@COF DVA-TAPB / PsIL column (a) and SiO2@COF DVA-TAPB Chromatographic separation diagram on column (b). Figure 13 The chromatographic peaks 1-6 in a and 13b are 2,6-dichlorophenol, hydroquinone, phenol, o-cresol, 2,5-xylenol, and 3-nitrophenol, respectively.

[0042] Figure 14 Organophosphorus pesticides in SiO2@COF DVA-TAPB / PsIL column (a) and SiO2@COF DVA-TAPB Chromatographic separation diagram on column (b). Figure 14 In chromatographic peaks 1-4 of a and 14b, the active ingredients are diazinon, chlorpyrifos, fenthion, and chlorpyrifos, respectively.

[0043] Figure 15 It is a benzoylurea insecticide in SiO2@COF DVA-TAPB / PsIL column (a) and SiO2@COFDVA-TAPB Chromatographic separation diagram on column (b). Figure 15 In a and 15b, chromatographic peaks 1-4 represent fluorouracil, chlorfenapyr, fluorouracil, and fluorobenzamide, respectively.

[0044] Figure 16 It is SiO2@COF DVA-TAPB / PsIL column stability test diagram. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of the embodiments of this invention will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0046] Example 1

[0047] A procedure for preparing a mixed-mode chromatographic stationary phase with an amphiphilic covalent organic framework is described in [reference needed]. Figure 1 Specifically, it includes the following steps:

[0048] 1. SiO2@COF DVA-TAPB Preparation of microspheres

[0049] 3.0 g of aminosilicone (purchased from Suzhou Nanomicro Technology Co., Ltd., 5 μm), 0.3 g of DVA, 0.4 g of TAPB, and 15 mL of acetic acid (12 mol / L) were added to 150 mL of acetonitrile and ultrasonically dispersed for 15 min. The reaction solution was then placed at room temperature and reacted for 72 h. After the reaction, the mixture was washed three times with tetrahydrofuran and anhydrous ethanol, and then centrifuged. The mixture was then dried in a vacuum drying oven at 60°C for 12 h to obtain SiO2@COF. DVA-TAPB Microspheres.

[0050] 2. SiO2@COF DVA-TAPB Optimization of PsIL microsphere preparation method

[0051] The SiO2@COF obtained in step 1 above DVA-TAPB Microspheres, SiL, and azobisisobutyronitrile were ultrasonically dispersed in dimethyl sulfoxide; under a nitrogen atmosphere, the mixture was stirred at room temperature for 1 h, then heated to 80°C and reacted for another 24 h; after the reaction was completed, the mixture was cooled to room temperature and washed three times successively with methanol and anhydrous ethanol by centrifugation; finally, it was dried in a vacuum drying oven at 60°C for 12 h to obtain SiO2@COF DVA-TAPB / PsIL microspheres.

[0052] SiO2@COF DVA-TAPBThe optimized dosages of microspheres, SIL, azobisisobutyronitrile, and dimethyl sulfoxide are shown in Table 1 below.

[0053] Table 1. SiO2@COF DVA-TAPB Optimization of raw material usage for core-shell microspheres

[0054] 3.0 2.0 500 80 3.0 1.0 300 100

[0055] Experimental results show that SiO2@COF DVA-TAPB When the ratio of SiO2@COF to sIL, azobisisobutyronitrile, and dimethyl sulfoxide was 3.0 g: 2.0 g: 500 mg: 80 mL, elemental analysis results showed that SiO2@COF DVA-TAPB The contents of C, H, N, and S elements in / PsIL are 13.39%, 1.50%, 1.87%, and 0.42%, respectively; the SiO2@COF content was adjusted. DVA-TAPB When the ratio of SiO2, SiIL, azobisisobutyronitrile (AIBN), and dimethyl sulfoxide (DMSO) was 3.0 g: 1.0 g: 300 mg: 100 mL, elemental analysis results showed that SiO2@COF DVA-TAPB The C, H, N, and S element contents in / PsIL are 22.84%, 2.57%, 2.94%, and 1.43%, respectively; therefore, selecting excessive sIL will lead to self-aggregation, which is detrimental to the formation of sIL in SiO2@COF. DVA-TAPB The polymerization on the surface was chosen, therefore SiO2@COF was selected. DVA-TAPB The ratio of SiO2, sIL, azobisisobutyronitrile (AIBN), and dimethyl sulfoxide (DMSO) was 3.0 g: 1.0 g: 300 mg: 100 mL. SiO2@COF prepared using this optimized ratio... DVA-TAPB / PsIL is denoted as optimized SiO2@COF DVA-TAPB / PsIL.

