An organic covalent framework composite membrane with staggered ab stacking structure and a preparation method and application thereof

Abstract

The present application relates to the technical field of polymer separation membrane, and discloses a preparation method of an organic covalent framework composite membrane with staggered AB stacking structure, which comprises the following steps: S1, dissolving an aldehyde group monomer in Tf2N ionic liquid; S2, dissolving an amine group monomer in an organic solvent, adding a base film and the ionic liquid with the aldehyde group monomer in step S1, and adding a catalyst; S3, performing microwave hydrothermal reaction to obtain the organic covalent framework composite membrane with staggered AB stacking structure. Through the selection of the ionic liquid, the polymer forms staggered AB stacking structure on the base film, and the composite membrane with smaller pore size is quickly and simply prepared, and accurate screening can be realized.

Description

Technical Field

[0001] This invention relates to the field of polymer separation membrane technology, and more specifically, to an organic covalent framework composite membrane with an interleaved AB stacking structure, its preparation method, and its application. Background Technology

[0002] A composite membrane is a membrane made by growing or coating a polymer onto a substrate. A typical composite membrane consists of a separation layer and a support layer. The thinner separation layer provides good flux, while the support layer provides good mechanical strength for the composite membrane.

[0003] Covalent organic framework polymers (COFs) possess excellent stability, tunable pore size, excellent mass transfer channels due to their ordered structure, high specific surface area, and functionalizable structures. COFs, with their uniform pores, have been widely used in separation, energy storage, and catalysis. Most COFs have relatively large pore sizes (between 1-7 nm), and the pore size of a single COF is generally fixed, making it difficult to achieve precise separation of small molecules, such as gases with small differences in molecular size. The pore size of COFs can be adjusted through molecular design, such as topological design, reducing linker length, introducing side groups, and adjusting the stacking configuration. However, these methods generally suffer from drawbacks such as long synthetic routes, complex processes, and high costs.

[0004] Existing COF membranes are mostly prepared using in-situ growth or interfacial polymerization methods. Compared to disordered polymer membranes, the synthesis of COF membranes is based on dynamic covalent chemistry with reversible reactions. The assembly process requires sufficient reaction time to allow the disordered structure to self-repair and correct itself, promoting the crystallization process of COF and forming a highly ordered framework structure. However, membranes prepared using existing technologies typically exhibit an AA (alloy-agent) stacked structure, making it difficult to sieve small-sized substances. Summary of the Invention

[0005] To address the aforementioned technical problems in existing technologies, this invention provides an organic covalent framework composite membrane with an alternating AB stacking structure, its preparation method, and its applications. By selecting and inducing assembly with Tf₂N-type ionic liquids, an organic covalent framework composite membrane with an alternating AB stacking structure was rapidly prepared using a microwave hydrothermal method, achieving both rapid and simple preparation while enabling precise molecular sieving.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] A method for preparing an organic covalent framework composite membrane with an interlaced AB stacking structure, comprising the following steps:

[0008] S1. Dissolve the aldehyde monomer in a Tf2N-type ionic liquid;

[0009] S2. Dissolve the amine monomer in an organic solvent, add the substrate membrane and the ionic liquid containing the aldehyde monomer from step S1, and add the catalyst.

[0010] S3. Microwave hydrothermal reaction is carried out to obtain an organic covalent framework composite membrane with an interleaved AB stacking structure.

[0011] Furthermore, the aldehyde monomer is an aldehyde monomer with C3 symmetry; the amino monomer is an amino monomer with C3 or C2 symmetry.

[0012] Furthermore, the base film is any one of polysulfone film, polyimide film, polyether nitrile (PIM-1) film or polyvinylidene fluoride (PVDF) film.

[0013] Furthermore, the molar ratio of the aldehyde monomer to the amino monomer is 0.85–1.05:1–1.5.

[0014] Furthermore, the molar ratio of the C3-symmetric aldehyde monomer to the C3-symmetric amine monomer is 0.85 to 1.05:1.

[0015] Furthermore, the molar ratio of the C3-symmetric aldehyde monomer to the C2-symmetric amine monomer is 0.85–1.05:1.5.

[0016] Furthermore, the chemical formula of the Tf₂N-type ionic liquid is [Bmim][Tf₂N] or [N 8888 [Tf2N]; its general structural formula is as follows:

[0017]

[0018] R is preferably any one of methyl, butyl, hexyl, heptyl, and dodecyl.

