Thiazole ring post-modification intrinsic microporous polymer and preparation method and application thereof

Abstract

The present application relates to a kind of inherent microporous polymer of thiazole ring post-modification and its preparation method and application, belong to polymer material and its membrane separation technical field.It has the structural general formula as formula I, the present application adopts two-step post-modification synthesis method, first the cyan side group of aromatic ether nitrile group inherent microporous polymer PIM-1 is modified into thioamide group, it is converted into thiazole unit by Hantzsch ring-closing reaction, different thiazole content can be obtained by adjusting reaction condition New inherent microporous polymer T-PIM-1.T-PIM-1 can be prepared into film by simple solution casting, the presence of thiazole ring and inert solvent processing improve the CO2 / N2 separation selectivity of membrane, and keep higher gas permeability, with wide industrial application value.

Description

Technical Field

[0001] This invention relates to the field of polymer materials and their membrane separation technology, and in particular to a thiazole ring post-modified inherently microporous polymer and its preparation method and application. Background Technology

[0002] Carbon emissions are one of the most prominent bottlenecks hindering global green and sustainable development. From a technological perspective, solving this problem requires CO2 capture, utilization, and storage. Typical carbon dioxide separation methods include membrane separation, cryogenic separation, chemical absorption, and adsorption. Membrane separation technology, in addition to its advantages of low energy consumption, high recovery rate, and high coupling capacity, also offers advantages such as no phase change, room temperature operation, and environmental friendliness. Therefore, membrane separation technology has become a research hotspot in carbon dioxide separation.

[0003] The two main indicators for evaluating the performance of gas separation membranes are gas permeability and separation selectivity. However, in reality, there is always a trade-off between permeability and selectivity. Therefore, the key to significantly improving membrane separation efficiency and widely promoting membrane separation technology lies in developing CO2 separation membranes that combine high permeability and high selectivity.

[0004] Polymers of Intrinsic Microporosity (PIMs) are a special class of polymers with very high specific surface areas. Due to the presence of various rigid and twisted structures within the molecule, the polymer chains cannot stack effectively when densely packed, resulting in a large number of micropores (most with channel sizes below 2 nm), providing an excellent channel for gas transport. In 2004, a research team led by McKeown and Budd in the UK synthesized a special type of PIM, PIM-1. This polymer membrane exhibited high permeability, but PIM-1's gas selectivity was unsatisfactory. Currently, most efforts to improve membrane separation performance involve strategies such as blending (PEI, PI, etc.), composites (MOFs, COFs, silica, etc.), and modification (amine oxime conversion, etc.). Currently, there are no reports on the direct conversion of cyano groups to thiazole rings. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention proposes a thiazole ring-modified intrinsically microporous polymer, its preparation method, and its applications. By converting the cyano group in PIM-1 into a thiazole ring, the selectivity of the gas separation membrane is improved without reducing permeability.

[0006] The thiazole ring-modified intrinsically microporous polymer proposed in this invention has a general structural formula as shown in Formula I:

[0007]

[0008] Where x, y, and z represent different degrees of substitution, x + y + z = 1, 2 > 2x + y > 0.2.

[0009] The present invention also provides a method for preparing the above-mentioned thiazole ring-modified intrinsically microporous polymer, which includes the following steps:

[0010] S1, Preparation of the inherently microporous polymer PIM-1;

[0011] S2. Preparation of S-PIM-1, an intrinsically microporous polymer containing thioamide side groups:

[0012] Under nitrogen protection, PIM-1 obtained in step S1 was placed in a solvent with phosphorus pentasulfide and sodium sulfite, and the mixture was magnetically stirred to carry out a thiolation reaction to obtain a crude product. The crude product was poured into distilled water, filtered, dissolved in tetrahydrofuran, and then precipitated in methanol, washed, and dried to obtain the inherent microporous polymer S-PIM-1 containing thioamide side groups.

[0013] Preparation of S3, the thiazole ring post-modified intrinsically microporous polymer T-PIM-1:

[0014] Under nitrogen protection, the S-PIM-1 obtained in step S2 was subjected to a Hantzsch ring-closure reaction with ethyl bromide acetal until the thioamide group was completely converted into a thiazole ring, and a crude product was obtained. The crude product was poured into distilled water, filtered, dissolved in chloroform, and then precipitated in methanol, washed, and dried to obtain a thiazole ring, which was then used to modify the inherent microporous polymer T-PIM-1.

