A composite material, its preparation and use

Abstract

The application discloses a composite material and a preparation method and application thereof. The composite material is composed of a porous carbon material as a carrier and a metal organic compound as a precursor; wherein oxygen groups of the porous carbon material are connected with metal centers of the metal organic compound through coordination bonds. The composite material is prepared by using a heating reflux method, and the composite material of graphene oxide loaded MOFs with high water stability is prepared by taking graphene oxide as a functionalized carrier. After adding a small amount of GO, the composite material shows smaller aggregated particles compared with MOFs, which is attributed to the coordination between oxygen groups in graphene oxide layers and metal centers in MOFs, so as to prevent the aggregation of MOFs microcrystals and increase the dispersity of the microcrystals, more adsorption active sites can be provided to increase the adsorption performance, and the composite material can be used for efficient capture of CO2.

Description

Technical Field

[0001] This invention relates to a composite material, its preparation method, and its application. Background Technology

[0002] Carbon dioxide, a typical greenhouse gas, is primarily emitted through various social activities, such as the combustion of fossil fuels and numerous chemical processes. Globally, approximately 44% of carbon dioxide emissions come from coal, oil, compressed natural gas (CNG), and fuel combustion. With rapid industrialization, energy consumption is increasing rapidly to meet growing human needs. Currently, about 85% of energy comes from the combustion of fossil fuels, ultimately leading to large amounts of CO2 emissions into the environment. To address global climate change, CO2 capture and further utilization are necessary. In recent years, carbon capture technologies have developed to some extent, with adsorption methods receiving widespread attention due to their simplicity, effectiveness, and low cost. For adsorption materials, adsorption characteristics are mainly affected by their specific surface area and pore volume. Among porous materials, inorganic-organic materials have attracted significant attention in recent years.

[0003] MOFs (organic metal-organic materials) are zeolite-like structures formed by the spontaneous assembly of organic ligands with metal clusters or nodes via covalent or non-covalent bonds. These adsorbents offer numerous advantages, including stable three-dimensional structures, high specific surface areas, controllable pore structures, and tunable pore surfaces. The shape and size of MOFs can be controlled by selecting different metal ions and organic ligands to improve gas adsorption or separation. Currently, MOFs are often combined with various substrate materials to adjust the porosity of the composite material and promote gas adsorption. Common substrate materials include alumina, silica, carbon nanotubes, amorphous carbon, and graphene oxide (GO). Summary of the Invention

[0004] To enrich the adsorption materials for capturing CO2 gas, this invention provides a composite material with strong stability and good adsorption performance.

[0005] As one aspect of the present invention, there is a composite material comprising a porous carbon material as a carrier and an organometallic compound as a precursor; wherein the oxygen groups of the porous carbon material are connected to the metal centers of the organometallic compound through coordination bonds.

[0006] In a specific embodiment, the porous carbon material is selected from graphene oxide material with a thickness of 0.3 to 1.0 nm and a sheet diameter of 0.5 to 10 μm.

[0007] In a specific embodiment, the organometallic compound is selected from one of UiO-66-OH, Cu-BTC, UiO-66, UiO-66-NO2, UiO-66-NH2, and UiO-66-CH3.

[0008] As another aspect of the present invention, a method for preparing the above-mentioned composite material is provided, the method comprising the following steps:

[0009] S1, Preparation of graphene oxide

[0010] Graphite powder and sodium nitrate were added to concentrated sulfuric acid in sequence and stirred until homogeneous to obtain system A. After lowering the temperature of system A, KMnO4 was added and the temperature was raised to obtain system B. System B was placed in an ice-water bath, deionized water was added, and then placed at room temperature. Hydrogen peroxide was added to continue the reaction. After washing and drying, graphene oxide was obtained.

[0011] S2, Preparation of graphene oxide suspension

[0012] The graphene oxide in S1 was dispersed into deionized water by ultrasonic treatment to obtain a graphene oxide suspension.

[0013] S3, Preparation of precursor solution

[0014] A precursor solution is obtained by adding a metal salt and an organic ligand to an acidic solvent and reacting under stirring conditions.

[0015] S4. Formulation of composite materials

[0016] The graphene oxide suspension prepared by S2 was added to the precursor solution prepared by S3 and mixed evenly to obtain system C. System C was placed in an oil bath for reaction, washed, and dried to obtain the composite material.

[0017] In a specific embodiment, in S1, the temperature of system A is reduced to 0-5°C.

[0018] In a specific embodiment, in step S1, the temperature is raised to 20–30°C, and the reaction is carried out for 10–14 hours to obtain system B.

[0019] In a specific embodiment, hydrogen peroxide is added in step S1 and the reaction continues for 0.5 to 1 hour.

[0020] In a specific embodiment, in S2, the amount of graphene oxide added accounts for 0.074% to 0.26% of the total mass of the reactants (i.e., graphene oxide, metal salt, and organic ligands). Specifically, the mass fraction of graphene oxide added is 0.074% to 0.26%.

[0021] In a specific embodiment, in S2, the ultrasonic treatment time is 6 to 8 hours.

[0022] In a specific embodiment, in S3, the acidic solvent is selected from acetic acid, formic acid, or oxalic acid.

[0023] In a specific embodiment, in S3, the metal salt is zirconium oxychloride or copper nitrate trihydrate.

[0024] In a specific embodiment, in S3, the organic ligand is selected from one of 2,5-dihydroxyterephthalic acid, terephthalic acid, 2-nitroterephthalic acid, 2-methylterephthalic acid, 2-hydroxyterephthalic acid, trimesic acid, or 2-aminoterephthalic acid.

