Three-dimensional covalent organic framework mixed matrix membrane as well as preparation method and application thereof

Abstract

The invention discloses a three-dimensional covalent organic framework mixed matrix membrane which is applied to a natural gas separation process. COF-301 nanosheets are prepared through a micelle template method, the COF-301 nanosheets and a high polymer material are subjected to solution pouring at a constant temperature to prepare the hybrid membrane, a high filling amount is achieved based on the regular nanosheet morphology, a gas mass transfer path is optimized, and the separation characteristic of a filling agent is exerted to the maximum extent. According to the three-dimensional covalent organic framework mixed matrix membrane provided by the invention, a continuous mass transfer channel is successfully constructed, an efficient CO2 / CH4 gas separation process is realized, the membrane preparation process is simple, convenient, controllable and high in universality, and meanwhile, the membrane has excellent pressure stability and long-term stability.

Description

Technical Field

[0001] This invention belongs to the field of gas separation membrane preparation technology, and relates to a three-dimensional covalent organic framework hybrid matrix membrane, its preparation method and application. Background Technology

[0002] Globally, natural gas provides about a quarter of energy, and this proportion is increasing year by year due to its cleanliness and ease of transportation. However, the presence of carbon dioxide, a major impurity in natural gas, limits its application in many fields. Currently, industrial CO2 / CH4 separation is mainly achieved through absorption and adsorption methods. Absorption methods face problems such as equipment corrosion, absorbent passivation, and pre-absorbent leakage causing environmental pollution, while adsorption methods suffer from poor separation efficiency and operational stability.

[0003] Membrane purification technology has advantages such as low energy consumption and minimal environmental pollution. However, the performance of polymer membranes based on the dissolution-diffusion mechanism is limited by the trade-off effect between permeability and selectivity, making it difficult to meet industrial requirements. In addition, most polymer membranes will undergo plasticization under high pressure, and there is currently a lack of ideal CO2 / CH4 separation membranes. Summary of the Invention

[0004] This invention addresses the problems existing in the traditional industrial separation process of CO2 / CH4 by proposing a three-dimensional covalent organic framework hybrid matrix membrane, its preparation method, and its application.

[0005] To achieve the above objectives, the present invention is implemented using the following technical solution: A three-dimensional covalent organic framework hybrid matrix membrane and its preparation method are disclosed. The membrane is prepared by solution casting from a three-dimensional covalent organic framework filler and a polymer matrix. The three-dimensional covalent organic framework filler is prepared by micellar template method from an aldehyde monomer and an amino monomer. The aldehyde monomer is 2,5-dihydroxyterephthalaldehyde, and the amino monomer is tetrakis(4-aminophenyl)methane. The polymer matrix is ​​obtained by reacting a dianhydride monomer and a diamine monomer. The dianhydride monomer is 4,4'-(hexafluoroisopropylidene)phthalic anhydride, and the diamine monomer is 2,4,6-trimethyl-1,3-phenylenediamine.

[0006] The above-mentioned three-dimensional covalent organic framework hybrid matrix membrane and its preparation method are as follows: (1) The diamine monomer was sublimated and dried under vacuum, and then added to anhydrous N-methylpyrrolidone to obtain dispersion A; the dianhydride monomer was dried under vacuum and added to anhydrous N-methylpyrrolidone, and dispersed evenly to obtain dispersion B; dispersion A and dispersion B were mixed and then stirred at low temperature under a nitrogen atmosphere, and then acetic anhydride and 3-methylpyridine were added. After a second low-temperature reaction, the reaction was carried out at room temperature. After the reaction was completed, methanol was poured in, the precipitated solid was washed and dried to obtain a white filamentous solid.

[0007] (2) Sodium dodecyl sulfate was added to sodium hydroxide solution, sonicated, and then deionized water was added. The mixture was sonicated until it was homogeneous. Then hydrochloric acid solution was added to adjust the pH to neutral to obtain mixture C. The amino monomer was added to p-toluenesulfonic acid solution and dispersed evenly to obtain dispersion D. Dispersion D was added to mixture C and mixed evenly. Then aldehyde monomer was added and dispersed evenly. The mixture was heated to carry out the reaction. After the reaction was completed, the solid obtained by centrifugation and washing was dried to obtain three-dimensional covalent organic framework nanosheets.

