Large-scale aqueous-based preparation process of a zinc-based MOF material and applications thereof

Abstract

The application belongs to the field of material and chemical process research, and particularly relates to a large-scale water-based preparation process of a zinc-based MOF material and application thereof, and comprises the following steps: configuring a mixed solution of a zinc salt and an anion regulator; configuring a solution of a first ligand 1,2,4-triazole and derivatives thereof; configuring a second ligand aqueous solution, adding an alkali, and configuring a mixed solution of the second ligand and the alkali; mixing the three solutions and adding them into a reactor, performing a reaction, filtering and separating after the reaction, washing with deionized water, and drying to obtain a zinc-based metal organic framework material. The application utilizes the synergistic effect of the anion regulator for regulating the crystal growth process and the alkali for promoting the deprotonation of the second ligand, so that the MOF crystal can be prepared within several minutes, the production efficiency is greatly improved, and an unprecedented space-time yield is achieved.

Description

Technical Field

[0001] This invention belongs to the field of materials and chemical processes research, and specifically relates to a large-scale water-based preparation process for zinc-based MOF materials and its application. Background Technology

[0002] Environmental pollution and energy crises caused by fossil fuel extraction have prompted the search for cleaner and more efficient energy sources. Natural gas, as a low-cost clean energy source, is widely used in both residential and industrial applications due to its high combustion efficiency. However, the challenges of global energy transition and extraction are intensifying, and traditional natural gas supplies can no longer meet the ever-increasing demand. Unconventional gas sources such as coalbed methane, shale gas, and biogas have large reserves and wide distribution, but their high N2 content hinders their application. CH4 is a major contributor to global warming, with an impact approximately 21 times that of CO2, and due to the underutilization of low-quality natural gas, CH4 already accounts for more than 30% of the greenhouse effect [Fletcher, SEM, Schaefer, H., Rising methane: A new climate challenge[J]. Science. 2019, 364 (6444): 932-933.]. To address environmental and energy shortages, it is urgent to capture CH4 from low-quality natural gas. Metal-organic frameworks (MOFs), as a novel type of adsorbent, have shown remarkable potential in CH4 / N2 separation due to their ultra-high specific surface area, diverse chemical structures, and modifiable pore sizes [Chang M., Zhao Y., et al., Methane-trapping metal–organic frameworks with analiphatic ligand for efficient CH4 / N2 separation[J].Sustain.Energ. Fuels, 2020, 4(1):138-142.]. However, the lack of green, low-cost, and large-scale production methods has greatly limited their application.

[0003] Zinc-based metal-organic frameworks (MOFs) constructed from triazole layers and their analogues and multidentate ligands are considered promising industrial separation adsorbents due to their high stability, low cost, and suitable pore size. However, due to the low solubility of the ligands, the common production process for these materials is still solvothermal synthesis. This process is characterized by the use of large amounts of organic solvents and harsh reaction conditions, resulting in severe pollution, high cost, high energy consumption, slow reaction, low yield, low space-time yield, and serious safety issues, making it difficult to meet the needs of industrial production [Chen K.-J., Lin R.-B., et al., New Zn-Aminotriazolate-Dicarboxylate Frameworks: Synthesis, Structures, and Adsorption Properties [J]. Cryst. Growth Des., 2013(5): 2118-2123.]. Patent CN116003815A discloses the preparation of a carbonate-constructed microporous zinc-based MOF material, ZnAtzCO3, through a solvothermal reaction of zinc salt, 3-amino-1,2,4-triazole, N,N-dimethylformamide, and water. The carbonate ions generated from the high-temperature decomposition of N,N-dimethylformamide are used to construct the novel microporous MOF material, resulting in high cost and significant environmental impact. Similarly, patent CN112105764A discloses a green and efficient synthesis method for CALF-20, characterized by using zinc salt, triazole, and oxalic acid as raw materials and water and ethanol as solvents. However, this reaction process inevitably uses lower alcohols as organic solvents, and the product quality and purity are affected in many ways, impacting production costs, safety, and product quality under large-scale synthesis conditions. Therefore, developing a green, economical, and large-scale pure water-based synthesis method for producing triazole layers and their derivatives and multidentate ligands of zinc-based metal-organic framework materials is of great significance.

[0004] In summary, current methods for synthesizing zinc-based metal-organic frameworks composed of triazole layers and their derivatives and multidentate ligands have the following problems:

[0005] (1) The use of organic solvents such as ethanol and DMF during the reaction process will not only increase production and post-processing costs, but also cause serious environmental pollution.

[0006] (2) The reaction time is long and the reaction temperature is high, which greatly increases the operating cost and will also create serious hidden dangers.

[0007] (3) Due to the limitation of ligand solubility in water, MOFs are difficult to synthesize in water, and there are few reports of pure water-based synthesis routes. Moreover, conventional synthesis methods are heavily polluting, energy-intensive, have low space-time yields, and require high reactors, making it difficult to produce MOFs on a large scale.