[0019] Furthermore, the preparation method of the Tf2N-type ionic liquid is as follows:

[0020] Dissolve 0.1 mol of a cationic donor monomer in 25-50 mL of water, and dissolve 0.1 mol of lithium bis(trifluoromethanesulfonyl)imide in 100-200 mL of water. Mix the two solutions and stir at room temperature until the reaction is complete. Wash with water until colorless and clear, and dry under vacuum at room temperature to obtain an ionic liquid.

[0021] Preferably, the cationic donor monomer is 1-butyl-3-methylimidazolium hydrobromide, tetra-n-octylammonium bromide, or trioctylmethylammonium bromide.

[0022] The chemical reaction equation is as follows:

[0023]

[0024]

[0025] Wherein, R is any one of methyl, butyl, hexyl, heptyl, or dodecyl.

[0026] Further, the organic solvent is an acetonitrile / dimethyl sulfoxide, acetonitrile / N,N-dimethylformamide, or acetonitrile / N,N-dimethylacetamide mixed solution; preferably, the molar ratio of acetonitrile to dimethyl sulfoxide or N,N-dimethylformamide or N,N-dimethylacetamide is 1:5 to 10.

[0027] Furthermore, the catalyst is a Lewis acid or a protic acid, preferably HOAc, and the molar ratio of HOAc to the aldehyde monomer is 15 to 30:1.

[0028] Furthermore, the molar ratio of HOAc to the C3 symmetrical aldehyde monomer is 25-30:1.

[0029] Furthermore, the molar ratio of HOAc to the C2-symmetric aldehyde monomer is 15–20:1.

[0030] Furthermore, the microwave hydrothermal reaction is carried out at a temperature of 30–60°C, a frequency of 10–100 GHz, and a reaction time of 1–12 h.

[0031] The present invention also provides an organic covalent framework composite membrane with an interlaced AB stacking structure prepared by the above preparation method.

[0032] Furthermore, the separation layer is a thin layer of 50nm to 40μm, and its surface is intact and without defects.

[0033] The present invention also provides the application of the above-mentioned organic covalent framework composite membrane with staggered AB stacking structure in liquid separation or gas separation.

[0034] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0035] (1) The present invention uses an impregnation method to load monomers onto a substrate, without the need for further modification of the substrate.

[0036] (2) This invention uses the ionic liquid [Bmim][Tf2N] / [N 8888 [Tf₂N] is used as a solvent in the ionic liquid [Bmim][Tf₂N] / [N] 8888[Tf2N] Because it can form strong hydrogen bonds with the imine bonds in the covalent organic framework, it is conducive to the rapid aggregation and crystallization of the covalent organic framework. It does not require complicated preparation processes such as flame sealing, and can quickly and easily prepare covalent organic framework membranes, which is easy to industrialize. In addition, as a green solvent, ionic liquids eliminate the use of solvents in the synthesis process, reducing environmental pollution.

[0037] (3) This invention is based on the ionic liquid [Bmim][Tf2N] / [N 8888 [Tf₂N] is covalently bound to an imine-based organic framework by strong hydrogen bonds, while the ionic liquid [Bmim][Tf₂N] / [N] is also bound together. 8888 The occupancy of [Tf2N] leads to steric hindrance, causing the covalent organic framework to undergo layer-by-layer misalignment and stacking, forming an interleaved AB stacking pattern, thereby achieving the effect of regulating pore size.

[0038] (4) At the same time, after the covalent organic framework layer stacking form is changed, the pore size is adjusted from 1.4nm to a smaller 1.1nm, and the interception rate of pollutant molecules below 1.4nm is significantly improved to more than 99%, realizing the precise separation of molecular sieving. Attached Figure Description

[0039] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0040] Figure 1 An optical photograph of the composite film prepared in the examples;

[0041] Among them, a) HZ-TF-COF-FILM-AA; b) HZ-TF-COF-FILM-AB; c) TAPT-TF-COF-FILM-AA; d) TAPT-TF-COF-FILM-AB; e) TAPT-TFPB-COF-FILM-AA; f) TAPT-TFPB-COF-FILM-AB.

[0042] Figure 2 Scanning electron microscope image of the composite film prepared in the examples. Figure 1 ;

[0043] Among them, a) HZ-TF-COF-FILM-AA; b) HZ-TF-COF-FILM-AB; c) TAPT-TF-COF-FILM-AA; d) TAPT-TF-COF-FILM-AB; e) TAPT-TFPB-COF-FILM-AA; f) TAPT-TFPB-COF-FILM-AB; g) P SF membrane.