[0008] (3) Add the white filamentous solid obtained in step (1) to chloroform and disperse it evenly. Then add three-dimensional covalent organic framework nanosheets, mix evenly, and place it in an ice-water bath for crushing treatment. Then let it stand to obtain casting solution.

[0009] (4) Filter the casting solution, then pour it onto a plate and let it stand to seal and form a film.

[0010] Preferably, in step (1), the mass ratio of diamine monomer to dianhydride monomer is 1:(2-5), in step (2), the mass ratio of amino monomer to aldehyde monomer is 1:(1-3), the concentration of diamine monomer in dispersion A is 0.1-0.5 g / mL, and the volume ratio of dispersion A to dispersion B is 1:(1-3).

[0011] As a preferred embodiment, in step (1), the sublimation temperature of the diamine monomer under vacuum is 95-101℃, the vacuum drying temperature of the diamine monomer is 55-65℃, the vacuum drying temperature of the dianhydride monomer is 100-120℃, the low-temperature stirring reaction temperature is 0-1℃, and the reaction time is 20-25h; the secondary low-temperature reaction temperature is 0-1℃, the reaction time is 20-40min, and the room temperature reaction time is 20-30h.

[0012] Preferably, in step (2), the concentration of sodium dodecyl sulfate in mixture C is 1-20 mg / mL, the concentration of sodium hydroxide solution is 0.05-0.2 mol / L, the concentration of amino monomer in dispersion D is 5-10 mg / mL, the volume ratio of mixture C to dispersion D is (10-15):1, the temperature for the reaction is 45-55℃, and the reaction time is 10-20 days.

[0013] Preferably, the static sealing temperature in step (3) is 20-30℃ and the time is 40-50h.

[0014] The amino and aldehyde monomers selected in this invention can provide multi-benzene rings with large steric hindrance and multiple amino-aldehyde reaction sites, which can generate three-dimensional nanosheets. The resulting covalent organic framework nanosheets are morphologically compatible with the polyimide polymer matrix and have good interfacial compatibility. The prepared three-dimensional covalent organic framework nanosheets have a multi-interpenetrating structure, and their three-dimensional channels exhibit dynamic response characteristics, enabling them to interact with CO2 gas, making it easier for CO2 gas to enter and thus preferentially adsorbing CO2. Furthermore, the three-dimensional covalent organic framework has an approximately square sheet-like structure. The good compatibility between the pure organic framework and the polymer results in a high-density uniform distribution of nanosheets in the transmembrane direction of the hybrid membrane. In the mixed matrix membrane structure, the nanosheets are continuous within the membrane, exhibiting a "percolation effect," which allows the three-dimensional covalent organic framework nanosheets to more easily exert the advantages of three-dimensional high-efficiency interconnected channels, thereby improving their separation performance. During the synthesis process, it is necessary to strictly control the amount of three-dimensional covalent organic framework filling. If the filling amount is too high, the nanosheets will aggregate in the mixed matrix membrane, resulting in interface defects and significantly reducing the selectivity of the separation membrane. If the filling amount is too low, there will be insufficient COF nanosheets on the upper and lower surfaces of the membrane, which will not be able to form a continuous structure and will affect the performance of the separation membrane.

[0015] Compared with the prior art, the advantages and positive effects of the present invention are as follows: 1. This invention blends organic fillers with polymers to prepare a three-dimensional covalent organic framework hybrid matrix membrane that combines high permeability and high selectivity, maintaining stable and efficient CO2 / CH4 separation even under high pressure and complex conditions.

[0016] 2. The process proposed in this invention can produce self-supporting flat membranes in a short time. The preparation process is convenient and controllable, and the membrane yield is high, making it suitable for large-scale promotion and application. Attached Figure Description

[0017] Figure 1 The image shows an electron microscope image of the membrane prepared in Example 1, where a is the front side of the membrane and b is the back side of the membrane.