[0025] In a specific embodiment, in S4, the system C is placed in an oil bath at 100-120°C and reacted for 18-24 hours.

[0026] As another aspect of the present invention, the application of the above-mentioned composite material is described, wherein the composite material is used as an adsorbent in the field of adsorption.

[0027] As another aspect of the invention, a method for capturing CO2 is provided, the method using the aforementioned composite material.

[0028] This invention uses graphene oxide as a functionalized carrier to prepare a composite material of graphene oxide-supported MOFs with high water stability. After adding a very small amount of GO, the composite material shows smaller aggregated particles compared with MOFs. This is attributed to the coordination between the oxygen groups in the graphene oxide sheets and the metal centers in the MOFs, which prevents the aggregation of MOF crystallites and increases their dispersibility. It can provide more adsorption active sites and thus increase adsorption performance, and can be used as a highly efficient CO2 capture material.

[0029] The method for preparing the composite material provided by this invention utilizes a heating reflux method, which is simpler than the commonly used hydrothermal reactor method. Furthermore, the composite material of graphene oxide supported on organometallic compounds can be used for efficient CO2 adsorption at room temperature, improving the problem of low CO2 adsorption capacity of single MOFs and solving the problem of low water stability of MOF materials.

[0030] This invention is not limited to the composite of graphene oxide and UiO-66-OH, but is also applicable to the combination with other MOFs, such as Cu-BTC, MOFs-Mg(74), etc. The adsorption performance of the composite material on CO2 can also be significantly improved.

[0031] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention are realized and obtained in accordance with the structures particularly pointed out in the description, claims and drawings. Attached Figure Description

[0032] Figure 1 Here is a SEM image of the GO / UiO-66-OH composite adsorbent obtained in Example 1;

[0033] Figure 2 The X-ray diffraction pattern of GO / UiO-66-OH obtained in Example 2;

[0034] Figure 3 The TGA image of GO / UiO-66-OH obtained in Example 3;

[0035] Figure 4 The images show the adsorption effect of the materials prepared in Examples (1, 2, 3) and Comparative Examples (1, 2, 3, 4) on CO2. Detailed Implementation

[0036] While researching related composite materials of MOFs, the inventors discovered that some researchers had reported a GO / UiO-66 composite material for CO2 pressure swing adsorption. However, the addition of GO significantly reduced the CO2 adsorption performance of UiO-66, resulting in a lower-than-expected adsorption effect. Professor Guan Guofeng of Nanjing University of Technology prepared a composite material of UiO-66 and graphene, which exhibited a high CO2 adsorption capacity of 3.37 mmol / g, 48% higher than that of UiO-66 alone. Professor Zhong Qin of Nanjing University of Science and Technology also studied a Cu-BTC and mesoporous silica composite material as a CO2 adsorbent, showing a 16% increase in CO2 adsorption capacity compared to Cu-BTC (HS-1:10⁸ cm⁻¹). 3 / g, 25℃ and 1.0 bar); Lu Anhui's research group at Dalian University of Technology reported a porous carbon-Cu-BTC composite material with an adsorption capacity of 22.7 cm⁻¹ for CO₂ (g, 25℃ and 1.0 bar); 3 The CO2 adsorption capacity ( / g) is significantly improved compared to that of single porous carbon.

[0037] Patent CN 116212831 A discloses a method for preparing UiO-66-(OH)2 / GO and its application in CO2 adsorption and separation. However, the inventors believe that although this method can improve the material's adsorption capacity for CO2, the CO2 adsorption capacity is still insufficient, and the amount of GO added is relatively large, resulting in high preparation costs. Furthermore, this invention is limited to the combination of one substrate material and one MOF, and is not applicable to the combination of other MOFs and substrate materials, thus having certain limitations.

[0038] In summary, the stability and CO2 adsorption capacity of the aforementioned materials are still below the inventors' expectations, and the amount of substrate material added is also relatively large. Based on this, the inventors developed this invention through further research and development.

[0039] The present invention will be further described below with reference to specific embodiments. The scope of protection of the present invention is not limited to the following embodiments. The main sources of materials involved in the following embodiments are shown in Table 1 below. Other materials not specified are all conventional commercially available products.

[0040] Table 1: Material Source Description

[0041] Serial Number name Specification factory 1 Zirconium oxychloride octahydrate 98％ Shanghai McLean Biochemical Technology Co., Ltd. 2 2,5-Dihydroxyterephthalic acid 98％ Shanghai McLean Biochemical Technology Co., Ltd. 3 terephthalic acid 98％ Shanghai McLean Biochemical Technology Co., Ltd. 4 2-Nitroterephthalic acid 98％ Shanghai McLean Biochemical Technology Co., Ltd. 5 Copper nitrate trihydrate 99％ Shanghai McLean Biochemical Technology Co., Ltd. 6 Tristyric acid 98％ Shanghai McLean Biochemical Technology Co., Ltd. 7 2-Methylterephthalic acid 98％ Shanghai McLean Biochemical Technology Co., Ltd. 8 2-Hydroxyterephthalic acid 98％ Shanghai McLean Biochemical Technology Co., Ltd.

[0042] Through extensive experimental research, the inventors obtained the following preferred embodiments, and Examples 1 to 9 are given.

