In-situ growth MOFs mixed matrix membrane and method and application thereof

Abstract

The invention discloses an in-situ growth MOFs (Metal-Organic Frameworks) mixed matrix membrane as well as a method and application thereof, and belongs to the technical field of membrane separation. The method disclosed by the invention comprises the following steps: adding a Zn source and 2-methylimidazole into a solvent, and carrying out hydrothermal reaction to obtain Polymer-ZIF-8; the preparation method comprises the following steps: mixing Polymer-ZIF-8 with a diluent, and sequentially heating, uniformly mixing and cooling, so as to obtain a Polymer-ZIF-8 / diluent uniform block; the Polymer-ZIF-8 / diluent uniform block is subjected to post-treatment, and the MOFs mixed matrix membrane is obtained; the Zn source is a zinc ion type polymer. The method overcomes the problem of interfacial compatibility in mixed matrix membranes.

Description

Technical Field

[0001] The present invention belongs to the technical field of membrane separation, and particularly relates to an in-situ grown MOFs mixed matrix membrane, a method and an application thereof. Background Art

[0002] In practical gas applications, gas purity has a decisive impact on the wide application of gases. Especially in the field of new energy, high-purity gas is a key factor for efficient energy conversion. Taking fuel cells as an example, the purity of hydrogen required for the anodic reaction must reach over 99.999% because trace impurities such as carbon monoxide, carbon dioxide or sulfides will poison the catalyst, significantly reducing the battery performance and lifespan. However, industrial by-product gases or hydrogen-rich gases usually contain a large amount of carbon dioxide (concentration can reach 20%-40%), carbon monoxide, nitrogen and other hydrocarbon impurities, which poses a huge challenge to directly obtaining high-purity hydrogen from industrial gas sources. Although traditional gas separation technologies can achieve a certain degree of purification, each has obvious limitations: pressure swing adsorption technology requires multi-stage adsorption tower cyclic operation, with problems such as high energy consumption for adsorbent regeneration and limited hydrogen recovery rate; cryogenic distillation method needs to cool the gas to extremely low temperatures (usually below -150°C), with huge equipment investment and astonishing operating energy consumption; chemical adsorption method has good selectivity, but the adsorbent capacity is limited and the regeneration process is complex, making it difficult to operate continuously. In contrast, membrane separation technology based on permeation selectivity exhibits significant advantages due to its unique mass transfer mechanism. This technology relies on the difference in the dissolution-diffusion rate of gas components in the membrane material to achieve separation, with outstanding features such as low energy consumption (usually only 1 / 5 - 1 / 10 of cryogenic distillation), compact device, simple operation and maintenance, and no phase change pollution, and is recognized as the most promising green separation technology. According to the chemical composition and microstructure of the membrane material, gas separation membranes are mainly divided into three categories: inorganic membranes (such as zeolite molecular sieve membranes, carbon molecular sieve membranes) rely on their regular microporous structure to achieve molecular size screening, with excellent thermal stability and chemical inertness; organic polymer membranes (such as polyimide, polysulfone) achieve gas permeation through the free volume between polymer chain segments, with good processing performance and low cost; mixed matrix membranes are obtained by dispersing inorganic fillers (such as metal-organic framework materials, silica nanoparticles) in the polymer matrix, combining the advantages of both, and can simultaneously improve permeability and selectivity. The current research focus is on developing new membrane materials with high selective permeability, long-term stability and anti-pollution performance, and further improving the separation efficiency by optimizing the membrane module design (such as hollow fiber, spiral wound) and process parameters (operating pressure, temperature, purge gas flow rate) to meet the requirements for ultra-high purity gases in major fields such as hydrogen energy and carbon capture.

[0003] Due to their unique structural design, mixed matrix membranes have become a research hotspot in the current gas separation field as they can combine the excellent properties of both inorganic and organic membranes simultaneously. By uniformly dispersing inorganic nano-fillers in an organic polymer matrix, this type of membrane material not only retains the good film-forming property and mechanical toughness of the polymer membrane but also introduces the molecular sieving effect and fast transport channels unique to inorganic materials, thus significantly enhancing the gas permeability and selectivity of the membrane. However, the actual performance of mixed matrix membranes depends not only on the intrinsic properties of the selected filler particles (such as pore size distribution, specific surface area, surface chemical properties, etc.), but more crucially on the interfacial compatibility between the filler and the organic matrix. If the compatibility between the two is poor, it will lead to the agglomeration of the filler in the matrix, forming non-selective defects and even interfacial voids, enabling gas molecules to diffuse through short circuits, severely reducing the separation performance. To improve the interfacial compatibility, researchers usually use surface modification techniques to functionalize inorganic fillers. For example, organic functional groups are introduced onto the zeolite surface through silane coupling agents, or an adhesion layer is constructed on the surface of carbon molecular sieves using dopamine, thereby enhancing the interfacial interaction between the filler and the polymer matrix. In addition, optimizing the filler particle size, morphology, and doping concentration, selecting a suitable polymer solvent system, and precisely controlling the film-forming process parameters (such as evaporation temperature, humidity, etc.) are all key factors to ensure the formation of defect-free and high-performance mixed matrix membranes. Current research also finds that some nanomaterials with specific topological structures (such as metal-organic framework materials) can form hydrogen bonds or coordination bonds with polymer segments due to their abundant coordinatively unsaturated sites on the surface, showing excellent interfacial binding ability, which provides an important direction for the development of a new generation of high-performance mixed matrix membranes.

