Metal organic framework / graphene composite material, preparation method thereof and application of metal organic framework / graphene composite material in carbon dioxide capture

Abstract

The invention discloses a metal organic framework / graphene composite material and a preparation method and application thereof in carbon dioxide capture, and in the composite material, a metal organic framework is dispersed between layers of graphene or graphene oxide and / or on the surface of the graphene or graphene oxide. The metal organic framework particles in the metal organic framework / graphene composite material are dispersed among the layered graphene or the graphene oxide, crystal growth of the metal organic framework is facilitated, and a graphene sheet layer or a graphene oxide sheet layer plays a role in stabilizing the metal organic framework.

Description

Technical Field

[0001] This invention belongs to the field of carbon dioxide capture or adsorption technology, specifically relating to a metal-organic framework / graphene composite material, its preparation method, and its application in carbon dioxide capture. Background Technology

[0002] Carbon dioxide (CO2) capture, utilization, and storage (CCUS) is a key technology for achieving emission reduction targets. It can directly reduce carbon emissions in critical sectors and lower existing atmospheric CO2 concentrations. The CCUS process can be divided into CO2 capture, transport, utilization, and storage. CO2 capture is at the forefront of the entire CCUS process, accounting for almost two-thirds of the total cost. Therefore, developing efficient and low-cost new CO2 capture materials is crucial for promoting the application of CCUS technology. Currently, commercially available CO2 capture technology utilizes traditional amine solvents for absorption. However, traditional amine solvent absorption suffers from problems such as toxic volatiles, corrosion, harmful byproducts, and solvent loss. Furthermore, this technology is chemical adsorption, and the regeneration process of the chemical absorbent requires high energy consumption, leading to a significant increase in cost. Therefore, using porous materials for physical adsorption to replace traditional chemical adsorption using corrosive amine solvents has become a development trend in this field.

[0003] Porous materials with nanoscale pore sizes, such as carbon-based materials, zeolites, mesoporous silica, and metal-organic frameworks (MOFs), are considered potential materials for CO2 adsorption due to their advantages such as high specific surface area, high pore volume, and easily tunable structural composition. MOFs, in particular, are assembled using metal ions and organic ligands, offering designability, tailorability, adjustable pore size, and easy functionalization of pore surfaces, making them promising for applications in gas adsorption, gas storage and separation, electrode materials, and catalysis. Currently, while many MOFs with high specific surface areas exhibit high CO2 adsorption capacity under high pressure conditions, their CO2 adsorption capacity is relatively low under low pressure conditions. Furthermore, in the presence of water vapor, MOFs show poor stability during CO2 capture, and their framework is prone to collapse; for example, they decompose or partially decompose after short-term exposure to ambient air (e.g., about 3 days). On the other hand, water molecules in the environment compete with CO2 for adsorption, hindering CO2 adsorption in MOFs and significantly reducing adsorption performance.

[0004] To address the above problems, current technologies mainly focus on the following aspects: (1) constructing MOFs with high water stability by selecting carboxylate ligands (hard Lewis bases) and high-valence metal ions (hard Lewis acids) or azo compound ligands (soft Lewis bases) and low-valence transition metal ions (soft Lewis acids); (2) functionalizing MOFs, such as selecting nonpolar functional groups or hydrophobic fluorinated alkyl chains for surface modification; and constructing hydrophobic surfaces using coatings or composite materials; (3) removing most of the water by installing a protective bed containing desiccant in front of the adsorption bed loaded with MOFs, thereby stabilizing the MOFs. The first two methods involve complex material preparation processes and increased costs, and the material's CO2 adsorption effect is not significantly improved; the latter method relies on a protective bed containing desiccant, which not only lengthens the process route and significantly increases system energy consumption, but also results in low material recycling efficiency and difficult operation. Therefore, it is necessary to explore alternative paths to improve the CO2 adsorption performance of materials and their stability against moisture (water molecules) in the application environment. Summary of the Invention

[0005] We have discovered that graphene possesses properties such as high specific surface area, structural stability, high mechanical strength, and low water molecule adsorption capacity. To overcome the problem of poor stability of metal-organic frameworks as CO2 capture (adsorption) and storage materials, this invention provides a metal-organic framework / graphene composite material, its preparation method, and its application in CO2 capture. In the composite material, the metal-organic framework is dispersed in the interlayer or surface of layered graphene or graphene oxide. During CO2 adsorption and desorption, graphene or graphene oxide can enhance the structural stability and adsorption performance stability of the metal-organic framework under humid environments or water molecule coexistence conditions, thereby improving the apparent CO2 capture (adsorption) and storage performance of the composite material, i.e., it has the ability to synergistically enhance CO2 capture. This composite material has promising prospects for industrial application.

