Solid solution membrane containing high-load porous organic cage CC3, preparation method and application of solid solution membrane in gas separation
High-load porous organic cage CC3 solid solution membranes were prepared by ball milling, which solved the problem of agglomeration of porous organic cages in polymer matrix and achieved high efficiency in CO2 and CH4 gas separation.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CHINA UNIV OF PETROLEUM (EAST CHINA)
- Filing Date
- 2026-04-07
- Publication Date
- 2026-05-05
AI Technical Summary
In the prior art, the loading capacity of porous organic cages in polymer matrices is limited, and they are prone to agglomeration, leading to interface defects and limiting the performance improvement of solid solution films.
A porous organic cage CC3 was mixed with polymer PI by ball milling, and a high-load solid solution film was prepared by the synergistic effect of mechanical shear force and a small amount of solvent, thus avoiding agglomeration and interface defects.
This method achieves high loading and uniform dispersion of porous organic cage CC3 in a polymer matrix, improving gas separation performance, especially permeability and selectivity in the separation of CO2 and CH4.
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Figure CN121972033A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of membrane materials and their separation technology, specifically relating to a solid solution membrane containing a highly loaded porous organic cage CC3, its preparation method, and its application in gas separation. Background Technology
[0002] Membrane separation technology has shown broad application prospects in the field of gas separation due to its advantages such as low energy consumption, simple operation, and environmental friendliness. Polymer membranes dominate the market due to their convenient processing and strong scalability, but their performance is limited by the trade-off between gas permeability and selectivity, i.e., the Robeson upper limit. To overcome this limitation, researchers have introduced porous packing materials into polymer matrices to prepare hybrid matrix membranes. Traditional packing materials such as zeolites, metal-organic frameworks, and covalent organic frameworks have excellent pore structures, but their insolubility in organic solvents leads to poor interfacial compatibility with the polymer matrix, easily forming non-selective defects and reducing gas separation efficiency.
[0003] Porous molecular cages (POCs), as a novel type of molecular porous material, are assembled from discrete molecules through weak interactions. They are soluble in specific solvents, fundamentally avoiding the interfacial incompatibility problem of traditional rigid fillers. Cooper et al. (Angewandte Chemie International Edition, 2013, 52, 1253-1256) co-dissolved POCs and PIM-1 polymers in chloroform. During solvent evaporation, POCs underwent in-situ nucleation and growth in the casting solution, achieving effective bonding between them and the polymer. However, in this work, the porous molecular cages only existed in molecular form in the casting solution, remaining as particles in the mixed matrix film, failing to fully utilize the discrete characteristics of the porous molecular cages. A solid solution film formed by dispersing porous organic cages as a molecular "solute" in a polymer "solvent" can achieve molecular-level mixing and eliminate interfacial defects. Lively et al. (Angewandte Chemie International Edition, 2019, 58, 2638-2643) combined vertex-functionalized CC3 cage molecules with Matrimid polymers, allowing them to be uniformly dispersed in the polymer "solvent" as molecular "solutes" to construct a single-phase solid solution film. This avoided the dispersion problem of particles in the polymer matrix and the interfacial compatibility problem between particles and polymers, and achieved a significant increase in CO2 permeability.
[0004] However, the loading capacity of POC in polymers is limited. When the loading exceeds the critical value (usually 5 wt%), the strong non-covalent interactions between cage molecules (such as hydrogen bonds and π-π stacking) will cause the molecular cages to aggregate and form crystals, resulting in non-selective interface defects between the filler and the polymer, which seriously restricts the further improvement of the solid solution film performance.
[0005] Therefore, effectively suppressing the aggregation of POC and achieving its high loading and uniform dispersion in the polymer matrix is the core challenge in preparing high-performance solid solution films. Summary of the Invention
[0006] To address the aforementioned problems, the present invention aims to provide a solid solution membrane containing a highly loaded porous organic cage CC3 that can achieve high loading capacity, defect-free and high separation performance, a preparation method thereof, and its application in gas separation, particularly for separating CO2 and CH4.