[0044] Figure 3 Scanning electron microscope image of the composite film prepared in the examples. Figure 2 ;

[0045] Among them, a) HZ-TF-COF-FILM-AA; b) HZ-TF-COF-FILM-AB; c) TAPT-TF-COF-FILM-AA; d) TAPT-TF-COF-FILM-AB; e) TAPT-TFPB-COF-FILM-AA; f) TAPT-TFPB-COF-FILM-AB; g) PSF membrane.

[0046] Figure 4 Here is a cross-sectional scanning electron microscope image of the composite membrane prepared in the examples;

[0047] Among them, a) HZ-TF-COF-FILM-AA; b) HZ-TF-COF-FILM-AB; c) TAPT-TF-COF-FILM-AA; d) TAPT-TF-COF-FILM-AB; e) TAPT-TFPB-COF-FILM-AA; f) TAPT-TFPB-COF-FILM-AB; g) PSF membrane.

[0048] Figure 5 The Fourier transform infrared spectrum of the composite film prepared in the example is shown below.

[0049] Among them, a) HZ-TF-COF; b) TAPT-TF-COF; c) TAPT-TFPB-COF.

[0050] Figure 6 The X-ray diffraction pattern and simulation calculation diagram of the composite film prepared in the examples are shown below;

[0051] Among them, a) HZ-TF-COF; b) TAPT-TF-COF; c) TAPT-TFPB-COF.

[0052] Figure 7 The nitrogen adsorption-desorption curves and test data of the COF of the composite membrane prepared in the examples were used to calculate the pore size distribution of the COF separation layer by calculating the pore size distribution using NL-DFT (nonlocal density functional theory).

[0053] Among them, a) nitrogen adsorption-desorption curves of different HZ-TF-COFs;

[0054] b) Pore size distribution diagrams of different HZ-TF-COFs;

[0055] c) Nitrogen adsorption-desorption curves of different TAPT-TF-COFs;

[0056] d) Pore diameter distribution diagrams of different TAPT-TF-COFs;

[0057] e) Nitrogen adsorption-desorption curves of different TAPT-TFPB-COFs;

[0058] f) Aperture distribution diagrams of different TAPT-TFPB-COFs.

[0059] Figure 8 The separation effect of HZ-TF-COF-FILM with different stacking methods on different pollutants;

[0060] Wherein, a) is the structural formula and kinetic diameter of p-nitroaniline;

[0061] b) Retention rate and water flux of HZ-TF-COF-FILM in p-nitroaniline solution;

[0062] c) Ultraviolet spectra of p-nitroaniline solution before and after separation;

[0063] d) Structural formula and kinetic diameter of acid fuchsin;

[0064] e) Retention rate and water flux of HZ-TF-COF-FILM in acidic fuchsin solution;

[0065] f) Ultraviolet spectra of acidic fuchsin solutions before and after separation.

[0066] Figure 9 The separation effect of TAPT-TF-COF-FILM with different stacking methods on different pollutants;

[0067] Wherein, a) is the structural formula and kinetic diameter of p-nitroaniline;

[0068] b) Retention rate and water flux of TAPT-TF-COF-FILM in p-nitroaniline solution;

[0069] c) Ultraviolet spectra of p-nitroaniline solution before and after separation;

[0070] d) Structural formula and kinetic diameter of methyl orange;

[0071] e) Retention rate and water flux of TAPT-TF-COF-FILM in methyl orange solution;

[0072] f) UV spectra of p-nitroaniline solution before and after separation;

[0073] g) Structural formula and dynamic diameter of Congo red;

[0074] i) Retention rate and water flux of TAPT-TF-COF-FILM in Congo red solution;

[0075] h) UV spectra of Congo red solutions before and after separation.

[0076] Figure 10 The separation effect of TAPT-TFPB-COF-FILM on different pollutants;

[0077] Among them, a) the structural formula and kinetic diameter of chrome black;

[0078] b) Retention rate and water flux of TAPT-TFPB-COF-FILM in chrome black solution;

[0079] c) Ultraviolet spectra of the chrome black solution before and after separation;

[0080] d) Structural formula and dynamic diameter of Congo red;

[0081] e) Retention rate and water flux of TAPT-TFPB-COF-FILM in Congo red solution;

[0082] f) UV spectra of Congo red solutions before and after separation. Detailed Implementation

[0083] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0084] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0085] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0086] Test instruments and methods :

