Multi-component metal organic framework (MOF) glass composite membrane for gas separation

Abstract

The invention discloses a multi-component MOF glass composite membrane for gas separation, which is prepared by the following steps of: generating a double-MOF crystal mixed membrane or a double-layer MOF crystal membrane on a porous ceramic substrate by using a plurality of MOF materials with similar melting points through a solvothermal method, placing the MOF crystal membrane in a vacuum tube furnace, heating to a common melting point of the MOF crystal membrane and the double-layer MOF crystal membrane under the protection of inert gas, and carrying out heat treatment on the MOF crystal membrane and the double-layer MOF crystal membrane to obtain the multi-component MOF glass composite membrane for gas separation. And then cooling to obtain the multi-component MOF glass composite film. Due to the fact that the two kinds of MOF glass have different microscopic pore structures, the MOF glass separation membrane with the adjustable pore structures can be obtained through melting fusion. The invention provides a design and preparation method of a novel MOF glass gas separation membrane. The novel MOF glass gas separation membrane can be applied to separation and purification of various gases.

Description

Technical Field

[0001] The invention relates to the technical field of membrane separation materials for gas separation, and in particular to a metal-organic framework multi-component glass composite membrane for gas separation. Background Art

[0002] Membrane separation technology has the advantages of low energy consumption, high efficiency and convenient application among many gas separation and purification technologies. Metal Organic Framework (MOF) materials are new porous materials that have emerged in recent years. They have the characteristics of adjustable components and pore structures, so they show great potential in the application of separation membranes. At present, the most studied are MOF crystal membranes, which are mostly self-supporting membranes formed using polymer materials as matrices, as well as MOF crystal membranes generated on porous substrates such as alumina or titanium dioxide. Due to the diverse chemical composition and topological structure of MOF materials, their pore structures are rich and adjustable, which can achieve targeted design for different gas separation requirements and achieve selective separation of specific gas molecules. However, at present, MOF crystal membranes also have problems such as high preparation cost, poor mechanical properties, and low durability, which limit the further development of MOF crystal membranes.

[0003] In recent years, researchers have found that MOF crystals can be made into MOF glass by melt quenching. MOF glass has a disordered network structure formed by inorganic metal ions and organic ligands connected by coordination bonds. Therefore, given the unique organic-inorganic hybrid chemical composition and coordination bond-dominated network structure of MOF glass, MOF glass can be classified as the fourth category of melt quenched glass. Although the macroporous structure of MOF materials disappears after being prepared into glass by melt quenching, its microporous structure still exists, and by further controlling the crystallization of MOF glass, porous MOF materials with certain mechanical strength can be obtained, and the pore structure can also be regulated by structural and chemical design. Subsequently, the researchers used ZIF-62 crystal thin films to make ZIF-62 glass films by melt quenching, and found that it showed high separation efficiency for mixed gases such as H2 / CH4 and CO2 / CH4. However, the pore structure of single-component MOF glass membranes is fixed and the performance is limited. Therefore, it is necessary to find new methods for designing MOF glass membranes and controlling pore structures. In order to solve this problem, this invention proposes a multi-component MOF glass composite membrane for gas separation, which has excellent separation performance and can be used in the field of gas separation. Summary of the invention

[0004] The present invention discloses a multi-component MOF glass composite membrane for gas separation. The method is to prepare different MOF crystal materials with similar melting points and vitrification capabilities, and to prepare a multi-component MOF glass composite membrane by compounding two MOF crystals. In addition, by changing the ratio of different MOF glasses, the structure and performance of the separation membrane can be regulated. The method provides a new path for the design of MOF glass gas separation membranes, which is conducive to the development of high-performance gas separation technology.

