Covalent organic framework / polyethersulfone mixed matrix membrane as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of covalent organic framework membrane materials, and provides a covalent organic framework / polyether sulfone mixed matrix membrane as well as a preparation method and application thereof. The method comprises the following steps: mixing polyether sulfone, a solvent and trialdehyde phloroglucinol to obtain a trialdehyde phloroglucinol solution; the glass fiber filter membrane is coated with the trialdehyde phloroglucinol solution, and a trialdehyde phloroglucinol / polyether sulfone membrane is obtained; the method comprises the following steps: mixing p-phenylenediamine, a catalyst and water to obtain a p-phenylenediamine solution; the trialdehyde phloroglucinol / polyether sulfone membrane is soaked in a p-phenylenediamine solution for a reaction, and the covalent organic framework / polyether sulfone mixed matrix membrane is obtained. The preparation method disclosed by the invention is mild in condition, the obtained membrane is uniform and stable, the advantages of high flux of a polymer and strong adsorption and separation of a covalent organic framework on CO2 are fully combined, and the H2 flux and H2 / CO2 selectivity of the covalent organic framework / polyether sulfone mixed matrix membrane are greatly improved.

Description

Technical Field

[0001] The invention relates to the technical field of covalent organic framework membrane materials, and in particular to a covalent organic framework / polyethersulfone mixed matrix membrane and a preparation method and application thereof. Background Art

[0002] Hydrogen (H2) is regarded as one of the carriers of clean energy in the future. The hydrogen production process usually contains CO2. In order to obtain high-purity hydrogen, it needs to be effectively separated. Membrane separation technology is one of the means to achieve efficient gas separation. Because of its advantages such as low operating cost, simple operation, low energy consumption and environmental friendliness, it is widely used in modern chemical separation processes.

[0003] Mixed matrix membranes can combine the advantages of polymers and fillers, allowing the selection layer, permeation layer and support layer to be designed separately, so that the selectivity, permeability and mechanical properties can be optimized. At the same time, due to the presence of the support layer, it is conducive to the realization of ultra-thin selection layers, thereby achieving the purpose of efficient selective separation. Traditional polymer membranes are usually affected by the trade-off between permeability and selectivity. Non-solvent induced phase separation (NIPS) is one of the most commonly used methods for preparing porous polymer membranes. In this process, a non-solvent for the polymer is introduced into a uniform polymer solution, and the solution is divided into two phases. The polymer-rich phase becomes the matrix of the membrane after condensation, and the non-polymer phase is removed from the precipitation solution to form membrane pores. Through this traditional NIPS process, an interconnected structure with adjustable size and porosity can be achieved to meet the requirements of material transmission and separation. After the introduction of polymers to achieve high gas permeability, it is necessary to consider how to use porous materials to achieve high gas selectivity. Therefore, the use of porous materials to prepare new membrane materials has an important impact on improving the performance of membranes.

[0004] Covalent organic framework (COF) is a periodic crystalline porous material linked by covalent bonds. The periodic and ordered pores are conducive to the transmission of gases, making it a new generation of materials for the construction of gas separation membranes. So far, people have successfully designed and synthesized COF membranes with gas separation properties, and proved that the membranes can effectively separate gases. However, the synthesis of COF membranes has some research difficulties, such as: the synthesis conditions of COF are harsh, the mechanical properties of the membranes are poor, and intercrystalline defects are easily generated, resulting in a significant reduction in the selectivity of COF membranes. Based on these problems, combined with the completely organic nature and high free volume of COF, it has good adhesion and compatibility with the polymer matrix, showing great potential in the preparation of COF-based mixed matrix membranes. Summary of the invention

[0005] The purpose of the present invention is to provide a covalent organic framework / polyethersulfone mixed matrix membrane and its preparation method and application, so as to solve the problems of poor filler dispersion, easy agglomeration, easy sedimentation, etc. in the existing mixed matrix membrane, and at the same time improve the brittleness problem of the covalent organic framework membrane, so as to improve the application of the membrane in gas separation.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a method for preparing a covalent organic framework / polyethersulfone mixed matrix membrane, comprising the following steps:

