Method for regulating and controlling pore structure of MOF glass gas separation membrane

Abstract

The invention discloses a method for regulating and controlling the pore structure of an MOF (Metal Organic Framework) glass gas separation membrane, which is characterized in that the pore structure configuration of the MOF glass gas separation membrane can be changed on the basis of not changing the crystal structure of the MOF glass gas separation membrane by changing the variety and proportion of metal sources added in the preparation process and the variety and proportion of organic ligands. The preparation method comprises the following steps: performing solvothermal reaction to generate an MOF crystal film on a substrate in situ, melting the MOF crystal film under the protection of inert atmosphere, and cooling to obtain the MOF glass film with various pore structure distributions. According to the preparation and structure regulation and control method of the novel MOF glass gas separation membrane, the problem that the MOF glass pore structure is single is solved, and the application range of the MOF glass separation membrane material is greatly expanded.

Description

Technical Field

[0001] The present invention relates to a method for preparing and controlling the performance of a novel MOF glass membrane for gas separation. The method can be used to control the separation efficiency of the MOF glass gas separation membrane, which can be extended to the functional applications of MOF glass in optoelectronics, energy storage, catalysis and the like. Background Art

[0002] With the increasing demand for efficient and clean energy with the development of society, energy gases represented by hydrogen and methane are being developed and utilized due to their advantages of high thermal efficiency and low pollution. However, the efficient separation of these gases is a major bottleneck restricting their application. Among the many gas separation and purification technologies, gas membrane separation technology has been focused on research and development due to its advantages of low energy consumption, high efficiency, easy device and industrialization. A new organic-inorganic hybrid porous crystalline material - Metal Organic Framework (MOF) has been developed into a new separation membrane material. MOF material is a porous ordered network structure formed by inorganic metal ions (Zn, Co, etc.) and organic ligands connected by coordination bonds. Due to its multiple chemical and topological compositions, it has a rich and diverse pore structure, which can realize the pore structure design required for the separation of multiple gases. At the same time, MOF material can also have the function of molecular sieve, and can achieve the selective separation of specific gas molecules by adding functional groups to its structure.

[0003] Glassy MOF materials are the fourth type of brand new melt-quenched glass that has recently emerged. They are mainly obtained by melting and cooling MOF crystals. MOF glass is a disordered network structure formed by inorganic metal ions (Zn, Co, etc.) and organic ligands connected by coordination bonds. The micropores in MOF crystals do not disappear due to structural collapse during the melt-quenching process, but exist in different pore sizes and distributions. The diameter of the micropores in MOF glass found so far is between Very suitable for gas molecules with similar diameters. As separation membrane materials, MOF crystal materials can achieve regulation of gas separation performance by changing the crystal structure, ligand size and type, etc. However, there are still few methods for regulating the gas separation performance of MOF glass separation membranes, which affects the application expansion of MOF glass in multiple functional fields. Summary of the invention

[0004] The present invention discloses a method for regulating the pore structure of MOF glass gas separation membrane. The method is based on the same MOF glass material and changes the pore structure of MOF glass separation membrane through chemical and structural design to achieve selective permeation of different gas molecules. The method is simple, efficient, and highly practical, and solves the problem of difficulty in the application of MOF glass to a certain extent.

[0005] The MOF glass pore structure control method described in the present invention includes the following two methods:

[0006] 1) Changing the type and proportion of metal ions in MOF glass: During the preparation of MOF materials, the type and proportion of metal sources added are changed, and then a MOF crystal film is prepared, and then a MOF glass film is obtained by melt quenching;

[0007] 2) Changing the type and ratio of organic ligands in MOF glass: During the preparation of MOF materials, the type and ratio of organic ligands in the reaction process are regulated, and then a MOF crystal film is prepared, and then a MOF glass film is obtained by melt quenching;

[0008] The metal sources used in step 1) include zinc nitrate, cobalt nitrate, ferrocene, zinc acetate, etc., which mainly provide metal ions in the MOF structure;

[0009] Step 1) The control method used is to change the type and proportion of the added metal source, wherein the type of metal source is changed to replace the commonly used Zn ion metal source with CoNO 3 Or other transition metal salts as metal sources, requiring these metal salts to be soluble in solvents such as DMF; changing the metal ion ratio means using two transition metal salts as metal sources at the same time, and adjusting the ratio of the two metal ions without changing the ratio of metal ions to organic ligands. Usually, the ratio can vary between 1:0 and 0:1, and both metal ions need to be reacted into the MOF framework structure;

