Large-scale water-based preparation process and application of zinc-based MOF material

Abstract

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

Description

Technical Field

[0001] The present invention belongs to the field of materials and chemical process research, and particularly relates to a large-scale aqueous preparation process of a zinc-based MOF material and its application. Background Art

[0002] Environmental pollution and energy crises caused by fossil fuel extraction have prompted people to seek cleaner and more efficient energy sources. As a low-cost clean energy source, natural gas is widely used in civil and industrial applications due to its high combustion efficiency. However, with the intensification of the global energy transition and extraction challenges, traditional natural gas supplies can no longer meet the escalating demand. Unconventional gas sources such as coalbed methane, shale gas, and biogas have large reserves and wide distributions, but their high N2 content hinders their application. CH4 is a major factor in 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, S.E.M., Schaefer, H., Rising methane: A new climate challenge[J].Science. 2019, 364 (6444): 932-933.]. To address environmental and energy shortage issues, it is urgent to capture CH4 from low-quality natural gas. As a new type of adsorbent, metal-organic frameworks (MOFs) have shown extraordinary potential in CH4 / N2 separation due to their ultra-high specific surface area, diverse chemical structures, and tunable pore sizes [Chang M., Zhao Y., et al., Methane-trapping metal–organic frameworks with an aliphatic ligand for efficient CH4 / N2 separation[J].Sustain. Energ. Fuels, 2020, 4(1):138-142.], but their applications have been greatly limited due to the lack of green, low-cost, and large-scale production methods.

[0003] Zinc-based metal-organic framework materials constructed from triazole layers, their analogues, and polydentate ligands are considered potential industrial separation adsorbents due to their high stability, inexpensive raw materials, and appropriate pore sizes. Due to the low solubility of the ligands, the common production process of this material is still solvothermal synthesis. Due to the use of a large amount of organic solvents and harsh reaction conditions, this reaction produces serious pollution, high costs, high energy consumption, slow reaction rates, low yields, and low space-time yields. There are also serious safety problems, making it difficult to meet the requirements 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 publication CN116003815A discloses the preparation of a microporous zinc-based MOF material ZnAtzCO3 constructed from carbonate. Through a solvothermal reaction of zinc salt, 3-amino-1,2,4-triazole, N,N-dimethylformamide, and water, a new microporous MOF material is constructed using the carbonate formed by the decomposition of N,N-dimethylformamide at high temperatures, resulting in high costs and a large environmental impact. Another example is patent CN112105764A, which discloses a green and efficient synthesis method for preparing CALF-20. It is characterized by using zinc salt, triazole, and oxalic acid as raw materials and using water and ethanol as solvents for preparation. However, this reaction process will inevitably use lower alcohols as organic solvents, and the product quality and purity will be affected in many ways, resulting in an impact on production costs, safety, and product quality under large-scale synthesis conditions. Therefore, it is of great significance to develop a pure water-based synthesis method for the large-scale production of zinc-based metal-organic framework materials of triazole layers, their derivatives, and polydentate ligands that is green and economical.

[0004] In summary, the current synthesis methods for zinc-based metal-organic framework materials composed of triazole layers, their derivatives, and polydentate ligands have the following problems: (1) The use of organic solvents such as ethanol and DMF during the reaction process not only increases production and post-treatment costs but also causes severe environmental pollution.

[0005] (2) The reaction time is long and the reaction temperature is high, greatly increasing the operating costs and also posing serious safety hazards.

[0006] (3) Limited by the solubility of the ligands in water, the synthesis of MOFs in water is extremely difficult, and there are few reports on pure water-based synthesis routes. Moreover, due to the serious pollution, high energy consumption, low space-time yield, and high requirements for reactors of conventional synthesis methods, it is difficult to produce MOFs on a large scale.

[0007] (4) Due to the lack of effective means to control crystal growth in conventional synthesis methods, it is difficult to control the particle size of MOFs synthesized on a large scale, the product quality cannot be guaranteed, and even the performance may decline. SUMMARY OF THE INVENTION

[0008] The purpose of the present invention is to overcome the shortcomings of the existing synthesis process of metal-organic framework materials, and utilize the synergistic effects of a monodentate anion regulator to regulate crystal growth and an alkali to promote ligand deprotonation and improve the solubility of the ligand in water, to provide a large-scale aqueous preparation process and application of a zinc-based MOF material, so as to solve the serious pollution caused by the use of a large amount of organic solvents in the production process and post-treatment process of metal-organic framework materials, and to overcome the disadvantages of slow reaction rate and low space-time yield of traditional production processes.