[0043] Example 1

[0044] A method for preparing a GO / UiO-66-OH composite adsorbent includes the following steps:

[0045] S1, Preparation of graphene oxide

[0046] 1.0 g of graphite powder and 0.5 g of sodium nitrate were added to 24 ml of concentrated sulfuric acid and stirred until homogeneous to obtain system A. After the temperature of system A dropped to 0℃, 3.0 g of KMnO4 was added, and the reaction was carried out at 20℃ for 12 h to obtain system B. System B was placed in an ice-water bath, deionized water was added, and then the reaction was carried out at room temperature. 15 ml of 30% hydrogen peroxide was added and the reaction was continued for 1 h. The reaction product was washed with 5% hydrochloric acid solution and deionized water to remove excess acid and byproducts. The product was then dried in an oven at 60℃ to obtain graphene oxide nanosheets.

[0047] S2, Preparation of graphene oxide suspension

[0048] 2 mg of graphene oxide nanosheets (mass fraction 0.074%, 2 mg / (1.7 g + 1.0 g + 2 mg)) prepared by S1 was ultrasonically treated for 7 h and then dispersed in 20 mL of deionized water to obtain a graphene oxide suspension.

[0049] S3, Preparation of precursor solution

[0050] Accurately weigh 1.7 g of zirconium oxychloride and 1.0 g of 2,5-dihydroxyterephthalic acid into a single-necked flask, add 30 mL of acetic acid, and react under stirring for 0.5 h to obtain a UiO-66-OH precursor dispersion;

[0051] S4. Formulation of composite materials

[0052] The graphene oxide suspension prepared by S2 was added to the UiO-66-OH precursor dispersion prepared by S3 and mixed evenly to obtain system C; system C was placed in an oil bath at 100℃ and reacted for 24h to obtain the crude product of the composite material.

[0053] The crude product of the composite material was washed six times with alternating water and methanol, with a 12-hour interval between each wash, to remove unreacted metal salts, organic ligands, and graphene oxide. Finally, the temperature was increased to 120°C at a heating rate of 5°C / min and dried for 12 hours to obtain the graphene oxide-supported UiO-66-OH composite material.

[0054] The scanning electron microscope image of the GO / UiO-66-OH composite material synthesized in this embodiment is shown below. Figure 1 GO / UiO-66-OH and pure UiO-66-OH exhibit similar three-dimensional morphologies. No graphene oxide structure was found in the GO / UiO-66-OH material, possibly because the mass fraction of GO in the composite material is small, and the particle size of UiO-66-OH in the composite material is smaller, accounting for only 0.074% of the precursor, which increases the particle dispersion and is beneficial to improving the adsorption performance.

[0055] Example 2

[0056] A method for preparing a GO / UiO-66-OH composite adsorbent includes the following steps:

[0057] S1, Preparation of graphene oxide

[0058] 1.0 g of graphite powder and 0.5 g of sodium nitrate were added to 24 ml of concentrated sulfuric acid and stirred until homogeneous to obtain system A. After the temperature of system A dropped to 2 °C, 3.0 g of KMnO4 was added, and the reaction was carried out at 25 °C for 12 h to obtain system B. System B was placed in an ice-water bath, deionized water was added, and then the reaction was carried out at room temperature. 15 ml of 30% hydrogen peroxide was added and the reaction was continued for 0.8 h. The reaction product was washed with 5% hydrochloric acid solution and deionized water to remove excess acid and byproducts. The product was then dried in an oven at 60 °C to obtain graphene oxide nanosheets.

[0059] S2, Preparation of graphene oxide suspension

[0060] 4 mg of graphene oxide nanosheets (mass fraction 0.15%) prepared by S1 were ultrasonically treated for 6.5 h and then dispersed in 20 mL of deionized water to obtain a graphene oxide suspension.

[0061] S3, Preparation of precursor solution

[0062] Accurately weigh 1.7 g of zirconium oxychloride and 1.0 g of 2,5-dihydroxyterephthalic acid into a single-necked flask, add 30 mL of acetic acid, and react under stirring for 0.5 h to obtain a UiO-66-OH precursor dispersion;

[0063] S4. Formulation of composite materials

[0064] The graphene oxide suspension prepared by S2 was added to the UiO-66-OH precursor dispersion prepared by S3 and mixed evenly to obtain system C; system C was placed in an oil bath at 100℃ and reacted for 24h to obtain the crude product of the composite material.

[0065] The crude product of the composite material was washed six times with alternating water and methanol, with a 12-hour interval between each wash, to remove unreacted metal salts, organic ligands, and graphene oxide. Finally, the temperature was increased to 120°C at a heating rate of 5°C / min and dried for 12 hours to obtain the graphene oxide-supported UiO-66-OH composite material.

[0066] The XRD pattern of the synthetic composite material in this embodiment is as follows: Figure 2 As shown.

[0067] The diffraction peaks of GO / UiO-66-OH are consistent with those of pure UiO-66-OH reported in the literature, indicating that both materials were successfully prepared. The introduction of GO did not change the crystal structure.

[0068] Example 3

[0069] A method for preparing a GO / UiO-66-OH composite adsorbent includes the following steps:

[0070] S1, Preparation of graphene oxide

[0071] 1.0 g of graphite powder and 0.5 g of sodium nitrate were added to 24 ml of concentrated sulfuric acid and stirred until homogeneous to obtain system A. After the temperature of system A dropped to 5 °C, 3.0 g of KMnO4 was added, and the mixture was reacted at 20 °C for 12 h to obtain system B. System B was placed in an ice-water bath, deionized water was added, and the mixture was placed at room temperature. 15 ml of 30% hydrogen peroxide was added, and the reaction was continued for 0.5 h. The reaction product was washed with 5% hydrochloric acid solution and deionized water to remove excess acid and byproducts. The product was then dried in an oven at 60 °C to obtain graphene oxide nanosheets.