[0018] Figure 2 The images shown are (a) and (b) cross-sectional electron microscope images of the membrane prepared in Example 1. Detailed Implementation

[0019] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described below with reference to specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0020] Numerous specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways than those described herein, and therefore the invention is not limited to the specific embodiments disclosed in the following specification.

[0021] In the following embodiments, some of the material manufacturers or specifications are as follows: 2,4,6-Trimethyl-1,3-phenylenediamine: CAS No. 3102-70-3, manufactured by TCI (Shanghai) Chemical Industry Development Co., Ltd., purity >99%.

[0022] 4,4'-(hexafluoroisopropylidene)diphthalic anhydride: CAS number 1107-00-2, manufacturer is Tianjin Zhongtai Chemical Technology Co., Ltd., purity >99%.

[0023] Tetra(4-aminophenyl)methane: CAS No. 60532-63-0, manufactured by Shanghai Mairui Chemical Technology Co., Ltd., purity 98%.

[0024] 2,5-Dihydroxyterephthalaldehyde: CAS No. 1951-36-6, manufacturer: Jilin Zhongke Science & Technology Co., Ltd., purity 95%.

[0025] Cell disruptor: manufactured by Qsonica, USA, model Q-700.

[0026] Example 1 3.104 g of 2,4,6-trimethyl-1,3-phenylenediamine (DAM) monomer was added to a sublimation tube and sublimated under vacuum at 100 °C for 120 min (0.1 MPa) to obtain flaky colorless crystals. These crystals were then dried in a vacuum drying oven at 60 °C for 12 h (0.1 MPa). 8.9244 g of 4,4'-(hexafluoroisopropylidene) phthalic anhydride (6FDA) monomer was weighed and dried under vacuum at 110 °C for 12 h (0.1 MPa). All of the treated DAM monomer was added to 20 mL of anhydrous N-methylpyrrolidone (NMP), and the treated 6FDA monomer was added to 30 mL of anhydrous NMP. Both liquids were manually stirred with a glass rod for 2 min each, then mixed and stirred at 850 rpm at 0 °C for 24 h under a N2 atmosphere. Then, 15 mL of acetic anhydride and 15 mL of 3-methylpyridine were added, and the mixture was stirred at 0 °C and 850 rpm for 30 min. The mixture was then allowed to rise naturally to room temperature and allowed to stand for 24 h. After the reaction was completed, the solution was poured into 500 mL of methanol, at which point a solid precipitated. The solid was filtered and washed three times with 1500 mL of methanol. The solid was then dried in an oven at 200 °C for 24 h to obtain a white filamentous solid, namely polymer 6FDA-DAM.

[0027] Weigh 288.38 mg of sodium dodecyl sulfate (SDS) and add it to 4 mL of 0.1 mol / L NaOH solution. Sonicate for 10 min, then add 40 mL of deionized water and sonicate at 50 °C for 2 h. While maintaining 50 °C, add 2 mL of 0.2 mol / L hydrochloric acid solution and mix thoroughly; this is designated as solution A. Weigh 38.05 mg of tetrakis(4-aminophenyl)methane (TAM) monomer and add it to 4 mL of 0.1 mol / L p-toluenesulfonic acid solution. Sonicate at 50 °C for 30 min, then pour the mixture into solution A. Continue sonicating at 50 °C for 1 h, then add 50 mg of 2,5-dihydroxyterephthalaldehyde (DHTA) and continue sonicating at 50 °C for 30 min. Then, it was transferred to a 50 ℃ oven and allowed to stand for 2 weeks. After the reaction was completed, it was taken out and allowed to cool naturally to room temperature. Then, it was centrifuged at 10000 rpm for 10 min in sequence with deionized water, methanol, and tetrahydrofuran, with a volume of 25 mL each time, and repeated 3 times. The solid obtained by centrifugation was then placed in a vacuum dryer at 60 ℃ overnight with a vacuum degree of 0.1 MPa to obtain a reddish-brown solid powder, which is the three-dimensional covalent organic framework nanosheet COF-301NS.