[0009] The present invention is realized through the following technical solutions: A large-scale aqueous preparation process of a zinc-based MOF material, comprising the following steps: Prepare a mixed solution of a zinc salt and an anion regulator; prepare a solution of a first ligand 1, 2, 4-triazole and its derivatives; prepare an aqueous solution of a second ligand, add an alkali, and prepare a mixed solution of the second ligand and the alkali; mix the three solutions and add them to a reactor for reaction, and after the reaction is completed, filter and separate, wash with deionized water, and dry to obtain a zinc-based metal-organic framework material.

[0010] Further, the monodentate ligand anion regulator is one of formate, acetate or trifluoroacetate ions.

[0011] Further, 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.

[0012] Further, 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 acids or polycarboxylic acids, heterocyclic monocarboxylic acids or polycarboxylic acids, carbonic acids, aliphatic monocarboxylic acids or polycarboxylic acids, etc., and other positions of the main chain, aromatic ring or heterocyclic ring can independently be selected from one or more of hydrogen, hydroxyl group, nitro group, amino group, methyl group, ether and halide groups.

[0013] Further, the molar ratio of the second ligand to the alkali is 1:(2 - 5); the molar ratio of the second ligand to the anion regulator is 1:(1 - 6).

[0014] Further, the mixing order of the three solutions is as follows: First, mix the mixture solution of zinc salt and anion regulator with the solution of the first ligand 3-amino-1,2,4-triazole and its derivatives, and then add the mixed solution of the second ligand and base. The reaction conditions at this time are: react at 20-80 °C for 1-12 h.

[0015] Further, the mixing order of the three solutions is as follows: First, mix the solution of 3-amino-1,2,4-triazole and its derivatives with the mixed solution of the second ligand and base, and then add the mixture solution of zinc salt and anion regulator. The reaction conditions at this time are: react at 20-80 °C for 5-120 min.

[0016] The second object of the present invention is to provide the application of the zinc-based MOF material in the separation of CH4 and N2.

[0017] The beneficial technical effects of the present invention are as follows: (1) By utilizing the synergistic effect of the anion regulator in regulating crystal growth and the base promoting the deprotonation of the second ligand, MOF crystals with high specific surface area, good morphology and high quality can be prepared within a few minutes, greatly improving the production efficiency and having an unprecedented space-time yield; (2) In the production and cleaning processes of the present invention, water is completely used as the solvent without using any organic solvents such as ethanol, methanol, and DMF, which not only greatly reduces the production cost and waste liquid treatment cost, but also minimizes environmental pollution to the greatest extent; (3) The reaction of the present invention can be carried out under normal pressure, and the selected synthesis temperature can be as low as room temperature without high pressure. The low reaction temperature not only reduces costs, energy consumption and requirements for reactors, but also improves production safety performance; (4) The present invention utilizes the regulator / base assisted system strategy to achieve precise control of the MOF particle size; (5) The MOF material synthesized by the present invention has excellent CH4 and N2 gas adsorption and separation performance, showing 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. Description of the Drawings

[0018] Figure 1 (a) is the structural diagram of Example 1; Figure 1 (b) is the structural diagram of Example 28; Figure 1 (c) is the structural diagram of Example 29; Figure 1 (d) is the structural diagram of Example 30; Figure 1(e) is the structural diagram of Example 31; Figure 1 (f) is the structural diagram of Example 32.

[0019] Figure 2 is the XRD pattern of Examples 1 - 5.

[0020] Figure 3 is the nitrogen adsorption isotherm of Examples 1 - 4.

[0021] Figure 4 is the (a) XRD pattern and (b) nitrogen adsorption isotherm of Examples 9 - 12.

[0022] Figure 5 is the (a) XRD pattern and (b) nitrogen adsorption isotherm of Examples 12 - 15.

[0023] Figure 6 is the SEM image of Zn2(atz)2ipa - Y, where Y is 20°C, 40°C, 60°C, 80°C.

[0024] Figure 7 is the XRD pattern of Zn2(atz)2ipa - Y, where Y is 20°C, 40°C, 60°C, 80°C.