[0072] S2, Preparation of graphene oxide suspension

[0073] 5 mg of graphene oxide nanosheets (mass fraction 0.18%) prepared by S1 were ultrasonically treated for 6 h and then dispersed in 20 mL of deionized water to obtain a graphene oxide suspension.

[0074] S3, Preparation of precursor solution

[0075] Accurately weigh 1.7 g of zirconium oxychloride and 1.0 g of 2,5-dihydroxyterephthalic acid into a single-necked flask, add 30 mL of acetic acid, and react under stirring for 0.5 h to obtain a UiO-66-OH precursor dispersion;

[0076] S4. Formulation of composite materials

[0077] The graphene oxide suspension prepared by S2 was added to the UiO-66-OH precursor dispersion prepared by S3 and mixed evenly to obtain system C; system C was placed in an oil bath at 100℃ and reacted for 24h to obtain the crude product of the composite material.

[0078] The crude product of the composite material was washed six times with alternating water and methanol, with a 12-hour interval between each wash, to remove unreacted metal salts, organic ligands, and graphene oxide. Finally, the temperature was increased to 120°C at a heating rate of 5°C / min and dried for 12 hours to obtain the graphene oxide-supported UiO-66-OH composite material.

[0079] The TGA curve of the synthesized GO / UiO-66-OH in this embodiment is as follows: Figure 3 As shown, the major temperature inflection points of the composite material coincide. Two distinct weight loss steps were observed, similar to those of pure UiO-66-OH. The first weight loss below 280°C is caused by the desorption of physically adsorbed water and small organic molecules. The second weight loss in the 280-500°C range likely originates from the framework decomposition of the adsorbent material.

[0080] Example 4

[0081] A method for preparing a GO / UiO-66-OH composite adsorbent includes the following steps:

[0082] S1, Preparation of graphene oxide

[0083] 1.0 g of graphite powder and 0.5 g of sodium nitrate were added to 24 ml of concentrated sulfuric acid and stirred until homogeneous to obtain system A. After the temperature of system A dropped to 3 °C, 3.0 g of KMnO4 was added, and the mixture was reacted at 30 °C for 12 h to obtain system B. System B was placed in an ice-water bath, deionized water was added, and the mixture was placed at room temperature. 15 ml of 30% hydrogen peroxide was added, and the reaction was continued for 0.5 h. The reaction product was washed with 5% hydrochloric acid solution and deionized water to remove excess acid and byproducts. The product was then dried in an oven at 60 °C to obtain graphene oxide nanosheets.

[0084] S2, Preparation of graphene oxide suspension

[0085] 7 mg of graphene oxide nanosheets (mass fraction 0.26%) prepared by S1 were ultrasonically treated for 7.5 h and then dispersed in 20 mL of deionized water to obtain a graphene oxide suspension.

[0086] S3, Preparation of precursor solution

[0087] Accurately weigh 1.7 g of zirconium oxychloride and 1.0 g of 2,5-dihydroxyterephthalic acid into a single-necked flask, add 30 mL of acetic acid, and react under stirring for 0.5 h to obtain a UiO-66-OH precursor dispersion;

[0088] S4. Formulation of composite materials

[0089] The graphene oxide suspension prepared by S2 was added to the UiO-66-OH precursor dispersion prepared by S3 and mixed evenly to obtain system C; system C was placed in an oil bath at 100℃ and reacted for 24h to obtain the crude product of the composite material.

[0090] The crude product of the composite material was washed six times with alternating water and methanol, with a 12-hour interval between each wash, to remove unreacted metal salts, organic ligands, and graphene oxide. Finally, the temperature was increased to 120°C at a heating rate of 5°C / min and dried for 12 hours to obtain the graphene oxide-supported UiO-66-OH composite material.

[0091] Example 5

[0092] A method for preparing a GO / Cu-BTC composite adsorbent includes the following steps:

[0093] S1, Preparation of graphene oxide

[0094] 1.0 g of graphite powder and 0.5 g of sodium nitrate were added to 24 ml of concentrated sulfuric acid and stirred until homogeneous to obtain system A. After the temperature of system A dropped to 2 °C, 3.0 g of KMnO4 was added, and the mixture was reacted at 25 °C for 14 h to obtain system B. System B was placed in an ice-water bath, deionized water was added, and the mixture was placed at room temperature. 15 ml of 30% hydrogen peroxide was added, and the reaction was continued for 0.8 h. The reaction product was washed with 5% hydrochloric acid solution and deionized water to remove excess acid and byproducts. The product was then dried in an oven at 60 °C to obtain graphene oxide nanosheets.

[0095] S2, Preparation of graphene oxide suspension

[0096] 5 mg of graphene oxide nanosheets (mass fraction 0.26%) prepared by S1 were ultrasonically treated for 8 h and then dispersed in 12 mL of deionized water to obtain a graphene oxide suspension.

[0097] S3, Preparation of precursor solution

[0098] Accurately weigh 0.875 g of copper nitrate trihydrate and dissolve it in the graphene oxide suspension prepared by S2; then accurately weigh 0.42 g of trimesic acid and dissolve it in 12 mL of anhydrous ethanol, and mix it with the solution mentioned above to obtain a mixed solution of the precursor.

[0099] S4. Formulation of composite materials

[0100] The precursor mixture solution obtained from S3 was transferred to a 200 mL polyethylene reactor, and the reactor was transferred to a drying oven and reacted at 120 °C for 12 h. The reactor was cooled to room temperature, washed twice with 30 mL of ethanol by centrifugation (at 8000 rpm), and finally dried at 120 °C for 10 h at a heating rate of 5 °C / min to obtain light blue powder crystals GO / Cu-BTC.