[0087] In the test, COF represents the COF membrane material obtained by dissolving a commercial polysulfone membrane in tetrahydrofuran (THF) to remove the COF separation layer, while COF-FILM represents the COF / PSF composite membrane with a substrate. FTIR spectroscopy (ATR-FTIR, Nicolet iS50, America) was used to characterize the COF, with a scan range of 4000-500 cm⁻¹. -1 X-ray diffraction (XRD) patterns were acquired using a Bruker Advanced D8 diffractometer with a step size of 0.02° and a scanning range of 2°–30°. Nitrogen adsorption and desorption isotherms and pore size distribution curves of the porous materials were measured at 77 K using an ASAP 2020C (Micromeritics Instrument Corporation, America). All samples were degassed under high vacuum at 100 °C for 10 h. The pore size distribution was calculated using nonlocal density functional theory (NL-DFT). The microstructure of the COF composite membrane samples was observed using a scanning electron microscope (SEM, FEI SIRION200, America). The interception rate was measured using a UV-Vis spectrophotometer (UV 8100A) for membrane performance testing.

[0088] The membrane liquid-phase separation performance was tested using a self-built permeation device to measure the membrane's interception rate and water flux. The concentrations of contaminant molecules on both the feed and permeate sides were determined using a UV-Vis spectrophotometer (UV 8100A). The feed-side pressure was maintained at 1.0 MPa, and measurements were taken at room temperature. The effective membrane area was approximately 21.23 cm². 2 Record the water flux under steady-state conditions, collect the osmotic fluid, and use the average of at least three observations to ensure the accuracy of the values.

[0089] The membrane gas phase separation performance testing method is as follows: The Wicke-Kallenbach technology is used to test the membrane's gas separation performance on a self-built gas permeation device. The specific operating steps are as follows: The composite membrane is sealed and fixed in a custom-designed permeation cell. The feed gas flow rate and purge gas flow rate are controlled by a mass flow controller. During single-component gas permeation experiments, the gas flow rate on the feed side of the membrane module is controlled at 50 mL / min. -1 During the two-component gas permeation experiment, the total gas flow rate on the feed side of the membrane module was controlled at 100 mL / min. -1 The flow rates of the two gases are each 50 mL·min. -1 Argon was used as the purge gas on the permeate side to introduce the permeate gas into a gas chromatograph (Agilent GC 8860), enabling online detection of gas components. During the test, the purge gas flow rate was consistently set to 15 mL / min. -1After the gas path stabilizes, the test is repeated 5 times under the same test conditions to ensure data accuracy. The gas separation performance test is conducted at room temperature (298K) with the pressure on both sides of the membrane maintained at 0.1MPa.

[0090] In this application, a commercial polysulfone membrane (PSF) is used as an example as the base membrane. The preparation method of the commercial polysulfone membrane is as follows:

[0091] First, add 80g of DMF and 2g of PVP (K30) to the reactor (three-necked flask), turn on the stirring system, and slowly add 18g of polysulfone particles after the stirring system has stabilized. After the polysulfone particles are added, heat the reactor to 75°C and stir continuously for 6 hours. After the polysulfone is completely dissolved, cool the polysulfone solution to room temperature, degas under vacuum for 2 hours, and keep it at 25°C overnight.

[0092] On the film-coating equipment, the water temperature in the condensation tank is set to 15℃, the water temperature in the ambient temperature tank is set to 30℃, and the water temperature in the high temperature tank is set to 75℃. The cooling and heating equipment are turned on respectively to bring the water temperature to the set value. The doctor blade roller gap is adjusted to 250μm. The machine speed is set to 5m / min. After the water temperature reaches the set value, the equipment is turned on and the polysulfone liquid is poured into the doctor blade groove. During the coating process, the polysulfone thickness is maintained at 5.1±0.2mil by adjusting the doctor blade roller gap (the time for the polysulfone film to pass through the condensation tank, ambient temperature tank, and high temperature tank are 30s, 60s, and 90s, respectively).

[0093] The synthesis steps for Tf₂N-type ionic liquids are as follows:

[0094] 0.1 mol of 1-butyl-3-methylimidazolium hydrobromide, tetra-n-octylammonium bromide, or trioctylmethylammonium bromide was dissolved in 25-50 ml of water, and 0.1 mol of lithium bis(trifluoromethanesulfonyl)imide was dissolved in 100-200 ml of water. The two solutions were mixed and stirred at room temperature for 12 h. After the reaction was complete, the solution was washed three times with 100 ml of water, and the resulting colorless and clear liquid was dried under vacuum at room temperature for 6 h to obtain the ionic liquid (40.28 g) with a yield of 82.22%.

