A MOF-polyimide composite fiber membrane, a preparation method and application thereof

Abstract

The application provides a MOF-polyimide composite fiber membrane and a preparation method and application thereof, and the preparation method comprises the following steps: mixing diamine, dianhydride, a solvent and an additive, and obtaining a polyamide acid mixed solution after reaction; wherein the additive at least comprises phenethylamine, pectin and citrate; an MOF solution is added into the polyamide acid mixed solution to obtain a mixed solution; and after the mixed solution is subjected to electrostatic spinning treatment and imidization treatment in sequence, a MOF-polyimide composite fiber membrane is obtained, and the MOF-polyimide composite fiber membrane with excellent gas separation performance can be efficiently and simply prepared.

Description

Technical Field

[0001] This invention belongs to the field of membrane technology, specifically relating to a MOF-polyimide composite fiber membrane, its preparation method, and its application. Background Technology

[0002] CO2 separation and capture have broad application prospects in carbon emission reduction. Compared with traditional separation technologies such as distillation and absorption, gas membrane separation technology has attracted widespread attention due to its advantages such as high efficiency, energy saving, and environmental friendliness. In the gas separation process, the CO2 selectivity and permeability of the membrane material are among the important factors affecting the industrial application of membrane separation.

[0003] Polymers are widely used in gas separation membrane materials due to their excellent mechanical properties and film-forming properties. However, pure polymer membranes struggle to balance gas selectivity and permeability during separation. Currently, blending polymers with metal-organic frameworks (MOFs) is used to improve both gas selectivity and permeability. However, the blending process presents challenges such as MOF deposition and poor compatibility between MOFs and polymers, which in turn affect the gas separation performance of the membrane material.

[0004] Currently, the in-situ synthesis of polymers on MOFs is often used to improve the gas separation performance of composite membranes. For example, patent document CN111087635A discloses a PDMS@F-MOF composite film and its preparation method, which involves adding an MOF suspension to a PDMS precursor and curing it to prepare the composite film. However, the improvement in gas separation performance of the composite membrane achieved by the above method is far from satisfactory. Therefore, how to provide a composite membrane with excellent gas separation performance is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] This invention provides a method for preparing MOF-polyimide composite fiber membranes, which can efficiently and easily produce MOF-polyimide composite fiber membranes with excellent gas separation performance.

[0006] The present invention also provides a MOF-polyimide composite fiber membrane, which has excellent CO2 selectivity and permeability and performs excellently in gas separation performance.

[0007] The present invention also provides a method for separating carbon dioxide from a mixed gas containing carbon dioxide. Since the above-mentioned MOF-polyimide composite fiber membrane is used to separate the mixed gas, it has the advantages of high separation efficiency.

[0008] In a first aspect, the present invention provides a method for preparing a MOF-polyimide composite fiber membrane, comprising the following steps: mixing MOF with a solvent to obtain a MOF solution;

[0009] A polyamic acid mixture is obtained by mixing diamine, dianhydride, solvent, and additives and reacting the mixture; wherein the additives include at least phenylethylamine, pectin, and citrate.

[0010] MOF solution is added to the polyamic acid mixture to obtain a mixed solution; the mixed solution is then subjected to electrospinning and imidization treatments to obtain a MOF-polyimide composite fiber membrane.

[0011] In the preparation method described above, the phenylethylamine content is 0.04-3% based on the total mass of the solvent; and / or,

[0012] The mass ratio of pectin to MOF in the MOF solution is (0.01-0.5):1; and / or,

[0013] The mass ratio of the sum of the diamine and dianhydride to the citrate ester is 1:(0.007-0.1).

[0014] In the preparation method described above, the diamine is selected from at least one of p-phenylenediamine, 4,4'-diaminodiphenyl ether, hydroquinone diether diamine, 4,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenylmethane, ethylenediamine, 1,6-hexanediamine, and bisphenol A diether diamine; and / or,

[0015] The dianhydride is selected from at least one of pyromellitic dianhydride, biphenyltetracarboxylic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, triphenyl diether dianhydride, diphenyl ether dianhydride, diphenyl sulfide dianhydride, 4,4'-diphenyl ether tetracarboxylic dianhydride, hydroquinone diether dianhydride, hexafluoro dianhydride, resorcinol diether dianhydride, and bisphenol A diether dianhydride.