[0008] (4) Conventional synthesis methods lack effective means to control crystal growth, making it difficult to control the particle size of MOFs synthesized on a large scale, resulting in unreliable product quality and even performance degradation. Summary of the Invention

[0009] The purpose of this invention is to overcome the shortcomings of existing metal-organic framework (MOF) material synthesis processes. By utilizing the synergistic effect of monodentate anion regulators to regulate crystal growth and alkali-promoted ligand deprotonation to improve ligand solubility in water, this invention provides a large-scale water-based preparation process for zinc-based MOF materials and its application. This addresses the serious pollution caused by the use of large amounts of organic solvents in the production and post-processing of metal-organic framework materials, and overcomes the disadvantages of slow reaction rates and low space-time yields in traditional production processes.

[0010] This invention is achieved through the following technical solution:

[0011] A large-scale water-based preparation process for zinc-based MOF materials includes the following steps:

[0012] Prepare a mixed solution of zinc salt and anion regulator; prepare a solution of the first ligand 1,2,4-triazole and its derivatives; prepare an aqueous solution of the second ligand, add alkali, and prepare a mixed solution of the second ligand and alkali; mix the three solutions and add them to the reactor to carry out the reaction. After the reaction is completed, filter and separate the solutions, wash with deionized water, and dry to obtain the zinc-based metal-organic framework material.

[0013] Furthermore, the monodentate ligand anion modifier is one of formate, acetate, or trifluoroacetate ions.

[0014] Furthermore, the zinc salt is one of zinc sulfate, zinc chloride, zinc nitrate, and zinc acetate, and the alkali is one or more of sodium hydroxide, potassium hydroxide, calcium hydroxide, and aluminum hydroxide.

[0015] Furthermore, the first ligand is 1,2,4-triazole and its derivatives, and the second ligand is characterized by containing one or more carboxylic acid groups, including aromatic monocarboxylic or polycarboxylic acids, heterocyclic monocarboxylic or polycarboxylic acids, carbonic acid, aliphatic monocarboxylic or polycarboxylic acids, etc., and other positions of the main chain, aromatic ring or heterocycle can be independently selected from one or more of hydrogen, hydroxyl, nitro, amino, methyl, ether and halide groups.

[0016] Furthermore, the molar ratio of the second ligand to the base is 1:(2-5); the molar ratio of the second ligand to the anion modifier is 1:(1-6).

[0017] Furthermore, the mixing order of the three solutions is as follows: first, the mixture of zinc salt and anion regulator is mixed with the solution of the first ligand 3-amino-1,2,4-triazole and its derivatives, and then the mixture of the second ligand and base is added. The reaction conditions are: 20-80℃ for 1-12 hours.

[0018] Furthermore, the mixing order of the three solutions is as follows: first, the solution of 3-amino-1,2,4-triazole and its derivatives and the mixed solution of the second ligand and the base are mixed, and then the mixed solution of zinc salt and anion regulator is added. The reaction conditions are: reaction at 20-80℃ for 5-120 min.

[0019] A second objective of this invention is to provide the application of the zinc-based MOF material in the separation of CH4 and N2.

[0020] The beneficial technical effects of the present invention are as follows:

[0021] (1) This invention utilizes the synergistic effect of regulating the crystal growth process by an anion regulator and promoting the deprotonation of the second ligand by the base to prepare MOF crystals with high specific surface area, good morphology and high quality in a few minutes, which greatly improves production efficiency and has an unprecedented space-time yield.

[0022] (2) In the production and cleaning process, the present invention uses water as the solvent and does not use any organic solvents such as ethanol, methanol, DMF, etc., which not only greatly reduces the production cost and waste liquid treatment cost, but also minimizes the pollution to the environment.

[0023] (3) The reaction of the present invention can be carried out under normal pressure, and the synthesis temperature can be as low as room temperature. High pressure is not required. The low reaction temperature not only reduces cost, energy consumption and requirements on the reactor, but also improves production safety performance.

[0024] (4) This invention utilizes a regulator / base-assisted system strategy to achieve precise control of MOF particle size;

[0025] (5) The MOF material synthesized in this invention exhibits excellent CH4 and N2 gas adsorption and separation performance, demonstrating a high separation factor. Compared with other MOF material adsorbents, this type of MOF has low production cost, is simple, green, and can be prepared on a large scale, providing research for industrial applications. Attached Figure Description

[0026] Figure 1 (a) is a structural diagram of Example 1;

[0027] Figure 1 (b) is a structural diagram of Example 28;

[0028] Figure 1(c) is a structural diagram of Example 29;

[0029] Figure 1 (d) is a structural diagram of Example 30;

[0030] Figure 1 (e) is a structural diagram of Example 31;

[0031] Figure 1 (f) is a structural diagram of Example 32.