[0004] Generally speaking, the compatibility between MOF fillers and the substrate is better than that of traditional inorganic fillers (such as ceramics, carbon, metals), and MOFs have better gas separation performance. Currently, MOF filler mixed matrix membranes have shown certain excellent properties. However, the interfacial compatibility problem between the filler and the substrate is the main factor limiting the membrane separation performance. Summary of the Invention

[0005] The purpose of the present invention is to provide an in-situ grown MOFs mixed matrix membrane, method, and application to solve the technical problem of poor interfacial compatibility between the filler and the substrate in the filler mixed matrix membrane.

[0006] To achieve the above purpose, the present invention adopts the following technical solutions: The present invention discloses a method for in-situ growing MOFs mixed matrix membranes, comprising the following steps: Adding a Zn source and 2-methylimidazole into a solvent for hydrothermal reaction to obtain Polymer-ZIF-8; Heat and mix Polymer-ZIF-8 with a diluent, and then cool to obtain a Polymer-ZIF-8 / diluent homogeneous block; Post-treat the Polymer-ZIF-8 / diluent homogeneous block to obtain a MOFs mixed matrix membrane; The Zn source is a zinc ion-based polymer.

[0007] Furthermore, the zinc ion-based polymer is Surlyn resin; the mass ratio of the zinc ion-based polymer to 2-methylimidazole is (1~10):(1~200); the solvent is methanol; the mass ratio of 2-methylimidazole to methanol is (1~20):(1~200); The temperature of the hydrothermal reaction is 60~200 °C, and the reaction time is 24~120 h; after the hydrothermal reaction, wash and dry the obtained reaction product in sequence to obtain Polymer-ZIF-8.

[0008] Furthermore, the heating method is oil bath heating; the temperature of the oil bath heating is 100~250 °C; the cooling method is room temperature cooling; the mass ratio of Polymer-ZIF-8 to the diluent is (1~10):(1~200).

[0009] Furthermore, the diluent is one of diphenyl ether, liquid paraffin, and mineral oil.

[0010] Furthermore, before post-treating the Polymer-ZIF-8 / diluent homogeneous block, cut the Polymer-ZIF-8 / diluent homogeneous block into small pieces, and the mass of the small pieces is 0.1~3 g.

[0011] Furthermore, the post-treatment includes hot pressing into a film, cooling, extraction, and drying processes carried out in sequence.

[0012] Furthermore, the hot pressing temperature for hot pressing into a film is 60~250 °C, the pressure is 0.5~10 MPa, and the hot pressing duration is 5~600 s; the cooling medium used for cooling is normal temperature water or ice water at 0 °C; the extraction agent used for extraction is cyclohexane.

[0013] The present invention also discloses an in-situ grown MOFs mixed matrix membrane prepared by the above preparation method.

[0014] The present invention also discloses the application of the above in-situ grown MOFs mixed matrix membrane in the separation of mixed gases. The mixed gas is H2 / CO2 or C3H6 / C3H8.

[0015] Furthermore, Compared with the prior art, the present invention has the following beneficial effects: The present invention discloses a method for in-situ growing MOFs mixed matrix membranes. A zinc ion-based polymer is used as the Zn source, which reacts with 2-methylimidazole to in-situ generate MOFs. The in-situ synthesis method in the present invention overcomes the interfacial compatibility problem in the mixed matrix membranes. The zinc ion-based polymer provides the metal source, thus effectively growing ZIF-8 which provides the main gas screening performance. At the same time, the polymer substrate has a stable structure. Therefore, the MOFs mixed matrix membrane with in-situ grown ZIF-8 in the present invention can balance performance and structural stability.

[0016] Furthermore, the ZIF-8 in-situ grown in the MOFs mixed matrix membrane of the present invention has a suitable effective pore size, playing a major gas screening role; and while the used zinc ion-based polymer provides the metal source for MOF synthesis, it can also enhance the structural stability of the membrane.