[0016] The preparation method described above further includes: mixing MOF with a solvent to obtain a MOF solution, wherein the mass ratio of MOF to solvent is (0.05-1):1; and / or,

[0017] The mass ratio of the polyamic acid mixture to the MOF solution is 1:(0.05-1); and / or,

[0018] The molar ratio of diamine to dianhydride is 1:(0.99-1.05).

[0019] The preparation method described above uses the following reaction conditions: temperature -15-30℃, time 1-10 h; and / or,

[0020] The imidization treatment is performed at a temperature of 280-300℃.

[0021] In the preparation method described above, the MOF is selected from at least one of MIL-101(Cr), MIL-101(Cr)-NH2, MIL-100(Fe), HKUST-1, ZIF-8, ZIF-71, ZIF-301, CAU-1(Al), CAU-23(Al), UiO-66, UiO-66-NH2, KAUST-7, KAUST-8, MOF-801, MOF-199, MOF-804, MOF-841, DUT-67(Zr), DUT-51(Zr), DUT-53(Zr), MOF-5, MOF-74(Mg), and MOF-74(Ni).

[0022] In the preparation method described above, the dianhydride is added either all at once or in batches; and / or,

[0023] The MOF solution can be added either all at once or in batches.

[0024] In the preparation method described above, the solvent is selected from at least one of dimethylformamide, N-methylpyrrolidone, dimethylacetamide, dimethyl sulfoxide, and hexamethylphosphoric triamine.

[0025] In a second aspect, the present invention provides a MOF-polyimide composite fiber membrane, which is prepared by the preparation method described above.

[0026] A third aspect of the present invention provides a method for separating carbon dioxide from a mixed gas containing carbon dioxide, wherein the mixed gas is separated using a MOF-polyimide composite fiber membrane as described above.

[0027] The implementation of this invention has at least the following beneficial effects:

[0028] The method for preparing MOF-polyimide composite fiber membranes provided by this invention, by introducing additives, not only avoids subsequent MOF deposition in the polyamic acid mixture but also improves the compatibility between MOF and polyamic acid, thereby facilitating the preparation of MOF-polyimide composite fiber membranes with excellent gas separation performance. Furthermore, the preparation method provided by this invention also has advantages such as high efficiency and ease of operation. Attached Figure Description

[0029] Figure 1 This is a scanning electron microscope image of the MOF solution from Example 5. Detailed Implementation

[0030] The specific embodiments listed below are merely descriptions of the principles and features of the present invention. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] In a first aspect, the present invention provides a method for preparing a MOF-polyimide composite fiber membrane, comprising the following steps: mixing MOF with a solvent to obtain a MOF solution;

[0032] A polyamic acid mixture is obtained by mixing diamine, dianhydride, solvent, and additives and reacting the mixture; wherein the additives include at least phenylethylamine, pectin, and citrate.

[0033] MOF solution was added to a polyamic acid mixture to obtain a mixed solution; the mixed solution was then subjected to electrospinning and imidization treatments to obtain a MOF-polyimide composite fiber membrane.

[0034] This invention does not limit the mixing method of diamine, dianhydride, solvent, and additives, as long as the diamine, dianhydride, solvent, and additives can be mixed. For example, the solvent, additives, and diamine are first added to the reactor and mixed, and then the dianhydride is added and mixed.

[0035] In this invention, the reaction of mixing diamine, dianhydride, solvent, and additives is essentially a polymerization reaction between the diamine and dianhydride to form polyamic acid. The imidization treatment is essentially the dehydration and cyclization of polyamic acid to form polyimide. This invention does not limit the specific method of imidization treatment; for example, it can be thermal imidization or chemical imidization.

[0036] This invention does not limit the specific operating steps of electrospinning treatment, and can be carried out using conventional electrospinning equipment in the field.