[0032] Figure 2 The XRD patterns are those of Examples 1-5.

[0033] Figure 3 The nitrogen adsorption isotherms are from Examples 1-4.

[0034] Figure 4 The XRD patterns (a) and nitrogen adsorption isotherms (b) of Examples 9-12 are shown.

[0035] Figure 5 The images shown are (a) XRD patterns and (b) nitrogen adsorption isotherms for Examples 12-15.

[0036] Figure 6 The image shows the SEM spectra of Zn2(atz)2ipa-Y, where Y represents 20℃, 40℃, 60℃, and 80℃.

[0037] Figure 7 The image shows the XRD pattern of Zn2(atz)2ipa-Y, where Y represents 20℃, 40℃, 60℃, and 80℃.

[0038] Figure 8 (a) Nitrogen adsorption isotherm and (b) Yield vs. BET bar graph for Zn2(atz)2ipa-Y, where Y represents 20℃, 40℃, 60℃, and 80℃.

[0039] Figure 9 The images are SEM images of Examples 19-22.

[0040] Figure 10 The images shown are (a) XRD pattern and (b) nitrogen adsorption isotherm of Example 21.

[0041] Figure 11 The XRD pattern of Example 22 changes over time.

[0042] Figure 12 The XRD pattern of Example 23 changes over time.

[0043] Figure 13 The XRD pattern of Example 24 changes over time.

[0044] Figure 14 This is the nitrogen adsorption isotherm of Example 24.

[0045] Figure 15 The XRD pattern is shown in Example 27.

[0046] Figure 16 The XRD pattern is shown in Example 28.

[0047] Figure 17 The XRD patterns (a) of Examples 29 and 30 and the SEM pattern (b) of Example 29 are shown.

[0048] Figure 18 The image shown is the XRD pattern of Example 31.

[0049] Figure 19 The XRD pattern is shown in Example 32.

[0050] Figure 20 The single-component (CH4 and N2) adsorption isotherms of Zn2(atz)2ipa at 298 K (a) and 273 K (b). (c) Schematic diagram of CH4 adsorption regeneration at 298 K; Breakthrough curves of Zn2(atz)2ipa at 298 K and 1 bar with CH4 / N2 ratios of (d) 50:50, (e) 30:70 and (f) 15:85. Detailed Implementation

[0051] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention. It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the present invention.

[0052] Furthermore, regarding the numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, are also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0053] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar to or equivalent to those described herein may be used in the implementation or testing of this invention.

[0054] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0055] Example 1

[0056] A mixture of zinc salt and anion regulator was prepared by dissolving Zn(NO3)2•6H2O (1.192 g, 4 mmol) and sodium acetate (0.984 mg, 12 mmol) in 10 mL of water.

[0057] 3-Amino-1,2,4-triazole (0.336 g, 4 mmol) was dissolved in 10 mL of water to prepare a 3-amino-1,2,4-triazole solution;

[0058] Sodium isophthalate (Na2ipa) solution is prepared by dissolving NaOH (0.160 g, 4 mmol) and isophthalic acid (0.332 g, 2 mmol) in 10 mL of water.

[0059] A solution of 3-amino-1,2,4-triazole was first mixed with a solution of sodium isophthalate (Na2ipa), followed by the addition of a mixture of zinc salt and anion modifier. The mixture was then stirred at 60°C for 2 hours, filtered, washed with deionized water, and vacuum dried at 120°C for 12 hours to obtain the MOF product Zn2(atz)2ipa, the structural diagram of which is shown below. Figure 1 As shown in figure a, in its structure, each Zn(II) ion is coordinated in a distorted tetrahedral geometry by two carboxyl oxygen atoms from the isophthalic acid anion and three nitrogen atoms from three 3-amino-1,2,4-triazolium ions. The structure of Zn2(atz)2ipa has a one-dimensional channel (void = 26.6%)10 with a maximum and minimum pore size of 5.5 Å and 2.8 Å, respectively. The amino groups of the atz-ligands point towards the spherical cavities, but only hydrogen atoms, not nitrogen atoms, are exposed on the pore surface.

[0060] Example 2

[0061] The difference between Example 2 and Example 1 is that the amount of sodium acetate added is 8 mmol (ipa). 2- / OAc - (1 / 4), meaning the remaining conditions are exactly the same.

[0062] Example 3

[0063] The difference between Example 3 and Example 1 is that the amount of sodium acetate added is 4 mmol (ipa). 2- / OAc - :1 / 1), meaning the remaining conditions are complete.

[0064] Example 4

[0065] The difference between Example 4 and Example 1 is that the amount of sodium acetate added is 0.5 mmol (ipa). 2- / OAc - (4 / 1), meaning the remaining conditions are complete.

[0066] Example 5

[0067] The difference between Example 5 and Example 1 is that the amount of sodium acetate added is 0 mmol (ipa). 2- / OAc - :1 / 0), meaning the remaining conditions are complete.