[0056] SiO2@COF was observed using SEM DVA-TAPB and optimized SiO2@COF DVA-TAPB Microstructure of / PsIL. Figure 2 a shows that the particle size of the amino silica gel is approximately 5 μm; Figure 2 b shows SiO2@COF DVA-TAPB The particle size is approximately 5.4 μm, and numerous protruding DVA-TAPB-COF particles can be observed on its rough surface; SiO2@COF DVA-TAPB / PsIL exhibits a regular spherical morphology with a particle size of approximately 5.6 μm. Figure 2 c). SiO2@COF DVA-TAPB X-ray energy spectrum image of / PsIL ( Figure 2 The dh) diagram shows that, in addition to Si and O, C, N, and S elements are uniformly distributed in SiO2@COF. DVA-TAPB / PsIL surface. The presence of S element fully confirms that the polymerized 1-propylsulfonic acid-3-vinylimidazolium chloride ionic liquid (polymerized sIL, PsIL) was successfully modified in the DVA-TAPB-COFs framework.

[0057] Detection of SiO2@COF DVA-TAPB and optimized SiO2@COF DVA-TAPB / PsIL water contact angle, results as follows Figure 3 As shown in a, SiO2@COF DVA-TAPB Its water contact angle can reach 104.7°, exhibiting strong hydrophobic characteristics. Figure 3 b shows that after modifying PsIL, SiO2@COF DVA-TAPB / PsIL exhibits a water contact angle of 69.2°, demonstrating good hydrophilicity. This property is expected to promote the development of SiO2@COF DVA-TAPB The / PsIL stationary phase exhibits excellent separation performance for polar analytes in hydrophilic chromatography mode.

[0058] Amino silica gel, SiO2@COF DVA-TAPB and optimized SiO2@COF DVA-TAPB The infrared spectrum of / PsIL is as follows Figure 4 As shown. SiO2@COF DVA-TAPB At 1620cm -1 The absorption peaks at 1519 and 1428 cm⁻¹ are attributed to the C=N stretching vibration in the DVA-TAPB-COF framework. -1 The absorption peaks at 1046, 816, and 470 cm⁻¹ are attributed to the aromatic skeleton vibrations of DVA-TAPB-COFs. Furthermore, absorption peaks at 1046, 816, and 470 cm⁻¹ are also observed. -1 The absorption peaks at this point are attributed to the Si-O-Si antisymmetric stretching vibration, SiO-H symmetric stretching vibration, and Si-O bending vibration of amino silica gel. (SiO2@COF) DVA-TAPB / PsIL at 1620cm -1 The absorption peak at 1190 cm⁻¹ is significantly enhanced, which may be due to the skeletal vibration of the imidazole ring. It should be noted that the sulfonic acid group shows a significant increase in absorption at 1190 cm⁻¹. -1 With 1068cm -1 The characteristic peaks on the left and right are covered by strong Si-O characteristic peaks.

[0059] SiO2@COF DVA-TAPB and optimized SiO2@COF DVA-TAPB / PsIL N2 adsorption / desorption isotherms, such as Figure 5 As shown in a. It is worth noting that in SiO2@COF DVA-TAPB and SiO2@COF DVA-TAPBTypical type IV isotherms with an H1 hysteresis loop were observed on / PsIL, indicating the presence of a mesoporous structure. For example... Figure 5 As shown in b, relative to amino silica gel, SiO2@COF DVA-TAPB A new pore of 2.32 nm was observed, originating from COFs, indicating successful COF growth on the amino silica surface. The molecular size of PsIL is... It can penetrate into pores as small as 2.32 nm to polymerize. The resulting SiO2@COF DVA-TAPB No pores of 2.28 nm were observed in PsIL, suggesting that PsIL has limitations in COF. DVA-TAPB Polymerization was successfully achieved within the pores.