[0007] The present invention discloses a method for preparing a solid solution membrane containing a highly loaded porous organic cage CC3, comprising the following steps:
[0008] (1) Mix porous organic cage CC3, polymer PI and N-methylpyrrolidone to form a premix;
[0009] (2) The premixed liquid obtained in step (1) is ball-milled to form a ball-milled mixed solution;
[0010] (3) The ball milling mixture obtained in step (2) is evenly and evenly spread in the film forming apparatus, and then heated to completely evaporate the solvent, forming a solid solution film containing a highly loaded porous organic cage CC3.
[0011] In step (1), the doping amount is 10wt%~30wt%, preferably 10wt%~20wt%, and the doping amount = [mass of porous organic cage CC3 / (mass of porous organic cage CC3 + mass of polymer PI)]*100%; (mass of porous organic cage CC3 + mass of polymer PI): mass of N-methylpyrrolidone = 1: 12.5~12.9;
[0012] In step (2), the ball mill speed is 600~700 rpm, the ball milling time is 2~4 hours, and the ball-to-material mass ratio is 18~20:1;
[0013] In step (3), the heat treatment temperature is 60~80℃;
[0014] In step (3), the solvent evaporates completely, and the solid solution membrane containing the highly loaded porous organic cage CC3 contains only the porous organic cage CC3 and the polymer PI.
[0015] The polymer PI used in this invention is a commercially available product, and CC3 is obtained using conventional methods.
[0016] The specific steps for preparing the porous organic cage CC3 in step (1) are as follows:
[0017] (a) Mix pyromellitic aldehyde and dichloromethane in a mass ratio of 1:40~45 to form solution A;
[0018] (b) Mix 1,2-cyclohexanediamine and dichloromethane in a mass ratio of 1:40~45 to form solution B;
[0019] (c) Slowly mix solution A and solution B, with the mass ratio of pyromellitic aldehyde to 1,2-cyclohexanediamine being 1:1.0~1.5, and then react at 25~35℃ for 5~7 days; after centrifugation to collect the product, wash to remove unreacted reactants, and dry the obtained product;
[0020] Preferably, in step (c), the product is washed 3 to 5 times with dichloromethane and then 3 to 5 times with ethanol to remove unreacted reactants.
[0021] In step (c), the drying temperature is 70~80℃ and the drying time is 8~10 hours.
[0022] The solid solution membrane containing a highly loaded porous organic cage CC3 described in this invention is prepared by the above-described preparation method.
[0023] The gas separation described in this invention includes the separation of CO2 and CH4.
[0024] The beneficial effects of this invention are as follows:
[0025] This invention utilizes the synergistic effect of the mechanical shearing force of ball milling and a small amount of solvent to sever the non-covalent interactions between CC3 cage molecules on the one hand, and to restrict molecular mobility by using a high-viscosity medium and combine it with rapid solvent evaporation to achieve kinetic quenching on the other hand. This successfully increases the loading of porous organic cage CC3 to 10~30wt%, and there is no aggregation or interface defects in the membrane. The resulting solid solution membrane exhibits excellent permeability and selectivity in CO2 separation.
[0026] The relevant test conditions and methods involved in this invention are as follows:
[0027] X-ray electron diffraction (XRD) test: The structure of the prepared film sample was characterized using a Rigaku MiniFlex 600 desktop X-ray diffractometer.
[0028] Scanning electron microscopy (SEM) testing: The morphology of the prepared membrane samples was characterized using a Hitachi Regulus 8100 high-resolution scanning electron microscope.
[0029] The gas separation test was performed using the Wicke-Kallenbach Technique apparatus (Angew. Chem. Int. Ed. 2006, 45, 7053-7056). The flow rates of CO2, CH4 and carrier gas Ar were controlled by a mass flow controller. The feed gas permeating the membrane was purged by the carrier gas and entered the gas chromatograph. The contents of different gases were measured to determine the separation effect.
