A method for preparing a MOF-based mixed matrix ionic gel membrane

Abstract

This invention provides a method for preparing a MOF-based hybrid matrix ionogel membrane. The hybrid matrix ionogel membrane utilizes an imidazole-based BF4 ionic liquid as an intermediate medium to disperse ZIF-67 encapsulated with [C5mim][BF4] into a defect-free ionogel matrix, forming a defect-free MOF-based hybrid matrix ionogel membrane. This invention has the following advantages: the hybrid matrix ionogel membrane avoids the generation of interface defects between the filler and the polymer, achieves a uniform and continuous distribution of the MOF filler within the polymer matrix, and realizes a relatively continuous and highly selective CO2 transport channel within the polymer. The hybrid matrix ionogel membrane exhibits excellent separation performance, exceeding the latest separation limits. This invention provides a reference for the design and preparation of high-performance MOF-based hybrid matrix membranes.

Description

Technical Field

[0001] This invention relates to the field of gas separation membranes, and more specifically to a method for preparing a high-loading, continuously distributed, defect-free MOF-based mixed matrix ionogel membrane. Background Technology

[0002] Membrane separation technology has attracted widespread attention in the field of gas separation due to its unique advantages such as high efficiency, low cost, low energy consumption, and environmental friendliness, and has been applied in many chemical separation fields such as natural gas purification and CO2 capture. Among various membrane materials, polymer materials occupy the main market due to their easy processability, low cost, and high stability. However, due to the limitation of the "trade-off" effect, MOF-based hybrid matrix membranes have been proposed and extensively studied.

[0003] MOF-based hybrid matrix membranes combine the advantages of polymer processability and MOF packing porosity, simultaneously improving gas permeability and separation selectivity. Currently, the loading of MOF packings is mostly between 20wt% and 30wt%, which cannot fully utilize the molecular sieving advantages of MOF materials. However, further increasing the loading can cause non-selective defects between the packing and the polymer, leading to a decrease in membrane separation performance.

[0004] Therefore, the present invention provides a high-load, continuously distributed, defect-free MOF-based mixed matrix ionogel membrane, in which ionic liquid (IL) serves as a binder between MOF filler and polymer, achieving a uniform dispersion of up to 70 wt% MOF, and exhibiting good CO2 permeability coefficient and CO2 / N2 separation selectivity, exceeding the latest separation upper limit. Summary of the Invention

[0005] Addressing the issue of non-selective defects arising between MOF fillers and polymers under high loading in current MOF-based hybrid matrix membranes, which prevents the full expression of the molecular sieving performance of MOF materials in polymer matrices, this invention mixes MOF fillers with an IL / Pebax solution. Utilizing the excellent binding properties between IL, MOF, and polymer matrices, the compatibility problem at the MOF filler-polymer interface is effectively improved, increasing the CO2 transport channels within the membrane and enhancing the CO2 / N2 separation performance. This results in the preparation of a continuously distributed, defect-free MOF-based hybrid matrix ionogel membrane with a loading of up to 70 wt%.

[0006] The technical solution of this invention is: a method for preparing a MOF-based mixed matrix ionogel membrane, characterized in that: the mixed matrix ionogel membrane utilizes an imidazole-based BF4-type ionic liquid ([C5mim][BF4]1-pentyl-3-methylimidazolium tetrafluoroborate) as an intermediate medium to encapsulate...

[0007] [C5mim][BF4]ZIF-67 ([C5mim][BF4]@ZIF-67(IL@ZIF)) is dispersed in a defect-free polyether block polyamide Pebax and [C5mim][BF4](Pebax 1657 / C5mimBF4) mixed solution ionogel matrix to form a defect-free MOF-based mixed matrix ionogel film; the method includes the following steps:

[0008] Furthermore, in step S11, the molar ratio of cobalt hydroxide to dimethylimidazole is 1:4.

[0009] Furthermore, the IL is tetrafluoroborate-based ([BF4]). - ) of [C5mim][BF4].

[0010] Furthermore, the IL@ZIF refers to the process of in-situ encapsulating IL into the cavity of ZIF-67 during the synthesis process.

[0011] Furthermore, IL@ZIF is dispersed in an IL / Pebax solution. The IL in the solution acts as a link between IL@ZIF and polyether block polyamide Pebax, ensuring that no defects are generated at the polymer-MOF interface even with a MOF filler loading of up to 70 wt%, and that IL@ZIF is uniformly and continuously distributed within the Pebax matrix.

[0012] The advantages and beneficial effects of this invention are as follows:

[0013] (1) The MOF-based mixed matrix ionogel membrane of the present invention has good binding ability between IL and IL@ZIF and Pebax 1657, which effectively improves the interfacial compatibility between the two, enabling IL@ZIF to be relatively continuous and uniformly dispersed inside Pebax 1657, increasing the transport channels of CO2 in the membrane, improving the separation performance of CO2 / N2, and providing a solution to the problem of poor interfacial compatibility of MOF-based mixed matrix membrane under high loading.

[0014] (2) The mixed matrix ion gel membrane of the present invention avoids the generation of defects at the interface between the filler and the polymer, and can achieve a uniform and continuous distribution of MOF filler in the polymer matrix, realizing a relatively continuous and highly selective CO2 transport channel inside the polymer; the mixed matrix ion gel membrane exhibits good separation performance with a CO2 permeability of 408 Barrer and a CO2 / N2 selectivity of 97.2, exceeding the latest separation upper limit.

