Hierarchical pore COF membrane based on pillararene as well as preparation method and application of hierarchical pore COF membrane

Abstract

The invention relates to the technical field of covalent organic frameworks, in particular to a hierarchical pore COF membrane based on pillararene as well as a preparation method and application of the hierarchical pore COF membrane. The COF membrane is prepared through the synergistic effect of the organic acid catalyst, the TFB and the APP5, the structure of the COF membrane comprises dispersed nanopores and sub-nanopores, and the COF membrane has high porosity and accurate structural arrangement, so that the stability of a COF framework is enhanced, the permeability and selectivity are balanced, and the performance of the COF membrane in organic solvent nanofiltration is remarkably improved. Therefore, the COF membrane has a wide application prospect in the fields of organic solvent recovery, drug concentration and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of covalent organic frameworks, and in particular to a pillararomatic multi-level porous COF membrane and a preparation method and application thereof. Background Art

[0002] In modern chemical separation processes, the recycling and reuse of organic solvents is crucial for the green development of the pharmaceutical industry. Organic solvent nanofiltration (OSN) is an emerging membrane separation technology used for the selective separation and purification of organic solvents based on molecular size and chemical properties. Compared with traditional methods such as distillation, extraction, and chromatography, OSN offers advantages such as low energy consumption, environmental friendliness, and safety, making it particularly suitable for the pharmaceutical, chemical, food, and energy industries.

[0003] The core of OSNs lies in their membrane materials, which must exhibit high solvent flux, high solute retention, and excellent chemical stability. Currently, most OSN membranes are asymmetric membranes prepared by phase separation. In recent years, the introduction of advanced materials such as covalent organic frameworks (COFs) has further enhanced their performance. COF membranes are porous materials formed by covalently linked organic molecules, exhibiting a highly ordered structure and tunable pore size. Currently, common COF membranes are composed of groups such as 1,3,5-tris(4-aminophenyl)triazine (Tp), p-phenylenediamine (Pa), NO2, and OH, chemically linked to form a membrane with a specific pore structure. However, existing COF membranes typically have large pore sizes, making it difficult to achieve efficient retention of small molecule salts, limiting their application in nanofiltration. Furthermore, constructing COF membranes with sub-nanometer pore sizes remains challenging, particularly in achieving high selectivity and ultra-fast molecular sieving.

[0004] Therefore, how to achieve the best possible balance between membrane selectivity and flux to improve the performance of COF membranes in organic solvent nanofiltration remains a fundamental challenge in the field of COF membranes. Summary of the Invention

[0005] The present invention aims to address at least one of the technical problems existing in the related art. To this end, the first object of the present invention is to provide a method for preparing a pillararene-based hierarchical COF membrane; the second object of the present invention is to provide a pillararene-based hierarchical COF membrane; and the third object of the present invention is to provide applications of pillararene-based hierarchical COF membranes.

[0006] In order to achieve the first purpose, the technical solution adopted by the present invention is: The preparation method of a hierarchical COF membrane based on pillar aromatics comprises the following steps: S100, adding an organic acid catalyst to water to prepare an aqueous solution; S200, dissolving TFB and APP5 in organic solvent I to prepare an organic phase solution; Among them, TFB is trimesic acid, and the molecular structure of APP5 is as follows: ; The molar concentration of APP5 in the organic phase solution ranges from 1 to 10 mM, and the ratio of the molar concentration of TFB in the organic solution to the molar concentration of APP5 is 1:2 to 2:3; S300, after adding the organic solvent II to the aqueous phase solution, add the organic phase solution, react at 15-25°C for 48-72 hours to obtain a hierarchical COF membrane based on pillar aromatics.

[0007] Furthermore, the synthetic route of APP5 is as follows: .

[0008] Furthermore, in step S100, the organic acid catalyst is selected from PTSA, and PTSA is p-toluenesulfonic acid.

[0009] Furthermore, in step S100, after the organic acid catalyst is added to the water, an ultrasonic treatment process is also included.

[0010] Furthermore, in step S200 , the molar concentration of TFB is 4.60-4.70 mM, the molar concentration of APP5 is 6.9-7.1 mM, and the molar concentration of the organic acid catalyst in step S100 is 13.9-14.1 mM.

[0011] Furthermore, the organic solvent I in step S200 and the organic solvent II in step S300 are both selected from ethyl acetate.

[0012] In order to achieve the second purpose, the technical solution adopted by the present invention is: The hierarchical COF membrane based on pillar aromatics is prepared by using any of the above methods for preparing a hierarchical COF membrane based on pillar aromatics.