[0015] Further, the preparation of the inherently microporous polymer PIM-1 in step S1 specifically includes: under nitrogen protection, 5,5',6,6'-tetrahydroxy-3,3,3',3'-tetramethyl-1,1'-spirobisindane, tetrafluoroterephthalonitrile and potassium carbonate are placed in a solvent, mixed together and magnetically stirred to carry out a polymerization reaction to obtain a crude product. The crude product is poured into distilled water, filtered, dissolved in chloroform and then precipitated in methanol, washed and dried to obtain the inherently microporous polymer PIM-1.

[0016] Preferably, in step S1, the molar ratio of 5,5',6,6'-tetrahydroxy-3,3,3',3'-tetramethyl-1,1'-spirobisindane, tetrafluoroterephthalonitrile, and potassium carbonate is 1:1:3.

[0017] Preferably, in step S1, the solvent is N,N-dimethylformamide (DMF) or N,N-dimethylacetamide (DMAC).

[0018] Preferably, in step S1, the polymerization reaction temperature is 65–70°C and the reaction time is 48–72 h.

[0019] Furthermore, in step S2, the molar ratio of phosphorus pentasulfide and sodium sulfite is 1:1.

[0020] Furthermore, the degree of substitution is adjusted by controlling the molar ratio of PIM-1 to phosphorus pentasulfide and sodium sulfite in step S2.

[0021] Further, the solvent in step S2 is a mixture of ethanol and 1,4-dioxane in a volume ratio of 1:10.

[0022] Furthermore, the thiolation reaction temperature in step S2 is 105–115°C, and the reaction time is 4–20 h.

[0023] Furthermore, the Hantzsch cyclization reaction in step S3 is carried out at a temperature of 115–120 °C for 5–24 h.

[0024] The present invention also provides a gas separation membrane, which is prepared by solution casting casting film formation process of the above-mentioned thiazole ring-modified inherent microporous polymer.

[0025] Furthermore, the solvent for the inherently microporous polymer is chloroform, and the concentration of the casting solution is 4 wt%.

[0026] Furthermore, it also includes immersion treatment in an inert solvent after film formation, wherein the inert solvent is any one or more of methanol, ethanol, and propanol; to improve the separation performance of CO2 / N2.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] This invention uses the PIM-1 main chain structure and replaces the cyano group with a thiazole ring to obtain a thiazole ring-modified inherent microporous polymer as the matrix to construct a separation membrane, which ensures good CO2 gas permeability. By modifying the side cyano groups with functional groups, the high affinity of the thiazole ring for CO2 is utilized to improve the CO2 / N2 selectivity of the membrane, which has broad prospects for industrial application. Attached Figure Description

[0029] Figure 1 The synthesis route diagrams for S-PIM-1 and T-PIM-1 in Examples 1-3 are shown.

[0030] Figure 2 Fourier transform infrared spectra of S-PIM-1 and T-PIM-1 in Examples 1-3;

[0031] Figure 3 The 1H NMR spectra of S-PIM-1 and T-PIM-1 in Examples 1-3 are shown below.

[0032] Figure 4The above are the 1H NMR spectra used to determine the degree of substitution (DS) of T-PIM-1 in Examples 1-3;

[0033] Figure 5 The pore size distribution diagrams are for T-PIM-1 in Examples 1-3;

[0034] Figure 6 Optical photographs and scanning electron microscope images of the T-PIM-1 gas separation membrane in Example 4;

[0035] Figure 7 The graphs show the gas separation performance of the T-PIM-1 gas separation membranes after being soaked in methanol in Examples 7-9. Detailed Implementation

[0036] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described in detail below. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0037] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0038] It should be noted that in this embodiment of the invention, a Rayleigh WQF-510A Fourier transform infrared spectrometer was used for infrared spectral characterization in the wavenumber range of 4000–400 cm⁻¹, and the sample preparation method was KBr crystal powder pelleting. It should also be pointed out that all infrared spectra in this paper are within the range of 2350 cm⁻¹. 1 The characteristic band at that location is contributed by carbon dioxide.

[0039] In this embodiment of the invention, a Bruker Avance III 400MHz nuclear magnetic resonance spectrometer was used with tetramethylsilane as an internal standard for characterization by liquid phase proton spectroscopy.

[0040] In this embodiment of the invention, a Waters 1515 gel permeation chromatograph (GPC) was used to determine the molecular weight of the polymer. The mobile phase was HPLC-grade tetrahydrofuran, the flow rate was 1 mL / min, and the test temperature was 40 °C. Before measurement, a calibration curve was plotted using polystyrene, which has a narrow molecular weight distribution, as a reference sample.