[0025] Figure 8 is the (a) nitrogen adsorption isotherm and (b) yield vs. BET bar chart of Zn2(atz)2ipa - Y, where Y is 20°C, 40°C, 60°C, 80°C.

[0026] Figure 9 is the SEM image of Examples 19 - 22.

[0027] Figure 10 is the (a) XRD pattern and (b) nitrogen adsorption isotherm of Example 21.

[0028] Figure 11 is the change of the XRD pattern of Example 22 over time.

[0029] Figure 12 is the change of the XRD pattern of Example 23 over time.

[0030] Figure 13 is the change of the XRD pattern of Example 24 over time.

[0031] Figure 14 is the nitrogen adsorption isotherm of Example 24.

[0032] Figure 15 is the XRD pattern of Example 27.

[0033] Figure 16XRD pattern of Example 28.

[0034] Figure 17 XRD patterns of Examples 29 and 30 (a) and SEM pattern of Example 29 (b).

[0035] Figure 18 XRD pattern of Example 31.

[0036] Figure 19 XRD pattern of Example 32.

[0037] Figure 20 Single-component (CH4 and N2) adsorption isotherms of Zn2(atz)2ipa at 298 K (a) and 273 K (b). (c) Schematic diagram of the adsorption regeneration of CH4 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 Description of the Invention

[0038] Now, various exemplary embodiments of the present invention will 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 implementation manners of the present invention. It should be understood that the terms used in the present invention are only for describing specific embodiments and are not intended to limit the present invention.

[0039] In addition, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0040] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of the present invention.

[0041] Regarding the terms "comprising", "including", "having", "containing", etc. used herein, they are all open-ended terms, meaning including but not limited to.

[0042] Example 1 Dissolve Zn(NO3)2•6H2O (1.192 g, 4 mmol) and sodium acetate (0.984 mg, 12 mmol) in 10 mL of water to prepare a mixed solution of zinc salt and anion regulator; 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; NaOH (0.160 g, 4 mmol) and isophthalic acid (0.332 g, 2 mmol) were dissolved in 10 mL of water to prepare a sodium isophthalate (Na2ipa) solution; The 3-amino-1,2,4-triazole solution was first mixed with the sodium isophthalate (Na2ipa) solution, and then a mixture solution of zinc salt and anion regulator was added. Then, the mixture was stirred and reacted 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. Its structural diagram is as Figure 1 shown in a. In its structure, each Zn(II) ion is coordinated by two carboxyl oxygen atoms from the isophthalic acid anion and three nitrogen atoms from three 3-amino-1,2,4-triazole root ions in a distorted tetrahedral geometry. The structure of Zn2(atz)2ipa has a one-dimensional channel (void = 26.6%) 10, with the maximum and minimum pore diameters being 5.5 Å and 2.8 Å, respectively. The amino group of the atz-ligand points to the spherical cavity, but only hydrogen atoms rather than nitrogen atoms are exposed on the pore surface.

[0043] Example 2 The difference between Example 2 and Example 1 is that the addition amount of sodium acetate is 8 mmol (ipa 2- / OAc - : 1 / 4), that is, the remaining conditions are exactly the same.

[0044] Example 3 The difference between Example 3 and Example 1 is that the addition amount of sodium acetate is 4 mmol (ipa 2- / OAc - : 1 / 1), that is, the remaining conditions are completely the same.

[0045] Example 4 The difference between Example 4 and Example 1 is that the addition amount of sodium acetate is 0.5 mmol (ipa 2- / OAc - : 4 / 1), that is, the remaining conditions are completely the same.

[0046] Example 5 The difference between Example 5 and Example 1 is that the addition amount of sodium acetate is 0 mmol (ipa 2- / OAc - : 1 / 0), that is, the remaining conditions are completely the same.

[0047] Examples 1 - 5 explored the influence of acetate ions on the reaction results, and the results are shown as follows: Sodium acetate was first introduced into the MOF synthesis as a regulator, and its dosage significantly affected the properties of the MOF product. When the addition amount of sodium acetate was 0, the formation of the target MOF Zn2(atz)2ipa was not observed, while increasing its dosage led to a continuous increase in the crystallinity of the sample, showing a trend of first increasing and then leveling off. As the ratio of ipa 2- to sodium acetate increased from 1:1 to 1:6 (see Table 1 and Figure 2 ), the yield increased significantly, from 36% to 82%, while the BET specific surface area increased slightly (see Figure 3 ). Therefore, the molar ratio of ipa 2- and OAc - is preferably 1:(1 - 6).