[0030] Permeability coefficient (P) i It can be calculated using formula (1):
[0031] (1)
[0032] Where P i (Barrer, 1 Barrer = 3.35 × 10 -16 mol m -1 s -1 Pa -1 ) is the permeability coefficient, N i (mol s) -1 ) is the permeation flow rate of gas component i, l (μm) is the membrane thickness, and Δp i (Pa) is the pressure difference across the membrane of component i, A(m 2 ) is the effective area of the membrane;
[0033] Selectivity (α) i / j It can be calculated using formula (2):
[0034] (2)
[0035] Where i and j represent CO2 and CH4, respectively.
[0036] Gas chromatography (GC) analysis: HORP GC-9860-5C-NJ; column temperature: 80℃; detector: TCD; the mixed gas composition was CO2 and CH4 in a volume ratio of 1:1. Attached Figure Description
[0037] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific 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 from these drawings without creative effort.
[0038] Figure 1 The XRD patterns of the CC3 / PI solid solution films in Examples 1-3 are shown below.
[0039] Figure 2 The images shown are SEM images of the CC3 / PI solid solution films in Examples 1-3 (the top image is a planar SEM image, and the bottom image is a cross-sectional SEM image).
[0040] Figure 3 The graph shows the CO2 / CH4 separation performance of the CC3 / PI solid solution membranes in Examples 1-3;
[0041] Figure 4 The image shows the SEM image of MMM-CHCl3 in Comparative Example 1.
[0042] Figure 5 The image shows the SEM image of MMM-NMP in Comparative Example 2. Detailed Implementation
[0043] The present invention will be further described in detail below with reference to embodiments, but the implementation methods and protection scope of the present invention are not limited thereto.
[0044] Example 1
[0045] (1) Preparation of porous organic cage CC3:
[0046] 100 mg of trimesaldehyde was added to 3 mL of dichloromethane to prepare solution A. Subsequently, 100 mg of 1,2-cyclohexanediamine was dispersed in another 3 mL of dichloromethane to prepare solution B. Solution B was gradually added to solution A, and the mixture was allowed to react at room temperature for 5 days. The product was collected by centrifugation, washed three times with dichloromethane, then three times with ethanol, and dried at 80 °C for 8 hours to obtain porous organic cage CC3 with a product mass of 145 mg.
[0047] (2) Preparation of CC3 / PI solid solution film:
[0048] Accurately weigh 8 mg of CC3 sample, 72 mg of PI sample, and 1 mL of N-methylpyrrolidone obtained in step (1) and place them in a grinding jar (the total mass ratio of porous organic cage CC3 and polymer PI to N-methylpyrrolidone is 1:12.9), and add 20 g of grinding balls (the ball-to-material mass ratio is 18:1). The ball milling speed is set to 600 rpm, and the ball milling time is 4 hours. Pour the ball-milled solution into a film-forming mold, and then place it at 60°C for 3 hours to obtain a CC3 / PI solid solution film with a loading of 10 wt%, denoted as CC3 / PI-10%.
[0049] Membrane characterization:
[0050] Figure 1The XRD curve of the CC3 / PI-10% film showed that no characteristic peaks of CC3 crystals were observed, indicating that CC3 exists in the CC3 / PI-10% film in the form of unimolecular molecules. Figure 2 SEM images of the CC3 / PI-10% membrane show that the CC3 / PI-10% membrane is uniform and flat, without defects.
[0051] The separation performance of the membrane for CO2 / CH4 gases was tested at 2 bar and 25 °C. The results are shown in Table 1. The CO2 permeability coefficient of the CC3 / PI-10% membrane was 39.2 Barrer, and the CO2 / CH4 selectivity was 40.3.