[0006] The technical solution of the present invention is as follows:

[0007] A metal-organic framework / graphene composite material, wherein the metal-organic framework is dispersed in the interlayer of graphene or graphene oxide and / or on its surface.

[0008] According to an embodiment of the present invention, the metal-organic framework is, for example, Cu(BF4)2(4,4'-bpy)2, wherein 4,4'-bpy is 4,4'-bipyridine.

[0009] According to an embodiment of the present invention, the weight ratio of the metal-organic framework to graphene or graphene oxide is 1:0.01 to 1:0.2, more preferably 1:0.05 to 1:0.12.

[0010] According to an embodiment of the present invention, the metal-organic framework is dispersed in particulate form between and / or on the surface of graphene or graphene oxide.

[0011] According to an embodiment of the present invention, the average particle size of the particulate metal-organic framework is 1-1000 μm.

[0012] According to an embodiment of the present invention, the thickness of the layers in graphene or graphene oxide is 0.34-30 nm, and the total number of layers in graphene or graphene oxide is from a single layer to dozens of layers.

[0013] This invention also provides a method for preparing the above-mentioned metal-organic framework / graphene composite material, the method comprising the following steps:

[0014] The raw materials for forming metal-organic frameworks are mixed with graphene or graphene oxide and heated to react, thereby obtaining the metal-organic framework / graphene composite material.

[0015] According to an embodiment of the present invention, the graphene or graphene oxide is added in the form of a dispersion. Specifically, it is added in the form of an aqueous dispersion.

[0016] According to an embodiment of the present invention, the graphene or graphene oxide aqueous dispersion is a dispersion obtained by dispersing graphene or graphene oxide in water.

[0017] Preferably, when graphene or graphene oxide is dispersed in water, a surfactant may be added. The type and amount of surfactant are not particularly limited, as long as the graphene or graphene oxide is uniformly dispersed in the water. For example, the surfactant is selected from sodium dodecylbenzenesulfonate (NaDDBS).

[0018] Preferably, in the graphene or graphene oxide aqueous dispersion, the mass ratio of graphene or graphene oxide to water is (1-20):4500, more preferably (3-15):4500, and most preferably (5-15):4500.

[0019] According to an embodiment of the present invention, the metal-organic framework is Cu(BF4)2(4,4'-bpy)2, and the method includes the following steps:

[0020] Copper tetrafluoroborate (Cu(BF4)2·H2O), an aqueous dispersion of graphene or graphene oxide, and a 4'4-bipyridine solution were mixed and heated to obtain the metal-organic framework / graphene composite material.

[0021] According to an embodiment of the present invention, in the method, copper tetrafluoroborate (Cu(BF4)2·H2O) and graphene or graphene oxide aqueous dispersion are first mixed, and then 4'4-bipyridine solution is added and mixed.

[0022] According to an embodiment of the present invention, the 4'4-bipyridine solution is 4'4-bipyridine dissolved in an organic solvent, wherein the organic solvent is selected from one or two of ethanol, methanol, etc., preferably ethanol.

[0023] Preferably, the concentration of the 4',4-bipyridine solution is 0.1 to 1 g / mL, more preferably 0.1 to 0.6 g / mL.

[0024] According to an embodiment of the present invention, the mass ratio of graphene or graphene oxide, Cu(BF4)2·H2O and 4'4-bipyridine is (1-20):(20-95):(10-90).

[0025] According to an embodiment of the present invention, the temperature of the reaction is 0 to 100°C, more preferably 40 to 80°C, and most preferably 65 to 75°C; the reaction time is 0.5 to 12 hours, more preferably 1 to 6 hours, and most preferably 2 to 4 hours.

[0026] According to an embodiment of the present invention, the method further includes post-treatment of the reaction products, including separation, washing, and drying. Preferably, the solvent used for washing is selected from at least one of ethanol, methanol, and acetone, with ethanol being the most preferred.

[0027] According to an embodiment of the present invention, the method includes the following steps:

[0028] (1) Prepare or prepare an aqueous dispersion of graphene or graphene oxide.

