A copper-zinc bimetallic organometallic framework compound and a synthesis method and application thereof

Abstract

The application discloses a copper-zinc bimetallic organic metal framework compound and a synthesis method and application thereof, and is based on a hydrothermal solvent method and a strong alkali compound surface layer activation process to prepare a novel porous composite material, and the specific steps comprise zinc-based "core" layer MOF material synthesis, surface strengthening activation of the core layer material by using a strong alkali, copper-based loading, in-situ growth of a "shell" layer MOF, and application of the material to CO2 adsorption and capture; the optimal sample has a CO2 adsorption capacity of up to 151.8 cm 3 / g under normal temperature and pressure, a CO2 gas adsorption capacity of up to 271.2 cm 3 / g in a high pressure section, a separation coefficient of the material for 400 ppm CO2 / N2 is up to 26.34, a separation coefficient of the material for 40 / 60 v / v CO2 / H2 is up to 141.07, and after an adsorption-desorption cycle test, the adsorption capacity performance is still retained to be not less than 95%, compared with a traditional single-metal MOF material, the method can significantly improve the adsorption separation performance and stability of the material.

Description

Technical Field

[0001] This invention belongs to the technical field of bimetallic organometallic framework compounds, specifically relating to a copper-zinc bimetallic organometallic framework compound, its synthesis method, and its applications. Background Technology

[0002] Carbon dioxide adsorption and capture technology using porous materials has gained significant attention in recent years due to its advantages in terms of a wide operating temperature window and cycling stability. Developing novel, highly efficient, and environmentally friendly adsorbents is key to expanding the application of carbon dioxide adsorption and capture technology.

[0003] Metal-organic frameworks (MOFs), as a novel material, have emerged as a leading carbon dioxide adsorption material in recent years due to their ultra-high specific surface area, high porosity, and flexible molecular structure. However, the application of MOFs in carbon dioxide capture still faces several challenges: material stability issues, namely, the relatively unstable physicochemical properties of some MOFs make it difficult to meet the actual needs of material recycling in conventional industrial carbon capture sites; and the unstable selective adsorption performance of materials for carbon dioxide gas, especially for low-concentration carbon dioxide, which often results in poor selective adsorption performance, thus seriously affecting their widespread application in direct air capture. Summary of the Invention

[0004] To address the shortcomings of existing materials in carbon capture applications, the present invention aims to provide a copper-zinc bimetallic organometallic framework compound, its synthesis method, and its applications.

[0005] The specific technical solution is as follows:

[0006] 1) Synthesis of zinc-based core MOF (ZIF-8) material:

[0007] Mix 12-20 g / L Zn(NO3)2·6H2O ethanol solution with 15-35 g / L 2-mIm ethanol solution thoroughly and allow the synthesis reaction to proceed for 2-5 hours. Allow the "core" layer material ZIF-8 to precipitate in layers. Slowly pour off the upper ethanol solution, retaining the bottom ZIF-8 suspension. Transfer the suspension to a centrifuge tube and then use a high-speed centrifuge to separate the precipitate for 10 minutes. After the precipitate is separated, pour off the supernatant from the centrifuge tube, add ethanol, and wash the material using a vortex mixer. Repeat the centrifugation-washing step three times to obtain the "core" layer MOF matrix material.

[0008] 2) Surface strengthening and activation of the "core" layer material using strong alkali:

[0009] Pour a saturated NaOH-MeOH solution with a concentration of 200-400 g / L into a centrifuge tube containing the "core" layer MOF matrix material. After dispersing the matrix material precipitate with a vortex mixer, place the centrifuge tube in a rotary shaker and wash for 5-30 minutes to activate the "core" surface layer. Centrifuge to separate the surface-activated "core" material, add ethanol, repeat the above washing steps once, and then centrifuge again to obtain the cleaned surface-activated "core" layer MOF matrix material.

[0010] 3) Copper-based secondary metal load

[0011] A 2.5-150 g / L Cu(NO3)2·3H2O methanol solution was poured into centrifuge tubes containing the activated and cleaned "core" layer MOF matrix material. After dispersing the matrix material precipitate with a vortex mixer, the centrifuge tubes were placed in a rotary shaker for 2-5 hours to perform the second metal copper-based loading. The copper-based loaded precursor material was separated by centrifugation, ethanol was added, and the above cleaning steps were repeated once. Then, the material was centrifuged again to obtain the second metal-loaded and cleaned precursor material.