[0008] (1) mixing polyethersulfone, a solvent and trialdehyde phloroglucinol to obtain a trialdehyde phloroglucinol solution; coating the trialdehyde phloroglucinol solution on a glass fiber filter membrane to obtain a trialdehyde phloroglucinol / polyethersulfone membrane;

[0009] (2) mixing p-phenylenediamine, a catalyst and water to obtain a p-phenylenediamine solution;

[0010] (3) immersing the trialdehyde phloroglucinol / polyethersulfone membrane in a p-phenylenediamine solution to react and obtain the covalent organic framework / polyethersulfone mixed matrix membrane;

[0011] There is no order of precedence between steps (1) and (2).

[0012] Preferably, the solvent in step (1) is N-methylpyrrolidone;

[0013] The mass ratio of polyethersulfone to solvent is 10-20:80-90; the mass fraction of trialdehyde phloroglucinol in the trialdehyde phloroglucinol solution is 1-2%.

[0014] Preferably, the pore size of the glass fiber filter membrane in step (1) is 0.2 to 0.24 μm.

[0015] Preferably, the ratio of the volume of the trialdehyde phloroglucinol solution in step (1) to the diameter of the glass fiber filter membrane is 1-1.5 mL: 2.3-2.5 cm.

[0016] Preferably, the catalyst in step (2) is p-toluenesulfonic acid monohydrate;

[0017] The mass fraction of p-phenylenediamine in the p-phenylenediamine solution is 0.48-0.5%, and the mass fraction of the catalyst in the p-phenylenediamine solution is 1.68-1.76%.

[0018] Preferably, the reaction temperature in step (3) is 20-30° C., and the reaction time is 24-72 h.

[0019] The present invention also provides a covalent organic framework / polyethersulfone mixed matrix membrane prepared by the preparation method of the covalent organic framework / polyethersulfone mixed matrix membrane.

[0020] The invention also provides application of the covalent organic framework / polyethersulfone mixed matrix membrane in gas separation.

[0021] The beneficial effects of the present invention are:

[0022] (1) The present invention provides a method for preparing a covalent organic framework / polyethersulfone mixed matrix membrane, comprising the following steps: mixing polyethersulfone, a solvent and trialdehyde phloroglucinol to obtain a trialdehyde phloroglucinol solution; coating the trialdehyde phloroglucinol solution on a glass fiber filter membrane to obtain a trialdehyde phloroglucinol / polyethersulfone membrane; mixing p-phenylenediamine, a catalyst and water to obtain a p-phenylenediamine solution; immersing the trialdehyde phloroglucinol / polyethersulfone membrane in the p-phenylenediamine solution for reaction to obtain a covalent organic framework / polyethersulfone mixed matrix membrane. In the reaction process of the present invention, the non-solvent induced phase separation effect of the polymer polyethersulfone is used to generate a solid / liquid interface, so that the COF layer is polymerized in situ at the interface, thereby preparing a uniform and stable covalent organic framework / polyethersulfone mixed matrix membrane.

[0023] (2) The covalent organic framework / polyethersulfone mixed matrix membrane provided by the present invention directly uses commercial ultra-low-cost glass fiber filter membrane as a macroporous substrate, which greatly reduces the substrate cost; in addition, the glass fiber filter membrane is rich in oxygen-containing groups such as silanol, which can form hydrogen bonds and other effects with the abundant oxygen-containing groups on the surface of polyethersulfone, and form a mutually woven structure with the unique fiber structure of the glass fiber filter membrane, thereby further improving the stability of the covalent organic framework / polyethersulfone mixed matrix membrane.