[0068] Examples 1-5 investigated the effect of acetate ions on the reaction results, and the results are shown below: Sodium acetate was introduced into MOF synthesis for the first time as a regulator, and its amount significantly affected the properties of the MOF product. When the amount of sodium acetate added was 0, no formation of the Zn2(atz)2ipa target MOF was observed, while increasing its amount led to a continuous increase in the crystallinity of the sample, showing a trend of first increasing and then leveling off, with the crystallinity increasing with IPa. 2- The ratio with sodium acetate was increased from 1:1 to 1:6 (see Table 1 and 2). Figure 2 The yield increased significantly, from 36% to 82%, while the BET specific surface area increased slightly (see...). Figure 3 Therefore, IPA 2- and OAc - The preferred molar ratio is 1:(1-6).

[0069] Table 1. Effect of sodium acetate addition on yield and BET

[0070]

[0071] Example 6

[0072] The difference between Example 6 and Example 2 is that the metal salt used is zinc sulfate, while the other conditions are the same.

[0073] Example 7

[0074] The difference between Example 7 and Example 2 is that the metal salt used is zinc chloride, while the other conditions are the same.

[0075] Example 8

[0076] The difference between Example 8 and Example 2 is that the metal salt used is zinc acetate. Since the metal salt contains acetate ions, there is no need to add sodium acetate. The other conditions are the same.

[0077] Examples 2 and 6-8 were mainly to investigate the effect of metal salts on the reaction. The results are shown in Table 2. Different metal salts had little effect on the yield. Zinc acetate was the preferred choice after comprehensive comparison.

[0078] Table 2. Effects of metal salts on yield and BET

[0079]

[0080] Example 9

[0081] A 0.3925 mol / L solution of zinc salt and anion regulator was prepared by placing Zn(OAc)2·2H2O (8.595 g; 0.03925 mmol) in a 100 ml volumetric flask, adding water;

[0082] 3-Amino-1,2,4-triazole (5.6 g, 0.06675 mmol) was placed in a 100 ml volumetric flask, and water was added to prepare a 0.6675 mol / L 3-amino-1,2,4-triazole solution.

[0083] NaOH (7.802 g, 0.047 mmol) and isophthalic acid (3.76 g, 0.094 mmol) were placed in a 100 mL volumetric flask, and water was added to prepare a 0.47 mol / L sodium isophthalate (Na2ipa) solution in 100 mL.

[0084] 7.5 ml of 3-amino-1,2,4-triazole solution was first mixed with 5.35 ml of sodium isophthalate (Na2ipa) solution, and then 12.75 ml of a mixture of zinc salt and anion modifier was added. The mixture was stirred at 20 °C for 2 hours, filtered, washed with deionized water, and dried under vacuum at 120 °C for 12 hours to obtain the MOF product.

[0085] Example 10

[0086] The difference between Example 10 and Example 9 is that the molar ratio of each component remains unchanged, the amount of each component added is increased by 2 times compared to Example 9, the amount of solvent added remains unchanged, thereby changing the concentration of the raw materials, and the other conditions remain unchanged.

[0087] Example 11

[0088] The difference between Example 11 and Example 9 is that the molar ratio of each component remains unchanged, the amount of each component added is increased by 3 times compared to the example, the amount of solvent added remains unchanged, thereby changing the concentration of the raw materials, and the other conditions remain unchanged.

[0089] Example 12

[0090] The difference between Example 12 and Example 9 is that the molar ratio of each component remains unchanged, the amount of each component added is increased by 4 times compared to Example 9, and the amount of solvent added remains unchanged, thereby changing the concentration of the raw materials. All other conditions remain the same. The detailed steps are as follows:

[0091] A 1.57 mol / L solution of zinc salt and anion regulator was prepared by placing Zn(OAc)2·2H2O (34.38 g; 0.157 mmol) in a 100 ml volumetric flask, adding water;

[0092] 3-Amino-1,2,4-triazole (22.428 g, 0.267 mmol) was placed in a 100 mL volumetric flask, and water was added to prepare a 2.67 mol / L 3-amino-1,2,4-triazole solution.

[0093] NaOH (31.208 g, 0.188 mmol) and isophthalic acid (15.04 g, 0.376 mmol) were placed in a 100 mL volumetric flask, and water was added to prepare a 1.88 mmol / L sodium isophthalate (Na2ipa) solution in 100 mL.

[0094] 7.5 ml of 3-amino-1,2,4-triazole solution was first mixed with 5.35 ml of sodium isophthalate (Na2ipa) solution, and then 12.75 ml of a mixture of zinc salt and anion modifier was added. The mixture was stirred at 20 °C for 2 hours, filtered, washed with deionized water, and vacuum dried at 120 °C for 12 hours. The resulting MOF product was named Zn2(atz)2ipa-20 °C.