[0017] The present invention also discloses an in-situ grown MOFs mixed matrix membrane prepared by the above preparation method. The composite structure of the in-situ grown MOFs mixed matrix membrane is stable and can be reused. It is a type of stable, efficient, and environmentally friendly mixed matrix membrane, having good stability and gas separation effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the H2 / CO2 gas separation performance of the MOFs mixed matrix membrane prepared in Example 1 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0019] To enable those skilled in the art to understand the features and effects of the present invention, the following provides a general description and definition of the terms and phrases mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used herein shall have the ordinary meaning as understood by those skilled in the art regarding the present invention. In case of conflict, the definition in this specification shall prevail.

[0020] The theories or mechanisms described and disclosed herein, whether correct or incorrect, shall not limit the scope of the present invention in any way, that is, the content of the present invention can be implemented without being limited by any specific theory or mechanism.

[0021] In this article, all features defined in the form of numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are only for the sake of brevity and convenience. Accordingly, the description of numerical ranges or percentage ranges should be regarded as having covered and specifically disclosed all possible sub-ranges and individual numerical values within the ranges (including integers and fractions).

[0022] In this article, unless otherwise specified, the terms "include", "including", "contain", "have" or similar terms cover the meanings of "consist of" and "consist essentially of". For example, "A includes a" covers the meanings of "A includes a and others" and "A only includes a".

[0023] In this article, for the sake of brevity of description, all possible combinations of all technical features in each embodiment or example are not described. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each embodiment or example can be combined arbitrarily, and all possible combinations should be considered as the scope described in this specification.

[0024] The present invention provides a method for in-situ growing MOFs mixed matrix membranes, comprising the following steps: Using a zinc ion-based polymer as the Zn source; Subjecting the Zn source and 2-methylimidazole to a hydrothermal reaction in a methanol solvent to obtain Polymer-ZIF-8; Applying the thermally induced phase separation method (TIPS) to the Polymer-ZIF-8, heating, mixing, and cooling the Polymer-ZIF-8 and the diluent to obtain a homogeneous Polymer-ZIF-8 / diluent block; Thermally pressing the Polymer-ZIF-8 / diluent block into a film, cooling, extracting, and drying to obtain the MOFs mixed matrix membrane.

[0025] Preferably, the zinc ion ionomer includes Surlyn resin; the Surlyn resin is Surlyn 9910 / 1855 / 1650 / 1652 / 1857 / 9020 / 9120 / 9150 / 9320 / 9520 / 9650 / 9720 / 9950, etc.), ExxonMobillotek 7510, A. Schulman FORMION™ FI 120, Honeywell A-C® 540 / 580, Iotek™ 8000 / 8200, Admer™ NF-911, etc., and is not limited thereto.

[0026] Preferably, the mass ratio of the 9910 type Surlyn resin to 2-methylimidazole is 1:4.5 g, and the mass of methanol is 45 g, and is not limited thereto; the 9910 type Surlyn resin can be in the form of particles or films.

[0027] Preferably, specifically, a zinc ion-based polymer, 2-methylimidazole, and methanol are mixed and subjected to a hydrothermal reaction at 100 °C for 40 to 60 hours, and then washed with ethanol and dried to obtain Polymer-ZIF-8; more preferably, the temperature of the hydrothermal reaction can be appropriately increased and the reaction time is 60 hours; the number of ethanol washing times is 2 to 3 times and drying is carried out at room temperature.

[0028] Preferably, the zinc ion-based polymer is in the shape of a small film or a large film; the mass ratio of the zinc ion-based polymer to 2-methylimidazole is 1:4.5; more preferably, the mass ratio of 2-methylimidazole to methanol is 1:10.

[0029] Preferably, Polymer-ZIF-8 and a diluent are heated and mixed in an oil bath at 170 °C and cooled with water at room temperature to obtain a uniform Polymer-ZIF-8 / diluent block.

[0030] Preferably, the diluent is diphenyl ether, liquid paraffin, or mineral oil, and is not limited thereto; the mass ratio of Polymer-ZIF-8 to the diluent is 1:1, 1:2.

[0031] Preferably, the Polymer-ZIF-8 / diluent block is cut into uniform small pieces according to the mass and then hot-pressed into a film, cooled, extracted, and dried.

[0032] Preferably, the mass of the small piece is 0.1 to 0.5 g; the hot-pressing temperature is 100 to 130 °C, the pressure is 1 to 1.5 MPa, and the hot-pressing duration is 20 to 120 s; the cooling medium includes water at room temperature, ice water at 0 °C, liquid nitrogen, etc., and preferably water at room temperature; the extractant is cyclohexane and is not limited thereto; the drying is carried out at room temperature.

[0033] The present invention also discloses a MOFs mixed matrix membrane prepared by the above preparation method, in which ZIF-8 in the MOFs mixed matrix membrane effectively grows on the surface of the polymer; the MOFs mixed matrix membrane is flat, smooth, and dense; the Zn source in ZIF-8 in the MOFs mixed matrix membrane comes from the zinc ion-based polymer.