[0012] 4) In-situ growth of the "shell" layer MOF (MOF-199)

[0013] Saturated H3BTC methanol solution with a concentration of 25-40 g / L was poured into centrifuge tubes containing the second metal-loaded precursor material. After dispersing the matrix material precipitate using a vortex mixer, the centrifuge tubes were placed in a rotary shaker for 2-5 hours to perform in-situ growth of the "shell" layer second metal MOF (MOF-199). The above "core-shell" bimetallic MOF was separated by centrifugation, ethanol was added, and the above washing steps were repeated four times. Then, it was dried at room temperature to obtain the final zinc-copper "core-shell" bimetallic MOF product.

[0014] The beneficial effects of this invention are as follows:

[0015] This invention presents a synthesis process for bimetallic MOF materials combining a hydrothermal solvent method and a strong base activation process. The materials prepared by this method retain relatively high specific surface area and porosity while exhibiting specific adsorption affinity for carbon dioxide gas: the optimal sample group achieved an optimal adsorption capacity of 151.8 cm⁻¹ for carbon dioxide gas at ambient pressure (1 bar, 298.15 K). 3 / g, with a CO2 adsorption capacity as high as 271.2cm³ at high pressure (50 bar, 298.15 K). 3The material exhibits adsorption heats of 21.3 kJ / mol for CO2 at normal pressure and 34.9 kJ / mol at high pressure, representing typical physical adsorption performance. The obtained product demonstrates significant separation efficiency for both low-concentration CO2 at normal pressure (air) and high-concentration CO2 at high pressure (in industrial settings such as coal gas power generation). The optimal sample group shows a separation coefficient of 26.34 for 400 ppm CO2 / N2 and 141.07 for 40 / 60 v / v CO2 / H2. The sample prepared using this synthesis method exhibits exceptional stability in the CO2 adsorption-desorption process, retaining over 95% of its effective adsorption capacity after more than twenty cycles of testing. Attached Figure Description

[0016] Figure 1 This is a comparison diagram of nitrogen adsorption at 77K for the synthesized material in Example 1;

[0017] Figure 2 The image shows the pore size distribution of ZIF-8@MOF-199-2.5 in Example 1.

[0018] Figure 3 The pore size distribution diagram of ZIF-8@MOF-199-25 in Example 1 is shown.

[0019] Figure 4 The image shows the pore size distribution of ZIF-8@MOF-199-75 in Example 1.

[0020] Figure 5 The pore size distribution diagram of ZIF-8@MOF-199-150 in Example 1;

[0021] Figure 6 The pore size distribution diagram is for a pure-phase ZIF-8 reference sample.

[0022] Figure 7 Pore ​​size distribution diagram of pure phase MOF-199 reference sample;

[0023] Figure 8 A comparison of the adsorption capacity and heat of adsorption of the synthesized material for carbon dioxide gas under different pressure ranges and temperatures;

[0024] Figure 9 A comparison of the cyclic adsorption capacity of the synthesized materials for CO2 gas at room temperature and atmospheric pressure.

[0025] Figure 10 Separation curves and dry-point adsorption capacity test plots of ZIF-8@MOF-199-2.5 against a simulated mixture of 400 ppm CO2-N2;

[0026] Figure 11Separation curves and dry-point adsorption capacity test diagrams for ZIF-8@MOF-199-25 against a simulated mixture of 400 ppm CO2-N2;

[0027] Figure 12 Separation curves and dry-point adsorption capacity test diagrams for ZIF-8@MOF-199-75 against a simulated mixture of 400 ppm CO2-N2;

[0028] Figure 13 Separation curves and dry-point adsorption capacity test diagrams for ZIF-8@MOF-199-150 against a simulated mixture of 400 ppm CO2-N2;

[0029] Figure 14 Separation curves and dry-point adsorption capacity test plots for ZIF-8@MOF-199-75 against a simulated 40 / 60 v / v CO2 / H2 mixture;

[0030] Figure 15 Separation curves and dry-point adsorption capacity test plots for ZIF-8@MOF-199-150 against simulated CO2 / H2 mixtures at 40 / 60 v / v. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the protection scope of this invention.