[0048] Table 1. Influence of Sodium Acetate Addition Amount on Yield and BET Example 6 The difference between Example 6 and Example 2 is that the metal salt used is zinc sulfate, and the other conditions are the same.

[0049] Example 7 The difference between Example 7 and Example 2 is that the metal salt used is zinc chloride, and the other conditions are the same.

[0050] Example 8 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 additionally, and the other conditions are the same.

[0051] Examples 2 and 6 - 8 were mainly to explore the influence of metal salts on the reaction. The results are shown in Table 2. Selecting different metal salts has little influence on the yield. After comprehensive comparison, zinc acetate is preferred.

[0052] Table 2. Influence of Metal Salts on Yield and BET Example 9 By placing Zn(OAc)2·2H2O (8.595 g; 0.03925 mmol) in a 100 ml volumetric flask and adding water to prepare a mixture solution of 0.3925 mol / L zinc salt and anion regulator; Place 3 - amino - 1,2,4 - triazole (5.6 g, 0.06675 mmol) in a 100 ml volumetric flask and add water to prepare a 0.6675 mol / L 3 - amino - 1,2,4 - triazole solution; 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 100 mL sodium isophthalate (Na2ipa) solution; First, 7.5 ml of 3-amino-1,2,4-triazole solution was mixed with 5.35 ml of sodium isophthalate (Na2ipa) solution, and then 12.75 ml of a mixture solution of zinc salt and anion regulator was added. Then, the mixture was stirred and reacted at 20 °C for 2 hours, filtered, washed with deionized water, and vacuum dried at 120 °C for 12 hours to obtain the MOF product.

[0053] Example 10 The difference between Example 10 and Example 9 is that while keeping the molar ratio of each component unchanged, the addition amount of each component is increased by 2 times compared to Example 9, and the addition amount of the solvent remains unchanged, so as to change the concentration of the raw materials, and the rest of the conditions remain unchanged.

[0054] Example 11 The difference between Example 11 and Example 9 is that while keeping the molar ratio of each component unchanged, the addition amount of each component is increased by 3 times compared to Example 9, and the addition amount of the solvent remains unchanged, so as to change the concentration of the raw materials, and the rest of the conditions remain unchanged.

[0055] Example 12 The difference between Example 12 and Example 9 is that while keeping the molar ratio of each component unchanged, the addition amount of each component is increased by 4 times compared to Example 9, and the addition amount of the solvent remains unchanged, so as to change the concentration of the raw materials, and the rest of the conditions remain unchanged. The detailed steps are as follows: By placing Zn(OAc)2·2H2O (34.38 g; 0.157 mmol) in a 100 ml volumetric flask and adding water to prepare a 1.57 mol / L mixture solution of zinc salt and anion regulator; 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; 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 100 mL sodium isophthalate (Na2ipa) solution; First, 7.5 ml of 3-amino-1,2,4-triazole solution was mixed with 5.35 ml of sodium isophthalate (Na2ipa) solution, and then 12.75 ml of a mixture solution of zinc salt and anionic regulator was added. Then, the mixture was stirred and reacted at 20 °C for 2 hours, filtered, washed with deionized water, and vacuum-dried at 120 °C for 12 hours. The obtained MOF product was named Zn2(atz)2ipa - 20 °C.

[0056] Examples 9 - 12 explored the influence of raw material concentration on the reaction, and the results are as Figure 4 shown. The crystallinity, yield, surface area, size, and morphology of the samples obtained in the above four examples remained roughly unchanged, verifying that the physicochemical properties of the samples are independent of the reagent concentration. According to classical crystallization theory, the nucleation rate is more sensitive to changes in supersaturation rather 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 are different from classical crystallization theory. The anionic regulator regulates the nucleation process through competitive coordination, preventing the uncontrolled appearance of nuclei at high concentrations and thus maintaining the physicochemical properties of the product. Although the product yield and properties are not affected, using saturated solutions during the synthesis can improve the space-time yield.