[0010] The MOF crystal film preparation method described in step 1) is to dissolve the metal source and the organic ligand in DMF according to the designed formula to form a reaction solution; place the separation membrane support substrate at the bottom of the polytetrafluoroethylene reactor, add the reaction solution, and then tighten the reactor shell; react at a temperature of 100 to 160° C. for 8 to 36 hours, thereby forming a MOF crystal film on the surface of the substrate;

[0011] The MOF glass film preparation method described in step 1) is to place the prepared MOF crystal film with different metal ion ratios in a vacuum tube furnace, heat it to 400-500° C. under the protection of an inert atmosphere, keep it warm for 1-30 minutes, and then cool it to room temperature with the furnace to obtain a uniform MOF glass film;

[0012] The method of changing the type and proportion of organic ligands in MOF glass described in step 2) comprises the organic ligands used including imidazole, benzimidazole, 2-methylbenzimidazole, 5,6-dimethylbenzimidazole, etc.;

[0013] Step 2) by changing the type and ratio of the added organic ligands, a MOF crystal that can be melted into glass is generated, which requires two ligands, wherein imidazole is the main ligand, and the proportion of imidazole in the ligand is not less than 75%; the two ligands include imidazole and other benzimidazole ligands, and the ratio of imidazole: benzimidazole ligands can vary from 20:1 to 3:1. It is necessary to control the ligand to be able to react with the metal ions without affecting the main structure of the generated crystal;

[0014] The method for preparing the MOF crystal film described in step 2) is to dissolve the ligands with different ratios in DMF to form a reaction solution with a metal ion source; then, as described above, a solvothermal method is used to in-situ prepare the MOF crystal film;

[0015] In the method for preparing the MOF glass membrane described in step 2), the MOF crystal membrane having different ligand compositions is melted under the protection of an inert atmosphere and then cooled to room temperature to obtain a MOF glass membrane having different pore structures.

[0016] Compared with the prior art, the advantages of the present invention are:

[0017] This patent realizes the regulation of the pore structure of the metal organic framework glass gas separation membrane, and can change the pore structure of the MOF glass membrane over a large range, so that it can adapt to the requirements of different gas separations, thereby expanding the performance and application range of the MOF glass separation membrane. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is the X-ray diffraction pattern of MOF crystals with different ligand (imidazole:benzimidazole) ratios; DETAILED DESCRIPTION

[0019] The following examples are intended to further illustrate the present invention. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention. Other specific implementation methods obtained according to the present invention are also within the scope of the claims described in this application.

[0020] Embodiment 1:

[0021] Take Zn(NO 3 ) 2 (chemically pure, 99.9%) as zinc source and Co(NO 3 ) 2(chemically pure, 99.9%) was used as the zinc source, imidazole (Im, chemically pure, 99.5%) and benzimidazole (bIm, chemically pure, 99.5%) were used as ligands, the raw materials were dissolved in DMF solvent to prepare concentrated solutions, and then the corresponding volume of the concentrated solution was added according to the proportion of the added raw materials to prepare a 60ml mixed solution, the molar ratio of zinc source: cobalt source: imidazole: benzimidazole in the reaction was 0.5:0.5:13.5:1.5, wherein the Zn:Co ratio can be adjusted between 1:0 and 0:1, and then the mixed solution was stirred for 1h; the acid-washed porous Al 2 O 3 The ceramic substrate was placed on the bottom of a 100 ml polytetrafluoroethylene liner, and then the mixed reaction solution was added, and then sealed with a stainless steel jacket and placed in a 130 ° C drying oven to start the solvent thermal reaction for 96 hours. After the reaction was completed, the Al 2 O 3 A Zn / Co-ZIF-62 crystal film is obtained on the substrate surface;

[0022] The prepared Zn / Co-ZIF-62 crystal film was placed in a tube furnace and N was introduced at 40-100 ml / min. 2 Or Ar gas protective gas, heat up to 450-470℃ at a heating rate of 5-10℃ / min, keep warm for 5-10min, and cool with the furnace after the holding time to obtain Zn / Co-ZIF-62 glass films with different pore structures.