[0024] (3) The present invention directly dissolves the ligand trialdehyde pyrogallol into the polyethersulfone solution, and utilizes the non-solvent induced phase separation method of the polymer to form a solid / liquid interface, so that the COF layer is polymerized in situ at the interface, thereby avoiding the problem of poor dispersibility of fillers in traditional mixed matrix membranes, and solving the brittleness problem and complex post-processing problem of COF membranes prepared by interfacial polymerization, thereby simplifying the preparation process.

[0025] (4) The preparation method of the covalent organic framework / polyethersulfone mixed matrix membrane provided by the present invention has mild conditions, and the obtained membrane is uniform and stable. It fully combines the advantages of high flux of polymer and strong adsorption and separation of CO2 by covalent organic framework, and greatly improves the H2 flux and H2 / CO2 selectivity of the covalent organic framework / polyethersulfone mixed matrix membrane. After application in gas separation tests, the H2 flux can reach 2671GPU, and the H2 / CO2 separation selectivity is as high as 82. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1Schematic diagram of the structure of COF TpPa-1 in Comparative Example 1;

[0027] Figure 2 X-ray diffraction patterns of different materials (2Theta—2θ, Intensity—intensity);

[0028] Figure 3 This is a microscopic morphology characterization diagram of the covalent organic framework / polyethersulfone mixed matrix membrane in Example 1; Figure 3 In the figure, (a) is a microscopic morphology characterization diagram of the outer surface of the covalent organic framework / polyethersulfone mixed matrix membrane; (b) is a microscopic morphology characterization diagram of the cross section of the covalent organic framework / polyethersulfone mixed matrix membrane;

[0029] Figure 4 Schematic diagram of the gas separation performance of the covalent organic framework / polyethersulfone mixed matrix membrane obtained in Examples 1 to 3 (Permeance—flux, H2 / CO2 selectivity—H2 / CO2 selectivity). DETAILED DESCRIPTION

[0030] The present invention provides a method for preparing a covalent organic framework / polyethersulfone mixed matrix membrane, comprising the following steps:

[0031] (1) mixing polyethersulfone, a solvent and trialdehyde phloroglucinol to obtain a trialdehyde phloroglucinol solution; coating the trialdehyde phloroglucinol solution on a glass fiber filter membrane to obtain a trialdehyde phloroglucinol / polyethersulfone membrane;

[0032] (2) mixing p-phenylenediamine, a catalyst and water to obtain a p-phenylenediamine solution;

[0033] (3) immersing the trialdehyde phloroglucinol / polyethersulfone membrane in a p-phenylenediamine solution to react and obtain the covalent organic framework / polyethersulfone mixed matrix membrane;

[0034] There is no order of precedence between steps (1) and (2).

[0035] In the present invention, the solvent in step (1) is preferably N-methylpyrrolidone.

[0036] In the present invention, the mass ratio of polyethersulfone to solvent is preferably 10-20:80-90, more preferably 12-18:82-88, and more preferably 15:85; the mass fraction of trialdehyde phloroglucinol in the trialdehyde phloroglucinol solution is preferably 1-2%, more preferably 1.2-1.8%, and more preferably 1.5%.

[0037] In the present invention, in step (1), the mixing is preferably: firstly, polyethersulfone is added to the solvent, stirred until dissolved, to obtain a polyethersulfone solution; then, trialdehyde phloroglucinol is added to the polyethersulfone solution, stirred until dissolved, and the mixing is completed to obtain a trialdehyde phloroglucinol solution.

[0038] In the present invention, the pore size of the glass fiber filter in step (1) is preferably 0.2 to 0.24 μm, more preferably 0.21 to 0.23 μm, and more preferably 0.22 μm.

[0039] In the present invention, the ratio of the volume of the trialdehyde phloroglucinol solution in step (1) to the diameter of the glass fiber filter membrane is preferably 1-1.5 mL: 2.3-2.5 cm, more preferably 1.2-1.4 mL: 2.35-2.45 cm, and more preferably 1.3 mL: 2.4 cm.