[0037] According to the technical solution provided by the present invention, the MOF-polyimide composite fiber membrane prepared by the above-mentioned method can significantly improve the gas separation performance of the MOF-polyimide composite fiber membrane. Based on this phenomenon, the inventors analyzed it and believe that it may be due to the following: Firstly, during the polymerization reaction of diamine and dianhydride, the presence of phenylethylamine can weaken the chain transfer efficiency during the polymerization reaction, promoting the forward reaction and thus preventing intramolecular depolymerization between the carboxylic acid hydroxyl group and the amide carbonyl group in polyamic acid, improving the viscosity and stability of polyamic acid, and enhancing the compatibility between MOF and polyamic acid; secondly, citrate can increase the solubility of polyamic acid in solvents, and the long side chains of citrate can adjust the spacing between polyamic acid molecular chains, thereby improving the stability of polyamic acid mixtures and solutions; thirdly, phenylethylamine and pectin can help enhance the adhesion stability between MOF and polyamic acid, preventing MOF deposition. This is because: First, the high molecular weight acids in pectin can increase the free hydrogen ions in the mixed system, promote the formation of polyamic acid, and ensure that MOF exists stably without deposition. Second, the amino group (-NH2) in phenylethylamine can promote the conversion of methoxy groups in pectin into amino groups of amides, which is conducive to the formation of a stable interface between polyamic acid and MOF, ensuring that MOF and polyamic acid are evenly dispersed in the mixed solution, which is beneficial to the subsequent formation of MOF-polyimide composite fiber membrane with excellent gas separation performance.

[0038] This invention does not limit the amount of each component of the additive, and can be adjusted according to actual needs. In one embodiment, based on the total mass of the solvent, the mass content of phenylethylamine is 0.04-3%, the mass ratio of pectin to MOF in the MOF solution is (0.01-0.5):1; the mass ratio of the sum of the masses of diamine and dianhydride to the mass of citrate is 1:(0.007-0.1). The solvent includes the solvent used in forming the MOF solution and the solvent used in forming the polyamic acid mixture.

[0039] This invention does not limit the specific types of diamines and dianhydrides, as long as they can undergo a polymerization reaction to form polyamic acid. For example, the diamine is selected from at least one of p-phenylenediamine, 4,4'-diaminodiphenyl ether, hydroquinone diether diamine, 4,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenylmethane, ethylenediamine, 1,6-hexanediamine, and bisphenol A diether diamine; the dianhydride is selected from at least one of pyromellitic dianhydride, biphenyltetracarboxylic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, triphenyl diether dianhydride, diphenyl ether dianhydride, diphenyl sulfide dianhydride, 4,4'-diphenyl ether tetracarboxylic dianhydride, hydroquinone diether dianhydride, hexafluoro dianhydride, resorcinol diether dianhydride, and bisphenol A diether dianhydride.

[0040] This invention does not limit the method of obtaining the MOF solution; it can be commercially available or prepared using conventional methods. For example, in one embodiment, it further includes: mixing MOF with a solvent to obtain a MOF solution, wherein the mass ratio of MOF to solvent is (0.05-1):1.

[0041] This invention does not limit the mass of the polyamic acid mixture and the MOF solution, and can adjust them according to actual needs. In one embodiment, the mass ratio of the polyamic acid mixture to the MOF solution is 1:(0.05-1), which is beneficial for obtaining a MOF-polyimide composite fiber membrane with excellent gas separation performance.

[0042] This invention does not limit the amount of diamine and dianhydride added, nor the reaction conditions between the diamine and dianhydride, as long as polyamic acid can be obtained. In one embodiment, the molar ratio of diamine to dianhydride is 1:(0.99-1.05). The reaction conditions are: temperature -15-30℃, time 1-10h.

[0043] This invention does not limit the conditions of imidization treatment, as long as MOF-polyimide composite fiber membranes can be obtained. In one embodiment, thermal imidization treatment is used, and the imidization treatment temperature is 280-300℃.

[0044] This invention does not limit the specific type of MOF, and can be any MOF material conventional in the art. For example, the MOF is selected from at least one of MIL-101(Cr), MIL-101(Cr)-NH2, MIL-100(Fe), HKUST-1, ZIF-8, ZIF-71, ZIF-301, CAU-1(Al), CAU-23(Al), UiO-66, UiO-66-NH2, KAUST-7, KAUST-8, MOF-801, MOF-199, MOF-804, MOF-841, DUT-67(Zr), DUT-51(Zr), DUT-53(Zr), MOF-5, MOF-74(Mg), and MOF-74(Ni).