[0023] Embodiment 2:

[0024] Take Zn(NO 3 ) 2 (chemically pure, 99.9%) was used as the zinc source, imidazole (Im, chemically pure, 99.5%) and benzimidazole (bIm, chemically pure, 99.5%) were used as ligands, the raw materials were dissolved in DMF solvent to prepare concentrated solutions, and then the corresponding volume of the concentrated solution was added according to the added raw material ratio to prepare a 60 ml mixed solution, the molar ratio of zinc source: imidazole: benzimidazole in the reaction was 1:13.5:1.5, based on the molar amount of the zinc source, the imidazole: benzimidazole ratio could be adjusted between 20:1 and 3:1, and then the mixed solution was stirred for 1 hour; the acid-washed porous Al 2 O 3 The ceramic substrate was placed on the bottom of a 100 ml polytetrafluoroethylene liner, and then the mixed reaction solution was added, and then sealed with a stainless steel jacket and placed in a 130 ° C drying oven to start the solvent thermal reaction. The reaction time was 36 to 96 hours. After the reaction was completed, the Al 2 O 3 ZIF-62 crystal films with different ligand ratios were obtained on the substrate surface;

[0025] The prepared ZIF-62 crystal films with different ligand ratios were placed in a tube furnace and introduced with 40-100 ml / min of N 2 Or Ar gas protective gas, heat up to 450-470℃ at a heating rate of 5-10℃ / min, keep warm for 5-10min, and cool with the furnace after the holding time to obtain ZIF-62 glass membranes with different pore structures.

[0026] Embodiment 3:

[0027] Take Zn(NO 3 ) 2 (chemically pure, 99.9%) was used as the zinc source, imidazole (Im, chemically pure, 99.5%) and 5,6-dimethylbenzimidazole (mbIm, chemically pure, 99.5%) were used as ligands, the raw materials were dissolved in DMF solvent to prepare concentrated solutions, and then the corresponding volume of concentrated solutions was added according to the added raw material ratio to prepare a 60ml mixed solution, the molar ratio of Zn:Im:mbIm in the reaction was 1:15.5:1.5, and then the mixed solution was stirred for 1h; the acid-washed porous Al 2 O 3 The ceramic substrate was placed on the bottom of a 100 ml polytetrafluoroethylene liner, and then the mixed reaction solution was added, and then sealed with a stainless steel jacket and placed in a 120 ° C drying oven to start the solvent thermal reaction for 48 hours. After the reaction was completed, the Al 2 O 3 A MOF crystal film with different ligand types is obtained on the substrate surface;

[0028] The prepared MOF crystal membranes with different ligand ratios were placed in a tube furnace and N was introduced at 40-100 ml / min. 2 Or Ar gas protective gas, heat up to 450-470℃ at a heating rate of 5-10℃ / min, keep warm for 5-10min, and cool with the furnace after the holding time to obtain MOF glass membranes with different pore structures.

[0029] 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 method for regulating the pore structure of MOF glass gas separation membrane, characterized in that: The control methods include the following two: 1) Changing the type and proportion of metal ions in MOF glass: During the preparation of MOF materials, the type and proportion of metal sources added are changed, and then a MOF crystal film is prepared, and then a MOF glass film is obtained by melt quenching; 2) Changing the type and proportion of organic ligands in MOF glass: During the preparation of MOF materials, the type and proportion of organic ligands in the reaction process are regulated, and then a MOF crystal film is prepared, and then a MOF glass film is obtained by melt quenching.

2. A method for regulating the pore structure of a MOF glass gas separation membrane according to claim 1, characterized in that: Metal sources include zinc nitrate, cobalt nitrate, ferrocene, zinc acetate.

3. A method for regulating the pore structure of a MOF glass gas separation membrane according to claim 1, characterized in that: The organic ligands include imidazole, benzimidazole, 2-methylbenzimidazole, and 5,6-dimethylbenzimidazole.

4. A method for regulating the pore structure of a MOF glass gas separation membrane according to claim 1, characterized in that: A single metal source or a dual metal source is used, and the ratio of the dual metal sources can be varied between 1:0 and 0:

1.

5. A method for regulating the pore structure of a MOF glass gas separation membrane according to claim 1, characterized in that: The organic ligands used must have two kinds, imidazole and other benzimidazole ligands, and the ratio of imidazole:benzimidazole ligands varies between 1.85:0.15 and 1.50:0.

50.

6. A method for regulating the pore structure of a MOF glass gas separation membrane according to claim 1, characterized in that: By using different metal sources / organic ligands, MOF crystal films were prepared on substrate materials using an in situ solvothermal method.

7. The preparation method according to claim 1, characterized in that: The prepared MOF crystal film is heated to 420-500°C in an inert atmosphere and kept warm for 1-20 minutes to obtain a dense MOF glass film with different microporous structures.

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