[0101] Example 6

[0102] A method for preparing a GO / UiO-66 composite adsorbent includes the following steps:

[0103] S1, Preparation of graphene oxide

[0104] 1.0 g of graphite powder and 0.5 g of sodium nitrate were added to 24 ml of concentrated sulfuric acid and stirred until homogeneous to obtain system A. After the temperature of system A dropped to 3 °C, 3.0 g of KMnO4 was added, and the mixture was reacted at 30 °C for 12 h to obtain system B. System B was placed in an ice-water bath, deionized water was added, and the mixture was placed at room temperature. 15 ml of 30% hydrogen peroxide was added, and the reaction was continued for 0.5 h. The reaction product was washed with 5% hydrochloric acid solution and deionized water to remove excess acid and byproducts. The product was then dried in an oven at 60 °C to obtain graphene oxide nanosheets.

[0105] S2, Preparation of graphene oxide suspension

[0106] 7 mg of graphene oxide nanosheets (mass fraction 0.20%) prepared by S1 were ultrasonically treated for 7.5 h and then dispersed in 20 mL of deionized water to obtain a graphene oxide suspension.

[0107] S3, Preparation of precursor solution

[0108] Accurately weigh 1.7g of zirconium oxychloride and 1.0g of terephthalic acid into a single-necked flask, add 30mL of formic acid, and react under stirring for 1h to obtain a UiO-66 precursor dispersion; S4, Preparation of composite materials

[0109] The graphene oxide suspension prepared by S2 was added to the UiO-66 precursor dispersion prepared by S3 and mixed evenly to obtain system C; system C was placed in an oil bath at 100℃ and reacted for 24h to obtain the crude product of the composite material.

[0110] The crude product of the composite material was washed six times with alternating water and methanol, with a 12-hour interval between each wash, to remove unreacted metal salts, organic ligands, and graphene oxide. Finally, the temperature was increased to 120°C at a heating rate of 5°C / min and dried for 12 hours to obtain the composite material of graphene oxide-supported UiO-66.

[0111] Example 7

[0112] A method for preparing a GO / UiO-66-NO2 composite adsorbent includes the following steps: S1, preparation of graphene oxide.

[0113] 1.0 g of graphite powder and 0.5 g of sodium nitrate were added to 24 ml of concentrated sulfuric acid and stirred until homogeneous to obtain system A. After the temperature of system A dropped to 3 °C, 3.0 g of KMnO4 was added, and the mixture was reacted at 30 °C for 10 h to obtain system B. System B was placed in an ice-water bath, deionized water was added, and the mixture was placed at room temperature. 15 ml of 30% hydrogen peroxide was added, and the reaction was continued for 0.5 h. The reaction product was washed with 5% hydrochloric acid solution and deionized water to remove excess acid and byproducts. The product was then dried in an oven at 60 °C to obtain graphene oxide nanosheets.

[0114] S2, Preparation of graphene oxide suspension

[0115] 7 mg of graphene oxide nanosheets (mass fraction 0.26%) prepared by S1 were ultrasonically treated for 7.5 h and then dispersed in 20 mL of deionized water to obtain a graphene oxide suspension.

[0116] S3, Preparation of precursor solution

[0117] Accurately weigh 1.7 g of zirconium oxychloride and 1.0 g of 2-nitroterephthalic acid into a single-necked flask, add 30 mL of oxalic acid, and react for 1 h under stirring to obtain a UiO-66-NO2 precursor dispersion.

[0118] S4. Formulation of composite materials

[0119] The graphene oxide suspension prepared by S2 was added to the UiO-66-NO2 precursor dispersion prepared by S3 and mixed evenly to obtain system C; system C was placed in an oil bath at 100℃ and reacted for 24h to obtain the crude product of the composite material.

[0120] The crude product of the composite material was washed six times with alternating water and methanol, with a 12-hour interval between each wash, to remove unreacted metal salts, organic ligands, and graphene oxide. Finally, the temperature was increased to 120°C at a heating rate of 5°C / min and dried for 12 hours to obtain the graphene oxide-supported UiO-66-NO2 composite material.

[0121] Example 8

[0122] A method for preparing a GO / UiO-66-NH2 composite adsorbent includes the following steps: S1, preparation of graphene oxide.

[0123] 1.0 g of graphite powder and 0.5 g of sodium nitrate were added to 24 ml of concentrated sulfuric acid and stirred until homogeneous to obtain system A. After the temperature of system A dropped to 3 °C, 3.0 g of KMnO4 was added, and the mixture was reacted at 30 °C for 12 h to obtain system B. System B was placed in an ice-water bath, deionized water was added, and the mixture was placed at room temperature. 15 ml of 30% hydrogen peroxide was added, and the reaction was continued for 0.5 h. The reaction product was washed with 5% hydrochloric acid solution and deionized water to remove excess acid and byproducts. The product was then dried in an oven at 60 °C to obtain graphene oxide nanosheets.

[0124] S2, Preparation of graphene oxide suspension

[0125] 7 mg of graphene oxide nanosheets (mass fraction 0.26%) prepared by S1 were ultrasonically treated for 7.5 h and then dispersed in 20 mL of deionized water to obtain a graphene oxide suspension.