[0060] 3. Take 2.5g of the optimized SiO2@COF prepared in step 2 above. DVA-TAPB Microspheres were ultrasonically dispersed in 50 mL of methanol, then loaded into a homogenate column (4.6 mm × 150 mm, Dalian Elite Analytical Instruments Co., Ltd.) at a pressure of 40 MPa and maintained for 30 min. Finally, a liquid chromatography infusion pump was used to deliver the microspheres at a rate of 0.2 mL / min. -1 The column was washed with pure methanol for 10 hours to complete the SiO2@COF process. DVA-TAPB / PsIL column packing. Additionally, SiO2@COF DVA-TAPB A microsphere-packed chromatographic column was used as a control. SiO2@COF DVA-TAPB The steps of microsphere-packed chromatographic columns and the optimization of SiO2@COF DVA-TAPB The same applies to microsphere-packed chromatographic columns.

[0061] Example 2

[0062] The SiO2@COF prepared in Example 1 DVA-TAPB / PsIL column and SiO2@COF DVA-TAPB The chromatographic column was used as a high-performance liquid chromatography column to test SiO2@COF. DVA-TAPB The hydrophilic selectivity of the / PsIL column and its ability to separate nucleosides / bases. Chromatographic analysis conditions: mobile phase: acetonitrile / ammonium acetate solution (10 mmol / L) = 95 / 5; column temperature: 40℃; flow rate: 1.0 mL / min; injection volume: 5 μL; detection wavelength: 260 nm.

[0063] like Figure 6 As shown, when the volume fraction of water in the mobile phase varies from 5% to 40%, the seven nucleosides / bases in SiO2@COF DVA-TAPBThe retention values ​​on the / PsIL column decreased accordingly, consistent with hydrophilic retention characteristics. Notably, the retention factors of the two analytes, 2-amino-4-chloro-6-methoxypyrimidine and 6-chloro-7-azapurine, exhibited a U-shaped curve with respect to the volume fraction of water in the mobile phase, indicating that the column also possesses mixed-mode retention characteristics. Figure 7 As shown in Figure a, chromatographic peaks 1-9 represent 2-amino-4-chloro-6-methoxypyrimidine, 6-chloro-7-azapurine, thymine, β-thymidine, 2'-deoxyuridine, 5-methyluridine, adenosine, 2-aminoadenosine, and cytosine, respectively. These nine nucleosides / bases are observed in SiO2@COF... DVA-TAPB Good separation was achieved using the / PsIL column; however, under the same chromatographic conditions, the nine nucleosides / bases were separated using SiO2@COF. DVA-TAPB Ineffective separation cannot be achieved on the chromatographic column ( Figure 7 b), and its retention order is the same as that of SiO2@COF DVA-TAPB The PsIL columns also differ. These results indicate that PsIL enhances SiO2@COF DVA-TAPB The hydrophilic selectivity of PsIL for nucleosides / bases further confirms the important role of PsIL in hydrophilic separation.

[0064] Example 3

[0065] The SiO2@COF prepared in Example 1 DVA-TAPB / PsIL column and SiO2@COF DVA-TAPB The chromatographic column, as a high-performance liquid chromatography column, is used to detect SiO2@COF. DVA-TAPB / PsIL column separation capability for sulfonamide antibiotics. Chromatographic analysis conditions: mobile phase: acetonitrile / water = 82.5 / 17.5; column temperature: 40℃; flow rate: 1.0 mL / min; injection volume: 5 μL; detection wavelength: 270 nm.

[0066] like Figure 8 As shown in Figure a, chromatographic peaks 1-6 represent sulfonamides, sulfaguanidine, sulfapyridine, sulfadimethylpyrimidine, sulfamethoxypyridazine, and sulfamethylpyrimidine, respectively. These six sulfonamide antibiotics were detected in SiO2@COF. DVA-TAPB Rapid and efficient separation was achieved within 8 minutes on the / PsIL column; however, due to the SiO2@COF DVA-TAPB It has relatively weak hydrophilicity, which is present in SiO2@COF. DVA-TAPB The chromatographic peaks on the column overlapped significantly. Figure 8 b). For example Figure 9 As shown, sulfonamide antibiotics in SiO2@COF DVA-TAPBThe retention on the / PsIL column shows a U-shaped trend with respect to the water content in the mobile phase. This means that as the water content increases, the separation of sulfonamide antibiotics shifts from a hydrophilic-dominated mechanism to a reverse-phase-dominated mechanism, indicating multiple interactions involving SiO2@COF. DVA-TAPB The separation process of the / PsIL stationary phase.