[0052] Table 1: CO2 / CH4 gas permeability coefficient and selectivity at 2 bar pressure
[0053] <![CDATA[CO2 Permeability Coefficient (Barrer)]]> <![CDATA[CO2 / CH4 selectivity]]> 39.2 40.3
[0054] 1 Barrer = 3.35 × 10 -16 mol m -1 s -1 Pa -1 .
[0055] Example 2
[0056] The preparation steps of the CC3 solid solution film are the same as those in Example 1. The difference is that in step (2), the sample mass of CC3 is changed to 16 mg, the sample mass of PI is changed to 64 mg, the loading of CC3 is 20 wt%, and the film is denoted as CC3 / PI-20%.
[0057] Membrane characterization:
[0058] Figure 1 The XRD curves of the CC3 / PI-20% film show that the characteristic diffraction peaks of CC3 completely disappear in the composite film, confirming that CC3 molecules are uniformly dispersed in the PI matrix in a monomolecular state. Figure 2 SEM images of the CC3 / PI-20% membrane show that the CC3 / PI-20% membrane structure is continuous and dense, with a smooth surface and no obvious phase separation or interface defects.
[0059] The separation performance of the membrane for CO2 / CH4 gases was tested at 2 bar and 25°C, and the results are shown in Table 2. Compared with the CO2 / CH4 separation performance of the CC3 / PI-10% membrane in Example 1, the membrane with 20 wt% CC3 showed improved CO2 permeability and CO2 / CH4 selectivity. This is attributed to the pore size sieving effect of CC3 and the defect-free membrane material.
[0060] Table 2: CO2 / CH4 gas permeability coefficient and selectivity at 2 bar pressure
[0061] <![CDATA[CO2 Permeability Coefficient (Barrer)]]> <![CDATA[CO2 / CH4 selectivity]]> 57.9 53.8
[0062] 1 Barrer = 3.35 × 10 -16 mol m -1 s -1 Pa -1 .
[0063] Example 3
[0064] The preparation steps of the CC3 solid solution film are the same as those in Example 1. The difference is that in step (2), the sample mass of CC3 is changed to 24 mg, the sample mass of PI is changed to 56 mg, the loading of CC3 is 30 wt%, and the film is denoted as CC3 / PI-30%.
[0065] Membrane characterization:
[0066] Figure 1 The XRD curve of the CC3 / PI-30% film did not show the characteristic peaks of CC3 crystals, indicating that CC3 achieved uniform molecular-level dispersion in the polymer matrix. Figure 2 SEM images of the CC3 / PI-30% membrane show that the CC3 / PI-30% membrane has a uniform structure and no defects.
[0067] The separation performance of the membrane for CO2 / CH4 gases was tested at 2 bar and 25°C, and the results are shown in Table 3. Compared with the CO2 / CH4 separation performance of the CC3 / PI-20% membrane in Example 3, the CO2 permeability coefficient of the membrane doped with 30 wt% CC3 was improved, but the CO2 / CH4 selectivity decreased. This is because the increase in CC3 provides more gas transport channels, thus improving the CO2 permeability coefficient. However, excessive filler makes it impossible for ball milling to ensure that all CC3 molecules are dispersed, leading to inter-cage agglomeration and defects, thus reducing the CO2 / CH4 selectivity.
[0068] Table 3: CO2 / CH4 gas permeability coefficient and selectivity at 2 bar pressure
[0069] <![CDATA[CO2 Permeability Coefficient (Barrer)]]> <![CDATA[CO2 / CH4 selectivity]]> 77.6 44.6
[0070] 1 Barrer = 3.35 × 10 -16 mol m -1 s -1 Pa -1 .
[0071] Comparative Example 1
[0072] (1) Preparation of porous organic cage CC3:
[0073] 100 mg of trimesaldehyde was added to 3 mL of dichloromethane to prepare solution A. Subsequently, 100 mg of 1,2-cyclohexanediamine was dispersed in another 3 mL of dichloromethane to prepare solution B. Solution B was gradually added to solution A, and the mixture was allowed to react at room temperature for 5 days. The product was collected by centrifugation, washed three times with dichloromethane, then three times with ethanol, and dried at 80 °C for 8 hours to obtain porous organic cage CC3 with a product mass of 145 mg.