[0032] Example 1: Preparation of synthetic materials with different copper loadings

[0033] 1) Synthesis of zinc-based core MOF (ZIF-8) material:

[0034] 15 g of Zn(NO3)2·6H2O was ultrasonically dispersed and dissolved in 1 L of anhydrous ethanol to prepare a Zn(NO3)2·6H2O ethanol solution; 32 g of 2-mIm (dimethylimidazole) was dissolved in 1 L of anhydrous ethanol to prepare a 2-mIm ethanol solution; 200 mL each of the Zn(NO3)2·6H2O ethanol solution and the 2-mIm ethanol solution were measured and thoroughly mixed by magnetic stirring (500 r / min). The synthesis reaction was carried out for 2 hours, and the "core" layer material ZIF-8 was allowed to precipitate in layers. The upper ethanol solution was slowly poured off, while the bottom ZIF-8 suspension was retained. The suspension was transferred to a 50 mL centrifuge tube, and the precipitate was separated by high-speed centrifugation for 10 minutes. After the precipitate was separated, the supernatant of the centrifuge tube was poured off, ethanol was added, and the material was washed by vortex mixer. The centrifugation-washing steps were repeated three times to obtain the "core" layer MOF matrix material by centrifugation.

[0035] 2) Surface strengthening and activation of the "core" layer material using strong alkali:

[0036] Prepare a 400 g / L saturated NaOH-MeOH solution. Pour the above saturated NaOH-MeOH solution into a centrifuge tube containing the "core" layer MOF matrix material (fill to the 50 mL mark). After dispersing the matrix material precipitate with a vortex mixer, place the centrifuge tube in a rotary shaker for 5 minutes to activate the "core" surface layer. Centrifuge to separate the surface-activated "core" material, add ethanol, repeat the above washing steps once, and then centrifuge again to obtain the cleaned surface-activated "core" layer MOF matrix material.

[0037] 3) Copper-based secondary metal load

[0038] 2.5 g, 25 g, 75 g, and 150 g of Cu(NO3)2·3H2O were dissolved in 1 L of anhydrous methanol to prepare Cu(NO3)2·3H2O methanol solutions of different concentrations. The Cu(NO3)2·3H2O methanol solutions of different concentrations were poured into centrifuge tubes containing the activated and cleaned "core" layer MOF matrix material (filled to the 50 mL mark). After dispersing the matrix material precipitate with a vortex mixer, the centrifuge tubes were placed in a rotary shaker for 2 hours to perform the second metal copper-based loading. The copper-based loaded precursor material was separated by centrifugation, ethanol was added, and the above cleaning steps were repeated once. Then, centrifugation was performed again to obtain the second metal-loaded and cleaned precursor material.

[0039] 4) In-situ growth of the "shell" layer MOF (MOF-199)

[0040] Prepare a 40 g / L saturated H3BTC methanol solution. Pour the H3BTC methanol solution into centrifuge tubes containing the second metal-loaded precursor material (fill to the 50 mL mark). After dispersing the matrix material precipitate using a vortex mixer, place the centrifuge tubes in a rotary shaker for 2 hours to perform in-situ growth of the "shell" layer second metal MOF (MOF-199). Centrifuge to separate the above "core-shell" bimetallic MOF, add ethanol, wash four times repeatedly, and then dry at room temperature to obtain the final zinc-copper "core-shell" bimetallic MOF products, named ZIF-8@MOF-199-2.5, ZIF-8@MOF-199-25, ZIF-8@MOF-199-75, and ZIF-8@MOF-199-150, respectively.

[0041] Characterization of basic physical and chemical properties of materials

[0042] 1) Material specific surface area and pore distribution

[0043] The testing equipment used was a specific surface area and pore size analyzer manufactured by Bestech, model BSD-660M. The specific testing procedures are as follows:

[0044] The empty sample tube was weighed and the sample was degassed and activated. The mass of the empty test tube was weighed using a 0.01 g balance. Then, the test sample (50.0 mg) was filled into the test tube, and the sample tube was assembled onto the test well station. It was heated to 110°C and vacuumed for in-situ activation for 2 hours. Liquid nitrogen was prepared by adding liquid nitrogen to a Dewar flask to about 5 cm above the mouth of the flask, and then placing the Dewar flask on the instrument test stage. The liquid nitrogen (77K) - micropore test (60 points) program was selected on the instrument operation interface, and the next operation was performed according to the instructions. After the instrument test process was completed, the sample tube was removed, and the mass of the sample tube and the degassed sample was weighed. The relevant mass information of the sample was entered into the test analysis software. Based on the nitrogen adsorption-desorption data, the specific surface area of ​​the sample was calculated using the BET equation, the micropore ratio was calculated using the t-Plot model, and the pore size distribution was calculated using the DFT pore size distribution model.