[0040] In the present invention, in step (1), the coating method is preferably spin coating, and the glass fiber filter membrane is preferably purchased from Shanghai Xinya Purification Device Factory; the glass fiber filter membrane is placed on a spin coater, and a trialdehyde phloroglucinol solution is slowly spin-coated to obtain a trialdehyde phloroglucinol / polyethersulfone membrane; the spin coating speed is preferably 800-1200 r / min, more preferably 900-1100 r / min, and more preferably 1000 r / min; the spin coating time is preferably 50-70 s, more preferably 55-65 s, and more preferably 60 s.

[0041] In the present invention, the catalyst in step (2) is preferably p-toluenesulfonic acid monohydrate.

[0042] In the present invention, the mass fraction of p-phenylenediamine in the p-phenylenediamine solution is preferably 0.48-0.5%, more preferably 0.485-0.495%, more preferably 0.49%; the mass fraction of the catalyst in the p-phenylenediamine solution is preferably 1.68-1.76%, more preferably 1.685-1.756%, more preferably 1.75%.

[0043] In the present invention, in step (3), the amount relationship between the trialdehyde phloroglucinol / polyethersulfone membrane and the p-phenylenediamine solution is not specifically limited, as long as the trialdehyde phloroglucinol / polyethersulfone membrane can be immersed in the p-phenylenediamine solution.

[0044] In the present invention, the reaction temperature in step (3) is preferably 20-30°C, more preferably 22-28°C, and more preferably 25°C; the reaction time is preferably 24-72h, more preferably 36-60h, and more preferably 48h.

[0045] In the present invention, in step (3), after the reaction is completed, drying is carried out to obtain a covalent organic framework / polyethersulfone mixed matrix membrane; the drying temperature is preferably 20 to 30°C, more preferably 22 to 28°C, and more preferably 25°C; the drying time is preferably 12 to 36 hours, more preferably 18 to 30 hours, and more preferably 24 hours.

[0046] The present invention also provides a covalent organic framework / polyethersulfone mixed matrix membrane prepared by the preparation method of the covalent organic framework / polyethersulfone mixed matrix membrane.

[0047] The invention also provides application of the covalent organic framework / polyethersulfone mixed matrix membrane in gas separation.

[0048] In the present invention, the covalent organic framework / polyethersulfone mixed matrix membrane is applied to gas separation. The covalent organic framework / polyethersulfone mixed matrix membrane can selectively separate the two mixed gases H2 / CO2, and its H2 flux can reach 2671GPU, and the separation selectivity of H2 / CO2 is as high as 82.

[0049] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0050] Example 1

[0051] 15 g of polyethersulfone (PES) was added to 85 g of N-methylpyrrolidone (NMP) solution, and the mixture was stirred to dissolve to obtain a polyethersulfone solution; trialdehyde phloroglucinol (Tp) was added to the polyethersulfone solution, and the mixture was stirred until dissolved to obtain a trialdehyde phloroglucinol solution having a mass fraction of 1.5% of trialdehyde phloroglucinol; a glass fiber filter membrane having a pore size of 0.22 μm and a diameter of 2.5 cm was placed on a spin coater, 1 mL of the trialdehyde phloroglucinol solution was taken, and the mixture was slowly spin-coated (the spin coating speed was set to 1000 r / min and the time was set to 60 s) to obtain a trialdehyde phloroglucinol / polyethersulfone membrane, which was recorded as Tp@PES;

[0052] Mixing p-phenylenediamine (Pa-1), p-toluenesulfonic acid monohydrate (PTSA) and water, and stirring until dissolved to obtain a p-phenylenediamine solution, wherein the mass fraction of p-phenylenediamine in the p-phenylenediamine solution is 0.49%, and the mass fraction of the catalyst is 1.75%;

[0053] The Tp@PES membrane was immediately immersed in a p-phenylenediamine solution and reacted at 25°C for 24 hours. After the reaction, it was taken out and dried at 25°C for 24 hours to obtain a covalent organic framework / polyethersulfone mixed matrix membrane, which was recorded as TpPa-1@PES-24.