[0028] Add 80 g of 6FDA-DAM to 3 mL of anhydrous chloroform and stir at 200 rpm for 30 min. Add 20 g of COF-301NS, sonicate for 10 min, and then stir at 800 rpm for 2 h. Then place in an ice-water bath (0℃) for cell lysis (350 W) for 1 h, and then let stand naturally in an ice-water bath for 10 min to obtain the casting solution. Pass the casting solution through an 80-mesh nylon filter cloth to remove insoluble large particles and impurities, and then pour it into a 4 cm inner diameter ultra-flat glass culture dish. Seal the culture dish with plastic wrap, and use a 1.0 mm diameter needle to poke a small hole in the center of the plastic wrap to control the evaporation rate. Place in a 25 ℃ oven for 48 h to form a film.

[0029] Small pieces were cut with scissors for electron microscopy and photographing of the actual object. The results are as follows: Figure 1 (Surface SEM) and Figure 2 (Actual photos and cross-sectional SEM images are shown.) From Figures 1a and 1b, as well as Figure 2a, it can be seen that the front and back surfaces of the membrane have a uniform structure and no obvious defects. From Figure 2b, it can be seen that the separation layer of the membrane has good density.

[0030] The membrane prepared in this embodiment was used in a CO2 / CH4 separation system. Under conditions of 25 °C, a CO2:CH4 molar ratio of 3:7, and a pressure of 2 bar, the CO2 permeation flux was 6579 Barrer, and the selectivity was 24.1. After continuous monitoring for 120 h, the membrane's separation performance showed no significant change, with CO2 permeability fluctuations of less than 1% and CO2 / CH4 separation factor fluctuations of less than 5%, demonstrating excellent long-term stability. After the continuous monitoring was completed, the pressure was further increased to 10 bar while keeping other monitoring conditions unchanged. The CO2 flux was 5247 Barrer, and the CO2 / CH4 selectivity was 22, verifying the membrane's excellent high-pressure resistance.

[0031] Example 2 3.104 g of 2,4,6-trimethyl-1,3-phenylenediamine monomer was added to a sublimation tube and sublimed under vacuum at 100 °C for 120 min (0.1 MPa) to obtain flaky colorless crystals. These crystals were then dried in a vacuum drying oven at 60 °C for 12 h (0.1 MPa). 17.8488 g of 4,4'-(hexafluoroisopropylidene) phthalic anhydride monomer was weighed and dried under vacuum at 120 °C for 12 h (0.1 MPa). The treated DAM monomer was added to 20 mL of anhydrous N-methylpyrrolidone, and the treated 6FDA monomer was added to 30 mL of anhydrous NMP. Both liquids were manually stirred with a glass rod for 2 min each, then mixed and stirred at 850 rpm at 0 °C for 24 h under a N2 atmosphere. Then, 15 mL of acetic anhydride and 15 mL of 3-methylpyridine were added, and the mixture was stirred at 0 °C and 850 rpm for 30 min. The mixture was then allowed to rise naturally to room temperature and allowed to stand for 24 h. After the reaction was completed, the solution was poured into 500 mL of methanol, at which point a solid precipitated. The solid was filtered and washed three times with 1500 mL of methanol. The solid was then dried in an oven at 200 °C for 24 h to obtain a white filamentous solid, namely polymer 6FDA-DAM.

[0032] Weigh 576.76 mg of sodium dodecyl sulfate and add it to 4 mL of 0.05 mol / L NaOH solution. Sonicate for 10 min, then add 40 mL of deionized water and sonicate at 50 °C for 2 h. While maintaining 50 °C, add 1 mL of 0.2 mol / L hydrochloric acid solution and mix thoroughly; this is designated as solution A. Weigh 76.1 mg of tetrakis(4-aminophenyl)methane monomer and add it to 4 mL of 0.1 mol / L p-toluenesulfonic acid solution. Sonicate at 50 °C for 30 min, then pour the mixture into solution A. Continue sonicating at 50 °C for 1 h, then add 50 mg of 2,5-dihydroxyterephthalaldehyde and continue sonicating at 50 °C for 30 min. Then, it was transferred to a 50℃ oven and allowed to stand for 2 weeks. After the reaction was completed, it was taken out and allowed to cool naturally to room temperature. Then, it was centrifuged at 10000 rpm for 10 min in sequence with deionized water, methanol, and tetrahydrofuran, with a volume of 25 mL each time, and repeated 3 times. The solid obtained by centrifugation was then placed in a vacuum dryer at 60℃ overnight with a vacuum degree of 0.1 MPa to obtain a reddish-brown solid powder, which is the three-dimensional covalent organic framework nanosheet COF-301NS.