[0013] Furthermore, it includes sub-nanopores and nanopores dispersed therein.

[0014] Furthermore, the pore size of the sub-nanopore is in the range of 0.5 to 0.8 nm, and the pore size of the nanopore is in the range of 1.5 to 1.8 nm.

[0015] In order to achieve the third purpose, the technical solution adopted by the present invention is: Applications of the pillararene-based hierarchical COF membrane, such as any of the pillararene-based hierarchical COF membranes described above, include use for recovery of organic solvents and / or concentration of drugs.

[0016] Furthermore, the drug includes any one or more of tetracycline, rifampicin and vitamin B12.

[0017] The above one or more technical solutions in the embodiments of the present invention have at least one of the following technical effects: The present invention provides a pillararomatic multi-level porous COF membrane, its preparation method, and applications. This COF membrane is prepared through the synergistic action of an organic acid catalyst, TFB, and APP5. Its structure contains dispersed nanopores and sub-nanopores, exhibiting high porosity and precise structural arrangement. This enhances the stability of the COF framework while balancing permeability and selectivity, significantly improving its performance in organic solvent nanofiltration. Therefore, this COF membrane has broad application prospects in areas such as organic solvent recovery and drug concentration.

[0018] Additional aspects and advantages of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description which follows, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is the hydrogen nuclear magnetic resonance spectrum of the synthesized APP5 provided in Example 1 of the present invention.

[0020] Figure 2 Schematic diagram of the distribution of sub-nanopores and nanopores of the pillararomatic multi-level COF membrane provided in Example 2 of the present invention.

[0021] Figure 3 This is a photograph of a hierarchical COF membrane based on pillararenes provided in Example 2 of the present invention.

[0022] Figure 4 This is an SEM image of the hierarchical porous COF membrane based on pillar aromatics provided in Example 2 of the present invention.

[0023] Figure 5 This is the microscopic morphology and crystal structure characterization of the hierarchical porous COF membrane based on pillar aromatics provided in Example 2 of the present invention.

[0024] Figure 6 This is a TEM image of the pillararene-based hierarchical COF membrane provided in Example 2 of the present invention and a local magnified image of the crystal surface features (d=0.44 nm).

[0025] Figure 7 This is the characterization result of the APP5-TFB-COF film provided in Example 2 of the present invention on the SiO2 / Si substrate.

[0026] Figure 8 This is a pore size distribution curve of the APP5-TFB-COF membrane provided in Example 2 of the present invention.

[0027] Figure 9 This is a UV-visible absorption spectrum of the feed solution and the permeate measured using a dead-end filtration device provided in Test Example 1 of the present invention.

[0028] Figure 10 It is a scatter fitting diagram of the relationship between membrane permeability and inverse viscosity of different solvents provided in Test Example 1 of the present invention.

[0029] Figure 11 This is the retention of dyes of different molecular weights in methanol solvent provided in Test Example 1 of the present invention.

[0030] Figure 12 This is the retention of different molecular active drug molecules provided in Test Example 1 of the present invention.

[0031] Figure 13 This is a schematic diagram of the distribution of TP-TFB-COF membrane pores provided in Test Example 1 of the present invention.

[0032] Figure 14 This is a bar graph showing the retention of dyes with different molecular weights by the TP-TFB-COF membrane and the APP5-TFB-COF membrane provided in Test Example 1 of the present invention.

[0033] Figure 15 It is a scatter plot of methanol permeation separation performance of different types of OSN membranes provided in Test Example 2 of the present invention. DETAILED DESCRIPTION

[0034] To make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the embodiments described are part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. The following embodiments are used to illustrate the present invention, but are not used to limit the scope of the present invention.

[0035] In the following examples, the experimental methods used are conventional methods unless otherwise specified, and are carried out according to the techniques or conditions described in the literature in this field or according to the product instructions. The materials, reagents, etc. used are all commercially available unless otherwise specified.

[0036] Example 1 The raw material APP5 was prepared, and its synthetic route is as follows: ; Wherein, OTf represents trifluoromethanesulfonate; The synthesis process of APP5 is as follows: 1. Synthesis of Compound II.