[0054] Example 2

[0055] The other conditions in Example 1 were kept unchanged, and the reaction time after the Tp@PES membrane was immediately immersed in the p-phenylenediamine solution was changed to 48 h to obtain a covalent organic framework / polyethersulfone mixed matrix membrane, which was recorded as TpPa-1@PES-48.

[0056] Example 3

[0057] The other conditions in Example 1 were kept unchanged, and the reaction time after the Tp@PES membrane was immediately immersed in the p-phenylenediamine solution was changed to 72 h to obtain a covalent organic framework / polyethersulfone mixed matrix membrane, which was recorded as TpPa-1@PES-72.

[0058] Comparative Example 1

[0059] 6.3 mg of trialdehyde phloroglucinol (Tp) was dispersed in 20 mL of dichloromethane to obtain a Tp solution; 97.4 mg of p-phenylenediamine (Pa-1) and 342.3 mg of p-toluenesulfonic acid monohydrate (PTSA) were dissolved in 20 mL of water to obtain a Pa-1 solution;

[0060] The Pa-1 solution was slowly dripped from the top to the upper layer of the Tp solution, and allowed to stand at 25°C for 72 hours to polymerize at the interface of the water and organic phases to form a COF TpPa-1 layer. The COF TpPa-1 formed at the interface was collected, washed 4 times with anhydrous acetone, and finally washed 4 times with anhydrous ethanol to obtain COF TpPa-1 prepared by interfacial polymerization, which was marked as TpPa-1.

[0061] The schematic diagram of the structure of COF TpPa-1 in this comparative example is as follows Figure 1 shown.

[0062] The TpPa-1@PES-72 prepared in Example 3, the TpPa-1 prepared in Comparative Example 1, and GF (the glass fiber filter membrane in Example 1) were tested using an X-ray diffractometer to obtain X-ray diffraction patterns of different materials, as shown in FIG. Figure 2 As shown. Figure 2 It can be seen that TpPa-1@PES-72 prepared in Example 3 and TpPa-1 prepared in Comparative Example 1 both have the characteristic peak of COF TpPa-1 at 4.7°.

[0063] The microscopic morphology of the covalent organic framework / polyethersulfone mixed matrix membrane prepared in Example 1 was characterized by scanning electron microscopy, and a microscopic morphology characterization diagram of the covalent organic framework / polyethersulfone mixed matrix membrane in Example 1 was obtained, as shown in FIG. Figure 3 As shown; Figure 3In the figure, (a) is a microscopic morphology characterization image of the outer surface of the covalent organic framework / polyethersulfone mixed matrix membrane; (b) is a microscopic morphology characterization image of the cross section of the covalent organic framework / polyethersulfone mixed matrix membrane. Figure 3 It can be seen that the covalent organic framework / polyethersulfone mixed matrix membrane covers the surface of the glass fiber microporous filter membrane and enters the interior of the glass fiber filter membrane, forming a mutually woven structure with the fiber structure of the glass fiber microporous filter membrane.

[0064] The covalent organic framework / polyethersulfone mixed matrix membranes prepared in Examples 1 to 3 were respectively subjected to gas separation performance tests (wherein, the specific operation process of the test is: the covalent organic framework / polyethersulfone mixed matrix membrane is installed in a mold and fixed, and the membrane sample to be tested is sealed with a perforated aluminum foil tape, and the flow rate of all gas components is controlled by a mass flow meter so that the molar ratio of the two gas components is 1:1, and the total flow rate of the mixed gas is 100 mL·min -1 , N2 was used as the purge gas at a flow rate of 100 mL min -1 , the gas was kept flowing for more than 2 h before each measurement to ensure that the gas permeated through the membrane surface at a uniform rate, and the permeate flow rate was measured using a soap bubble flowmeter), and a schematic diagram of the gas separation performance of the covalent organic framework / polyethersulfone mixed matrix membrane obtained in Examples 1 to 3 was obtained, as shown in Figure 4 As shown. Figure 4 It can be seen that the H2 flux of the membrane can reach 2671GPU and the H2 / CO2 selectivity is as high as 82.