[0033] Add 80 g of 6FDA-DAM to 3 mL of anhydrous chloroform and stir at 200 rpm for 30 min. Add 20 g of COF-301NS, sonicate for 10 min, and then stir at 800 rpm for 2 h. Then place in an ice-water bath (0 ℃) for cell lysis (350 W power) for 1 h, and then let stand naturally in an ice-water bath for 10 min to obtain the casting solution. Pass the casting solution through an 80-mesh nylon filter cloth to remove insoluble large particles and impurities, and then pour it into a 4 cm inner diameter ultra-flat glass culture dish. Seal the culture dish with plastic wrap, and use a 1.0 mm diameter needle to poke a small hole in the center of the plastic wrap to control the evaporation rate. Place in a 20 ℃ oven for 24 h to form a film.

[0034] When the membrane prepared in this embodiment was used in a CO2 / CH4 separation system, under the same detection conditions (pressure 2 bar) as in Example 1, the CO2 permeation flux was 6557 Barrer and the selectivity was 22.7.

[0035] Example 3 3.104 g of 2,4,6-trimethyl-1,3-phenylenediamine monomer was added to a sublimation tube and sublimed under vacuum at 100 °C for 120 min (0.1 MPa) to obtain flaky colorless crystals. These crystals were then dried in a vacuum drying oven at 60 °C for 12 h (0.1 MPa). 17.8488 g of 4,4'-(hexafluoroisopropylidene) phthalic anhydride monomer was weighed and dried under vacuum at 120 °C for 12 h (0.1 MPa). The treated DAM monomer was added to 20 mL of anhydrous N-methylpyrrolidone, and the treated 6FDA monomer was added to 30 mL of anhydrous NMP. Both liquids were manually stirred with a glass rod for 2 min each, then mixed and stirred at 850 rpm at 0 °C for 24 h under a N2 atmosphere. Then, 15 mL of acetic anhydride and 15 mL of 3-methylpyridine were added, and the mixture was stirred at 0 °C and 850 rpm for 30 min. The mixture was then allowed to rise naturally to room temperature and allowed to stand for 24 h. After the reaction was completed, the solution was poured into 500 mL of methanol, at which point a solid precipitated. The solid was filtered and washed three times with 1500 mL of methanol. The solid was then dried in an oven at 200 °C for 24 h to obtain a white filamentous solid, namely polymer 6FDA-DAM.

[0036] Weigh 1153.52 mg of sodium dodecyl sulfate and add it to 4 mL of 0.2 mol / L NaOH solution. Sonicate for 10 min, then add 40 mL of deionized water and sonicate at 50 °C for 2 h. While maintaining 50 °C, add 4 mL of 0.2 mol / L hydrochloric acid solution and mix thoroughly; this is designated as solution A. Weigh 76.1 mg of tetrakis(4-aminophenyl)methane monomer and add it to 4 mL of 0.1 mol / L p-toluenesulfonic acid solution. Sonicate at 50 °C for 30 min, then pour the mixture into solution A. Continue sonicating at 50 °C for 1 h, then add 50 mg of 2,5-dihydroxyterephthalaldehyde and continue sonicating at 50 °C for 30 min. Then, it was transferred to a 50℃ oven and allowed to stand for 2 weeks. After the reaction was completed, it was taken out and allowed to cool naturally to room temperature. Then, it was centrifuged at 10000 rpm for 10 min in sequence with deionized water, methanol, and tetrahydrofuran, with a volume of 25 mL each time, and repeated 3 times. The solid obtained by centrifugation was then placed in a vacuum dryer at 60℃ overnight with a vacuum degree of 0.1 MPa to obtain a reddish-brown solid powder, which is the three-dimensional covalent organic framework nanosheet COF-301NS.