[0095] The reaction equations are as follows:

[0096]

[0097] Example 1: Preparation of HZ-TF-COF / PSF composite membrane

[0098] 1. Preparation of HZ-TF-COF composite film (AA stacking mode) (Solv) (1.1nm)

[0099] At room temperature, a commercial polysulfone membrane was placed in a reactor. Hydrazine (0.1–0.3 mmol) was dissolved in 3 ml of acetonitrile / DMSO (5–15):1 and added to the reactor. The membrane was dried to adsorb a layer of hydrazine monomer onto the polysulfone surface. Trimethylolpropane monomer (0.1–0.3 mmol) was dissolved in 3 ml of acetonitrile / DMSO (5–15):1 and HOAc catalyst (100–300 μL) was added to the reactor. The reaction was carried out at 30–120 °C for 6–72 h. The membrane was then removed, washed with ethanol, and vacuum dried at room temperature. Optical photographs are shown below. Figure 1 As shown in a).

[0100] 2. Preparation of HZ-TF-COF composite film (staggered AB stacking mode) (0.7nm)

[0101] At room temperature, a commercial polysulfone membrane was placed in a reactor. Hydrazine (0.1–0.3 mmol) was dissolved in 3 ml of acetonitrile / DMSO (5–15):1 and added to the reactor. The membrane was dried, allowing a layer of hydrazine monomer to adsorb onto the polysulfone surface. Trimethylbenzaldehyde monomer was dissolved in 6 ml of [Bmim][Tf₂N] ionic liquid and HOAc catalyst (100–300 μL) was added to the reactor. The reaction was carried out at 30–120 °C for 6–72 h. After the reaction, the membrane was soaked in acetonitrile for 1–12 h, with the solution changed every h to remove the ionic liquid. The membrane was then removed, vacuum dried at room temperature, and optical photographs are shown below. Figure 1 As shown in b).

[0102] The synthesis route is as follows:

[0103]

[0104] This embodiment relates to the application of dye separation:

[0105] Two different sizes of pollutant molecules were fed into an aqueous solution (30 mL) and passed through an ultrafiltration device under an upstream pressure of 1 MPa. The effective separation area of ​​each membrane was 21.23 cm². 2 Two different dye feed solutions were used: Acid Fuchsin (50 mg) (AF) (1.13*1.17 nm) and p-Nitroaniline (50 mg) (4-NC) (0.7*0.44 nm). Each was dissolved in 1 L of water to obtain a 50 mg / L dye feed solution. See below for specific results. Figure 8 .

[0106] This embodiment relates to the application of gas separation:

[0107] Two different sizes of gas were introduced into the feed side of the membrane chamber and passed through the membrane device at an upstream pressure of 0.1 MPa. The gas was then discharged at 15 mL / min on the permeate side of the membrane chamber. -1 Argon gas was purged into the gas chromatograph, and the effective separation area of ​​each membrane was 19.625 cm². 2 The two different gases are H2 and CO2.

[0108]

[0109] The H2 / CO2 selectivity of the COF composite membrane in the AA stacking mode is 4.24, while that in the COF composite membrane in the AB stacking mode is 10.42.

[0110] Example 2: Preparation of TAPT-TF-COF / PSF composite membrane

[0111] 1. Preparation of TAPT-TF-COF composite film (AA stacking mode) (Solv) (1.4nm)

[0112] At room temperature, a commercial polysulfone membrane was placed in a reactor. 0.1–0.3 mmol of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine was dissolved in 3 ml of acetonitrile / DMSO (5–15):1 and added to the reactor. The membrane was dried, allowing a layer of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine monomer to be adsorbed onto the polysulfone surface. Trimethylbenzaldehyde monomer was dissolved in 3 ml of acetonitrile / DMSO (5–15):1 and 100–300 μL of HOAc catalyst was added to the reactor. The reaction was carried out at 30–120 °C for 6–72 h. The membrane was then removed, washed with ethanol, and vacuum dried at room temperature. Optical photographs are shown below. Figure 1 As shown in c).