[0034] The present invention also discloses the use of the above MOFs mixed matrix membrane for gas separation such as H2 / CO2, C3H6 / C3H8, etc.

[0035] The present invention also discloses a mixed matrix membrane for gas separation, comprising the above MOFs mixed matrix membrane.

[0036] In the mixed matrix membrane with in-situ grown MOF of the present invention, ZIF-8 has been effectively grown. Through experimental characterization and testing methods, it is verified that the thin film of the present invention contains ZIF-8. At the same time, the surface of the prepared thin film is smooth and flat without obvious defects. The in-situ synthesis method in the present invention overcomes the interfacial compatibility problem in the mixed matrix membrane. The polymer provides the metal source, and the effectively grown ZIF-8 provides the main gas screening performance. At the same time, the polymer substrate has a stable structure. Therefore, the MOFs mixed matrix membrane with in-situ grown ZIF-8 of the present invention can take into account both performance and structural stability.

[0037] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

[0038] In the following embodiments, conventional instruments and equipment in the art are used. For the experimental methods without specific conditions noted in the following embodiments, they are usually carried out under conventional conditions or according to the conditions recommended by the manufacturer. In the following embodiments, various raw materials are used. Unless otherwise stated, commercially available products are used, and their specifications are conventional specifications in the art. In the specification of the present invention and the following embodiments, unless otherwise specified, "%" represents weight percentage, "parts" represents weight parts, and the ratio represents weight ratio.

[0039] Example 1 A method for in-situ growing MOFs mixed matrix membrane, comprising the following steps: Add 2 g of 9910 type Surlyn resin particles and 4.5 g of 2-methylimidazole to 45 g of methanol, divide them into two equal parts and place them in a 50 mL high-pressure hydrothermal reaction kettle, react at 100 °C for 60 h, then naturally cool to room temperature, and then wash with ethanol two to three times to obtain white blocks. After drying, collect them. The main purpose of this step is to uniformly mix the diluent into 9910-ZIF-8, and the washing is to remove the unreacted 2-methylimidazole; Take 1 g of 9910-ZIF-8 and place it in a flask, add 1 g of liquid paraffin, stir and mix evenly in an oil bath at 170 °C. The main purpose of this step is to uniformly mix the diluent into 9910-ZIF-8, and after this step, quickly cool the mixture to room temperature water to obtain a 9910-ZIF-8 / Lp uniform block; Divide the 9910-ZIF-8 / Lp uniform block into small pieces of about 0.15 g, place them between PTFE membranes, perform hot pressing at 100 °C, 1 MPa for 30 s, and then quickly place it in deionized water at room temperature for cooling. After a few minutes, carefully desorb the membrane from the PTFE membrane and place it in a beaker, add cyclohexane, and extract for 24 h. Use cyclohexane to extract the diluent. After the extraction is completed, place the thin film in a glass dish for drying to obtain the in-situ grown MOFs mixed matrix membrane.

[0040] Under the test conditions of 25 °C and 200 kPa, the hydrogen permeation flux is 315810 Barrer, and the H2 / CO2 selectivity is 4.2.

[0041] Example 2 A method for in-situ growing MOFs mixed matrix membrane, comprising the following steps: Hot press 2 g of 9910 type Surlyn resin into 4 films of 0.5 g at 130 °C, 1 MPa for 30 s by a hot press. Divide the 2 g of 9910 type resin film into two parts and fix them in two 50 mL high-pressure hydrothermal reaction kettles; dissolve 4.5 g of 2-methylimidazole in 45 g of methanol and divide it into two parts and add them to the high-pressure hydrothermal reaction kettles; the purpose of making the resin into a film is to increase the reaction contact area and improve the MOF generation rate; then react at 100 °C for 60 h, then naturally cool to room temperature, and then wash with ethanol 3 times, and obtain 9910-ZIF-8 after drying; Take 1 g of 9910-ZIF-8 and place it in a flask, add 1 g of diphenyl ether, stir and mix evenly in an oil bath at 170 °C, and then quickly cool it in deionized water at room temperature to obtain a 9910-ZIF-8 / DPE uniform block; Take 0.2 g of the uniform block and perform hot pressing at 100 °C, 1 MPa for 30 s to obtain a mixed matrix membrane, and then quickly cool it in deionized water. After extracting with cyclohexane for 24 h, dry it to obtain the in-situ grown MOFs mixed matrix membrane.