[0095] Examples 9-12 investigated the effect of reactant concentration on the reaction, and the results are as follows: Figure 4 As shown, the crystallinity, yield, surface area, size, and morphology of the samples obtained in the four embodiments remained largely unchanged, verifying that the physicochemical properties of the samples were independent of reagent concentration. According to classical crystallization theory, the nucleation rate is more sensitive to changes in supersaturation than to changes in growth rate, which leads to a decrease in particle size and an increase in crystal number density as the solution concentration increases. Therefore, the above results differ from classical crystallization theory. The anion regulator regulates the nucleation process through competitive coordination, preventing uncontrolled nucleation at high concentrations and thus maintaining the physicochemical properties of the product. Although the product yield and properties were not affected, using a saturated solution during synthesis can improve the space-time yield.

[0096] Example 13

[0097] The difference between Example 13 and Example 12 is that the amount of NaOH added is 30 mmol, that is, the molar ratio of H2ipa:NaOH is 1:3, and the other conditions are exactly the same.

[0098] Example 14

[0099] The difference between Example 14 and Example 12 is that the amount of NaOH added is 40 mmol, that is, the molar ratio of H2ipa:NaOH is 1:4, and the other conditions are exactly the same.

[0100] Example 15

[0101] The difference between Example 15 and Example 12 is that the amount of NaOH added is 50 mmol, that is, the molar ratio of H2ipa:NaOH is 1:4, and the other conditions are exactly the same.

[0102] Examples 12-15 investigated the effect of the molar ratio of H2ipa:NaOH on the reaction, and the results are shown in Table 3. Figure 5 As shown.

[0103] Base-assisted synthesis facilitates the deprotonation of carboxylic acid groups; however, excessively high basicity can rapidly generate unwanted deprotonated ligands, inhibiting the formation of the desired MOF structure and leading to amorphous products, metal hydroxides, or other unknown impurities. When the molar ratio of H₂ipa to NaOH was 1:2 or 1:3, pure Zn₂(atz)₂ipa samples were obtained with high yields of 83% and 85%, respectively. When the basicity was high, with a molar ratio of H₂ipa to NaOH of 1:4, characteristic peaks of Zn-atz-OAc appeared in the XRD pattern of the obtained product, indicating the presence of Zn-atz-OAc in the sample. Furthermore, excessively high basicity significantly reduced the sample surface area. Figure 5 (a and 5b) The main reason is that the coordination affinity of the ligands is affected by the pH of the solution. Further increasing the NaOH content (the molar ratio of H2ipa:NaOH is 1:5) leads to the disappearance of crystals. Figure 5 a). Therefore, an IPA:NaOH ratio of 1:2 was chosen for subsequent synthesis to produce high-quality crystals and reduce the amount of alkali used.

[0104] Table 3. Effect of the molar ratio of H2ipa:NaOH on the reaction

[0105]

[0106] Example 16

[0107] The difference between this embodiment and Example 12 is that the reaction temperature is 40°C, while the other conditions are exactly the same. The resulting MOF product is named Zn2(atz)2ipa-40 °C.

[0108] Example 17

[0109] The difference between this embodiment and Example 12 is that the reaction temperature is 60°C, while the other conditions are exactly the same. The resulting MOF product is named Zn2(atz)2ipa-60 °C.

[0110] Example 18

[0111] The difference between this embodiment and Embodiment 12 is that the reaction temperature is 80°C, while the other conditions are exactly the same. The resulting MOF product is named Zn2(atz)2ipa-80 °C.

[0112] Examples 12 and 16-18 investigated the effect of synthesis temperature, and the results are shown below:

[0113] Table 4. Effect of synthesis temperature on yield and BET

[0114]

[0115] As shown in Table 4, the yield initially increased and then decreased with increasing synthesis temperature. Furthermore, the MOF products obtained in Examples 12 and 16-18 were subjected to scanning electron microscopy (SEM), and the SEM images are shown below. Figure 6 As shown, through Figure 6 It can be concluded that the crystal size increases significantly with increasing temperature; powder X-ray diffraction characterization of the above products yields the following results: Figure 7 As shown, the X-ray diffraction peaks of the four products are in complete agreement. Finally, a nitrogen adsorption experiment was conducted on the above products, and the results are as follows. Figure 8 As shown, the nitrogen adsorption isotherm does not change much with increasing synthesis temperature. However, with increasing temperature, the specific surface area calculated by the Brunauer-Emmett-Teller (BET) method first increases and then decreases. Based on the above analysis, it can be seen that when the temperature is raised to 80℃, the mass and yield of the MOF sample decrease. Therefore, the preferred synthesis temperature is 60℃.

[0116] Example 19

[0117] The difference between this embodiment and Embodiment 12 is that the reaction time is 2 minutes, while the other conditions are exactly the same.

[0118] Example 20

[0119] The difference between this embodiment and Embodiment 12 is that the reaction time is 5 minutes, while the other conditions are exactly the same.