[0057] Example 13 The difference between Example 13 and Example 12 is that the addition amount of NaOH is 30 mmol, that is, the molar ratio of H2ipa:NaOH is 1:3, and the other conditions are exactly the same.

[0058] Example 14 The difference between Example 14 and Example 12 is that the addition amount of NaOH is 40 mmol, that is, the molar ratio of H2ipa:NaOH is 1:4, and the other conditions are exactly the same.

[0059] Example 15 The difference between Example 15 and Example 12 is that the addition amount of NaOH is 50 mmol, that is, the molar ratio of H2ipa:NaOH is 1:4, and the other conditions are exactly the same.

[0060] Examples 12 - 15 explored the influence of the molar ratio of H2ipa:NaOH on the reaction, and the results are shown in Table 3 and Figure 5 as follows.

[0061] Base-assisted synthesis helps to deprotonate carboxylic acid groups. However, excessive alkalinity rapidly generates unnecessary deprotonated ligands, inhibiting the formation of the desired MOF structure and resulting in amorphous products, metal hydroxides, or other unknown impurities. When the molar ratio of H2ipa:NaOH was 1:2 or 1:3, pure samples of Zn2(atz)2ipa were obtained with relatively high yields of 83% and 85%, respectively. When the alkalinity was higher, with a molar ratio of H2ipa:NaOH of 1:4, characteristic peaks of Zn-atz-OAc appeared in the XRD pattern of the resulting product, indicating that the obtained sample contained Zn-atz-OAc. Additionally, when the alkalinity was too high, the surface area of the sample decreased significantly ( Figure 5 a and 5b), mainly because the coordination affinity of the ligand is affected by the pH of the solution. Further increasing the content of NaOH (molar ratio of H2ipa:NaOH of 1:5) led to the disappearance of the crystals ( Figure 5 a). Therefore, an ipa:NaOH ratio of 1:2 was selected for subsequent synthesis to produce high-quality crystals and reduce the amount of base used.

[0062] Table III. Influence of the molar ratio of H2ipa:NaOH on the reaction Example 16 The difference between this example and Example 12 is that the reaction temperature was 40 °C, and the other conditions were exactly the same. The obtained MOF product was named Zn2(atz)2ipa-40 °C.

[0063] Example 17 The difference between this example and Example 12 is that the reaction temperature was 60 °C, and the other conditions were exactly the same. The obtained MOF product was named Zn2(atz)2ipa-60 °C.

[0064] Example 18 The difference between this example and Example 12 is that the reaction temperature was 80 °C, and the other conditions were exactly the same. The obtained MOF product was named Zn2(atz)2ipa-80 °C. Examples 12 and 16 - 18 explored the influence of the synthesis temperature, and the results are as follows: Table IV. Influence of the synthesis temperature on the yield and BET As can be seen from Table IV, as the synthesis temperature increased, the yield first increased and then decreased. Additionally, scanning electron microscopy was performed on the MOF products obtained in Examples 12 and 16 - 18, and the scanning electron micrographs are as Figure 6 shown. Through Figure 6It can be concluded that when the temperature rises, the size of the crystal increases significantly; the above products were characterized by powder X-ray diffraction, and the results are as Figure 7 shown. The X-ray diffraction peaks of the four products are completely consistent. Finally, the above products were subjected to a nitrogen adsorption experiment, and the results are as Figure 8 shown, indicating that as the synthesis temperature increases, the nitrogen adsorption isotherm changes little, but as the temperature increases, the specific surface area calculated by the Brunauer-Emmett-Teller (BET) method first increases and then decreases. From the above analysis, it can be seen that when the temperature is raised to 80 °C, the mass and yield of the MOF sample both decrease. Therefore, the preferred synthesis temperature is 60 °C.

[0065] Example 19 The difference between this example and Example 12 is that the reaction time is 2 minutes, and the rest of the conditions are exactly the same.

[0066] Example 20 The difference between this example and Example 12 is that the reaction time is 5 minutes, and the rest of the conditions are exactly the same.

[0067] Example 21 The difference between this example and Example 12 is that the reaction time is 10 minutes, and the rest of the conditions are exactly the same.

[0068] Example 22 The difference between this example and Example 12 is that the reaction time is 20 minutes, and the rest of the conditions are exactly the same.

[0069] Examples 12, 19 - 22 explored the effect of reaction time on the synthesis.