[0037] Add 80 g of 6FDA-DAM to 3 mL of anhydrous chloroform and stir at 200 rpm for 30 min. Add 20 g of COF-301NS, sonicate for 10 min, and then stir at 800 rpm for 2 h. Then, place the mixture in an ice-water bath (0 ℃) for cell lysis (350 W power) for 1 h, and then allow it to stand naturally in an ice-water bath for 10 min to obtain the casting solution. Pass the casting solution through an 80-mesh nylon filter cloth to remove insoluble large particles and impurities, and then pour it into a 4 cm inner diameter ultra-flat glass culture dish. Seal the culture dish with plastic wrap, and use a 1.0 mm diameter needle to poke a small hole in the center of the plastic wrap to control the evaporation rate. Place the dish in a 30 ℃ oven for 72 h to form a film.

[0038] When the membrane prepared in this embodiment was used in a CO2 / CH4 separation system, under the same detection conditions (pressure 2 bar) as in Example 1, the CO2 permeation flux was 5310 Barrer and the CO2 / CH4 selectivity was 25.7.

[0039] Comparative Example 1 The remaining preparation processes and conditions of this comparative example have been adapted, and unless otherwise specified, they are consistent with those of Example 1.

[0040] The synthesized 6FDA-DAM polymer was modified to 50 g and added to 3 mL of anhydrous chloroform. The mixture was stirred at 200 rpm for 30 min. The synthesized COF-301NS was also modified to 50 g, and the mixture was sonicated for 10 min, followed by stirring at 800 rpm for 2 h. Cells were then lysed in an ice-water bath (0 °C) (350 W power) for 1 h, followed by natural standing in an ice-water bath for 10 min to obtain the casting solution. The casting solution was passed through an 80-mesh nylon filter to remove insoluble large particles and impurities. The solution was then poured into a 4 cm inner diameter ultra-flat glass culture dish, sealed with plastic wrap, and a small hole was made in the center of the plastic wrap using a 1.0 mm needle to control the evaporation rate. The dish was then placed in a 25 °C oven for 48 h to form a film.

[0041] The ultra-high packing density membrane prepared in this comparative example was used for CO2 / CH4 separation. Under the same detection conditions (pressure 2 bar) as in Example 1, the CO2 permeation flux was 7160 Barrer, and the CO2 / CH4 selectivity was 13.7. Excessive packing density leads to the aggregation of nanosheets within the mixed matrix membrane, accompanied by interfacial defects, resulting in a non-selective structure and thus lower selectivity.

[0042] Comparative Example 2 The remaining preparation processes and conditions of this comparative example have been adapted, and unless otherwise specified, they are consistent with those of Example 1.

[0043] The synthesized 6FDA-DAM polymer was modified to 95 g and added to 3 mL of anhydrous chloroform. The mixture was stirred at 200 rpm for 30 min. The synthesized COF-301NS was then modified to 5 g and added to the mixture. The mixture was sonicated for 10 min and then stirred at 800 rpm for 2 h. Cells were then lysed in an ice-water bath (0 ℃) (power 350 W) for 1 h, followed by natural standing in an ice-water bath for 10 min to obtain the casting solution. The casting solution was passed through an 80-mesh nylon filter to remove insoluble large particles and impurities. The solution was then poured into a 4 cm inner diameter ultra-flat glass culture dish, sealed with plastic wrap, and a small hole was made in the center of the plastic wrap using a 1.0 mm needle to control the evaporation rate. The dish was then placed in a 25 ℃ oven for 48 h to form a film.

[0044] The ultra-low packing membrane prepared in this comparative example was used for CO2 / CH4 separation. Under the same detection conditions (pressure 2 bar) as in Example 1, the CO2 permeation flux was 1470 Barrer, and the CO2 / CH4 selectivity was 30.2. At excessively low packing levels, very few COF nanosheets were observable on the upper and lower surfaces of the membrane, failing to form a continuous structure and thus failing to leverage the advantages of continuous channel structures within the membrane, resulting in poor flux.