[0113] 2. Preparation of TAPT-TF-COF composite membranes (AA stacking mode) (other ionic liquids)

[0114] At room temperature, a commercial polysulfone membrane was placed in a reactor. 2,4,6-Tris(4-aminophenyl)-1,3,5-triazine (0.1-0.3 mmol) was dissolved in 3 ml of acetonitrile / DMSO (5-15):1 and added to the reactor. The membrane was then dried, resulting in the adsorption of a layer of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine monomer onto the polysulfone surface. Trimethylolpropane (0.1-0.3 mmol) monomer was dissolved in 6 ml of the ionic liquid Bmim[Br] and HOAc catalyst (100-300 μL) was added to the reactor. The reaction was carried out at 30-120 °C for 6-72 h. After the reaction, the membrane was immersed in acetonitrile for 1-12 h, with the solution changed every 3 h to remove the ionic liquid. The membrane was then removed and vacuum dried at room temperature. Because Bmim[Br] ionic liquid does not possess the bond length and hydrogen bond structure of Tf2N-type ionic liquids, it cannot form a perforation anchoring effect. Therefore, the COF-FILM formed in Bmim[Br] ionic liquid is an AA-stacking pattern. Figure 6 The XRD in b) demonstrates the COF-FILM of the AA stacking pattern generated in the Bmim[Br] ionic liquid.

[0115] 3. Preparation of TAPT-TF-COF composite film (staggered AB stacking mode) (1.1 nm)

[0116] At room temperature, a commercial polysulfone membrane was placed in a reactor. 2,4,6-Tris(4-aminophenyl)-1,3,5-triazine (0.1-0.3 mmol) was dissolved in 3 ml of acetonitrile / DMSO (5-15):1 and added to the reactor. The membrane was then dried, allowing a layer of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine monomer to be adsorbed onto the polysulfone surface. Trimethylolpropionate (0.1-0.3 mmol) monomer was dissolved in [N... 8881 [T2N] Ionic liquid was added to 6 ml of solvent along with 100–300 μL of HOAc catalyst, and then added to a reactor. The reaction was carried out at 30–120 °C for 6–72 h. After the reaction was complete, the mixture was soaked in acetonitrile for 1–12 h, with the solution being changed every 3 h to remove the ionic liquid. The mixture was then removed, vacuum dried at room temperature, and optical photographs are shown below. Figure 1 As shown in d).

[0117] The synthesis route is as follows:

[0118]

[0119] This embodiment relates to the application of dye separation:

[0120] Three different sizes of pollutant molecules were fed into an aqueous solution (30 mL) and passed through an ultrafiltration device under an upstream pressure of 1 MPa. The effective separation area of ​​each membrane was 21.23 cm². 2 The three different dye feed solutions were methyl orange (50 mg) (MO) (1.13*0.42 nm), Congo red (50 mg) (CoR) (2.56*0.73 nm), and p-nitroaniline (50 mg) (4-NC) (0.7*0.44 nm), which were dissolved in 1 L of water to obtain a 50 mg / L dye feed solution.

[0121] Collect 5 ml of the filtrate for characterization.

[0122] The dye concentrations in the feed and permeate were measured using UV-Vis spectroscopy. The percentage cutoff (R%) was calculated using the formula:

[0123]

[0124] Among them, C F Indicates the dye concentration in the feed solution; C P This indicates the dye concentration in the permeate. Separation performance is as follows: Figure 9 As shown, after structural changes in the packing mode, the interception rate of methyl orange molecules was significantly improved, which is the result of precise sieving after adjusting the pore size with different packing modes.

[0125] This embodiment relates to the application of gas separation:

[0126] Two different sizes of gas were introduced into the feed side of the membrane chamber and passed through the membrane device at an upstream pressure of 0.1 MPa. The gas was then discharged at 15 mL / min on the permeate side of the membrane chamber. -1 Argon gas was purged into the gas chromatograph, and the effective separation area of ​​each membrane was 19.625 cm². 2 The two different gases are H2 and CO2.

[0127]

[0128] The H2 / CO2 selectivity of the COF composite membrane in the AA stacking mode is 5.28, while that in the COF composite membrane in the staggered AB stacking mode is 12.05.

[0129] Example 3: Preparation of TAPT-TFPB-COF / PSF composite membrane

[0130] 1. Preparation of TAPT-TFPB-COF composite film (AA stacking mode) (Solv) (2.3nm)

[0131] At room temperature, a commercial polysulfone membrane was placed in a reactor. 2,4,6-tris(4-aminophenyl)-1,3,5-triazine (0.1–0.3 mmol) was dissolved in 3 ml of acetonitrile / DMSO (5–15):1 and added to the reactor. The membrane was dried to adsorb an amino monomer layer onto the polysulfone surface. 1,3,5-tris(4-formylphenyl)benzene monomer (0.1–0.3 mmol) was dissolved in 3 ml of acetonitrile / DMSO (5–15):1 and 100–300 μL of HOAc catalyst was added to the reactor. The reaction was carried out at 30–120 °C for 6–72 h. The membrane was then removed, washed with ethanol, and vacuum dried at room temperature. Optical photographs are shown below. Figure 1 As shown in e).