[0045] This invention does not limit the method of adding diamine and dianhydride, as long as the above-mentioned ratio is maintained. In one embodiment, the dianhydride is added either all at once or in batches, and / or the MOF solution is added either all at once or in batches. Specifically, the solvent, additive, and diamine are added to the reactor and mixed, then the dianhydride is added all at once or in batches to react, and after the reaction, the MOF solution is added all at once or in batches to obtain a mixed solution. The batch addition can be done in two, three, or four batches, as long as the total amount added in each batch meets the above-mentioned ratio.

[0046] This invention does not limit the specific type of solvent. For example, the solvent may be selected from at least one of dimethylformamide, N-methylpyrrolidone, dimethylacetamide, dimethyl sulfoxide, and hexamethylphosphoric triamine.

[0047] In a second aspect, the present invention provides a MOF-polyimide composite fiber membrane, prepared by the method described above. This MOF-polyimide composite fiber membrane exhibits excellent performance in terms of carbon dioxide permeability and selectivity.

[0048] In a third aspect, the present invention provides a method for separating carbon dioxide from a mixed gas containing carbon dioxide, which utilizes the MOF-polyimide composite fiber membrane as described in the second aspect above to separate the mixed gas, and has advantages such as good carbon dioxide separation effect.

[0049] The present invention will be further described below through specific embodiments and comparative examples. Unless otherwise specified, the reagents, materials and instruments used below are all conventional reagents, materials and instruments, all of which are commercially available, and the reagents and materials involved can also be synthesized by conventional synthetic methods.

[0050] Example 1

[0051] 1 g ZIF-8 was dissolved in 10 g N-methylpyrrolidone, and the mixture was continuously stirred and ultrasonically dispersed until completely dissolved to obtain a MOF solution. 49.57 g N-methylpyrrolidone, 2.489 g p-phenylenediamine (0.023 mol), 0.037 g phenethylamine, 0.13 g pectin, 0.156 g citrate, and the MOF solution were added to a reactor, followed by the addition of 10.08 g (0.0227 mol) hexafluorodianhydride. The mixture was stirred at -15 °C for 1 hour to obtain a mixed solution with an intrinsic viscosity of 1.73 dL / g.

[0052] The mixed solution was loaded into the syringe of the electrospinning equipment, with nonwoven fabric as the collector, the injection voltage was 16kV, and the spinning time was 3h to obtain a composite material membrane; the composite material membrane was subjected to 300℃ thermal imidization treatment to obtain a MOF-polyimide composite fiber membrane.

[0053] Example 2

[0054] 3.04 g ZIF-301 was dissolved in 20 g N-methylpyrrolidone, and the mixture was continuously stirred and ultrasonically dispersed until completely dissolved to obtain a MOF solution. 20.24 g N-methylpyrrolidone, 1.082 g ethylenediamine (0.018 mol), 0.042 g phenylethylamine, 0.21 g pectin, 0.183 g citrate, and the MOF solution were added to a reactor, followed by the addition of 5.243 g biphenyl dianhydride (0.01782 mol). The mixture was stirred at -10 °C for 2 hours to obtain a mixed solution with an intrinsic viscosity of 2.12 dL / g.

[0055] The mixed solution was loaded into the syringe of the electrospinning equipment, and the release paper was used as the collector. The injection voltage was 16kV and the spinning time was 3h to obtain a composite material membrane. The composite material membrane was subjected to thermal imidization treatment at 280℃ to obtain a MOF-polyimide composite fiber membrane.

[0056] Example 3

[0057] 2.5 g of MOF-5 was dissolved in 30 g of dimethylformamide, and the mixture was continuously stirred and ultrasonically dispersed until completely dissolved to obtain a MOF solution. 40.12 g of dimethylformamide, 3.965 g (0.02 mol) of 4,4'-diaminodiphenylmethane, 2.0024 g of phenethylamine, 1.23 g of pectin, 0.183 g of citrate, and the MOF solution were added to a reactor, followed by the addition of 6.412 g (0.0199 mol) of 3,3',4,4'-benzophenone tetracarboxylic dianhydride. The mixture was stirred at -5 °C for 2 hours to obtain a mixed solution with an intrinsic viscosity of 2.4 dL / g.