[0005] The multi-component MOF glass composite membrane for gas separation described in the present invention mainly includes the following preparation steps:

[0006] 1) Generating a multi-component MOF crystal film on a substrate, mainly by a solvothermal method, and controlling the reaction conditions to generate two MOF crystal mixed films or a double-layer MOF crystal film;

[0007] 2) heating the pre-prepared multi-component MOF crystal film to above the melting point, melting and fusing, and then cooling to room temperature to form a MOF glass composite film with a multi-level pore structure;

[0008] The multi-component MOF crystal composite film described in step 1) refers to a film layer containing two MOF glass materials, including ZIF-62, ZIF-4, TIF-4 and other materials;

[0009] There are two ways to form the multi-component MOF crystal film in step 1). One is that two MOF crystals are formed on the substrate at the same time to form a mixed MOF crystal film layer; the other is a MOF glass double-layer film form, that is, firstly a MOF crystal layer is generated on the substrate, and then another MOF crystal layer is generated after another round of reaction, that is, a double-layer MOF crystal film;

[0010] The preparation method of the multi-component MOF crystal film described in step 1) is mainly to generate a MOF crystal film on a porous ceramic substrate by in-situ solvent thermal reaction;

[0011] Step 1) The in-situ solvent thermal preparation method of the multi-component MOF crystal membrane is to place the cleaned substrate at the bottom of a polytetrafluoroethylene hydrothermal reactor, then add the prepared reaction solvent and seal it tightly; then, react at a temperature of 100 to 160° C. and a heat preservation time of 12 to 96 hours; after the reaction is completed, cool it with the furnace to obtain a multi-component MOF crystal membrane;

[0012] In the two configurations of the multi-component MOF crystal membrane described in step 1), the mixed crystal membrane only needs to undergo one solvothermal reaction process, while the double-layer crystal membrane needs to undergo two solvothermal reaction processes;

[0013] The method for preparing the multi-component MOF glass membrane described in step 2) is to heat the pre-prepared multi-component MOF crystal membrane to above the melting point, in the range of 400°C-500°C, in a tubular furnace under the protection of an inert atmosphere, and then keep it warm for 1 to 10 minutes, and cool it with the furnace to obtain a MOF glass composite membrane with different pore structures.

[0014] Compared with the prior art, the advantages of the present invention are:

[0015] This patent prepares a MOF crystal composite membrane with different component ratios by fusing a variety of MOF materials that can be melted into glass. The different component ratios can be used to more easily control the pore structure of the gas separation membrane, thereby adapting to the requirements of separation of different types of gases, which is conducive to promoting the large-scale application of MOF glass gas separation membranes. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The SEM images of ZIF-4 and ZIF-62 mixed crystal film (left) and glass film (right); DETAILED DESCRIPTION

[0017] The technical solution of the present invention is described clearly and completely below, and the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained without making creative changes are within the scope of protection of the present invention.

[0018] Embodiment 1:

[0019] Zn(NO3)2 (chemically pure, 99.9%) was used as a metal ion source, imidazole (Im, chemically pure, 99.5%) and benzimidazole (bIm, chemically pure, 99.5%) were used as organic ligands, and DMF was used as a solvent. According to the raw material molar ratio of Zn:Im:bIm:DMF=1:20:1.5:111, 50 ml of DMF solvent was used as a reference, the corresponding reactant raw materials were weighed, dissolved in DMF solvent to form a reaction solution, and the mixed solution was magnetically stirred for 0.5 to 2 hours;

[0020] A porous Al2O3 ceramic substrate washed with acid and water is placed on the bottom of a 100ml polytetrafluoroethylene inner liner, and a reaction solvent that has been fully stirred is added. The inner liner of the reactor is placed in a stainless steel jacket and tightened; the reaction vessel is placed in a drying oven for a solvent thermal reaction, the reaction temperature is 120-160°C, and the insulation time is 12-96h; after the reaction, the reactor is cooled with the furnace, the base liner is taken out, and a ZIF-4 and ZIF-62 mixed crystal film is formed on the surface of the base liner, which is then rinsed with DMF and finally dried;

[0021] The prepared ZIF-4 and ZIF-62 mixed crystal film is placed in a vacuum tube furnace, and 60-100 ml / min of Ar gas protection gas is introduced. The temperature is raised to 470-500°C at a heating rate of 5°C / min and kept warm for 5-10 minutes. The film is then cooled with the furnace to obtain a multi-component MOF glass film containing ZIF-4 and ZIF-62 glass phases.