[0041] In this embodiment of the invention, a Bruker Avance III 600MHz nuclear magnetic resonance spectrometer was used, with a contact time of 2.0 ms and a relaxation time of 10.0 s, to characterize solid-state carbon spectra.

[0042] In this embodiment of the invention, a JW-BK132F surface area and pore size analyzer was used to conduct N2 adsorption-desorption experiments at 77K. The test results were calculated and analyzed using theoretical methods. Adsorption isotherms for CO2 and N2 were measured at 273K and 298K. Before the adsorption test, the sample was degassed under vacuum at 100℃ for 12 hours.

[0043] In this embodiment of the invention, a JSM-7610FPlus field emission scanning electron microscope from JEOL Corporation of Japan was used to characterize the macroscopic morphology of the polymer film material.

[0044] In this embodiment of the invention, a constant volume pressure swing gas permeation device is used. The diffusion coefficient of the gas in the polymer membrane is measured by the time lag method, and the calculation formula is as follows:

[0045]

[0046] In the formula, D is the diffusion coefficient (cm). 2 / s); 1 is the film thickness (cm); θ is the hysteresis time (s).

[0047] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0048] Comparative Example 1

[0049] Preparation of PIM-1: Under a nitrogen atmosphere, 2.0 g of 5,5',6,6'-tetrahydroxy-3,3,3',3'-tetramethyl-1,1'-spirobisindane, 1.1756 g of tetrafluoroterephthalonitrile, 2.43 g of anhydrous potassium carbonate, and 40 mL of anhydrous N,N-dimethylformamide were added to a dry two-necked flask, and the mixture was stirred at 65 °C for 72 hours. After the reaction was completed, the mixture was cooled to room temperature, and the reaction solution was poured into distilled water. The crude product was collected by filtration. The crude product was dissolved in chloroform and precipitated in methanol. The above dissolution-reprecipitation process was repeated three times. The filter cake obtained was dried under vacuum at 80 °C to obtain a bright yellow solid PIM-1 with a yield of 92%.

[0050] Examples 1-3

[0051] Preparation of T-PIM-1 with different degrees of substitution (DS):

[0052] Different dosages of phosphorus pentasulfide, sodium sulfite, and 10 mL of ethanol were added to a single-necked round-bottom flask. The mixture was stirred at room temperature for 1 hour, then 1 g of PIM-1 and 100 mL of 1,4-dioxane were added, and the reaction mixture was stirred at 110 °C for different durations. The specific dosages and reaction times are shown in Table 1. After cooling to room temperature, the reaction solution was poured into distilled water, and the mixture was stirred for another 6 hours. The precipitate was collected by filtration, washed with chloroform, and then treated with hot methanol to remove byproducts and impurities. The crude product was dissolved in tetrahydrofuran, and precipitated in methanol. The above dissolution-reprecipitation process was repeated three times. The resulting filter cake was dried under vacuum at 80 °C overnight to obtain orange S-PIM-1 solid.

[0053] Weigh 1 g of S-PIM-1, 0.75 g of 2-bromo-1,1-diethoxyethane, and 0.03 g of p-toluenesulfonic acid and place them in a solvent. Stir the mixture at 120 °C for 24 hours. After the reaction is complete, pour the mixture into distilled water and filter to collect the filter cake. Dissolve the crude product in chloroform and precipitate it in methanol. Repeat the above dissolution-reprecipitation process three times. The filtered product is dried under vacuum at 80 °C to obtain a dark green T-PIM-1 solid with a yield of 90%.

[0054] Table 1

[0055]

[0056] FTIR is applied to confirm the evolution of PIMs obtained at each step. For example... Figure 2 As shown, 3446cm- 1 3350cm- 1 and 3174cm- 1 The nearby absorption peak is attributed to the characteristic vibrations of the thioamide group. Following the cyclization reaction, the peak at 3116 cm⁻¹... 1 and 3081cm- 1 The thiazole ring was successfully introduced into the PIM-1 framework, as observed in the spectral peaks. Compared to PIM-1, the -CN stretching vibration was still visible at 2240 cm⁻¹, indicating that complete conversion was not achieved.