[0074] (2) Preparation of MMM-CHCl3:
[0075] Accurately weigh 8 mg of the CC3 sample obtained in step (1) and dissolve it in 3 mL of chloroform by stirring and sonicating for 30 minutes each. Add 72 mg of PI sample in three portions according to 1 / 10, 2 / 10 and 7 / 10 of the total mass to the chloroform solution of CC3 obtained in the previous step, and repeat the stirring and sonication for 10 minutes each time to ensure thorough dispersion. Sonicate the final mixed solution again for 10 minutes, and then slowly spread it evenly in a film-forming mold calibrated with a level. Cover the film-forming mold with a glass plate to prevent the chloroform from evaporating too quickly to obtain a relatively uniform mixed matrix film. Then place it at 25°C for evaporation for 12 hours. The initially obtained membrane material is vacuum dried at 80°C overnight to remove excess solvent, resulting in a CC3 / PI-10% mixed matrix film with CC3 doping of 10 wt%, denoted as MMM-CHCl3.
[0076] Membrane characterization:
[0077] Figure 4 SEM images showed that there were obvious CC3 crystal particles in the MMM-CHCl3 membrane, and there were significant interface defects at the interface between CC3 crystals and polymer. This indicates that although the traditional mixed matrix membrane preparation method can dissolve CC3 in the early stage, CC3 will still precipitate in the form of crystal particles during the solvent evaporation and film formation process.
[0078] Comparative Example 2
[0079] (1) Preparation of porous organic cage CC3:
[0080] 100 mg of trimesaldehyde was added to 3 mL of dichloromethane to prepare solution A. Subsequently, 100 mg of 1,2-cyclohexanediamine was dispersed in another 3 mL of dichloromethane to prepare solution B. Solution B was gradually added to solution A, and the mixture was allowed to react at room temperature for 5 days. The product was collected by centrifugation, washed three times with dichloromethane, then three times with ethanol, and dried at 80 °C for 8 hours to obtain porous organic cage CC3 with a product mass of 145 mg.
[0081] (2) Preparation of MMM-NMP:
[0082] Accurately weigh 8 mg of the CC3 sample obtained in step (1) and disperse it in 3 mL of N-methylpyrrolidone by stirring and sonicating for 30 minutes each. Add 72 mg of PI sample in three portions according to 1 / 10, 2 / 10 and 7 / 10 of the total mass to the CC3 N-methylpyrrolidone solution obtained in the previous step, and repeat the stirring and sonication for 10 minutes each time to ensure thorough dispersion. Sonicate the final mixed solution again for 10 minutes, then pour it into a film forming mold and place it at 60°C to evaporate the solvent for 8 hours to obtain a CC3 / PI-10% mixed matrix film with CC3 doping of 10 wt%, denoted as MMM-NMP.
[0083] Membrane characterization:
[0084] Figure 5 SEM images showed the presence of large CC3 particles in the MMM-NMP film. This is because N-methylpyrrolidone cannot dissolve CC3, and ultrasonic stirring also fails to promote CC3 dissolution. Significant interfacial defects exist at the CC3 crystal-polymer interface, indicating that traditional stirring and ultrasonic methods cannot weaken the interactions between cage molecules and thus cannot obtain a solid solution film with dispersed CC3 molecules.
[0085] Figure 1 The images show the XRD patterns of the CC3 / PI solid solution films in Examples 1-3. CC3 solid solution films with different filler loadings were prepared by ball milling. The XRD diffraction patterns show that ball milling can prepare high-load solid solution films with dispersed CC3 molecules.