[0070] The MOF products obtained in Examples 19 - 22 were scanned by electron microscopy, and the scanning electron micrographs are as Figure 9 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, as shown in Figure 10 . As the reaction time further increases, its crystallinity no longer changes, and the results are shown in Figure 11 .

[0071] Example 23 The difference between Example 23 and Example 2 is that the mixing order of the solutions was changed. First, the mixture solution of the zinc salt and the anion regulator was mixed with the 3-amino-1,2,4-triazole solution, and then the prepared sodium isophthalate (Na2ipa) solution was added. The rest of the conditions are exactly the same.

[0072] Example 24 The difference between this example and Example 2 is as follows: First, the mixed solution of zinc salt and anion regulator is mixed with the sodium isophthalate (Na2ipa) solution, and then the 3-amino-1,2,4-triazole solution is added, and the remaining conditions are exactly the same.

[0073] In Examples 2, 23, and 24, the influence of the addition sequence on the reaction was explored.

[0074] In Example 23 of this example, when the mixed solution of zinc salt and anion regulator is mixed with the 3-amino-1,2,4-triazole solution, a white precipitate will be formed first, and the characteristic peaks of its PXRD conform to the characteristic diffraction pattern of the layered structure Zn-atz-OAc. When the sodium isophthalate (Na2ipa) solution is added again, the pattern of the white precipitate gradually evolves (see Figure 12 ). After 2 hours of synthesis, the characteristic peaks of Zn2(atz)2ipa begin to appear at 6.5° and 12.2°. After heating for 12 hours, pure Zn2(atz)2ipa is finally obtained. Therefore, Zn-atz-OAc exists as a crystal precursor during the crystal formation process and is subsequently gradually transformed into Zn2(atz)2ipa, where the bridging ligand ipa² - gradually replaces OAc - and connects the Zn-atz layer. The reason is that the kinetics of this solid-phase transformation is limited by mass diffusion, thus significantly prolonging the crystallization process.

[0075] For Example 2 and Example 24, the precursors generated in Example 23 are not produced. In Example 2 and Example 24, once the third component is added, Zn2(atz)2ipa will be rapidly generated. The initial peak of Zn2(atz)2ipa begins to appear 2 minutes after the reaction (see Figure 13 ), indicating the start of nucleation. One hour is sufficient to synthesize a product with high crystallinity and sufficient surface area (see Figure 14 ). Compared with Case 23, the synthesis process is significantly accelerated. Therefore, the addition sequence has an important influence on the crystallization path and kinetics of Zn2(atz)2ipa. The crystallization process of Example 2 undergoes solid-state transformation and rearrangement, belonging to an atypical path.

[0076] Example 25 The difference between Example 25 and Example 2 is that the anion regulator selected is the formate ion, and the remaining conditions are exactly the same.

[0077] Example 26 The difference between Example 26 and Example 2 is that the anion regulator selected is the trifluoroacetate ion, and the remaining conditions are exactly the same.

[0078] Example 2 and Examples 25-26 explored the influence of the anion regulator, and the results showed that there were little changes in the quality, morphology and yield of the products obtained in the three examples.

[0079] Example 27 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, and the remaining conditions are exactly the same.

[0080] The XRD image of the MOF sample obtained in Example 27 is as Figure 15 shown, proving that a series of Zn-based MOF materials have been successfully synthesized by using the method of the present invention.

[0081] Example 28 Dissolve zinc acetate (0.876 g, 4 mmol) in 10 mL of water to prepare a mixed solution of zinc salt and monodentate ligand anion regulator; dissolve 3-amino-1,2,4-triazole (0.336 g, 4 mmol) in 10 mL of water to prepare a 3-amino-1,2,4-triazole solution; dissolve NaOH (0.80 g, 2 mmol) and sodium carbonate (2 mmol) in 100 mL of water to prepare a basic solution of sodium carbonate. After adding the mixed solution of zinc salt and monodentate ligand anion regulator to the 3-amino-1,2,4-triazole solution and the basic solution of sodium carbonate, a white precipitate is immediately formed. After stirring at 90 °C for 10 min to 120 min, filter, wash with deionized water, and dry at 120 °C for 12 hours to obtain the MOF product.