[0042] Example 3 A method for in-situ growing MOFs mixed matrix membrane, comprising the following steps: Dissolve 2.25 g of 2-methylimidazole in 22.5 g of methanol, transfer it into a 50 mL high-pressure hydrothermal reaction kettle, add 1 g of 9910 type Surlyn resin, place it in a homogeneous reactor at 100 °C and react for 24 h, wash with ethanol 3 times, and dry to obtain 9910-ZIF-8; Take 1 g of 9910-ZIF-8 and 10 g of liquid paraffin, stir evenly in an oil bath at 170 °C and then quickly cool it in deionized water at room temperature to obtain a 9910-ZIF-8 / Lp uniform block; Take 0.1 g of the above-mentioned block, perform hot pressing at 60 °C and 5 MPa for 300 s, then quickly place it in an ice-water mixture at 0 °C for cooling. After extracting with cyclohexane for 24 h and drying, the MOFs mixed matrix membrane can be obtained. Example 4 A method for in-situ growing MOFs mixed matrix membrane, comprising the following steps: Add 2 g of 9910 type Surlyn resin and 4.5 g of 2-methylimidazole to 45 g of methanol, and place them in two 50 mL high-pressure hydrothermal reaction kettles; react at 200 °C for 24 h, wash with ethanol, and dry to obtain 9910-ZIF-8; Take 1 g of 9910-ZIF-8 and 2 g of liquid paraffin, heat and mix them evenly in an oil bath at 170 °C, and quickly place them in deionized water at room temperature to obtain a uniform block of 9910-ZIF-8 / Lp; Cut 0.2 g, 0.15 g, and 0.1 g of the above-mentioned block, perform hot pressing at 100 °C and 1 MPa for 20 s, then place it in an ice-water mixture at 0 °C for cooling. After extracting with cyclohexane for 24 h and drying, the MOFs mixed matrix membrane is obtained.

[0043] Example 5 A method for in-situ growing MOFs mixed matrix membrane, comprising the following steps: Hot press 9910 type Surlyn resin at 130 °C and 1 MPa for 30 s to make small flakes. Take 1 g of the small flake 9910 type Surlyn resin and place it in a 50 mL high-pressure hydrothermal reaction kettle. Then add 2-methylimidazole and methanol to the reaction kettle at a mass ratio of 1:10, and react at 120 °C for 120 h to obtain 9910-ZIF-8; Take 9910-ZIF-8 and mineral oil at a mass ratio of 1:20, heat and mix them evenly, and place them in deionized water at room temperature to obtain a uniform block of 9910-ZIF-8 / mineral oil; Cut 0.1 g of the above-mentioned block, perform hot pressing at 100 °C and 1 MPa for 100 s, place it in an ice-water mixture at 0 °C, extract with cyclohexane for 24 h, and dry to obtain the MOFs mixed matrix membrane.

[0044] Example 6 A method for in-situ growing MOFs mixed matrix membrane, comprising the following steps: Add 2 g of 1855 type Surlyn resin particles and 10 g of 2-methylimidazole to 10 g of methanol, divide them into two equal parts and place them in 50 mL high-pressure hydrothermal reaction kettles. React at 130 °C for 40 h, then naturally cool to room temperature, and then wash with ethanol two to three times to obtain white blocks. After drying, collect them. The main purpose of this step is to uniformly mix the diluent into 1855-ZIF-8, and the washing is to remove the unreacted 2-methylimidazole; Take 4 g of 1855-ZIF-8 and place it in a flask. Add 2 g of diphenyl ether and stir well in an oil bath at 180 °C. The main purpose of this step is to uniformly mix the diluent into 1855-ZIF-8. After this step, quickly cool the mixture in room-temperature water to obtain a uniform 1855-ZIF-8 / Lp block; Divide the uniform 1855-ZIF-8 / Lp block into small pieces of about 0.3 g, place them between PTFE membranes, perform hot pressing at 130 °C, 3 MPa for 20 s, and then quickly cool it in room-temperature deionized water. After a few minutes, carefully detach the membrane from the PTFE membrane and place it in a beaker. Add cyclohexane and extract for 24 h to extract the diluent with cyclohexane. After the extraction, dry the thin film in a glass dish to obtain an in-situ grown MOFs mixed matrix membrane.

[0045] Example 7 A method for in-situ growing MOFs mixed matrix membranes, comprising the following steps: Add 1.5 g of 1855 Surlyn resin particles and 6 g of 2-methylimidazole to 30 g of methanol. Divide it into two equal parts and place them in a 50 mL high-pressure hydrothermal reactor. React at 120 °C for 50 h, then naturally cool to room temperature, and then wash with ethanol two to three times to obtain a white block. After drying, collect it. The main purpose of this step is to uniformly mix the diluent into 1855-ZIF-8, and the washing is to remove the unreacted 2-methylimidazole; Take 3 g of 1855-ZIF-8 and place it in a flask. Add 1 g of diphenyl ether and stir well in an oil bath at 175 °C. The main purpose of this step is to uniformly mix the diluent into 1855-ZIF-8. After this step, quickly cool the mixture in room-temperature water to obtain a uniform 1855-ZIF-8 / Lp block; Divide the uniform 1855-ZIF-8 / Lp block into small pieces of about 0.2 g, place them between PTFE membranes, perform hot pressing at 250 °C, 0.5 MPa for 5 s, and then quickly cool it in room-temperature deionized water. After a few minutes, carefully detach the membrane from the PTFE membrane and place it in a beaker. Add cyclohexane and extract for 24 h to extract the diluent with cyclohexane. After the extraction, dry the thin film in a glass dish to obtain an in-situ grown MOFs mixed matrix membrane.