[0022] Embodiment 2:

[0023] Zn(NO3)2 (chemically pure, 99.9%) was used as a metal ion source, imidazole (Im, chemically pure, 99.5%) and benzimidazole (bIm, chemically pure, 99.5%) were used as organic ligands, and DMF was used as a solvent. According to the raw material molar ratio of Zn:Im:bIm:DMF=1:13.5:1.5:111, 50 ml of DMF solvent was used as a reference, the corresponding reactant raw materials were weighed, dissolved in DMF solvent to form a reaction solution, and the mixed solution was magnetically stirred for 1 hour.

[0024] The porous Al2O3 ceramic substrate which has been acid-washed and cleaned with water is placed on the bottom of a 100ml polytetrafluoroethylene inner liner, and a reaction solvent which has been fully stirred is added, and the inner liner of the reactor is placed in a stainless steel outer jacket and tightened; the reaction vessel is placed in a drying oven for a solvent thermal reaction, and the reaction temperature is 120-140°C and the insulation time is 24-96h; after the reaction is completed, the reactor is cooled with the furnace, and the base liner is taken out, and a ZIF-62 single-layer crystal film is formed on the surface of the base liner, and then it is rinsed with DMF and dried for use;

[0025] Then, Zn(NO3)2 and imidazole Im were used as raw materials, DMF was used as solvent, and according to the raw material molar ratio of Zn:Im:DMF=1:16:111, 50ml of DMF solvent was used as the reference, the corresponding reactant raw materials were weighed, dissolved in DMF solvent to form a reaction solution, and the mixed solution was magnetically stirred for 1h. Subsequently, the substrate with a ZIF-62 crystal film layer on the surface was placed at the bottom of the hydrothermal kettle, and a new reaction solution was added. After the same solvent thermal reaction process, the reaction temperature was 100-120℃ and the insulation time was 24-48h. After the reaction, a ZIF-4@ZIF-62 double-layer crystal film was formed;

[0026] The prepared ZIF-4@ZIF-62 double-layer crystal membrane is placed in a vacuum tube furnace, and 60-100 ml / min of Ar gas protection gas is introduced. The temperature is raised to 500°C at a heating rate of 5°C / min and kept warm for 5-10 minutes. The membrane is then cooled with the furnace to obtain a ZIF-4@ZIF-62 glass double-layer MOF separation membrane.

[0027] The preferred embodiments of the present invention disclosed above are only used to help explain the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to specific implementation methods. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A multi-component metal organic framework MOF glass composite membrane for gas separation, characterized in that: A multi-component MOF crystal film is generated on a substrate, and the multi-component MOF crystals are melted and fused by a melt quenching method to form a MOF glass composite film with a multi-level pore structure.

2. The multi-component MOF glass composite membrane for gas separation according to claim 1, characterized in that: The multi-component MOF glass composite film refers to a film layer containing two MOF glass materials, including ZIF-62, ZIF-4, and TIF-4.

3. The multi-component MOF glass composite membrane for gas separation according to claim 1, characterized in that: There are two ways to construct a multi-component MOF glass composite membrane: one is to mix two MOF glasses to form a membrane layer, and the other is a MOF glass double-layer membrane.

4. The multi-component MOF glass composite membrane for gas separation according to claim 1, characterized in that: The pre-prepared multi-component MOF crystalline membranes were synthesized on porous ceramic substrates using an in situ solvothermal method.

5. The multi-component MOF glass composite membrane for gas separation according to claim 1, characterized in that: The in-situ solvent thermal preparation temperature of the multi-component MOF crystal film is 100-160° C., and the insulation time is 12-96 hours; 6. The multi-component MOF glass composite membrane for gas separation according to claim 1, characterized in that: In the formation method of the multi-component MOF crystal film, two MOF crystals are precipitated simultaneously during the solvent thermal reaction process, thereby forming a film layer with mixed crystals.

7. The multi-component MOF glass composite membrane for gas separation according to claim 1, characterized in that: The multi-component MOF crystal film is formed by two solvent thermal reactions to form a double-layer MOF crystal film with different components.

8. The multi-component MOF glass composite membrane for gas separation according to claim 1, characterized in that: The multi-component MOF glass film is prepared by a melt-quenching method of a prepared MOF crystal film layer.

9. The multi-component MOF glass composite membrane for gas separation according to claim 1, characterized in that: The multi-component MOF glass composite membrane melt-quenching preparation process adopts inert atmosphere protection, and the heat treatment temperature is in the range of 400°C-500°C.

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