[0045] A comparison of the nitrogen adsorption isotherm and pore size distribution of the material is shown in the figure below. Figure 1 and Figures 2 to 7 As shown, by Figure 1 It can be seen that the nitrogen adsorption capacity gradually increases with the increase of copper salt content. Based on the values ​​obtained from BET surface area analysis (Table 1), the best specific surface area performance group for the synthesized material is ZIF-8@MOF-199-150, with a BET specific surface area of ​​1897.7 m². 2 / g.

[0046] Figure 2Aperture distribution diagram of ZIF-8@MOF-199-2.5; Figure 3 Aperture distribution diagram of ZIF-8@MOF-199-25; Figure 4 Aperture distribution diagram of ZIF-8@MOF-199-75; Figure 5 Aperture distribution diagram of ZIF-8@MOF-199-150; Figure 6 The pore size distribution diagram is for a pure-phase ZIF-8 reference sample. Figure 7 The pore size distribution diagram is for a pure phase MOF-199 reference sample. The ZIF-8 and MOF-199 matrix materials in the figure are used as reference samples. The synthesis method is the same as that reported in conventional literature (Li Z, Cao Z, Grande C, et al. A phase conversion method to anchor ZIF-8 onto a PAN nanofiber surface for CO2 capture[J]. RSC advances, 2022, 12(2): 664-670.). The difference between the reference materials and other materials mentioned in the figure, such as ZIF-8@MOF-199-2.5, ZIF-8@MOF-199-25, ZIF-8@MOF-199-75, ZIF-8@MOF-199-150, is that the reference materials only need to be prepared by mixing the corresponding metal salt-methanol solution with the organic ligand-methanol solution. The process operation parameters are the same as those reported in previous literature (Azhar MR, Abid HR, Sun H, et al.). One-pot synthesis of binary metal-organic frameworks (HKUST-1 and UiO-66) for enhanced adsorption and removal of water contaminants[J]. Journal of colloid and interface science, 2017, 490: 685-694., will not be elaborated further here.

[0047] 2) Actual density of the material

[0048] The testing equipment used was a true density (skeletal density) analyzer manufactured by Bestech, model BSD-TD. The test employed the helium gas expansion method (exhaust method), and the specific testing procedures are as follows:

[0049] ① Weighing the empty sample stage and activating the sample: Weigh the empty test stage using a 0.01 g balance, measure 3 mL of test sample and place it in the test column, assemble it onto the instrument test stage, and turn on helium to purge and degas in situ for 1 hour.

[0050] ② On the instrument operation interface, select the helium gas expansion method test program, specify 6 test times, and start the test program.

[0051] ③ Data analysis: After the test, remove the sample stage, weigh the sample stage and the degassed sample, and input the relevant mass information of the sample into the test analysis software. Calculate the true density of the sample based on the test data.

[0052] The average values ​​of the key parameters of the basic physicochemical properties of the synthesized materials obtained through the examples are shown in Table 1.

[0053] Table 1 Summary of key parameters of basic physicochemical properties of synthetic materials

[0054]

[0055] From Table 1, Figures 1 to 7 It can be concluded that the ZIF-8@MOF-199-75 and ZIF-8@MOF-199-150 materials prepared by this method have relatively stable density, retain a relatively high specific surface area pore structure, and have a large proportion of micropores, which indicates that these two materials theoretically have a greater advantage in CO2 adsorption.