[0046] Example 8 A method for in-situ growing MOFs mixed matrix membranes, comprising the following steps: 1.5 g of Surlyn resin particles of type 1857 and 6 g of 2-methylimidazole were added to 30 g of methanol. The mixture was evenly divided into two portions and placed in a 50 mL high-pressure hydrothermal reactor, and reacted at 120 °C for 50 h. Then it was naturally cooled to room temperature, and then washed with ethanol two to three times to obtain white blocks, which were collected after drying. The main purpose of this step was to evenly mix the diluent into 1857-ZIF-8, and the washing was to remove the unreacted 2-methylimidazole; 3 g of 1857-ZIF-8 was placed in a flask, 1 g of diphenyl ether was added, and the mixture was stirred and mixed evenly in an oil bath at 175 °C. The main purpose of this step was to evenly mix the diluent into 1857-ZIF-8, and after this step was completed, the mixture was quickly cooled in room-temperature water to obtain a uniform block of 1857-ZIF-8 / Lp; The uniform block of 1857-ZIF-8 / Lp was divided into small blocks of about 0.2 g, placed between PTFE membranes, and hot-pressed at 130 °C, 3 MPa for 20 s. Then it was quickly cooled in room-temperature deionized water. After a few minutes, the membrane was carefully detached from the PTFE membrane and placed in a beaker, and cyclohexane was added for extraction for 24 h. The diluent was extracted with cyclohexane. After the extraction was completed, the thin film was placed in a glass dish for drying to obtain an in-situ grown MOFs mixed matrix membrane.

[0047] Example 9 A method for in-situ growing MOFs mixed matrix membranes, comprising the following steps: 1.5 g of Surlyn resin particles of type 1857 and 6 g of 2-methylimidazole were added to 30 g of methanol. The mixture was evenly divided into two portions and placed in a 50 mL high-pressure hydrothermal reactor, and reacted at 120 °C for 50 h. Then it was naturally cooled to room temperature, and then washed with ethanol two to three times to obtain white blocks, which were collected after drying. The main purpose of this step was to evenly mix the diluent into 1857-ZIF-8, and the washing was to remove the unreacted 2-methylimidazole; 3 g of 1857-ZIF-8 was placed in a flask, 1 g of diphenyl ether was added, and the mixture was stirred and mixed evenly in an oil bath at 175 °C. The main purpose of this step was to evenly mix the diluent into 1857-ZIF-8, and after this step was completed, the mixture was quickly cooled in room-temperature water to obtain a uniform block of 1857-ZIF-8 / Lp; The 1857-ZIF-8 / Lp uniform bulk was divided into small pieces of about 0.2 g, placed between PTFE membranes, and hot-pressed at 115 °C, 3 MPa, and 25 s. Then, it was quickly placed in deionized water at room temperature for cooling. After a few minutes, the membrane was carefully desorbed from the PTFE membrane and placed in a beaker. Cyclohexane was added and extracted for 24 h. The diluent was extracted using cyclohexane. After the extraction was completed, the thin film was placed in a glass dish for drying, and an in-situ grown MOFs mixed matrix membrane could be obtained.

[0048] Example 10 A method for in-situ growing MOFs mixed matrix membranes, comprising the following steps: 1.5 g of 1857-type Surlyn resin particles and 6 g of 2-methylimidazole were added to 30 g of methanol, evenly divided into two portions and placed in a 50 mL high-pressure hydrothermal reaction kettle, and reacted at 120 °C for 50 h. Then, it was naturally cooled to room temperature, and then washed with ethanol two to three times to obtain white bulk, which was collected after drying. The main purpose of this step was to evenly mix the diluent into 1857-ZIF-8, and the washing was to remove the unreacted 2-methylimidazole; 3 g of 1857-ZIF-8 was taken and placed in a flask, 1 g of diphenyl ether was added, and it was stirred and mixed evenly in an oil bath at 175 °C. The main purpose of this step was to evenly mix the diluent into 1857-ZIF-8, and after this step was completed, the mixed body was quickly placed in water at room temperature for cooling to obtain 1857-ZIF-8 / Lp uniform bulk; The 1857-ZIF-8 / Lp uniform bulk was divided into small pieces of about 0.2 g, placed between PTFE membranes, and hot-pressed at 123 °C, 2 MPa, and 25 s. Then, it was quickly placed in deionized water at room temperature for cooling. After a few minutes, the membrane was carefully desorbed from the PTFE membrane and placed in a beaker. Cyclohexane was added and extracted for 24 h. The diluent was extracted using cyclohexane. After the extraction was completed, the thin film was placed in a glass dish for drying, and an in-situ grown MOFs mixed matrix membrane could be obtained.