[0057] To further demonstrate the molecular structure of PIMs, the 1H-NMR spectra of PIM-1 and T-PIM-1 dissolved in CDCv3, and S-PIM-1 dissolved in DMSO-d6 are shown below. Figure 3As shown, signal assignment was performed. S-PIM-1 exhibited a chemical shift of the non-equivalent proton of the thioamide group in the range of 9.4–10.9 ppm, and its signal in the range of 7.3–8.3 ppm was consistent with that of the thiazole ring of T-PIM-1. Simultaneously, the signal intensity ratio of the aromatic (6.0–7.0 ppm) and aliphatic (1.0–2.6 ppm) regions of the PIMs was observed to be exactly 4H:16H, indicating that the polymer backbone did not break after the modification reaction.

[0058] In addition, such as Figure 4 As shown, in the 1H-NMR of T-PIM-1, the percentage of cyano group converted to thiazole ring was calculated by integrating the thiazole protons (7.3-8.3 ppm) with the aromatic protons (6.0-7.0 ppm). The degree of substitution (DS) of Examples 1, 2 and 3 were determined to be 20%, 55% and 80%, respectively, and were named 20%-T-PIM-1, 55%-T-PIM-1 and 80%-T-PIM-1, respectively.

[0059] The pore structure of T-PIM-1 was investigated using nitrogen physical adsorption. For example... Figure 5 As shown, calculations using nonlocal density functional theory (NL-DFT) revealed that the micropores of T-PIM-1 are mainly concentrated at 1.1 nm, with the pore size distribution of 20%-T-PIM-1 being essentially consistent with that of PIM-1. With increasing degree of substitution (DS), a mesoporous distribution of 5–6 nm was generated, which is a result of introducing more large-volume thiazole side groups.

[0060] Comparative Example 2

[0061] Preparation of PIM-1 membrane: 0.2g of the obtained PIM-1 was dissolved in 4.8g of chloroform, and the clarified solution was cast onto a glass plate. After the solvent evaporated at room temperature, the PIM-1 membrane was obtained with a thickness of about 70μm.

[0062] Example 4

[0063] Preparation of 20%-T-PIM-1 membrane: 0.2 g of 20%-T-PIM-1 was dissolved in 4.8 g of chloroform. The clarified solution was cast onto a glass plate, and the 20%-T-PIM-1 membrane with a thickness of approximately 70 μm was obtained after the solvent evaporated at room temperature. Its optical photographs and scanning electron microscope images are shown below. Figure 6 As shown.

[0064] Example 5

[0065] Preparation of 55%-T-PIM-1 membrane: Dissolve 0.2g of 55%-T-PIM-1 in 4.8g of chloroform, cast the clarified solution onto a glass plate, and obtain the 55%-T-PIM-1 membrane with a thickness of about 70μm after the solvent evaporates at room temperature.

[0066] Example 6

[0067] Preparation of 80%-T-PIM-1 membrane: Dissolve 0.2g of 80%-T-PIM-1 in 4.8g of chloroform, cast the clarified solution onto a glass plate, and obtain the 80%-T-PIM-1 membrane with a thickness of about 70μm after the solvent evaporates at room temperature.

[0068] The constant pressure variable volume gas separation performance of the membranes prepared in Comparative Example 2 and Examples 4-6 was tested under the feed conditions of room temperature, 3 bar, and a CO2 / N2 volume ratio of 1 / 1. The results are shown in Table 2.

[0069] Table 2

[0070]

[0071] Generally, inert solvent treatment can remove residual trace amounts of chloroform from the membrane, increase the adsorption, diffusion, and permeation of gas molecules, enhance the interaction between polymer and gas molecules, and have a certain impact on membrane selectivity. At the same time, the increase in free volume due to the membrane swelling effect has a significant impact on membrane permeability.

[0072] Comparative Example 3

[0073] The PIM-1 membrane prepared in Comparative Example 2 was immersed in methanol for 24 hours, and then dried under vacuum at 50°C overnight to obtain a methanol-treated PIM-1 membrane with a thickness of about 75 μm.

[0074] Example 7

[0075] The 20%-T-PIM-1 membrane prepared in Example 4 was immersed in methanol for 24 hours, and then dried under vacuum at 50°C overnight to obtain a methanol-treated 20%-T-PIM-1 membrane with a thickness of about 75 μm.

[0076] Example 8

[0077] The 55%-T-PIM-1 membrane prepared in Example 5 was immersed in ethanol for 24 hours, and then dried under vacuum at 50°C overnight to obtain a methanol-treated 55%-T-PIM-1 membrane with a thickness of about 75 μm.

[0078] Example 9

[0079] The 80%-T-PIM-1 membrane prepared in Example 6 was immersed in ethanol for 24 hours, and then dried under vacuum at 50°C overnight to obtain a methanol-treated 80%-T-PIM-1 membrane with a thickness of about 75 μm.