[0067] Example 4

[0068] The SiO2@COF prepared in Example 1 DVA-TAPB / PsIL column and SiO2@COF DVA-TAPB The chromatographic column was used as a high-performance liquid chromatography column to test SiO2@COF. DVA-TAPB Hydrophobic selectivity of the / PsIL column and its separation ability for alkylbenzenes. Chromatographic analysis conditions: mobile phase: acetonitrile / water = 50 / 50; column temperature: 40℃; flow rate: 1.0 mL / min; injection volume: 5 μL; detection wavelength: 254 nm.

[0069] like Figure 10 As shown, with the increase of acetonitrile content in the mobile phase, the capacity factor k of alkylbenzene gradually decreases, indicating that SiO2@COF DVA-TAPB / PsIL columns have typical reversed-phase characteristics. For example... Figure 11 As shown in Figure a, chromatographic peaks 1-5 represent toluene, ethylbenzene, n-propylbenzene, n-butanebenzene, and n-pentanebenzene, respectively. These five alkylbenzenes are observed in SiO2@COF. DVA-TAPB The / PsIL column achieved excellent separation with good peak shape, but they were not well separated on SiO2@COF. DVA-TAPB Incomplete separation cannot be achieved on the chromatographic column ( Figure 11 b). Under the same chromatographic conditions, alkylbenzenes in SiO2@COF DVA-TAPB The separation time on the / PsIL column is less than that on the SiO2@COF column. DVA-TAPB The chromatographic column showed that although PsIL reduced the hydrophobicity of DVA-TAPB-COFs, it improved the hydrophobic selectivity for alkylbenzenes.

[0070] Example 5

[0071] Using SiO2@COF in Example 1 DVA-TAPB / PsIL column and SiO2@COF DVA-TAPB The chromatographic column, as a high-performance liquid chromatography column, is used to detect SiO2@COF. DVA-TAPB / PsIL column's ability to separate aniline compounds. Chromatographic analysis conditions: mobile phase: acetonitrile / water = 35 / 65; column temperature: 40℃; flow rate: 1.0 mL / min; injection volume: 5 μL; detection wavelength: 254 nm.

[0072] like Figure 12As shown in Figure a, chromatographic peaks 1-6 represent aniline, o-toluidine, N-methylaniline, m-nitroaniline, o-nitroaniline, and 1-naphthylamine, respectively; and SiO2@COF DVA-TAPB Compared to chromatographic columns ( Figure 12 b), SiO2@COF DVA-TAPB The / PsIL column exhibited higher selectivity for six anilines under high water content mobile phase conditions, with a column efficiency of up to 21,626 columns / meter. Except for m-nitroaniline, the other anilines showed better selectivity under SiO2@COF conditions. DVA-TAPB The peak sequence on the / PsIL column is consistent with its hydrophobicity, indicating a separation process driven by hydrophobic interactions. Due to the electron-withdrawing inductive effect of the nitro group, m-nitroaniline has a relatively high acidity, which interacts with SiO2@COF. DVA-TAPB / PsIL has stronger hydrogen bonding, which results in greater retention than o-methylaniline and N-methylaniline.

[0073] Example 6

[0074] Using SiO2@COF in Example 1 DVA-TAPB / PsIL column and SiO2@COF DVA-TAPB The chromatographic column, as a high-performance liquid chromatography column, is used to detect SiO2@COF. DVA-TAPB / PsIL column's ability to separate phenolic substances. Chromatographic analysis conditions: mobile phase: acetonitrile / water = 30 / 70; column temperature: 40℃; flow rate: 1.0 mL / min; injection volume: 5 μL; detection wavelength: 260 nm.