[0126] S3, Preparation of precursor solution

[0127] Accurately weigh 1.7 g of zirconium oxychloride and 1.0 g of 2-aminoterephthalic acid into a single-necked flask, add 30 mL of acetic acid, and react for 1 h under stirring to obtain a UiO-66-NH2 precursor dispersion;

[0128] S4. Formulation of composite materials

[0129] The graphene oxide suspension prepared by S2 was added to the UiO-66-NH2 precursor dispersion prepared by S3 and mixed evenly to obtain system C; system C was placed in an oil bath at 120℃ and reacted for 18h to obtain the crude product of the composite material.

[0130] The crude product of the composite material was washed six times with water and methanol alternately, with an interval of 12 hours between each wash, to remove unreacted metal salts, organic ligands, and graphene oxide. Finally, the temperature was increased to 120°C at a heating rate of 5°C / min and dried for 12 hours to obtain the graphene oxide-supported UiO-66-NH2 composite material.

[0131] Example 9

[0132] A method for preparing a GO / UiO-66-CH3 composite adsorbent includes the following steps: S1, preparation of graphene oxide.

[0133] 1.0 g of graphite powder and 0.5 g of sodium nitrate were added to 24 ml of concentrated sulfuric acid and stirred until homogeneous to obtain system A. After the temperature of system A dropped to 3 °C, 3.0 g of KMnO4 was added, and the mixture was reacted at 30 °C for 12 h to obtain system B. System B was placed in an ice-water bath, deionized water was added, and the mixture was placed at room temperature. 15 ml of 30% hydrogen peroxide was added, and the reaction was continued for 0.5 h. The reaction product was washed with 5% hydrochloric acid solution and deionized water to remove excess acid and byproducts. The product was then dried in an oven at 60 °C to obtain graphene oxide nanosheets.

[0134] S2, Preparation of graphene oxide suspension

[0135] 7 mg of graphene oxide nanosheets (mass fraction 0.26%) prepared by S1 were ultrasonically treated for 7.5 h and then dispersed in 20 mL of deionized water to obtain a graphene oxide suspension.

[0136] S3, Preparation of precursor solution

[0137] Accurately weigh 1.7 g of zirconium oxychloride and 1.0 g of 2-methylterephthalic acid into a single-necked flask, add 30 mL of acetic acid, and react for 1 h under stirring to obtain a UiO-66-CH3 precursor dispersion;

[0138] S4. Formulation of composite materials

[0139] The graphene oxide suspension prepared by S2 was added to the UiO-66-CH3 precursor dispersion prepared by S3 and mixed evenly to obtain system C; system C was placed in an oil bath at 100℃ and reacted for 24h to obtain the crude product of the composite material.

[0140] The crude product of the composite material was washed six times with alternating water and methanol, with a 12-hour interval between each wash, to remove unreacted metal salts, organic ligands, and graphene oxide. Finally, the temperature was increased to 120°C at a heating rate of 5°C / min and dried for 12 hours to obtain the graphene oxide-supported UiO-66-CH3 composite material.

[0141] During the research phase, the inventors selected experimental groups with poor adsorption performance as comparative examples of the present invention, and provided comparative examples 1 to 5.

[0142] Comparative Example 1

[0143] The difference from Example 1 is that a carrier is missing; specifically, the preparation method of the UiO-66-OH adsorbent in this comparative example includes the following steps:

[0144] (1) Accurately weigh 1.7g zirconium oxychloride and 1.0g 2,5-dihydroxyterephthalic acid into a single-necked flask, add 30mL acetic acid and 20mL water, and react for 0.5h under stirring to obtain a UiO-66-OH precursor dispersion;

[0145] (2) The UiO-66-OH precursor solution in step (1) was placed in an oil bath at 100°C and reacted for 24 hours. The solution was washed alternately with water and methanol and dried at 100°C for 12 hours to obtain UiO-66-OH crystal powder.

[0146] Comparative Example 2

[0147] The difference from Example 2 lies in the amount of graphene oxide added. Specifically, the preparation method of the UiO-66-OH / GO composite adsorbent in this comparative example includes the following steps:

[0148] (1) Add 1.0g of graphite powder and 0.5g of sodium nitrate to 24mL of concentrated sulfuric acid and stir evenly to obtain system A. Add 3.0g of KMnO4 to system A at a temperature of 0-5℃ and react at a temperature of 20-30℃ for 12h to obtain system B. Place system B in an ice-water bath, add deionized water, place it at room temperature, add 15mL of 30% hydrogen peroxide and continue to react for 0.5-1h. Wash and dry to obtain graphene oxide.

[0149] (2) Disperse 10 mg of graphene oxide (mass fraction 0.36%) from step (1) into 20 mL of secondary water by ultrasonic treatment to obtain a graphene oxide suspension;

[0150] (3) Accurately weigh 1.7g zirconium oxychloride and 1.0g 2,5-dihydroxyterephthalic acid into a single-necked flask, add 30mL formic acid, and react for 1h under stirring to obtain UiO-66-OH precursor dispersion;

[0151] (4) Add the graphene oxide suspension from step (2) to the UiO-66-OH precursor solution from step (3) and mix thoroughly to obtain system C;

[0152] (5) The system C from step (4) was placed in an oil bath at 100°C for 24 hours, washed alternately with water and methanol, and dried at 100°C for 12 hours to obtain a composite material of graphene oxide supported on UiO-66-OH.