[0045] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments for application in other fields. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A three-dimensional covalent organic framework hybrid matrix membrane and its preparation method, characterized in that, The material is prepared by solution casting from a three-dimensional covalent organic framework filler and a polymer matrix. The three-dimensional covalent organic framework filler is prepared by micellar template method from an aldehyde monomer and an amino monomer. The aldehyde monomer is 2,5-dihydroxyterephthalaldehyde and the amino monomer is tetra(4-aminophenyl)methane. The polymer matrix is ​​obtained by reacting a dianhydride monomer and a diamine monomer. The dianhydride monomer is 4,4'-(hexafluoroisopropylidene)diphthalic anhydride and the diamine monomer is 2,4,6-trimethyl-1,3-phenylenediamine.

2. The three-dimensional covalent organic framework hybrid matrix membrane and its preparation method according to claim 1, characterized in that, The steps are as follows: (1) The diamine monomer was sublimated and dried under vacuum, and then added to anhydrous N-methylpyrrolidone to obtain dispersion A; the dianhydride monomer was dried under vacuum and added to anhydrous N-methylpyrrolidone, and dispersed evenly to obtain dispersion B; dispersion A and dispersion B were mixed and then stirred at low temperature under a nitrogen atmosphere, and then acetic anhydride and 3-methylpyridine were added. After a second low-temperature reaction, the reaction was carried out at room temperature. After the reaction was completed, methanol was poured in, the precipitated solid was washed and dried to obtain a white filamentous solid; (2) Sodium dodecyl sulfate was added to sodium hydroxide solution, sonicated, and then deionized water was added. The mixture was sonicated until it was homogeneous. Then hydrochloric acid solution was added to adjust the pH to neutral to obtain mixture C. The amino monomer was added to p-toluenesulfonic acid solution and dispersed evenly to obtain dispersion D. Dispersion D was added to mixture C and mixed evenly. Then aldehyde monomer was added and dispersed evenly. The mixture was heated to carry out the reaction. After the reaction was completed, the solid obtained by centrifugation and washing was dried to obtain three-dimensional covalent organic framework nanosheets. (3) Add the white filamentous solid obtained in step (1) to chloroform and disperse it evenly. Then add three-dimensional covalent organic framework nanosheets, mix evenly, and place it in an ice-water bath for crushing treatment. Then let it stand to obtain casting solution. (4) Filter the casting solution, then pour it onto a plate and let it stand to seal and form a film.

3. The three-dimensional covalent organic framework hybrid matrix membrane and its preparation method according to claim 2, characterized in that, In step (1), the mass ratio of diamine monomer to dianhydride monomer is 1:(2-5), in step (2), the mass ratio of amino monomer to aldehyde monomer is 1:(1-3), the concentration of diamine monomer in dispersion A is 0.1-0.5 g / mL, and the volume ratio of dispersion A to dispersion B is 1:(1-3).

4. The three-dimensional covalent organic framework hybrid matrix membrane and its preparation method according to claim 2, characterized in that, Step (1) The sublimation temperature of the diamine monomer under vacuum is 95-101℃, the drying temperature of the diamine monomer under vacuum is 55-65℃, the drying temperature of the dianhydride monomer under vacuum is 100-120℃, the low-temperature stirring reaction temperature is 0-1℃, and the reaction time is 20-25h; the secondary low-temperature reaction temperature is 0-1℃, the reaction time is 20-40min, and the room temperature reaction time is 20-30h.

5. The three-dimensional covalent organic framework hybrid matrix membrane and its preparation method according to claim 2, characterized in that, In step (2), the concentration of sodium dodecyl sulfate in mixture C is 1-20 mg / mL, the concentration of sodium hydroxide solution is 0.05-0.2 mol / L, the concentration of amino monomer in dispersion D is 5-10 mg / mL, the volume ratio of mixture C to dispersion D is (10-15):1, the temperature for the reaction is 45-55℃, and the reaction time is 10-20 days.

6. The three-dimensional covalent organic framework hybrid matrix membrane and its preparation method according to claim 2, characterized in that, The static sealing temperature in step (3) is 20-30℃, and the static film formation time in step (4) is 24-72h.

Images