[0029] (2) Prepare or prepare a mixture of copper tetrafluoroborate and 4',4-bipyridine solution;

[0030] (3) Mix the graphene or graphene oxide aqueous dispersion from step (1) with the mixture from step (2) and heat to react;

[0031] (4) The reaction products obtained in step (3) are separated, washed and dried to prepare metal-organic framework / graphene composite material.

[0032] As an exemplary embodiment of the present invention, the method specifically includes the following steps:

[0033] (1) Add graphene or graphene oxide to water and disperse it by ultrasonication or by adding a surfactant to prepare an aqueous dispersion of graphene or graphene oxide.

[0034] (2) First, add copper tetrafluoroborate (Cu(BF4)2·H2O) to the graphene or graphene oxide aqueous dispersion in step (1) and mix, then add 4'4-bipyridine solution and mix; heat to carry out the reaction;

[0035] (3) The reaction products of step (2) are separated, washed and dried to prepare metal-organic framework / graphene composite material.

[0036] Furthermore, the method also includes: grinding the dried product to obtain a powdered metal-organic framework / graphene composite material.

[0037] The present invention also provides the application of the above-mentioned composite material as a carbon dioxide capture or adsorption material.

[0038] Specifically, the present invention provides a carbon dioxide capture or adsorption material, which is the aforementioned metal-organic framework / graphene composite material.

[0039] The beneficial effects of this invention are:

[0040] (1) The preparation process of the present invention is simple, has a short cycle, high efficiency, and can be mass-produced.

[0041] (2) In the metal-organic framework / graphene composite material of the present invention, the metal-organic framework particles are dispersed between layered graphene or graphene oxide, which facilitates the crystallization and growth of the metal-organic framework, and the graphene sheets or graphene oxide sheets play a stabilizing role for the metal-organic framework.

[0042] (3) The metal-organic framework / graphene composite material of the present invention exhibits excellent CO2 adsorption performance and stability under humid (water molecule) atmosphere conditions. The structure of metal-organic frameworks is rapidly destroyed in humid air (an atmosphere containing water molecules), resulting in a significant decrease in CO2 adsorption performance and making practical applications difficult. However, the composite material of the present invention maintains or even improves CO2 adsorption performance under the same conditions, making it practical. Attached Figure Description

[0043] Figure 1 This is a SEM image of the composite material in Example 1. Detailed Implementation

[0044] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention, and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0045] Unless otherwise stated, the raw materials and reagents used in the following examples are commercially available products or can be prepared by known methods.

[0046] Example 1

[0047] Preparation of a metal-organic framework / graphene composite material for synergistic enhancement of carbon dioxide capture:

[0048] (1) Prepare a mixture of graphene oxide, water, Cu(BF4)2·H2O, 4'4-bipyridine and ethanol by weight percentage (7.5:4500:86:78:395).

[0049] (2) First, add graphene oxide to water and ultrasonically disperse for 1.5 hours to obtain graphene oxide dispersion; then add Cu(BF4)2·H2O solution to graphene oxide dispersion; at the same time, fully dissolve 4'4-bipyridine in ethanol solution, then add it to the above mixture and stir evenly, transfer it to a reflux reactor or reflux reaction device, place it in a 70℃ water bath, reflux synthesis reaction for 3 hours, and then let it stand for a period of time at room temperature.

[0050] (4) Finally, the precipitate was washed and separated by centrifugation with ethanol, and dried to obtain the metal-organic framework / graphene composite material.

[0051] Figure 1 This is a SEM image of the composite material in Example 1.

[0052] Example 2

[0053] Test (1): At 0℃ and P / P0=0.03 ​​(P0 is the saturated vapor pressure of carbon dioxide, and P is the gas phase pressure of carbon dioxide at adsorption equilibrium), the composite material of Example 1 was placed in a carbon dioxide atmosphere. The CO2 adsorption capacity of this material was 0.152 kg per kilogram, while the CO2 adsorption capacity of the metal-organic framework material Cu(BF4)2(4,4'-bpy)2, which was not combined with graphene, was 0.139 kg per kilogram. It can be seen that the composite material of the present invention has excellent CO2 adsorption performance.