[0132] 2. Preparation of TAPT-TFPB-COF composite film (staggered AB stacking mode) (1.7nm)

[0133] At room temperature, a commercial polysulfone membrane was placed in a reactor. 2,4,6-Tris(4-aminophenyl)-1,3,5-triazine (0.1–3 mmol) was dissolved in 3 ml of acetonitrile / DMSO (5–15):1 and added to the reactor. The membrane was then dried, allowing a layer of hydrazine monomer to be adsorbed onto the polysulfone surface. 1,3,5-Tris(4-formylphenyl)benzene monomer was dissolved in [N... 8888 [Tf₂N] ionic liquid was added to 6 ml of solvent along with 100–300 μL of HOAc catalyst, and then added to a reactor. The reaction was carried out at 30–120 °C for 6–72 h. After the reaction was complete, the mixture was soaked in acetonitrile for 1–12 h, with the solution being changed every h, to wash away the ionic liquid. The mixture was then removed, vacuum dried at room temperature, and optical photographs are shown below. Figure 1 As shown in f).

[0134] The synthesis route is as follows:

[0135]

[0136] This embodiment relates to the application of dye separation:

[0137] Two different sizes of pollutant molecules were fed into an aqueous solution (30 mL) and passed through an ultrafiltration device under an upstream pressure of 1 MPa. The effective separation area of ​​each membrane was 21.23 cm². 2 Two different dye feed solutions were chrome black (50 mg) (CB-T) (1.55*0.88 nm) and Congo red (50 mg) (CRO) (2.56*0.73 nm), which were dissolved in 1 L of water to obtain a 50 mg / L dye feed solution.

[0138] The results are as follows Figure 10 As shown.

[0139] This embodiment relates to the application of gas separation:

[0140] Two different sizes of gas were introduced into the feed side of the membrane chamber and passed through the membrane device at an upstream pressure of 0.1 MPa. The gas was then discharged at 15 mL / min on the permeate side of the membrane chamber. -1 Argon gas was purged into the gas chromatograph, and the effective separation area of ​​each membrane was 19.625 cm². 2 The two different gases are H2 and CO2.

[0141]

[0142] The H2 / CO2 selectivity of the COF composite membrane in the AA stacking mode is 2.47, while that in the COF composite membrane in the staggered AB stacking mode is 5.21.

[0143] Optical photographs of the composite film, such as Figure 1 As shown, a) represents HZ-TF-COF-FILM-AA, b) represents HZ-TF-COF-FILM-AB, c) represents TAPT-TF-COF-FILM-AA, d) represents TAPT-TF-COF-FILM-AB, e) represents TAPT-TFPB-COF-FILM-AA, and f) represents optical photographs of the six films TAPT-TFPB-COF-FILM-AB.

[0144] like Figure 2 , Figure 3 As shown, under high-magnification scanning electron microscopy, neither the AA stacked structure nor the staggered AB stacked structure showed obvious defects and was relatively complete and continuous. The morphology of COF growth on the PSF substrate film surface could also be seen. By SEM comparison, the COF grains of the staggered AB stacked structure were larger than those of the AA stacked structure.

[0145] like Figure 4 As shown, the thickness of the separation layer in the composite membrane provided by the present invention is in the range of 30μm-50μm, and the thickness of the substrate PSF is about 55μm.

[0146] Fourier transform infrared spectroscopy was performed on the composite films with different stacking structures in Examples 1-3, and the results are as follows: Figure 5 As shown, at 1689cm -1 Position and 3327cm -1 The peaks at the positions of the aldehyde and amino groups, respectively, disappeared in the COF infrared spectrum and peaked at 1606 cm⁻¹. -1 The presence of a characteristic peak of a carbon-nitrogen double bond indicates the formation of an imine bond, confirming the successful synthesis of COF.

[0147] XRD tests were performed on the composite films with different stacking structures in Examples 1-3, such as... Figure 6 As shown, by simulating and calculating the peak positions of XRD and comparing the XRD values ​​of the materials, we can illustrate the different packing modes formed by the composite film under different synthesis conditions.