[0075] like Figure 13 As shown in Figure a, chromatographic peaks 1-6 represent 2,6-dichlorophenol, hydroquinone, phenol, o-cresol, 2,5-xylenol, and 3-nitrophenol, respectively. These six phenols were observed in SiO2@COF... DVA-TAPB Good separation was achieved on the / PsIL column, with a selectivity factor as high as 6.05 for hydroquinone and phenol; however, the same high-water-content mobile phase failed to separate the strongly hydrophobic 2,6-dichlorophenol from SiO2@COF within 35 min. DVA-TAPB Elution on the chromatographic column ( Figure 13 b) This may be due to the interaction of 2,6-dichlorophenol with SiO2@COF DVA-TAPB This is due to the strong hydrophobic interaction between them. This result further confirms that PsIL improves the hydrophobicity of SiO2@COF by reducing the hydrophobicity of DVA-TAPB-COFs. DVA-TAPB / PsIL separation selectivity.

[0076] Example 7

[0077] Using SiO2@COF in Example 1 DVA-TAPB / PsIL column and SiO2@COF DVA-TAPB The chromatographic column, as a high-performance liquid chromatography column, is used to detect SiO2@COF. DVA-TAPB / PsIL column separation capability for organophosphorus pesticides. Chromatographic analysis conditions: mobile phase: acetonitrile / water = 60 / 40; column temperature: 40℃; flow rate: 1.0 mL / min; injection volume: 5 μL; detection wavelength: 225 nm.

[0078] like Figure 14 As shown in Figure a, chromatographic peaks 1-4 represent diazinon, chlorpyrifos, fenthion, and chlorpyrifos, respectively. These four organophosphorus pesticides were detected in SiO2@COF... DVA-TAPB Rapid and efficient separation with symmetrical peak shape was achieved within 8 min on the / PsIL column; however, under the same chromatographic conditions, it was not as efficient on the SiO2@COF column. DVA-TAPB The peaks on the chromatographic column were severely broadened. Figure 14 b) Poor column efficiency.

[0079] Example 8

[0080] Using SiO2@COF in Example 1 DVA-TAPB / PsIL column and SiO2@COF DVA-TAPB The chromatographic column, as a high-performance liquid chromatography column, is used to detect SiO2@COF. DVA-TAPB / PsIL column separation capability for benzoylurea insecticides. Chromatographic analysis conditions: mobile phase: (methanol / acetonitrile = 90 / 10) / water = 95 / 5; column temperature: 40℃; flow rate: 1.0 mL / min; injection volume: 5 μL; detection wavelength: 254 nm.

[0081] like Figure 15 As shown in Figure a, chromatographic peaks 1-4 represent fluorouracil, chlorfenapyr, fluorouracil, and fluorobenzamide, respectively. (SiO2@COF) DVA-TAPB The / PsIL column rapidly separated four benzoylurea insecticides within 5 minutes; however, SiO2@COF DVA-TAPB The chromatographic column cannot effectively separate chlorfenapyr and flufenoxuron ( Figure 15 b). Four benzoylurea insecticides in SiO2@COF DVA-TAPB The peak order on the / PsIL column was flufenoxuron (logP = 6.78) < chlorfenapyr (logP = 4.55) < flufenoxuron (logP = 3.68) < fluorobenzyl urea (logP = 5.49), which is inconsistent with the separation mechanism of reversed-phase chromatography. The weak retention of flufenoxuron and chlorfenapyr may be due to the large number of strongly electronegative fluorine atoms in their structures reacting with SiO2@COF. DVA-TAPB / PsIL's SO3 - An electrostatic repulsion force was generated.

[0082] Example 9

[0083] Benzoylurea insecticides were used to evaluate SiO2@COF DVA-TAPB Stability of the / PsIL column. Chromatographic analysis conditions: Mobile phase: (methanol / acetonitrile = 90 / 10) / water = 95 / 5; Column temperature: 40℃; Flow rate: 1.0 mL / min; Injection volume: 5 μL; Detection wavelength: 254 nm.