[0153] Comparative Example 3

[0154] The difference from Example 3 lies in the amount of graphene oxide added. Specifically, the preparation method of the UiO-66-OH / GO composite adsorbent in this comparative example includes the following steps:

[0155] (1) Add 1.0g of graphite powder and 0.5g of sodium nitrate to 24mL of concentrated sulfuric acid and stir evenly to obtain system A. Add 3.0g of KMnO4 to system A at a temperature of 0-5℃ and react at a temperature of 20-30℃ for 14h to obtain system B. Place system B in an ice-water bath, add deionized water, place it at room temperature, add 15mL of 30% hydrogen peroxide and continue to react for 0.5-1h. Wash and dry to obtain graphene oxide.

[0156] (2) Disperse 20 mg of graphene oxide (mass fraction of 0.74%) from step (1) into 20 mL of secondary water by ultrasonic treatment to obtain graphene oxide suspension;

[0157] (3) Accurately weigh 1.7g zirconium oxychloride and 1.0g 2,5-dihydroxyterephthalic acid into a single-necked flask, add 30mL acetic acid, and react for 1h under stirring to obtain a UiO-66-OH precursor dispersion;

[0158] (4) Add the graphene oxide suspension from step (2) to the UiO-66-OH precursor solution from step (3) and mix thoroughly to obtain system C;

[0159] (5) The system C from step (4) was placed in an oil bath at 100°C and reacted for 20 h. It was washed alternately with water and methanol and dried at 100°C for 12 h to obtain a composite material of graphene oxide supported on UiO-66-OH.

[0160] Comparative Example 4

[0161] The difference from Example 4 lies in the choice of support. Specifically, the preparation method of the UiO-66-OH / GO composite adsorbent in this comparative example includes the following steps:

[0162] (1) Weigh urea and distilled water at a mass ratio of 3:5 to prepare a mixed solution. Pour the mixed solution into a ceramic crucible, seal it, and place it in a muffle furnace. Heat it to 400℃ at a heating rate of 10℃ / min and hold for 1 hour, then heat it to 550℃ and hold for 3 hours, and then cool it to room temperature. Dissolve the obtained light yellow loose block in distilled water and sonicate for 1 hour, then put it in a drying oven to dry, take it out and grind it to obtain g-C3N4 powder;

[0163] (2) Disperse 7 mg of g-C3N4 from step (1) into 20 mL of secondary water by ultrasonic treatment to obtain g-C3N4 suspension;

[0164] (3) Accurately weigh 1.7g zirconium oxychloride and 1.0g 2-hydroxyterephthalic acid into a single-necked flask, add 30mL acetic acid, and react for 1h under stirring to obtain a UiO-66-OH precursor dispersion;

[0165] (4) Add the g-C3N4 suspension from step (2) to the UiO-66-OH precursor solution from step (3) and mix thoroughly to obtain system C;

[0166] (5) The system C from step (4) was placed in an oil bath at 100°C for 24 hours, washed alternately with water and methanol, and dried at 100°C for 12 hours to obtain the composite material of g-C3N4 supported on UiO-66-OH.

[0167] Comparative Example 5

[0168] The difference from Example 4 lies in the amount of graphene oxide added. Specifically, the preparation method of this comparative example UiO-66-OH / GO composite adsorbent includes the following steps:

[0169] (1) Add 1.0g of graphite powder and 0.5g of sodium nitrate to 24mL of concentrated sulfuric acid and stir evenly to obtain system A. Add 3.0g of KMnO4 to system A at a temperature of 0-5℃ and react at a temperature of 20-30℃ for 12h to obtain system B. Place system B in an ice-water bath, add deionized water, place it at room temperature, add 15mL of 30% hydrogen peroxide and continue to react for 0.5-1h. Wash and dry to obtain graphene oxide.

[0170] (2) Disperse 1 mg of graphene oxide (mass fraction of 0.04%) from step (1) into 20 mL of secondary water by ultrasonic treatment to obtain a graphene oxide suspension;

[0171] (3) Accurately weigh 1.7g zirconium oxychloride and 1.0g 2,5-dihydroxyterephthalic acid into a single-necked flask, add 30mL formic acid, and react for 1h under stirring to obtain UiO-66-OH precursor dispersion;

[0172] (4) Add the graphene oxide suspension from step (2) to the UiO-66-OH precursor solution from step (3) and mix thoroughly to obtain system C;

[0173] (5) The system C from step (4) was placed in an oil bath at 100°C for 24 hours, washed alternately with water and methanol, and dried at 100°C for 12 hours to obtain a composite material of graphene oxide supported on UiO-66-OH.

[0174] Performance testing

[0175] The performance tests of Examples 1-9 and Comparative Examples 1-5 were performed as follows, and the test results are recorded in Table 2 below.

[0176] Adsorption performance testing: The adsorption isotherm of CO2 at 25℃ in the pressure range of 0.01–760 mmHg was determined using a TStarII-3000 physical adsorption analyzer manufactured by Micron Technology, Inc. (USA). The experiment was conducted according to the relevant description in the literature "Two microporous CoII-MOFs with dual active sites for highly selective adsorption of CO2 / CH4 and CO2 / N2" (Dalton Trans., 2019, 48, 13541-13545). The specific steps are as follows: A certain mass of adsorbent material was accurately weighed into a sample tube, and the sample was pretreated under vacuum at 120℃ for 4–8 h. Then, the adsorption isotherm at 25℃ was measured. The measurement data are shown in Table 2, and the results are illustrated in the appendix. Figure 4 .