[0056] Example 2: Carbon dioxide gas adsorption under different pressure scenarios

[0057] 1) Adsorption of CO2 gas by the material in normal and high pressure scenarios

[0058] In this embodiment, BSD-660M and BSD-PH instruments manufactured by Bestech were selected respectively. The static volumetric method was used to analyze the synthesized samples under different pressure and temperature conditions (0-1 bar / 0-50 bar; 25 / 0℃). Figure 8 (a), (b), and (d) in the figure) were subjected to adsorption-desorption atmospheric pressure / saturated adsorption pressure tests (considering the critical phase transition point of CO2 gas, the pressure test range was selected as 0-30 bar in the saturated adsorption test scenario at 0℃). Figure 8 (e)). And based on the Clausius-Clapeyron equation, the heat of adsorption of CO2 gas by the material is calculated by fitting. Figure 8 (c) and (f) in the text. The specific test steps are as follows:

[0059] The empty sample tubes were weighed and the samples were degassed and activated. The mass of the empty test tubes was weighed using a 0.01 g / L balance. The test samples were then filled into the test tubes (approximately 50 mg for low-pressure adsorption BSD-660M; approximately 400 mg for high-pressure adsorption BSD-PH). The sample tubes were then assembled onto the test well platform, heated to 110°C, and vacuumed for in-situ activation for 2 hours. A high-precision temperature-controlled water bath was prepared, with the water bath temperature set to the experimental temperature (0°C or 25°C). The water bath was placed on the automatic lifting platform of the relevant testing equipment. On the instrument operation interface, the program "Constant Temperature Water Bath - CO2 Adsorbate - Input Test Pressure Range (0-1 bar or 0-50 bar) - Adsorption-Desorption Test (34 points)" was selected, and the next step was performed according to the instructions. After the instrument testing process was completed, the sample tubes were removed, and the mass of the sample tubes and the degassed samples was weighed. The relevant sample mass information was entered into the testing and analysis software.

[0060] like Figure 8 As shown, Figure 8 (a) in the figure is a comparison of the adsorption of CO2 gas by different materials under the conditions of 0-1 bar and 25 °C; Figure 8 (b) in the figure is a comparison of the adsorption of CO2 gas by different materials under the conditions of 0-1 bar and 0℃; Figure 8 (c) in the figure is a comparison of the adsorption heat of CO2 gas on the material at normal pressure, calculated based on (a) and (b). Figure 8 (d) in the figure is a comparison of the adsorption of CO2 gas by different materials under the conditions of 0-50 bar and 25 °C; Figure 8 (e) in the figure is a comparison of the adsorption of CO2 gas by different materials under the conditions of 0-30 bar and 0 ℃; Figure 8 (f) is a comparison of the adsorption heat of CO2 gas on the material in the low-pressure section, calculated based on the fitting of (d) and (e).

[0061] Test results show that the sample synthesized by this method (ZIF-8@MOF-199-75) achieves adsorption capacities of up to 151.8 cm⁻¹ for CO₂ gas at both low pressure (0-1 bar) and high pressure (0-50 bar) at room temperature. 3 / g, 271.2 cm 3 / g, and the adsorption heats corresponding to the CO2 adsorption process of the synthesized material are 21.3kJ / mol and 34.9 kJ / mol, respectively, both of which are lower than 40 kJ / mol, belonging to the typical category of physical adsorption.

[0062] 2) The material's cyclic adsorption performance for CO2 gas

[0063] The adsorption-desorption process of CO2 gas by the synthesized material at room temperature and low pressure was investigated. A cyclic adsorption program was used in the test procedure, and 20 rounds of cyclic adsorption-desorption tests were conducted on the synthesized material involved in this invention. The results are as follows: Figure 9 As shown, Figure 9 (a) in the figure is a comparison of the adsorption capacity of ZIF-8@MOF-199-2.5; Figure 9 (b) in the figure is a comparison of the adsorption capacity of ZIF-8@MOF-199-25; Figure 9 (c) in the figure is a comparison of the adsorption capacity of ZIF-8@MOF-199-75; Figure 9 (d) in the figure is a comparison of the adsorption capacity of ZIF-8@MOF-199-150.

[0064] Tests show that the materials involved in this invention all exhibit excellent cycling stability, with an adsorption performance degradation of no more than 5% after 20 cycles. In particular, the materials ZIF-8@MOF-199-75 and ZIF-8@MOF-199-150 involved in this invention showed effective adsorption capacities of 132.4 and 122.3 cm³, respectively, after 20 adsorption cycles. 3 / g. This is still far higher than the CO2 adsorption capacity of the two pure-phase "core" and "shell" MOF matrix materials mentioned above, and also far higher than conventional MOF materials used for the physical adsorption of CO2 (current reports show that the adsorption capacity of MOF materials based on physical adsorption for CO2 capture is generally concentrated in the range of 40-90 cm⁻¹ under the same room temperature and atmospheric pressure conditions). 3 / g). The test results also indicate that, due to its high adsorption capacity and stable cyclic adsorption performance, the material is expected to be widely used in the field of commercial carbon capture materials.