[0084] like Figure 16 As shown, no significant changes in peak shape, retention time, or peak area were observed in the chromatograms of ten consecutive injections within a day. The relative standard deviation (RSD) of retention time ranged from 0.04% to 0.14%, and the intra-day RSD of peak area ranged from 1.36% to 1.47%. The relatively small RSDs of both retention time and peak area indicate that SiO2@COF DVA-TAPB The PsIL column exhibits good reproducibility and stability, further confirming that PsIL provides support within the pores of COFs.

[0085] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A mixed-mode chromatographic stationary phase for amphiphilic covalent organic frameworks, characterized in that, The chromatographic stationary phase uses silica gel as a carrier to immobilize a covalent organic framework in situ on the silica gel surface through chemical bonds; then, an ionic liquid with hydrophilic groups is polymerized into the covalent organic framework using an in-situ polymerization method, thus obtaining the final product. The covalent organic framework is obtained by reacting 1,4-dialdehyde-2,5-divinylbenzene and 1,3,5-tris(4-aminophenyl)benzene as raw materials; the hydrophilic group in the ionic liquid is a sulfonic acid group; the ionic liquid is introduced into the pores of the covalent organic framework for in-situ polymerization; The silica gel is aminosilicone, and the ionic liquid is 1-propylsulfonic acid-3-vinylimidazolium chloride ionic liquid. The structure formed by the polymerization of the ionic liquid in a covalent organic framework is shown in formula (I): Equation (I).

2. The method for preparing the amphiphilic covalent organic framework mixed-mode chromatographic stationary phase according to claim 1, characterized in that, include: Step 1: Disperse amino silica gel, 1,4-dialdehyde-2,5-divinylbenzene, 1,3,5-tris(4-aminophenyl)benzene and acetic acid in acetonitrile, react at room temperature for 72 h, wash and dry to obtain COFs modified silica gel; Step 2: Add the COFs-modified silica gel obtained in Step 1, 1-propylsulfonic acid-3-vinylimidazolium chloride ionic liquid, and azobisisobutyronitrile to dimethyl sulfoxide; react at room temperature under a nitrogen atmosphere for 0.5–2 h, then raise the temperature to 60–110 °C and react for 18–36 h, wash and dry to obtain the final product.

3. The preparation method according to claim 2, characterized in that, In step 1, the ratio of aminosilicone, 1,4-dialdehyde-2,5-divinylbenzene, 1,3,5-tris(4-aminophenyl)benzene and acetic acid is 3.0 g : 0.3 g : 0.4 g : 15 mL.

4. The preparation method according to claim 2, characterized in that, In step 2, the ratio of the amount of COFs-modified silica gel, 1-propylsulfonic acid-3-vinylimidazolium chloride ionic liquid, azobisisobutyronitrile and dimethyl sulfoxide is 3.0 g : 0.1-3 g : 0.1-0.5 g : 50-200 mL.

5. The application of the amphiphilic covalent organic framework mixed-mode chromatographic stationary phase according to claim 1 in the separation of compounds, characterized in that, The compound is at least one of the following: nucleoside / base compounds, sulfonamide antibiotics, alkylbenzenes, aniline compounds, phenolic compounds, organophosphorus pesticides, and / or benzoylurea insecticides; The nucleoside / base compounds include at least one of 2-amino-4-chloro-6-methoxypyrimidine, 6-chloro-7-azapurine, thymine, β-thymidine, 2'-deoxyuridine, 5-methyluridine, adenosine, 2-aminoadenosine, and cytosine. The sulfonamide antibiotics include at least one of sulfonamides, sulfaguanidine, sulfapyridine, sulfadimethylpyrimidine, sulfamethoxypyridazine, and sulfamethylpyrimidine; The alkylbenzene includes at least one of toluene, ethylbenzene, n-propylbenzene, n-butanebenzene, and n-pentanebenzene; The aniline compounds include at least one of aniline, o-toluidine, N-methylaniline, m-nitroaniline, o-nitroaniline, and 1-naphthylamine; The phenolic compounds include at least one of 2,6-dichlorophenol, hydroquinone, phenol, o-cresol, 2,5-xylenol, and 3-nitrophenol; The organophosphorus pesticides include at least one of diazinon, chlorpyrifos, fenthion, and chlorpyrifos. The benzoylurea insecticides include at least one of fluorourea, chlorfenapyr, fluorourea, and fluorobenzoylurea.

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