[0049] Example 11 A method for in-situ growing MOFs mixed matrix membranes, comprising the following steps: 1.5 g of 9320-type Surlyn resin particles and 6 g of 2-methylimidazole were added to 30 g of methanol, evenly divided into two portions and placed in a 50 mL high-pressure hydrothermal reaction kettle, and reacted at 120 °C for 50 h. Then, it was naturally cooled to room temperature, and then washed with ethanol two to three times to obtain white bulk, which was collected after drying. The main purpose of this step was to evenly mix the diluent into 9320-ZIF-8, and the washing was to remove the unreacted 2-methylimidazole; Take 3 g of 9320-ZIF-8 and place it in a flask. Add 1 g of diphenyl ether and stir well in an oil bath at 175 °C. The main purpose of this step is to uniformly mix the diluent into 9320-ZIF-8. After this step, quickly cool the mixture in room-temperature water to obtain a uniform 9320-ZIF-8 / Lp block; Divide the uniform 9320-ZIF-8 / Lp block into small pieces of about 0.2 g, place them between PTFE membranes, perform hot pressing at 123 °C, 2 MPa for 25 s, and then quickly cool it in room-temperature deionized water. After a few minutes, carefully detach the membrane from the PTFE membrane and place it in a beaker. Add cyclohexane and extract for 24 h to extract the diluent with cyclohexane. After the extraction, dry the thin film in a glass dish to obtain an in-situ grown MOFs mixed matrix membrane.

[0050] Example 12 A method for preparing an in-situ grown MOFs mixed matrix membrane, comprising the following steps: Add 1.5 g of 9320 type Surlyn resin particles and 6 g of 2-methylimidazole to 30 g of methanol. Divide it into two equal parts and place them in a 50 mL high-pressure hydrothermal reaction kettle. React at 120 °C for 50 h, then naturally cool to room temperature, and then wash with ethanol two to three times to obtain a white block. After drying, collect it. The main purpose of this step is to uniformly mix the diluent into 9320-ZIF-8, and the washing is to remove the unreacted 2-methylimidazole; Take 3 g of 9320-ZIF-8 and place it in a flask. Add 1 g of diphenyl ether and stir well in an oil bath at 175 °C. The main purpose of this step is to uniformly mix the diluent into 9320-ZIF-8. After this step, quickly cool the mixture in room-temperature water to obtain a uniform 9320-ZIF-8 / Lp block; Divide the uniform 9320-ZIF-8 / Lp block into small pieces of about 3 g, place them between PTFE membranes, perform hot pressing at 125 °C, 3 MPa for 20 s, and then quickly cool it in room-temperature deionized water. After a few minutes, carefully detach the membrane from the PTFE membrane and place it in a beaker. Add cyclohexane and extract for 24 h to extract the diluent with cyclohexane. After the extraction, dry the thin film in a glass dish to obtain an in-situ grown MOFs mixed matrix membrane.

[0051] Comparative Example Preparation of pure polymer 9910 type Surlyn resin membrane: Place 0.5 g of 9910 type Surlyn resin evenly between PTFE membranes and perform hot pressing with a hot press at 130 °C, 1 MPa for 30 s. After cooling, a pure polymer 9910 type Surlyn resin membrane can be obtained.

[0052] The obtained pure polymer membrane is dense and airtight.

[0053] In addition, the inventors of this case also referred to the foregoing embodiments and conducted tests using other raw materials, process operations, and process conditions described in this specification, and all obtained relatively ideal results.

[0054] Figure 1 It is a schematic diagram of the H2 / CO2 gas separation performance of the MOFs mixed matrix membrane prepared in Example 1 of the present invention. It can be seen from the figure that the prepared mixed matrix membrane has ultra-high permeability while having H2 / CO2 selectivity, exceeding the Robeson upper limit in 2008.

[0055] In summary, a method for in-situ growing MOFs mixed matrix membranes disclosed in the present invention uses the zinc ions of the polymer itself as the metal source of MOF (ZIF-8), avoiding the step of additionally adding metal salts in the traditional method, simplifying the process while enhancing the compatibility between MOFs and the polymer matrix, reducing interfacial defects, directly growing ZIF-8 crystals on the polymer skeleton through hydrothermal reaction to form a uniformly dispersed composite structure, and improving the loading and dispersibility of MOFs. Subsequently, by precisely controlling the reaction conditions, optimizing the hydrothermal reaction temperature (100~130°C) and time (40~60 h), ensuring the full growth and uniform size of ZIF-8 crystals; oil bath heating (170~180°C) realizes the rapid homogeneous mixing of the polymer and the diluent, and forms an easily processable block after cooling, and the diluent used is flexible in selection. The diluent not only promotes uniform mixing but also is removed by subsequent extraction (such as cyclohexane) to form a porous structure and enhance the gas permeability of the membrane.