[0065] Example 3: Gas separation of CO2 component from mixed gas by the material

[0066] 1) Material for gas separation (direct air capture) in low-concentration CO2 gas scenarios at normal pressure

[0067] In this embodiment, the synthetic sample involved in this invention was used to study the separation and capture of simulated air containing 400 ppm CO2 at ambient pressure (1 bar). The testing equipment was a Bestar Corporation competitive breakthrough curve analyzer (BSD-MAB), and the specific testing procedure is as follows:

[0068] The empty sample tube was weighed and the sample was degassed and activated. The mass of the empty test tube was weighed using a 0.01 g / L balance. The test sample was then filled into a 0.5 cm diameter breakthrough curve test tube (3 mL). The filling length was measured and recorded (for subsequent breakthrough curve testing). The sample and test tube were weighed again. The sample tube was then assembled onto the test well platform, heated to 110°C, and evacuated for in-situ activation for 2 hours. A 400 ppm CO2-N2 mixture was introduced, and the inlet valve of the test tube was closed. After 30 minutes, the mass spectrometry curve on the testing software screen stabilized. Once the mass spectrometry curve stabilized, the test recording program was started, the inlet valve of the test tube was opened, and the breakthrough curve was recorded. After the breakthrough curve stabilized a second time, the current test data was saved. The sample tube was removed, and the mass of the sample tube and the degassed sample was weighed. The relevant sample mass information was entered into the testing analysis software.

[0069] Figure 10 Separation curves and dry-point adsorption capacity test graphs for ZIF-8@MOF-199-2.5; Figure 11 Separation curve and dry-point adsorption capacity test graph for ZIF-8@MOF-199-25; Figure 12 Separation curves and dry-point adsorption capacity test results for ZIF-8@MOF-199-75; Figure 13 Separation curves and dry-point adsorption capacity test diagrams for ZIF-8@MOF-199-150.

[0070] As shown in Table 2, the test results indicate that, in terms of parameters such as breakthrough time, separation coefficient, and diffusion coefficient, although the ZIF-8@MOF-199-2.5 sample did not perform ideally in separating CO2 gas from the mixed gas, both ZIF-8@MOF-199-75 and ZIF-8@MOF-199-150 materials showed significant separation efficiency for low-concentration (400 ppm) CO2 gas mixtures. The breakthrough time and adsorption capacity of CO2 gas were significantly higher than those of pure-phase "core" and "shell" MOF matrix materials, with separation coefficients of 17.42 and 26.34, respectively, demonstrating a significant improvement in their separation performance. It is worth noting that the diffusion coefficients of the synthesized materials involved in this invention are all lower than those of the aforementioned pure-phase matrix MOFs. This is because the adsorption performance of the materials themselves for CO2 gas is significantly improved, delaying and retarding the non-adsorption diffusion of the materials. Furthermore, the ZIF-8@MOF-199-150 sample showed a flow-dry point adsorption capacity of 0.033 cm⁻¹ for 400 ppm CO2 gas. 3 / g is the optimal value for the synthesized composite material sample. Therefore, this test also shows that ZIF-8@MOF-199-150 is the optimal sample group for DAC air capture in this experimental system.

[0071] Table 2 Summary of test parameters for separation of synthetic materials in DAC direct air trap scenario

[0072] ;

[0073] Note: Table 2 The formula for calculating the separation coefficient is: S=(X1 / Y1) / (X2 / Y2), where X1 / Y1 is the mole fraction of component 1 in the adsorbed phase and the mole fraction of component 1 in the gas phase; X2 / Y2 is the mole fraction of component 2 in the adsorbed phase and the mole fraction of component 2 in the gas phase.

[0074] 2) Gas separation of materials in high-pressure, high-concentration CO2 gas scenarios (such as coal gas power plants).

[0075] In this embodiment, the preferred synthetic sample materials ZIF-8@MOF-199-75 and ZIF-8@MOF-199-150 involved in this invention were used to study the separation and capture of a simulated coal gasification power generation mixture of 40 / 60 v / v CO2 / H2 under a high-pressure environment (30 bar, simulating a real industrial scenario). The testing equipment and procedures were partially consistent with step 1) of Example 3, except that the test sample tubes were replaced with high-pressure resistant steel equipment.