[0120] Example 21

[0121] The difference between this embodiment and Embodiment 12 is that the reaction time is 10 minutes, while the other conditions are exactly the same.

[0122] Example 22

[0123] The difference between this embodiment and Embodiment 12 is that the reaction time is 20 minutes, while the other conditions are exactly the same.

[0124] Examples 12 and 19-22 investigate the effect of reaction time on the synthesis.

[0125] The MOF products obtained in Examples 19-22 were subjected to scanning electron microscopy (SEM), and the SEM images are shown below. Figure 9 As shown, when the reaction time is less than 5 minutes, the crystallinity is low. When the reaction time is extended to 10 minutes, the MOF material exhibits higher crystallinity and nitrogen adsorption capacity. Figure 10 As the reaction time further increased, its crystallinity no longer changed, as shown in the following figure. Figure 11 .

[0126] Example 23

[0127] The difference between Example 23 and Example 2 is that the mixing order of the solutions was changed. First, the mixture of zinc salt and anion regulator solution and 3-amino-1,2,4-triazole solution were mixed, and then the prepared sodium isophthalate (Na2ipa) solution was added. All other conditions were exactly the same.

[0128] Example 24

[0129] The difference between this embodiment and Embodiment 2 is that: first, the mixture of zinc salt and anion regulator solution and sodium isophthalate (Na2ipa) solution are mixed, and then 3-amino-1,2,4-triazole solution is added, while the other conditions are exactly the same.

[0130] Examples 2 and 23 and 24 investigated the effect of the order of addition on the reaction.

[0131] In this Example 23, when a mixture of zinc salt and anion modifier solution is mixed with a 3-amino-1,2,4-triazole solution, a white precipitate is initially formed. The characteristic peaks of this precipitate conform to the characteristic diffraction pattern of a layered Zn-atz-OAc structure. Upon further addition of sodium isophthalate (Na2ipa) solution, the pattern of the white precipitate gradually evolves (see...). Figure 12 Two hours after synthesis, characteristic peaks of Zn2(atz)2ipa began to appear at 6.5° and 12.2°. After 12 hours of heating, pure Zn2(atz)2ipa was finally obtained. Therefore, Zn-atz-OAc exists as a crystal precursor during crystal formation and is subsequently gradually transformed into Zn2(atz)2ipa, in which the bridging ligand ipa²⁻ gradually replaces OAc⁻, connecting the Zn-atz layers. This is because the kinetics of this solid-state transformation are limited by mass diffusion, thus significantly prolonging the crystallization process.

[0132] For Examples 2 and 24, the precursor produced in Example 23 was not generated. In Examples 2 and 24, Zn2(atz)2ipa was rapidly generated once the third component was added. The initial peak of Zn2(atz)2ipa began to appear after 2 minutes of reaction (see...). Figure 13 This indicates the start of nucleation. One hour is sufficient to synthesize a highly crystalline product with ample surface area (see...). Figure 14 Compared to case 23, the synthesis process is significantly faster. Therefore, the order of addition has an important influence on the crystallization path and kinetics of Zn2(atz)2ipa. The crystallization process in Example 2 involves solid-state transformation and rearrangement, which is an atypical path.

[0133] Example 25

[0134] The difference between Example 25 and Example 2 is that the anion regulator used is formate ion, while the other conditions are exactly the same.

[0135] Example 26

[0136] The difference between Example 26 and Example 2 is that the anion regulator used is trifluoroacetate ion, while the other conditions are exactly the same.

[0137] Examples 2 and 25-26 investigated the effect of anion regulators. The results showed that the quality morphology and yield of the products obtained in the three examples did not change significantly.

[0138] Example 27

[0139] The difference between Example 27 and Example 2 is that the second ligand is isophthalic acid with substituents at other positions on the aromatic ring, while the other conditions are exactly the same.

[0140] The XRD image of the MOF sample obtained in Example 27 is as follows: Figure 15 As shown, a series of Zn-based MOF materials were successfully synthesized using the method of the present invention.

[0141] Example 28

[0142] A mixture of zinc salt and monodentate ligand anion modifier was prepared by dissolving zinc acetate (0.876 g, 4 mmol) in 10 mL of water; a 3-amino-1,2,4-triazole solution was prepared by dissolving 3-amino-1,2,4-triazole in 10 mL of water; and an alkaline solution of sodium carbonate was prepared by dissolving NaOH (0.80 g, 2 mmol) and sodium carbonate (2 mmol) in 100 mL of water. Upon addition of the mixture of zinc salt and monodentate ligand anion modifier to the amino-3-amino-1,2,4-triazole solution and the alkaline sodium carbonate solution, a white precipitate immediately formed. After stirring at 90 °C for 10–120 min, the mixture was filtered, washed with deionized water, and dried at 120 °C for 12 hours to obtain the MOF product.