[0148] Nitrogen adsorption-desorption results are as follows Figure 7 As shown, Figure 7 a) Figure 7 c) Figure 7 e) Nitrogen adsorption-desorption curves of the composite membranes prepared in Examples 1-3, respectively. Figure 7 b) Figure 7 d) Figure 7 f) These are the pore sizes of the composite membranes prepared in Examples 1-3. After HZ-TF-COF changed from AA stacking to staggered AB stacking, the pore size changed from 1.1 nm to 0.7 nm. After TAPT-TF-COF changed from AA stacking to staggered AB stacking, the pore size changed from 1.7 nm to 1.1 nm. After TAPT-TFPB-COF changed from AA stacking to staggered AB stacking, the pore size changed from 2.3 nm to 1.7 nm.

[0149] like Figure 8 As shown, HZ-TF-COF-FILM-AA and HZ-TF-COF-FILM-AB were tested for their separation performance against two different sizes of pollutant molecules. HZ-TF-COF-FILM-AB showed a significant improvement in the interception rate, which is attributed to the precise molecular sieving effect resulting from the reduced pore size.

[0150] like Figure 9 As shown, TAPT-TF-COF-FILM-AA and TAPT-TF-COF-FILM-AB were tested for their separation performance against three different sizes of pollutant molecules. TAPT-TF-COF-FILM-AB showed a significant improvement in the interception rate, which is attributed to the precise molecular sieving effect resulting from the reduced pore size.

[0151] like Figure 10 As shown, TAPT-TFPB-COF-FILM-AA and TAPT-TFPB-COF-FILM-AB were tested for their separation performance against two different sizes of pollutant molecules. TAPT-TFPB-COF-FILM-AB showed a significant improvement in the interception rate, which is attributed to the precise molecular sieving effect resulting from the reduced pore size.

[0152] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0153] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing an organic covalent framework composite membrane with an interlaced AB stacking structure, characterized in that, Includes the following steps: S1. Dissolve the aldehyde monomer in a Tf2N-type ionic liquid; S2. In the reactor, the amine monomer is dissolved in an organic solvent, added to the base membrane, dried, and a layer of amine monomer is adsorbed on the surface of the base membrane. S3. Add the ionic liquid containing the aldehyde monomer from step S1 to the reactor, and add the catalyst. S4. Microwave hydrothermal reaction is carried out to obtain an organic covalent framework composite membrane with an interlaced AB stacking structure; The aldehyde monomer is a C3-symmetric aldehyde monomer; the amine monomer is a C3- or C2-symmetric amine monomer.

2. The preparation method according to claim 1, characterized in that, The base membrane is any one of polysulfone membrane, polyimide membrane, polyether nitrile membrane or polyvinylidene fluoride membrane.

3. The preparation method according to claim 1, characterized in that, The molar ratio of the aldehyde monomer to the amine monomer is 0.85~1.05:1~1.

5.

4. The preparation method according to claim 1, characterized in that, The chemical formula of the Tf2N-type ionic liquid is [Bmim][Tf2N] or [N 8888 [Tf2N]; Its general structural formulas are as follows: 、 ， Wherein, R is any one of methyl, butyl, hexyl, heptyl, and dodecyl.

5. The preparation method according to claim 4, characterized in that, The preparation method of the Tf2N-type ionic liquid is as follows: Dissolve 0.1 mol of a cationic donor monomer in 25-50 ml of water, and dissolve 0.1 mol of lithium bis(trifluoromethanesulfonyl)imide in 100-200 ml of water. Mix the two solutions and stir at room temperature until the reaction is complete. Wash with water until colorless and clear, and dry under vacuum at room temperature to obtain an ionic liquid.

6. The preparation method according to claim 1, characterized in that, The organic solvent is an acetonitrile / dimethyl sulfoxide, acetonitrile / N,N-dimethylformamide, or a mixed solution of acetonitrile / N,N-dimethylacetamide.

7. The preparation method according to claim 6, characterized in that, The molar ratio of acetonitrile to dimethyl sulfoxide or N,N-dimethylformamide or N,N-dimethylacetamide is 1:5~10.

8. The preparation method according to claim 1, characterized in that, The catalyst is a Lewis acid.

9. The preparation method according to claim 1, characterized in that, The catalyst is a protic acid.

10. The preparation method according to claim 1, characterized in that, The catalyst is HOAc, and the molar ratio of HOAc to the aldehyde monomer is 15~30:

1.

11. The preparation method according to claim 1, characterized in that, The microwave hydrothermal reaction has a temperature of 30~60℃, a frequency of 10~100GHz, and a reaction time of 1~12h.

12. An organic covalent framework composite membrane with an AB stacking structure prepared by the preparation method according to any one of claims 1-11.

13. The application of the organic covalent framework composite membrane with an interlaced AB stacking structure as described in claim 12 in liquid separation or gas separation.

Images