[0076] Figure 14 Separation curves and dry-point adsorption capacity test results for ZIF-8@MOF-199-75; Figure 15 Separation curves and dry-point adsorption capacity test plots for ZIF-8@MOF-199-150

[0077] As shown in Table 3, the test results demonstrate that the samples ZIF-8@MOF-199-75 and ZIF-8@MOF-199-150 synthesized in this invention exhibit significant separation effects on the simulated CO2 / H2 mixture of 40 / 60 v / v. Their breakthrough times for CO2 at the breakthrough point are 2317.1 S / g and 2024.0 S / g, respectively, far exceeding the breakthrough time for H2 (Table 3), indicating a significant separation effect of the materials on the mixture. The ZIF-8@MOF-199-150 sample shows a high separation coefficient of 141.07 for CO2 to H2 at the breakthrough point, demonstrating its excellent separation performance. Furthermore, even with an objective volume partial pressure of 60%, the saturated adsorption capacity of the two preferred materials synthesized in this invention for CO2 at the dry point is 206.8 cm³. 3 / g and 168.6 cm 3 / g, which is much higher than other MOF materials based on physical adsorption reported in existing literature.

[0078] Table 3. Summary of key parameters for high-pressure (30 bar) breakthrough separation test of synthetic materials against simulated CO2 / H2 mixtures of 40 / 60 v / v.

[0079]

[0080] The above description is only a preferred experimental embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the scope of protection of the present invention.

Claims

1. A method for synthesizing a copper-zinc bimetallic organometallic framework compound, characterized in that, Includes the following steps: 1) Synthesis of zinc-based "core" layer material: Prepare zinc nitrate ethanol solution and dimethylimidazole ethanol solution respectively, mix them and carry out the synthesis reaction for 2-5 hours. After the reaction is completed, let it stand and separate into layers. Slowly pour out the upper layer solution, centrifuge the bottom suspension, add ethanol to wash the supernatant, and repeatedly centrifuge and wash to obtain zinc-based "core" layer material; 2) Surface strengthening and activation of the "core" layer material using strong alkali: The zinc-based "core" layer material from step 1) was washed in a saturated strong alkali solution of sodium hydroxide-methanol for surface strengthening and activation, followed by centrifugation and cleaning; 3) Copper-based second metal loading: The material activated in step 2) is immersed in a copper nitrate methanol solution to achieve initial loading of a copper-based second metal on its surface; 4) In-situ growth of the "shell" layer: The precursor material loaded with the copper-based second metal in step 3) is immersed in a saturated methanol solution of trimellitic acid to achieve in-situ growth of the second metal in the "shell" layer. After centrifugation and washing, the copper-zinc bimetallic organometallic framework compound is obtained. The copper nitrate methanol solution in step 3) is prepared at a concentration of 75-150 g / L.

2. The method for synthesizing a copper-zinc bimetallic organometallic framework compound according to claim 1, characterized in that, In step 1), the zinc nitrate ethanol solution is prepared at a concentration of 12-20 g / L, and the dimethylimidazole ethanol solution is prepared at a concentration of 15-35 g / L.

3. The method for synthesizing a copper-zinc bimetallic organometallic framework compound according to claim 1, characterized in that, In step 2), the concentration of the saturated strong alkaline solution of sodium hydroxide-methanol is 200-400 g / L, and the washing time is 5-30 minutes.

4. The method for synthesizing a copper-zinc bimetallic organometallic framework compound according to claim 1, characterized in that, The soaking time for step 3) is 2-5 hours.

5. The method for synthesizing a copper-zinc bimetallic organometallic framework compound according to claim 1, characterized in that, In step 4), the concentration of the saturated methanol solution of pyromellitic acid is 25-40 g / L, and the soaking time is 2-5 hours.

6. A copper-zinc bimetallic organometallic framework compound prepared by the synthetic method according to any one of claims 1-5, characterized in that, Using zinc-based material as the "core" layer, copper-based material is grown in situ using pyromellitic acid solution to achieve the "shell" layer.

7. The application of a copper-zinc bimetallic organometallic framework compound as described in claim 6 in adsorption-based carbon capture.

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