[0143] The XRD pattern of the MOF product obtained in Example 28 is as follows: Figure 16 As shown, its structural diagram is as follows: Figure 1 As shown in b, another Zn-based MOF material with carbonic acid as the second ligand was successfully synthesized using the method of the present invention.

[0144] Example 29

[0145] A mixture of zinc salt and monodentate ligand anion modifier was prepared by dissolving zinc acetate (0.876 g, 4 mmol) in 10 mL of water; a 3-amino-1,2,4-triazole solution was prepared by dissolving 3-amino-1,2,4-triazole in 10 mL of water; and a sodium terephthalate solution was prepared by dissolving NaOH (0.160 g, 4 mmol) and terephthalic acid (0.332 g, 2 mmol) in 10 mL of water. Upon addition of the zinc salt and monodentate ligand anion modifier mixture to the 3-amino-1,2,4-triazole and sodium terephthalate solutions, a white precipitate immediately formed. After stirring at room temperature for 10–120 min, the mixture was filtered, washed with deionized water, and dried at 120 °C for 12 hours to obtain the MOF product.

[0146] The XRD and electron microscope images of the MOF product obtained in Example 29 are as follows: Figure 17 As shown, its structural diagram is as follows: Figure 1 As shown in Figure c, it is demonstrated that another Zn-based MOF material with terephthalic acid as the second ligand was successfully synthesized using the method of the present invention.

[0147] Example 30

[0148] A mixture of zinc salt and monodentate ligand anion modifier was prepared by dissolving zinc acetate (0.876 g, 4 mmol) in 10 mL of water; a 3-amino-1,2,4-triazole solution was prepared by dissolving 3-amino-1,2,4-triazole in 10 mL of water; and a sodium thiophene dicarboxylate solution was prepared by dissolving NaOH (0.160 g, 4 mmol) and thiophene dicarboxylic acid (0.0344 g, 2 mmol) in 10 mL of water. Upon addition of the zinc salt and monodentate ligand anion modifier mixture to the 3-amino-1,2,4-triazole and sodium thiophene dicarboxylate solutions, a white precipitate immediately formed. After stirring at room temperature for 10–120 min, the mixture was filtered, washed with deionized water, and dried at 120 °C for 12 hours to obtain the MOF product.

[0149] The XRD pattern of the MOF product obtained in Example 30 is shown below. Figure 17 As shown, its structural diagram is as follows: Figure 1 As shown in d, it is demonstrated that another Zn-based MOF material with the second ligand thiophene dicarboxylic acid was successfully synthesized using the method of the present invention.

[0150] Example 31

[0151] A mixture of zinc salt and monodentate ligand anion modifier was prepared by dissolving zinc acetate (0.876 g, 4 mmol) in 10 mL of water; a 1,2,4-triazole solution was prepared by dissolving 1,2,4-triazole in 10 mL of water; and a sodium isophthalate solution was prepared by dissolving NaOH (0.160 g, 4 mmol) and isophthalic acid (0.332 g, 2 mmol) in 10 mL of water. Upon addition of the zinc salt and monodentate ligand anion modifier mixture to the 1,2,4-triazole and sodium isophthalate solutions, a white precipitate immediately formed. After stirring at room temperature for 10–120 min, the mixture was filtered, washed with deionized water, and dried at 120 °C for 12 hours to obtain the MOF product.

[0152] The XRD pattern of the MOF product obtained in Example 31 is shown below. Figure 18 As shown, its structural diagram is as follows: Figure 1 As shown in Figure e, another Zn-based MOF material based on triazole ligands and their derivatives was successfully synthesized using the method of the present invention.

[0153] Example 32

[0154] A mixture of zinc salt and monodentate ligand anion modifier was prepared by dissolving zinc acetate (0.876 g, 4 mmol) in 10 mL of water; a 3-amino-1,2,4-triazole solution was prepared by dissolving 3-amino-1,2,4-triazole in 10 mL of water; and a sodium acetate solution was prepared by dissolving NaOH (0.160 g, 4 mmol) and acetic acid (2 mmol) in 10 mL of water. Upon addition of the zinc salt and monodentate ligand anion modifier mixture to the amino-3-amino-1,2,4-triazole and sodium acetate solutions, a white precipitate immediately formed. Subsequently, sodium acetate solution was added. After stirring at room temperature for 10–120 min, the mixture was filtered, washed with deionized water, and dried at 120 °C for 12 hours to obtain the MOF product.

[0155] The XRD pattern of the MOF product obtained in Example 32 is shown below. Figure 19 As shown, its structural diagram is as follows: Figure 1 As shown in f, it is demonstrated that another Zn-based MOF material with a fatty acid as the second ligand was successfully synthesized using the method of the present invention.