[0058] The mixed solution was loaded into the syringe of the electrospinning equipment, and the release paper was used as the collector. The injection voltage was 16kV and the spinning time was 3h to obtain a composite material membrane. The composite material membrane was then subjected to a 300℃ heat imidization treatment to obtain a MOF-polyimide composite fiber membrane.

[0059] Example 4

[0060] 6g of MIL-101(Cr) was dissolved in 20g of dimethylacetamide in three equal portions, and the solution was continuously stirred and ultrasonically dispersed until completely dissolved to obtain a MOF solution. 40.39g of dimethylacetamide, 7.0017g (0.06025mol) of 1,6-hexanediamine, 0.064g of phenylethylamine, 0.075g of pectin, 0.183g of citrate, and the MOF solution were added to a reactor. Then, 18.64g (0.0601mol) of diphenyl ether dianhydride was added in four equal portions at 10-minute intervals. The mixture was stirred at 0℃ for 5 hours to obtain a mixed solution with an intrinsic viscosity of 2.08dL / g. The mixed solution was loaded into the syringe of an electrospinning device, using release paper as a collector, with an injection voltage of 16kV and a spinning time of 3h to obtain a composite membrane. The composite membrane was subjected to thermal imidization treatment at 295℃ to obtain a MOF-polyimide composite fiber membrane.

[0061] Example 5

[0062] 4.85 g of KAUST-8 was dissolved in 50 g of dimethyl sulfoxide, and the mixture was continuously stirred and ultrasonically dispersed until completely dissolved to obtain a MOF solution. 20.48 g of dimethyl sulfoxide, 6.246 g (0.012 mol) of bisphenol A diether diamine, 0.064 g of phenylethylamine, 0.075 g of pectin, 0.183 g of citrate, and the MOF solution were added to a reactor, followed by the addition of 3.804 g (0.012 mol) of diphenyl ether dianhydride. The mixture was stirred at 10 °C for 2 hours to obtain a mixed solution with an intrinsic viscosity of 1.72 dL / g.

[0063] The mixed solution was loaded into the syringe of the electrospinning equipment, and the release paper was used as the collector. The injection voltage was 16kV and the spinning time was 3h to obtain a composite material membrane. The obtained composite material membrane was subjected to thermal imidization treatment at 300℃ to obtain a MOF-polyimide composite fiber membrane.

[0064] Example 6

[0065] 2.675 g of MOF-801 was dissolved in 53.5 g of hexamethylphosphoric triamine, and the mixture was continuously stirred and ultrasonically dispersed until completely dissolved to obtain a MOF solution. 72.92 g of hexamethylphosphoric triamine, 3.2445 g (0.015 mol) of 4,4'-diaminodiphenyl sulfide, 0.064 g of phenethylamine, 0.075 g of pectin, 0.183 g of citrate, and the MOF solution were added to a reactor, followed by the addition of 6.1506 g (0.0153 mol) of triphenyl ether dianhydride. The mixture was stirred at 20 °C for 5 hours to obtain a mixed solution with an intrinsic viscosity of 1.71 dL / g.

[0066] The mixed solution was loaded into the syringe of the electrospinning equipment, and the release paper was used as the collector. The injection voltage was 16kV and the spinning time was 3h to obtain a composite material membrane. The obtained composite material membrane was subjected to thermal imidization treatment at 300℃ to obtain a MOF-polyimide composite fiber membrane.

[0067] Example 7

[0068] 1.69 g of HKAUST-1 was dissolved in 24.14 g of dimethylformamide, and the mixture was continuously stirred and ultrasonically dispersed until completely dissolved. 78 g of dimethylformamide, 4.9566 g (0.025 mol) of 4,4'-diaminodiphenylmethane, 0.0423 g of phenethylamine, 0.676 g of pectin, 0.519 g of citrate, and MOF solution were added to a reactor, followed by the addition of 5.453 g (0.025 mol) of pyromellitic dianhydride. The mixture was stirred at 0 °C for 4 hours to obtain a mixed solution with an intrinsic viscosity of 2.26 dL / g.

[0069] The mixed solution was loaded into the syringe of the electrospinning equipment, and the release paper was used as the collector. The injection voltage was 16kV and the spinning time was 3h to obtain a composite material membrane. The obtained composite material membrane was subjected to thermal imidization treatment at 300℃ to obtain a MOF-polyimide composite fiber membrane.