[0037] 1,4-Dimethoxybenzene (10.0 g, 72.4 mmol) (Compound I) and paraformaldehyde (10.9 g, 350.3 mmol) were added to a 500 mL three-necked reaction flask. Under nitrogen protection, 1,2-dichloroethane (100 mL) was added. After stirring at 25°C for 2 h, boron trifluoride etherate [BF3O(C2H5)2, 9.4 ml, 175.5 mmol] was slowly added to the reaction system. After stirring for 1 h, the reaction solution was poured into methanol (200 mL) to stop the reaction. The resulting precipitate was collected by filtration and separated and purified by column chromatography (eluent: a mixed solvent of dichloromethane and petroleum ether, with a volume ratio of 1:1) to obtain Compound II (7.5 g) as a white powder with a yield of 69.0%.

[0038] 2. Synthesis of compound III.

[0039] Compound II (5.0 g, 6.667 mmol) and dichloromethane (100 mL) were added to a 250 mL three-necked reaction flask. After stirring and dissolving, a 42% mass concentration of ceric ammonium nitrate aqueous solution (17.3 g) was added dropwise. After stirring and reacting for 10 min at 25 ° C, the aqueous phase was extracted three times with dichloromethane, and the organic phases were combined, dried over anhydrous Na2SO4, concentrated under reduced pressure, and separated and purified by column chromatography (eluent: a mixed solvent of dichloromethane and petroleum ether, the volume ratio of the two was 1:1) to obtain a dark red solid compound III (3.0 g) with a yield of 62.4%.

[0040] 3. Synthesis of compound IV.

[0041] Compound III (5 g, 6.941 mmol) and sodium dithionite (27.5 g, 158.0 mmol) were added to a 500 mL two-necked reaction flask. Under a nitrogen atmosphere, dichloromethane (200 mL) and water (10 mL) were added. After stirring overnight at 25 ° C, the red solution turned light yellow. The aqueous phase was extracted three times with dichloromethane, the organic phase was extracted once with saturated brine, and extracted three times with water. The organic phases were combined, dried over anhydrous Na2SO4, and concentrated under reduced pressure to obtain a light yellow solid compound IV (4.4 g) with a yield of 84.0%.

[0042] 4. Synthesis of Compound V.

[0043] Compound IV (2 g, 2.65 mmol) was added to a 250 mL three-necked reaction flask. Under a nitrogen atmosphere, dichloromethane (120 mL) and anhydrous pyridine (6 mL) were added. Trifluoromethanesulfonic anhydride (Tf2O, 12 mL) was added dropwise to the reaction system at 0 ° C using a constant pressure dropping funnel. After the addition was completed, the reaction was carried out at 25 ° C for 24 h. The mixture was separated and purified by column chromatography (the eluent was a mixed solvent of dichloromethane and petroleum ether in a volume ratio of 1:1) to obtain a white powder synthetic compound V (1.7 g) with a yield of 47.2%.

[0044] 5. Synthesize APP5.

[0045] Compound V (1.0 g, 1.176 mmol), 4-aminophenylboronic acid pinacol ester (0.6 g, 2.727 mmol), potassium carbonate (1.64 g, 11.884 mmol), and Pd(PPh3)4 (0.18 g, 0.12 mmol) were added to a 200 mL reaction flask. Under a nitrogen atmosphere, water (8 mL) and tetrahydrofuran (32 mL) were added and stirred at 90°C overnight. After the reaction, the mixture was concentrated under reduced pressure and purified by column chromatography (dichloromethane) to obtain a white powder APP5 (0.4 g) with a yield of 39.4%. Its nuclear magnetic resonance spectrum is as follows: Figure 1 shown.

[0046] Example 2 The preparation process of the hierarchical COF membrane based on pillararenes is as follows: 1. Prepare aqueous solution: 7.3 mg of p-toluenesulfonic acid (PTSA) was dissolved in deionized water (3 mL) to obtain an aqueous solution having a PTSA concentration of 14 mM. 2. Preparation of organic phase solution: 2.8 mg of benzene trimesaldehyde (TFB) and APP5 (18.4 mg) were dissolved in ethyl acetate (3 mL) to obtain an organic phase solution in which the concentration of TFB was 4.67 mM and the concentration of APP5 was 7 mM; 3. The aqueous solution obtained above was added to a 10 mL wide-mouth glass bottle, and ethyl acetate (3 mL) was slowly added dropwise on top of the aqueous solution as a blank layer. Subsequently, the organic solution obtained above was slowly added dropwise on top of the blank layer. After 72 hours of interfacial reaction at 25°C, a multi-level porous COF membrane based on pillar aromatic hydrocarbons was obtained, which was named APP5-TFB-COF membrane. In subsequent tests, the membrane was transferred to a polyacrylonitrile (PAN) substrate for organic solvent nanofiltration performance testing.