[0177] Table 2 Adsorption performance test results

[0178]

[0179] Combining the above experiments, the data results in Table 2, and the appendix... Figure 4 We can obtain:

[0180] The CO2 adsorption capacities of the solid adsorbents prepared according to the various examples and comparative examples are shown in Table 2. The CO2 adsorption capacity of Comparative Example 1 is 4.12 mmol / g, which is attributed to the large specific surface area, pore volume, and metal sites of MOFs. To improve the pore utilization rate of MOFs, graphene oxide was introduced to adjust the pore properties. Compared with Comparative Example 1, graphene oxide was added in Examples 1-4. The composite adsorbents prepared under these conditions showed a certain degree of improvement in CO2 adsorption capacity, mainly because the introduction of graphene not only increased the specific surface area but also formed new pores.

[0181] Compared to Comparative Example 1, which did not contain graphene oxide, Comparative Examples 2 and 3, by increasing the mass fraction of graphene oxide, actually reduced the CO2 adsorption capacity. This is attributed to the excessive addition of graphene oxide clogging some of the pores of the MOFs, resulting in a decrease in adsorption performance. In Comparative Example 5, by reducing the mass fraction of graphene oxide, the adsorption capacity of the composite material for CO2 remained unchanged or showed no significant change. Based on this, the inventors believe that adding too little graphene oxide cannot effectively improve or significantly improve CO2 adsorption. Furthermore, the inventors also believe that the high cost of preparing graphene oxide increases production costs during large-scale production, thus reducing economic efficiency. Therefore, in this invention, the mass fraction of graphene oxide is reasonably controlled between 0.074% and 0.26%, meaning that a very small amount (in milligrams) of graphene oxide is used, which can improve the CO2 adsorption performance of the composite material. This not only reduces production costs and improves market competitiveness but also has excellent market application prospects.

[0182] Compared to Example 4, in Comparative Example 4, the carrier was replaced with g-C3N4. The introduction of g-C3N4 actually reduced the adsorption capacity of the adsorbent for CO2. This may be because g-C3N4 and MOFs did not form a specific coordination structure, but only pore blockage occurred.

[0183] Based on the above analysis results, graphene oxide was ultimately determined to be the additive support, with an added mass fraction of 0.26%. Simultaneously, similar results were obtained from the composites of other types of MOFs or UiO-66 with different functional groups and GO.

[0184] As can be seen from the product embodiments and comparative examples of this invention, this invention achieves an increase in the CO2 adsorption capacity of the composite adsorbent by generating MOFs in situ on the surface of graphene oxide, thus making it promising for carbon capture.

[0185] The above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. All modifications or applications made in accordance with the above embodiments are within the scope of protection of this technical solution.

[0186] Although specific embodiments of the invention have been described in detail, those skilled in the art will understand that various modifications and substitutions can be made to those details based on all the teachings disclosed, and all such changes are within the scope of protection of this invention. The full scope of this invention is given by the appended claims and any equivalents thereof.

Claims

1. A composite material, characterized in that, The composite material is composed of porous carbon material as carrier and organometallic compound as precursor; the oxygen groups of the porous carbon material are connected to the metal center of the organometallic compound through coordination bonds. The porous carbon material is selected from graphene oxide with a thickness of 0.3~1.0 nm and a sheet diameter of 0.5~10 µm; the organometallic compound is selected from one of UiO-66-OH, Cu-BTC, UiO-66, UiO-66-NO2, UiO-66-NH2, and UiO-66-CH3. The method for preparing the composite material includes the following steps: S1, Preparation of graphene oxide Graphite powder and sodium nitrate were added to concentrated sulfuric acid in sequence and stirred until homogeneous to obtain system A. The temperature of system A was lowered to 0-5℃, KMnO4 was added, the temperature was raised to 20-30℃, and the reaction was carried out for 10-14 hours to obtain system B. System B was placed in an ice-water bath, deionized water was added, and then the system was placed at room temperature. Hydrogen peroxide was added to continue the reaction. The system was washed and dried to obtain graphene oxide. S2, Preparation of graphene oxide suspension The graphene oxide in S1 was dispersed into deionized water by ultrasonic treatment to obtain a graphene oxide suspension. The mass fraction of the added graphene oxide is 0.074%~0.26%; S3, Preparation of precursor solution A precursor solution is obtained by adding a metal salt and an organic ligand to an acidic solvent and reacting under stirring conditions. S4. Formulation of composite materials The graphene oxide suspension prepared by S2 was added to the precursor solution prepared by S3 and mixed evenly to obtain system C. System C was placed in an oil bath for reaction, washed, and dried to obtain the composite material.

2. The composite material according to claim 1, characterized in that, In step S1, hydrogen peroxide is added and the reaction continues for 0.5 to 1 hour.

3. The composite material according to claim 1, characterized in that, In S2, the ultrasonic treatment time is 6-8 hours.

4. The composite material according to claim 1, characterized in that, In S3, the acidic solvent is selected from acetic acid, formic acid, or oxalic acid.

5. The composite material according to claim 1, characterized in that, In S3, the metal salt is zirconium oxychloride or copper nitrate trihydrate.

6. The composite material according to claim 1, characterized in that, In S3, the organic ligand is selected from one of 2,5-dihydroxyterephthalic acid, terephthalic acid, 2-nitroterephthalic acid, 2-methylterephthalic acid, 2-hydroxyterephthalic acid, trimesic acid, or 2-aminoterephthalic acid.

7. The composite material according to claim 1, characterized in that, In S4, system C is placed in an oil bath at 100~120℃ and reacted for 18~24h.

8. An application of the composite material as described in any one of claims 1 to 7, characterized in that, The composite material is used as an adsorbent in the field of adsorption.

9. A method for capturing CO2, characterized in that, The method uses the composite material as described in any one of claims 1 to 7.

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