[0070] Example 8

[0071] 2.68 g of MOF-841 was dissolved in 3.828 g of dimethylacetamide, and the mixture was continuously stirred and ultrasonically dispersed until completely dissolved to obtain a MOF solution. 110.17 g of dimethylacetamide, 12.33 g (0.114 mol) of p-phenylenediamine, 2.28 g of phenylethylamine, 0.0268 g of pectin, 0.37 g of citrate, and the MOF solution were added to a reactor, followed by the addition of 24.741 g (0.0113 mol) of pyromellitic dianhydride. The mixture was stirred at 0 °C for 4 hours to obtain a mixed solution with an intrinsic viscosity of 2.34 dL / g.

[0072] The mixed solution was loaded into the syringe of the electrospinning equipment, and the release paper was used as the collector. The injection voltage was 16kV and the spinning time was 3h to obtain a composite material membrane. The obtained composite material membrane was subjected to thermal imidization treatment at 300℃ to obtain a MOF-polyimide composite fiber membrane.

[0073] Example 9

[0074] 3.69 g of CAU-1(Al) was dissolved in 46.125 g of N-methylpyrrolidone, and the mixture was continuously stirred and ultrasonically dispersed until completely dissolved to obtain a MOF solution. 29.815 g of N-methylpyrrolidone, 0.817 g (0.0136 mol) of ethylenediamine, 0.075 g of phenylethylamine, 0.0738 g of pectin, 0.5174 g of citrate, and the MOF solution were added to a reactor, followed by the addition of 4.357 g (0.0135 mol) of 3,3',4,4'-benzophenone tetracarboxylic dianhydride. The mixture was stirred at 30 °C for 8 hours to obtain a mixed solution with an intrinsic viscosity of 2.17 dL / g.

[0075] The mixed solution was loaded into the syringe of the electrospinning equipment, and the release paper was used as the collector. The injection voltage was 16kV and the spinning time was 3h to obtain a composite material membrane. The obtained composite material membrane was subjected to thermal imidization treatment at 300℃ to obtain a MOF-polyimide composite fiber membrane.

[0076] Example 10

[0077] 2.36 g of DUT-67(Zr) was dissolved in 23.6 g of N-methylpyrrolidone, and the mixture was continuously stirred and ultrasonically dispersed until completely dissolved. 20.45 g of N-methylpyrrolidone, 1.4424 g (0.024 mol) of ethylenediamine, 0.075 g of phenylethylamine, 0.0738 g of pectin, 0.5174 g of citrate, and MOF solution were added to a reactor, followed by the addition of 10.662 g (0.024 mol) of hexafluorodianhydride. The mixture was stirred at -10 °C for 3 hours to obtain a mixed solution with an intrinsic viscosity of 2.25 dL / g.

[0078] The mixed solution was loaded into the syringe of the electrospinning equipment, with release paper as the collector, the injection voltage was 16kV, and the spinning time was 3h to obtain a composite material membrane; the obtained composite material membrane was subjected to 300℃ thermal imidization treatment to obtain MOF-polyimide composite fiber membrane.

[0079] Comparative Example 1

[0080] The preparation method is basically the same as in Example 2, except that phenylethylamine, pectin, and citrate are not added. The intrinsic viscosity of the resulting mixed solution is 1.64 dL / g. Other conditions remain unchanged, and the resulting MOF-polyimide composite fiber membrane is obtained.

[0081] Comparative Example 2

[0082] The preparation method is basically the same as that in Example 4, except that phenylethylamine, pectin and citrate are not added. The intrinsic viscosity of the resulting mixed solution is 1.71 dL / g. Other conditions remain unchanged, and MOF-polyimide composite fiber membrane is obtained.