[0047] Schematic diagram of the distribution structure of pores dispersed in the APP5-TFB-COF membrane, as shown in Figure 2 As shown in the figure, it can be seen that sub-nanopores and nanopores are dispersed in the COF membrane.

[0048] Photographs of APP5-TFB-COF membranes, such as Figure 3 As shown in the figure, it can be seen that the COF film is uniform, complete and defect-free.

[0049] Scanning electron microscope (SEM) images of APP5-TFB-COF films, such as Figure 4 As shown in the figure, it can be seen that the microscopic morphology of the COF film surface presents a continuous and dense texture structure. The result shows that the APP5-TFB-COF film provided by the present invention has good film-forming properties and has no obvious cracks or holes.

[0050] High-magnification transmission electron microscope (TEM) images (scale 20 nm) and selected electron diffraction patterns of APP5-TFB-COF films, such as Figure 5 The main image is a TEM image, from which we can see the grain boundaries, pores or agglomerations of the material. The small image in the lower right corner is a selected electron diffraction pattern, which shows symmetrical diffraction spots / rings, indicating that the COF film has a crystalline structure.

[0051] TEM image of APP5-TFB-COF film (scale 10 nm) and its local area magnification (scale 5 nm), as shown in Figure 6 The main image is a TEM image (scale 10nm), and the crystal plane feature (d=0.44nm) in the lower right corner is a local magnified image (scale 5nm). It can be seen from the image that the COF film has an ordered crystalline structure, which plays a fundamental role in supporting the performance of the COF film. In the figure, d=0.44nm represents the interplanar spacing.

[0052] Characterization results of APP5-TFB-COF film on SiO2 / Si substrate, such as Figure 7 As shown, Figure A is the AFM morphology of the APP5-TFB-COF film on the SiO2 / Si substrate, and Figure B is the height profile of the APP5-TFB-COF film on the SiO2 / Si substrate. It can be seen from the figure that the film thickness of the APP5-TFB-COF film is about 877±20nm.

[0053] The pore size distribution of APP5-TFB-COF membrane, such as Figure 8 As shown in the figure, it can be seen that the pore size of the COF membrane provided by the present invention is mainly distributed in the nanometer range and sub-nanometer range.

[0054] Test Example 1 The molecular sieving performance of the APP5-TFB-COF membrane was evaluated using a dead-end filtration device.

[0055] 1. The filter membrane of the dead-end filtration device is APP5-TFB-COF membrane, the feed solution is a mixed dye of methyl blue (MB) and methyl orange (MO), the permeate is obviously yellow, and the UV-visible absorption of the feed solution and the permeate is as follows: Figure 9 As shown in the figure, the results show that the APP5-TFB-COF membrane has a certain separation effect on two different dyes.

[0056] 2. The filter membrane of the dead-end filtration device is APP5-TFB-COF membrane, and the organic solvents are acetone, acetonitrile, methanol, water and ethanol. The relationship between the membrane permeability and the inverse of the viscosity of different solvents is as follows: Figure 10 As shown in the figure, it can be seen that with the increase of solvent viscosity, the permeability of the membrane decreases and the permeation resistance of the membrane to high viscosity solvents increases. 2 The coefficient of determination is a goodness of fit indicator in regression analysis, reflecting the closeness between the data point and the fitted line. 2 is 97%, indicating that about 97% of the permeability change can be explained by η -1 The change of (inverse viscosity) is explained and the fitting effect is better.

[0057] 3. The filter membrane of the dead-end filtration device is APP5-TFB-COF membrane, and the dyes are: methyl orange (MO), acid fuchsin (AF), Congo red (CR), methyl blue (MB), brilliant blue (RB) and Alcian blue (AB). The solvent is methanol. The retention of dyes with different molecular weights in COF membrane is as follows: Figure 11 As shown in the figure, the APP5-TFB-COF membrane has a high retention rate of 99% for Alcian Blue (1299 Da), Coomassie Brilliant Blue (826 Da), and Methyl Blue (800 Da), and a high retention rate of 98% for Congo Red (697 Da). In contrast, small molecules such as acid fuchsin (586 Da) and methyl orange (327 Da) have lower retention rates of 65% and 24%, respectively.