[0054] Test (2): At room temperature, after exposing the composite material of Example 1 to air with a humidity of 55-75% for 30 days, the CO2 adsorption capacity of each kilogram of the material was 0.16 kg. It can be seen that the composite material of the present invention can still maintain a stable and high CO2 adsorption capacity even in the presence of water.

[0055] At room temperature, when the metal-organic framework material Cu(BF4)2(4,4'-bpy)2 without graphene is exposed to air with a humidity of 55-75% for 30 days, the CO2 adsorption capacity is only 0.096 kg per kilogram.

[0056] Example 3

[0057] The difference between Example 3 and Example 2 is that the temperature in test (1) was 25°C and the CO2 adsorption capacity of each kilogram of the material was 0.129 kg.

[0058] Example 4

[0059] The difference between Example 4 and Example 2 is that the temperature in test (1) was 30°C and the CO2 adsorption capacity of each kilogram of the material was 0.125 kg.

[0060] The embodiments of the present invention have been described above by way of example. However, the scope of protection of the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made by those skilled in the art within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A metal organic framework / graphene composite material, characterized in that, The metal organic framework is dispersed in the interlayer and / or on the surface of the graphene or graphene oxide in the composite material.

2. The composite material of claim 1, wherein, The metal organic framework is Cu(BF4)2(4,4’-bpy)2, wherein 4,4’-bpy is 4,4’-bipyridine. The weight ratio of the metal organic framework to the graphene or graphene oxide is 1:0.01-1:0.

2.

3. The composite material according to claim 1 or 2, characterized in that, The metal organic framework is in the form of particles. The average particle size of the metal organic framework is 1-1000 μm. The thickness of the layer of the graphene or graphene oxide is 0.34-30 nm.

4. Process for the production of a composite material according to any one of claims 1 to 3, characterized in that, The method comprises the following steps: Mixing raw materials for forming the metal organic framework with graphene or graphene oxide, and heating to react to obtain the metal organic framework / graphene composite material.

5. The method of claim 4, wherein, The graphene or graphene oxide is added in the form of a dispersion liquid.

6. The method of claim 4, wherein, The metal organic framework is Cu(BF4)2(4,4’-bpy)2, and the method comprises the following steps: Mixing copper tetrafluoroborate (Cu(BF4)2·H2O), graphene or graphene oxide aqueous dispersion liquid, and 4’4-bipyridine solution, and heating to react to obtain the metal organic framework / graphene composite material.

7. The method of claim 6, wherein, The 4’4-bipyridine solution is 4’4-bipyridine dissolved in an organic solvent selected from one or both of ethanol and methanol.

8. The method of claim 6, wherein, The mass ratio of graphene or graphene oxide, Cu(BF4)2·H2O, and 4’4-bipyridine is (1-20):(20-95):(10-90).

9. Use of the composite material of any one of claims 1-3 as a carbon dioxide capturing or adsorbing material.

10. A carbon dioxide capture or adsorption material, characterized in that, It is the composite material of any one of claims 1-3. The metal organic framework is dispersed in the interlayer and / or on the surface of the graphene or graphene oxide in the composite material. The metal organic framework is Cu(BF4)2(4,4’-bpy)2, wherein 4,4’-bpy is 4,4’-bipyridine. The weight ratio of the metal organic framework to the graphene or graphene oxide is 1:0.01-1:0.

2. The metal organic framework is in the form of particles. The average particle size of the metal organic framework is 1-1000 μm. The thickness of the layer of the graphene or graphene oxide is 0.34-30 nm. The method comprises the following steps: Mixing raw materials for forming the metal organic framework with graphene or graphene oxide, and heating to react to obtain the metal organic framework / graphene composite material. The graphene or graphene oxide is added in the form of a dispersion liquid. The metal organic framework is Cu(BF4)2(4,4’-bpy)2, and the method comprises the following steps: Mixing copper tetrafluoroborate (Cu(BF4)2·H2O), graphene or graphene oxide aqueous dispersion liquid, and 4’4-bipyridine solution, and heating to react to obtain the metal organic framework / graphene composite material. The 4’4-bipyridine solution is 4’4-bipyridine dissolved in an organic solvent selected from one or both of ethanol and methanol. The mass ratio of graphene or graphene oxide, Cu(BF4)2·H2O, and 4’4-bipyridine is (1-20):(20-95):(10-90).

9. Use of the composite material of any one of claims 1-3 as a carbon dioxide capturing or adsorbing material. It is the composite material of any one of claims 1-3.

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