[0056] In terms of membrane forming and post-treatment optimization, the hot pressing film forming parameters are reasonable (100~130°C, 1~3 MPa, 20~30 s). The low temperature and low pressure conditions avoid the destruction of the MOFs structure while ensuring the membrane thickness and mechanical strength; rapid cooling (ice water or normal temperature water) fixes the membrane morphology; the extraction and drying process, cyclohexane extraction thoroughly removes the diluent, retains the porous channels, and the membrane structure is stable after drying.

[0057] In terms of excellent membrane performance and application potential, for the high efficiency of mixed gas separation, the in-situ grown MOFs mixed matrix membrane prepared in the present invention is suitable for the separation of key gas pairs such as H2 / CO2 or C3H6 / C3H8. Thanks to the molecular sieve effect of ZIF-8 and the flexibility of the polymer matrix, it has both high selectivity and permeability. The raw materials are easily available (such as Surlyn resin), and the process can be scaled up (both hydrothermal and hot pressing are mature technologies), suitable for large-scale production.

[0058] In terms of environmental protection and economic advantages, the hydrothermal reaction uses low-toxic methanol to reduce the environmental burden; the diluent can be recycled to reduce costs. Only zinc ion polymer, 2-methylimidazole and diluent are required, and the process is simple with less waste. This method solves the problems of uneven dispersion of MOFs and interfacial defects in traditional mixed matrix membranes through in-situ growth strategy and innovative design of polymer matrix. At the same time, the optimization of process parameters takes into account both efficiency and membrane performance, which has significant application value and commercialization prospects in the field of gas separation.

[0059] The above content is only to illustrate the technical idea of the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution according to the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A method for in-situ growing MOFs mixed matrix membranes, characterized in that, It includes the following steps: Adding a Zn source and 2-methylimidazole into a solvent for hydrothermal reaction to obtain Polymer-ZIF-8; Heating and mixing Polymer-ZIF-8 with a diluent and then cooling to obtain a Polymer-ZIF-8 / diluent uniform block; Performing post-treatment on the Polymer-ZIF-8 / diluent uniform block to obtain a MOFs mixed matrix membrane; The Zn source is a zinc ion-based polymer.

2. The method for in-situ growing MOFs mixed matrix membrane according to claim 1, wherein The zinc ion-based polymer is Surlyn resin; the mass ratio of the zinc ion-based polymer to 2-methylimidazole is (1~10):(1~200); the solvent is methanol; the mass ratio of 2-methylimidazole to methanol is (1~20):(1~200); The temperature of the hydrothermal reaction is 60~200 °C, and the reaction time is 24~120 h; after the hydrothermal reaction, the obtained reaction product is washed and dried in sequence to obtain Polymer-ZIF-8.

3. A method for in-situ growing MOFs mixed matrix membranes according to claim 1, characterized in that, The heating method is oil bath heating; the temperature of the oil bath heating is 100~250 °C; the cooling method is room temperature cooling; the mass ratio of Polymer-ZIF-8 to the diluent is (1~10):(1~200).

4. A method for in-situ growing MOFs mixed matrix membranes according to claim 1, characterized in that, The diluent is one of diphenyl ether, liquid paraffin and mineral oil.

5. A method for in-situ growing MOFs mixed matrix membranes according to claim 1, characterized in that, Before performing post-treatment on the Polymer-ZIF-8 / diluent uniform block, the Polymer-ZIF-8 / diluent uniform block is cut into small pieces, and the mass of the small pieces is 0.1~3 g.

6. A method for in-situ growth of MOFs mixed matrix membranes according to claim 1, characterized in that, The post-treatment includes hot pressing into a film, cooling, extraction and drying treatments carried out in sequence.

7. A method for in-situ growth of MOFs mixed matrix membrane according to claim 6, characterized in that, The hot pressing temperature for hot pressing into a film is 60~250 °C, the pressure is 0.5~10 MPa, and the hot pressing duration is 5~600 s; the cooling medium used for cooling is normal temperature water or ice water at 0 °C; the extractant used for extraction is cyclohexane.

8. An in-situ grown MOFs mixed matrix membrane, characterized in that, It is prepared by using the preparation method described in any one of claims 1~7.

9. Application of the in-situ growth MOFs mixed matrix membrane described in claim 8 in mixed gas separation.

10. Use of an in-situ grown MOFs mixed matrix membrane according to claim 9 in the separation of mixed gases, characterized in that, The mixed gas is H2 / CO2 or C3H6 / C3H8.

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