[0065] As can be seen from the above embodiments, the present invention provides a method for preparing a covalent organic framework / polyethersulfone mixed matrix membrane, comprising the following steps: mixing polyethersulfone, a solvent and trialdehyde phloroglucinol to obtain a trialdehyde phloroglucinol solution; coating the trialdehyde phloroglucinol solution on a glass fiber filter membrane to obtain a trialdehyde phloroglucinol / polyethersulfone membrane; mixing p-phenylenediamine, a catalyst and water to obtain a p-phenylenediamine solution; soaking the trialdehyde phloroglucinol / polyethersulfone membrane in the p-phenylenediamine solution for reaction to obtain a covalent organic framework / polyethersulfone mixed matrix membrane. The covalent organic framework / polyethersulfone mixed matrix membrane preparation method provided by the present invention has mild conditions, and the obtained membrane is uniform and stable, which fully combines the advantages of high flux of polymer and strong adsorption and separation of CO2 by the covalent organic framework, and greatly improves the H2 flux and H2 / CO2 selectivity of the covalent organic framework / polyethersulfone mixed matrix membrane; after being applied to gas separation tests, the H2 flux can reach 2671GPU, and the separation selectivity of H2 / CO2 is as high as 82.

[0066] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a covalent organic framework / polyethersulfone mixed matrix membrane, characterized in that: It includes the following steps: (1) mixing polyethersulfone, a solvent and trialdehyde phloroglucinol to obtain a trialdehyde phloroglucinol solution; coating the trialdehyde phloroglucinol solution on a glass fiber filter membrane to obtain a trialdehyde phloroglucinol / polyethersulfone membrane; (2) mixing p-phenylenediamine, a catalyst and water to obtain a p-phenylenediamine solution; (3) immersing the trialdehyde phloroglucinol / polyethersulfone membrane in a p-phenylenediamine solution to react and obtain the covalent organic framework / polyethersulfone mixed matrix membrane; There is no order of precedence between steps (1) and (2).

2. The method for preparing a covalent organic framework / polyethersulfone mixed matrix membrane according to claim 1, characterized in that: The solvent in step (1) is N-methylpyrrolidone; The mass ratio of polyethersulfone to solvent is 10-20:80-90; the mass fraction of trialdehyde phloroglucinol in the trialdehyde phloroglucinol solution is 1-2%.

3. The method for preparing a covalent organic framework / polyethersulfone mixed matrix membrane according to claim 1 or 2, characterized in that: The pore size of the glass fiber filter membrane in step (1) is 0.2 to 0.24 μm.

4. The method for preparing a covalent organic framework / polyethersulfone mixed matrix membrane according to claim 3, characterized in that: The ratio of the volume of the trialdehyde phloroglucinol solution in step (1) to the diameter of the glass fiber filter membrane is 1-1.5 mL: 2.3-2.5 cm.

5. The method for preparing a covalent organic framework / polyethersulfone mixed matrix membrane according to claim 4, characterized in that: The catalyst in step (2) is p-toluenesulfonic acid monohydrate; The mass fraction of p-phenylenediamine in the p-phenylenediamine solution is 0.48-0.5%, and the mass fraction of the catalyst in the p-phenylenediamine solution is 1.68-1.76%.

6. The method for preparing a covalent organic framework / polyethersulfone mixed matrix membrane according to claim 5, characterized in that: The reaction temperature in step (3) is 20 to 30° C., and the reaction time is 24 to 72 hours. 7 . The covalent organic framework / polyethersulfone mixed matrix membrane prepared by the method for preparing the covalent organic framework / polyethersulfone mixed matrix membrane according to any one of claims 1 to 6 .

8. Use of the covalent organic framework / polyethersulfone mixed matrix membrane according to claim 7 in gas separation.

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