[0058] 4. The filter membrane of the dead-end filtration device is APP5-TFB-COF membrane. The drugs are: tetracycline (444Da), rifampicin (823Da) and vitamin B12 (1355Da). The solvent is methanol. The retention of active drugs with different molecular weights in the COF membrane is as follows: Figure 12 As shown in the figure, it can be seen that the APP5-TFB-COF membrane has a certain retention effect on tetracycline, rifampicin and vitamin B12, with retention rates of 14.3%, 81.8% and 98.9% respectively.

[0059] Comparative Example 1 Taking TP-TFB-COF membrane as a comparative example, its preparation process is as follows except that APP5 in Example 2 is replaced by 1,1':4',1''-terphenyl-4,4''-diamine ([1,1':4',1''-terphenyl]-4,4''-diamine, TP). The molecular structure is as follows: ; The rest of the process is the same as in Example 2. The pore distribution of TP-TFB-COF membrane is as follows: Figure 13 As shown, the pores dispersed in the COF membrane are all nanopores, and there is no sub-nanopore distribution; the retention of dyes with different molecular weights by the APP5-TFB-COF membrane and TP-TFB-COF membrane provided by the present invention is investigated, and the results are as follows Figure 14 As shown, the results show that the rejection rate of TP-TFB-COF membrane for dyes with different molecular weights is lower than that of APP5-TFB-COF membrane; Among them, dyes with different molecular weights are: MO, AF, CR, MB, RB and AB, and the solvent is methanol.

[0060] Comparative Example 2 The methanol permeation and separation performance of different types of OSN membranes, such as Figure 15 As shown in Table 1, Figure 15 The scatter plot and data in Table 1 indicate that the APP5-TFB-COF membrane provided by the present invention exhibits superior methanol permeability compared to existing OSN membranes, and significantly higher vitamin B12 retention than other existing OSN membranes. Therefore, the APP5-TFB-COF membrane can effectively separate methanol from substances such as vitamin B12 with excellent separation efficiency and selectivity. Therefore, the APP5-TFB-COF membrane is expected to find widespread application in the field of organic solvent nanofiltration.

[0061] The OSN films a to i in Table 1 were all prepared according to conventional methods.

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for preparing a hierarchical COF membrane based on pillar aromatics, characterized in that: The steps include: S100, adding an organic acid catalyst to water to prepare an aqueous solution; S200, dissolving TFB and APP5 in organic solvent I to prepare an organic phase solution; Among them, TFB is trimesic acid, and the molecular structure of APP5 is as follows: ； The molar concentration of APP5 in the organic phase solution ranges from 1 to 10 mM, and the ratio of the molar concentration of TFB in the organic solution to the molar concentration of APP5 is 1:2 to 2:3; S300, after adding the organic solvent II to the aqueous phase solution, add the organic phase solution, react at 15-25°C for 48-72 hours to obtain a hierarchical COF membrane based on pillar aromatics.

2. The method for preparing a hierarchical COF membrane based on pillararenes according to claim 1, wherein: The synthetic route of APP5 is as follows: 。 3. The method for preparing a hierarchical COF membrane based on pillararenes according to claim 1, wherein: In step S100, the organic acid catalyst is selected from PTSA, and PTSA is p-toluenesulfonic acid.

4. The method for preparing a hierarchical COF membrane based on pillararenes according to claim 1, wherein: In step S200 , the molar concentration of TFB is 4.60-4.70 mM, the molar concentration of APP5 is 6.9-7.1 mM, and the molar concentration of the organic acid catalyst in step S100 is 13.9-14.1 mM.

5. The method for preparing a hierarchical COF membrane based on pillararenes according to claim 1, wherein: The organic solvent I in step S200 and the organic solvent II in step S300 are both selected from ethyl acetate.

6. A hierarchical COF membrane based on pillararenes, characterized in that: The multi-level porous COF membrane based on pillar aromatic hydrocarbons is prepared by the preparation method according to any one of claims 1 to 5.

7. The hierarchical COF membrane based on pillararenes according to claim 6, characterized in that: Including sub-nanopores and nanopores dispersed therein.

8. The pillararene-based hierarchical COF membrane according to claim 7, wherein: The pore size of the sub-nanopore is in the range of 0.5 to 0.8 nm, and the pore size of the nanopore is in the range of 1.5 to 1.8 nm.

9. Application of a hierarchical COF membrane based on pillararomatic hydrocarbons, characterized in that: The pillararene-based hierarchical COF membrane according to claim 6, wherein the application includes recovery of organic solvents and / or concentration of drugs.

10. The use of the pillararomatic COF membrane according to claim 9, wherein: The drugs include any one or more of tetracycline, rifampicin and vitamin B12.

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