[0086] Figure 2 The images show SEM images of the CC3 / PI solid solution films in Examples 1-3, demonstrating that a smooth, continuous CC3 / PI solid solution film without obvious defects can be successfully prepared by ball milling.
[0087] Figure 3 The diagram shows the CO2 / CH4 separation performance of the CC3 / PI solid solution membranes in Examples 1-3. The solid solution membrane with a CC3 packing loading of 20% has the best CO2 / CH4 selectivity and a good CO2 permeability coefficient (57.9 Barrer).
[0088] Figure 4 The SEM image of MMM-CHCl3 in Comparative Example 1 shows that although chloroform can dissolve CC3 as a solvent, crystals are formed between the molecular cages through interaction forces during the solvent evaporation and film formation process, resulting in two-phase defects.
[0089] Figure 5The SEM images of MMM-NMP in Comparative Example 2 show that, using N-methylpyrrolidone as a solvent, the traditional stirring and ultrasonic methods cannot disperse CC3 molecules in the PI polymer matrix.
[0090] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.
Claims
1. A method for preparing a solid solution membrane containing a highly loaded porous organic cage CC3, comprising the following steps: (1) Mix porous organic cage CC3, polymer PI and N-methylpyrrolidone to form a premix; (2) The premixed liquid obtained in step (1) is ball-milled to form a ball-milled mixed solution; (3) The ball milling mixture obtained in step (2) is evenly and evenly spread in the film forming apparatus, and then heated to completely evaporate the solvent, forming a solid solution film containing a highly loaded porous organic cage CC3.
2. The method for preparing a solid solution membrane containing a highly loaded porous organic cage CC3 as described in claim 1, characterized in that: In step (1), the doping amount is 10wt%~30wt%, and the doping amount = [mass of porous organic cage CC3 / (mass of porous organic cage CC3 + mass of polymer PI)]*100%; (mass of porous organic cage CC3 + mass of polymer PI): mass of N-methylpyrrolidone = 1: 12.5~12.
9.
3. The method for preparing a solid solution membrane containing a highly loaded porous organic cage CC3 as described in claim 1, characterized in that: In step (2), the ball mill speed is 600~700 rpm, the ball milling time is 2~4 hours, and the ball-to-material mass ratio is 18~20:
1.
4. The method for preparing a solid solution membrane containing a highly loaded porous organic cage CC3 as described in claim 1, characterized in that: In step (3), the temperature of the heat treatment is 60~80℃.
5. The method for preparing a solid solution membrane containing a highly loaded porous organic cage CC3 as described in claim 1, characterized in that: In step (1), the preparation steps of the porous organic cage CC3 are as follows: (a) Mix pyromellitic aldehyde and dichloromethane in a mass ratio of 1:40~45 to form solution A; (b) Mix 1,2-cyclohexanediamine and dichloromethane in a mass ratio of 1:40~45 to form solution B; (c) Slowly mix solution A and solution B, with the mass ratio of pyromellitic aldehyde to 1,2-cyclohexanediamine being 1:1.0~1.5, and then react at 25~35℃ for 5~7 days; after centrifugation to collect the product, wash to remove unreacted reactants, and dry the obtained product.
6. The method for preparing a solid solution membrane containing a highly loaded porous organic cage CC3 as described in claim 5, characterized in that: In step (c), the mixture is washed 3 to 5 times with dichloromethane and then 3 to 5 times with ethanol to remove unreacted reactants.
7. The method for preparing a solid solution membrane containing a highly loaded porous organic cage CC3 as described in claim 5, characterized in that: In step (c), the drying temperature is 70~80℃ and the drying time is 8~10 hours.
8. A solid solution membrane containing a highly loaded porous organic cage CC3, characterized in that: It is prepared by the preparation method described in any one of claims 1 to 7.
9. The application of the solid solution membrane containing a highly loaded porous organic cage CC3 as described in claim 8 in gas separation, characterized in that: Used to separate CO2 and CH4.