[0156] Application Examples

[0157] The gas separation capability of the Zn2(atz)2ipa material obtained in Example 1 in CH4 / N2 separation was evaluated. According to the corresponding adsorption isotherms, Zn2(atz)2ipa-(kg) exhibited significant adsorption capacity for CH4 at 298 K and 273 K under an absolute pressure of 1 bar, reaching 18.3 and 28.3 cm³ / g, respectively (see [link to relevant documentation]). Figure 20 (a and 20b). The decrease in adsorption capacity with increasing temperature indicates that the above gas adsorption is mainly physical adsorption. Conversely, the adsorption capacity for N2 is relatively low, at 4.8 and 8.6 cm³ / g at the same pressure and temperature, almost 4 times lower than that for CH4. This indicates the potential of the material for CH4 / N2 separation. The high CH4 adsorption capacity originates from the strong affinity between the pore walls and CH4 molecules, and regeneration can be easily achieved at room temperature by reducing the pressure, without additional heating. The CH4 adsorption capacity of Zn2(atz)2ipa at 298 K remained good after 10 regeneration cycles (see [link to relevant documentation]). Figure 20 c), highlighting its excellent stability for regeneration.

[0158] The adsorption heat Qst of Zn2(atz)2ipa was calculated using collected adsorption data, and the data were fitted using the virial equation. The selectivity for CH4 in the presence of N2 was also analyzed. Under 1 bar conditions, the CH4 selectivity of Zn2(atz)2ipa in an equimolar CH4 / N2 mixture was approximately 6.2 and 7.7, respectively. The adsorption heat of Zn2(atz)2ipa for CH4 was 28.0 kJ / mol, indicating its suitability for CH4 separation. The excellent adsorption performance and selectivity, coupled with a green, scalable, and cost-effective synthesis and regeneration process, make Zn2(atz)2ipa an ideal candidate material for industrial waste gas adsorption.

[0159] Gas separation experiments were conducted using a fixed-bed breakthrough apparatus at 298 K and 101 kPa. The sample prepared in Example 1 was packed into a quartz glass column, and an equimolar mixture of CH4 and N2 (50 / 50, volume / volume) was passed through the column. The breakthrough curves show that the release time of CH4 was 4.7 minutes later than that of N2 (see [link to breakthrough curve]). Figure 20 d), confirming its preferential adsorption on Zn2(atz)2ipa-(kg). Considering the practical conditions of methane recovery, a lower concentration gas mixture (i.e., CH4 / N2 = 30 / 70 and 15 / 85) was also introduced. The release time difference between CH4 and N2 increased to 6.2 minutes (see d). Figure 20 The breakthrough results show that the Zn2(atz)2ipa sample can completely separate the CH4N2 binary mixture even at low CH4 concentrations. These experiments confirm the potential application value of the material in the industrial separation of methane and nitrogen, providing a reference for promoting the large-scale preparation and commercial development of MOFs.

[0160] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A large-scale water-based preparation process for zinc-based MOF materials, characterized in that: Includes the following steps: Prepare a solution of a mixture of zinc salt and anion modifier; prepare a solution of the first ligand 1,2,4-triazole and its derivatives; prepare an aqueous solution of the second ligand, add alkali, and prepare a mixed solution of the second ligand and alkali. The three solutions were mixed and added to the reactor. After the reaction was completed, the mixture was filtered and separated, washed with deionized water, and dried to obtain the zinc-based metal-organic framework material. The anion regulator is one of formate, acetate, or trifluoroacetate ions; The molar ratio of the second ligand to the anion modifier is 1:(1-6); the molar ratio of the second ligand to the base is 1:(2-4); The second ligand is one of isophthalic acid, terephthalic acid, thiophene dicarboxylic acid, or carbonic acid.

2. The large-scale water-based preparation process of zinc-based MOF materials according to claim 1, characterized in that: The zinc salt is one of zinc sulfate, zinc chloride, zinc nitrate and zinc acetate, and the alkali is one or more of sodium hydroxide, potassium hydroxide, calcium hydroxide and aluminum hydroxide.

3. The large-scale water-based preparation process of zinc-based MOF materials according to claim 1, characterized in that: The mixing order of the three solutions is as follows: first, mix the solution of zinc salt and anion regulator with the solution of the first ligand 1,2,4-triazole and its derivatives, and then add the solution of the second ligand and base.

4. The large-scale water-based preparation process of zinc-based MOF materials according to claim 1, characterized in that: The mixing order of the three solutions is as follows: first, the solution of the first ligand 1,2,4-triazole and its derivatives is mixed with the solution of the second ligand and the base, and then the solution of the mixture of zinc salt and anion regulator is added.

5. The large-scale water-based preparation process of zinc-based MOF materials according to claim 3, characterized in that: The reaction conditions are: react at 20–80℃ for 1–12 h.

6. The large-scale water-based preparation process of zinc-based MOF materials according to claim 4, characterized in that: The reaction conditions are: react at 20–80℃ for 5–120 min.

7. The application of the zinc-based MOF material as described in any one of claims 1-6 in the separation of CH4 and N2.

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