[0015] (3) This invention provides a reference for the design and preparation of high-performance MOF-based hybrid matrix membranes. Attached Figure Description

[0016] Figure 1 This is a graph showing the CO2 / N2 separation performance of IL / Pebax ionogel membranes with different IL contents in this invention.

[0017] Figure 2 The figure shows the CO2 / N2 separation performance of IL@ZIF / IL / Pebax mixed matrix ionogel membranes with different IL@ZIF loadings in this invention.

[0018] Figure 3 This is a graph showing the CO2 / N2 separation performance of IL@ZIF / Pebax hybrid matrix membranes with different IL@ZIF loadings in this invention. Detailed Implementation

[0019] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, but it is not limited thereto. Any improvements or substitutions on the basic spirit of the embodiments of the present invention shall still fall within the scope of protection of the present invention.

[0020] Example 1

[0021] Step 1: Dissolve 400 mg IL in 4 mL of 3 wt% Pebax 1657 solution (ethanol / water: 70 / 30 wt%) and stir to obtain a homogeneous IL / Pebax solution;

[0022] Step 2: Disperse 230 mg of IL@ZIF powder ultrasonically in the above IL / Pebax solution and stir at room temperature for 24 h to obtain a uniformly dispersed casting solution;

[0023] Step 3: Sonicate the above casting solution for 2 hours to remove air bubbles, pour the casting solution into a flat petri dish, and let it stand at room temperature for 24 hours to evaporate.

[0024] Step 4: Remove the cured film from the petri dish and place it in a vacuum oven at 60°C for 10 hours to completely remove any residual solvent. Then seal the film for later testing.

[0025] Example 2

[0026] 4 mL of 3 wt% Pebax 1657 solution was directly poured into a petri dish to evaporate and form a film. The subsequent steps were the same as in Example 1 to obtain a pure Pebax film.

[0027] Examples 3-6

[0028] 150 mg, 230 mg, 400 mg, and 900 mg of IL were dissolved in 4 mL of Pebax 1657 solution, stirred evenly, and poured directly into a petri dish to evaporate and form a film. The subsequent steps were the same as in Example 1, and IL / Pebax ionogel membranes with IL contents of 60 wt%, 70 wt%, 80 wt%, and 90 wt% were obtained.

[0029] Examples 7-10

[0030] The preparation methods of Examples 7-10 are basically the same as those of Example 1, except for the doping amount of IL@ZIF filler. In Examples 7-10, the amount of IL@ZIF added is 10mg, 40mg, 100mg, 230mg, and 400mg, respectively, to obtain IL@ZIF / IL / Pebax mixed matrix ionogel membranes with MOF doping amounts of 10wt%, 30wt%, 50wt%, 70wt%, and 80wt%, respectively.

[0031] Examples 11-13

[0032] 10 mg, 40 mg, and 100 mg of IL@ZIF powder were directly ultrasonically dispersed into 4 mL of 3 wt% Pebax 1657 solution. The subsequent steps were the same as in Example 1, resulting in IL@ZIF / Pebax mixed matrix films with doping amounts of 10 wt%, 30 wt%, and 50 wt%, respectively.

[0033] like Figures 1-3 The figure shows the differences in gas separation performance of different membranes.

Claims

1. A method of preparing a MOF-based hybrid matrix ionic gel membrane, characterized by: The mixed matrix ionic gel membrane is prepared by dispersing ZIF-67 encapsulating [C5mim][BF4] into a mixed solution ionic gel matrix of defect-free polyether block polyamide Pebax and [C5mim][BF4] using imidazole-based BF4 type ionic liquid as an intermediate medium to form a MOF-based mixed matrix ionic gel membrane without interface defects; the method comprises the following steps: S1, preparation of MOF filler: S11, mix 0.93 g of cobalt hydroxide and 2.87 g of dimethylimidazole in a mortar to obtain a mixture; S12, grind the mixture in S11 in a mortar for 30 min, and drop 2 mL of 0.1 mol / L IL methanol solution into the mixture during grinding to obtain a powder; S13, place the powder obtained in S12 in an oven at 60°C and heat for 3h to obtain a purple powder, which is the crude product of IL@ZIF; S14, wash the purple powder obtained in S12 with methanol for 1-3 times to remove unreacted dimethylimidazole; S15, place the purple powder treated in S14 in a vacuum oven at 100°C for 12 h to obtain the required MOF filler, i.e. IL@ZIF filler; S2, preparation of MOF-based mixed matrix ionic gel membrane: S21, dissolve 400 mg of IL in 4 mL of 3wt% polyether block polyamide Pebax 1657 solution and stir uniformly to obtain an IL / Pebax solution; S22, ultrasonically disperse 230 mg of IL@ZIF filler powder obtained in S1 in the solution of S21, and stir at room temperature for 24 h to obtain a uniformly dispersed casting solution; S23, ultrasonically treat the casting solution obtained in S22 for 2 h to remove the gas bubbles therein, pour the casting solution into a flat culture dish, and stand at room temperature for 24 h to volatilize and solidify the membrane; S24, take the membrane obtained in S23 from the culture dish, place it in a vacuum oven at 60°C for 10 h to remove residual solvent, and seal and store the membrane in vacuum for subsequent testing and characterization; The IL is [C5mim][BF4] based on tetrafluoroboric acid; The IL@ZIF is encapsulated in the cavity of ZIF-67 in situ during synthesis.

Images