[0080] The constant pressure variable volume gas separation performance of the membranes prepared in Comparative Example 3 and Examples 7-9 was tested under the feed conditions of room temperature, 3 bar, and a CO2 / N2 volume ratio of 1 / 1. The results are shown in Table 3.

[0081] Table 3

[0082]

[0083] like Figure 7 As shown, the CO2 / N2 separation performance of the 20%-T-PIM-1 and 55%-T-PIM-1 membranes in Examples 4-6 exceeded the 2008 Robeson upper limit (Robeson LM. The upper boud revisited[J]. Journal of Membrane Science, 2008, 320(1-2): 390-400.). After treatment with inert solvents methanol or ethanol, the CO2 permeability and selectivity of the membranes in Examples 7-9 were improved to varying degrees, with the CO2 / N2 separation performance of the 20%-T-PIM-1 membrane being at the upper end. The excellent performance of the 20%-T-PIM-1 membrane is attributed to its introduction of a thiazole ring with high affinity for CO2 while maintaining a pore size distribution that is basically consistent with that of PIM-1.

[0084] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. 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, any combination of these technical features that does not contradict each other should be considered within the scope of this specification.

Claims

1. A thiazole ring-modified intrinsically microporous polymer having the general structural formula shown in Formula I: in, x, y, and z represent different degrees of substitution, x + y + z = 1, 2 > 2x + y > 0.

2.

2. The method for preparing the thiazole ring-modified intrinsically microporous polymer according to claim 1, characterized in that, Includes the following steps: S1, Preparation of the inherently microporous polymer PIM-1; S2. Preparation of S-PIM-1, an intrinsically microporous polymer containing thioamide side groups: Under nitrogen protection, PIM-1 obtained in step S1 was placed in a solvent with phosphorus pentasulfide and sodium sulfite, and the mixture was magnetically stirred to carry out a thiolation reaction to obtain a crude product. The crude product was poured into distilled water, filtered, dissolved in tetrahydrofuran, and then precipitated in methanol, washed, and dried to obtain the inherent microporous polymer S-PIM-1 containing thioamide side groups. Preparation of S3, the thiazole ring post-modified intrinsically microporous polymer T-PIM-1: Under nitrogen protection, the S-PIM-1 obtained in step S2 was subjected to a Hantzsch ring-closure reaction with ethyl bromide acetal until the thioamide group was completely converted into a thiazole ring, and a crude product was obtained. The crude product was poured into distilled water, filtered, dissolved in chloroform, and then precipitated in methanol, washed, and dried to obtain a thiazole ring, which was then used to modify the inherent microporous polymer T-PIM-1.

3. The preparation method according to claim 2, characterized in that, The preparation of the inherently microporous polymer PIM-1 in step S1 specifically includes: under nitrogen protection, 5,5',6,6'-tetrahydroxy-3,3,3',3'-tetramethyl-1,1'-spirobisindane, tetrafluoroterephthalonitrile and potassium carbonate are placed in a solvent, mixed together and magnetically stirred to carry out a polymerization reaction to obtain a crude product. The crude product is poured into distilled water, filtered, dissolved in chloroform and then precipitated in methanol, washed and dried to obtain the inherently microporous polymer PIM-1.

4. The preparation method according to claim 2, characterized in that, The degree of substitution is adjusted by controlling the molar ratio of PIM-1 to phosphorus pentasulfide and sodium sulfite in step S2.

5. The preparation method according to claim 4, characterized in that, In step S2, the molar ratio of phosphorus pentasulfide and sodium sulfite is 1:

1.

6. The preparation method according to claim 2, characterized in that, The solvent mentioned in step S2 is a mixture of ethanol and 1,4-dioxane in a volume ratio of 1:

10.

7. The preparation method according to claim 2, characterized in that, The thiolation reaction in step S2 is carried out at a temperature of 105–115°C for 4–20 h.

8. The preparation method according to claim 2, characterized in that, The Hantzsch cyclization reaction in step S3 is carried out at a temperature of 115–120 °C for 5–24 h.

9. A gas separation membrane, characterized in that, The film is prepared by solution casting and casting process from the thiazole ring-modified inherent microporous polymer as described in claim 1.

10. The gas separation membrane according to claim 9, characterized in that, It also includes immersion treatment in an inert solvent after film formation; the inert solvent is any one or more of methanol, ethanol, and propanol.

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