[0083] Test case

[0084] The composite fiber membrane was subjected to CO2 / N2 gas permeation tests at 35℃ and 2.0MPa. The composite fiber membrane was used for the separation of a CO2 / N2 mixture (50 / 50 vol%). The test results are shown in Table 1. The formula for calculating the CO2 permeation coefficient is:

[0085]

[0086] In the formula, P is the permeability (Barrer), and V is the permeability. d It is to calibrate the permeate volume (cm). 3 ), l is the film thickness (cm), p h A is the pressure on the high-pressure side (cmHg), and A is the effective membrane area (cm²). 2 T is the temperature during the test (K), R is the gas constant, and dp / dt is the rate of change of the low-pressure side pressure over time under steady state (cmHg). s－1 )

[0087] The formula for calculating CO2 / N2 selectivity is based on the gas permeability P, yielding the gas selectivity:

[0088]

[0089] In the formula, α A / B It is CO2 / N2 selectivity, P A It is CO2 permeability, P B It is the N2 penetration rate.

[0090] Table 1

[0091]

[0092]

[0093] according to Figure 1 It can be seen that the MOF is uniformly dispersed in the solution. According to Table 1, compared with the comparative example, the composite fiber membrane of the embodiment has higher carbon dioxide permeability and selectivity, and has better gas separation performance.

[0094] The preferred embodiments and experimental verifications of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A method for preparing a MOF-polyimide composite fiber membrane, characterized in that, The steps include: mixing MOF with a solvent to obtain a MOF solution; A polyamic acid mixture is obtained by mixing diamine, dianhydride, solvent, and additives and reacting the mixture; wherein the additives include at least phenylethylamine, pectin, and citrate. MOF solution is added to the polyamic acid mixture to obtain a mixed solution; the mixed solution is then subjected to electrospinning and imidization treatments in sequence to obtain a MOF-polyimide composite fiber membrane. Based on the total mass of the solvent, the phenylethylamine content is 0.04-3%; The mass ratio of pectin to MOF in the MOF solution is (0.01-0.5):1; The mass ratio of the sum of the diamine and dianhydride to the citrate ester is 1:(0.007-0.1).

2. The preparation method according to claim 1, characterized in that, The diamine is selected from at least one of p-phenylenediamine, 4,4'-diaminodiphenyl ether, hydroquinone diether diamine, 4,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenylmethane, ethylenediamine, 1,6-hexanediamine, and bisphenol A diether diamine; and / or, The dianhydride is selected from at least one of pyromellitic dianhydride, biphenyltetracarboxylic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, triphenyl diether dianhydride, diphenyl ether dianhydride, diphenyl sulfide dianhydride, 4,4'-diphenyl ether tetracarboxylic dianhydride, hydroquinone diether dianhydride, hexafluoro dianhydride, resorcinol diether dianhydride, and bisphenol A diether dianhydride.

3. The preparation method according to claim 1 or 2, characterized in that, It also includes: mixing MOF with a solvent to obtain a MOF solution, wherein the mass ratio of MOF to solvent is (0.05-1):1; and / or, The mass ratio of the polyamic acid mixture to the MOF solution is 1:(0.05-1); and / or, The molar ratio of diamine to dianhydride is 1:(0.99-1.05).

4. The preparation method according to any one of claims 1-3, characterized in that, The reaction conditions are: temperature -15 to 30°C, time 1 to 10 hours; and / or, The imidization treatment is performed at a temperature of 280-300℃.

5. The preparation method according to any one of claims 1-4, characterized in that, The MOF is selected from at least one of MIL-101(Cr), MIL-101(Cr)-NH2, MIL-100(Fe), HKUST-1, ZIF-8, ZIF-71, ZIF-301, CAU-1(Al), CAU-23(Al), UiO-66, UiO-66-NH2, KAUST-7, KAUST-8, MOF-801, MOF-199, MOF-804, MOF-841, DUT-67(Zr), DUT-51(Zr), DUT-53(Zr), MOF-5, MOF-74(Mg), and MOF-74(Ni).

6. The preparation method according to any one of claims 1-5, characterized in that, The dianhydride is added either all at once or in batches; and / or, The MOF solution can be added either all at once or in batches.

7. The preparation method according to any one of claims 1-6, characterized in that, The solvent is selected from at least one of dimethylformamide, N-methylpyrrolidone, dimethylacetamide, dimethyl sulfoxide, and hexamethylphosphoric triamine.

8. A MOF-polyimide composite fiber membrane, characterized in that, It is prepared by the preparation method according to any one of claims 1-7.

9. A method for separating carbon dioxide from a mixture of gases containing carbon dioxide, characterized in that, The MOF-polyimide composite fiber membrane described in claim 8 is used to separate mixed gases.

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