[0082] The XRD of the MOF product obtained in Example 28 is as Figure 16 shown, and its structural diagram is as Figure 1 shown in b, proving that another Zn-based MOF material with the second ligand being carbonic acid has been successfully synthesized by using the method of the present invention.

[0083] Example 29 Dissolve zinc acetate (0.876 g, 4 mmol) in 10 mL of water to prepare a mixture solution of zinc salt and monodentate ligand anion regulator; dissolve 3-amino-1,2,4-triazole (0.336 g, 4 mmol) in 10 mL of water to prepare a 3-amino-1,2,4-triazole solution; dissolve NaOH (0.160 g, 4 mmol) and terephthalic acid (0.332 g, 2 mmol) in 10 mL of water to prepare a sodium terephthalate solution. After adding the mixture solution of zinc salt and monodentate ligand anion regulator to the 3-amino-1,2,4-triazole solution and sodium terephthalate solution, a white precipitate is immediately formed. Stir at room temperature for 10 min to 120 min, then filter, wash with deionized water, and dry at 120 °C for 12 hours to obtain the MOF product.

[0084] The XRD and electron microscopy images of the MOF product obtained in Example 29 are as Figure 17 shown, and its structural diagram is as Figure 1 shown in c, which proves that by using the method of the present invention, another Zn-based MOF material with terephthalic acid as the second ligand is successfully synthesized.

[0085] Example 30 Dissolve zinc acetate (0.876 g, 4 mmol) in 10 mL of water to prepare a mixture solution of zinc salt and monodentate ligand anion regulator; dissolve 3-amino-1,2,4-triazole (0.336 g, 4 mmol) in 10 mL of water to prepare a 3-amino-1,2,4-triazole solution; dissolve NaOH (0.160 g, 4 mmol) and thiophene dicarboxylic acid (0.344, 2 mmol) in 10 mL of water to prepare a sodium thiophene dicarboxylate solution. After adding the mixture solution of zinc salt and monodentate ligand anion regulator to the 3-amino-1,2,4-triazole solution and sodium thiophene dicarboxylate solution, a white precipitate is immediately formed. Stir at room temperature for 10 min to 120 min, then filter, wash with deionized water, and dry at 120 °C for 12 hours to obtain the MOF product.

[0086] The XRD pattern of the MOF product obtained in Example 30 is as Figure 17 shown, and its structural diagram is as Figure 1 shown in d, which proves that by using the method of the present invention, another Zn-based MOF material with thiophene dicarboxylic acid as the second ligand is successfully synthesized.

[0087] Example 31 Dissolve zinc acetate (0.876 g, 4 mmol) in 10 mL of water to prepare a mixed solution of zinc salt and monodentate ligand anion regulator; dissolve 1,2,4-triazole (0.276 g, 4 mmol) in 10 mL of water to prepare a 1,2,4-triazole solution; dissolve NaOH (0.160 g, 4 mmol) and isophthalic acid (0.332, 2 mmol) in 10 mL of water to prepare a sodium isophthalate solution. After adding the mixed solution of zinc salt and monodentate ligand anion regulator to the 1,2,4-triazole solution and sodium terephthalate solution, a white precipitate is immediately formed. After stirring at room temperature for 10 min to 120 min, filter, wash with deionized water, and dry at 120 °C for 12 hours to obtain the MOF product.

[0088] The XRD pattern of the MOF product obtained in Example 31 is as Figure 18 shown, and its structure diagram is as Figure 1 shown in e, which proves that another Zn-based MOF material with triazole ligand and its derivatives has been successfully synthesized by the method of the present invention.

[0089] Example 32 Dissolve zinc acetate (0.876 g, 4 mmol) in 10 mL of water to prepare a mixed solution of zinc salt and monodentate ligand anion regulator; dissolve 3-amino-1,2,4-triazole (0.276 g, 4 mmol) in 10 mL of water to prepare a 3-amino-1,2,4-triazole solution; dissolve NaOH (0.160 g, 4 mmol) and acetic acid (2 mmol) in 10 mL of water to prepare a sodium acetate solution. After adding the mixed solution of zinc salt and monodentate ligand anion regulator to the 3-amino-1,2,4-triazole solution and sodium acetate solution, a white precipitate is immediately formed, and then the sodium acetate solution is added. After stirring at room temperature for 10 min to 120 min, filter, wash with deionized water, and dry at 120 °C for 12 hours to obtain the MOF product.

[0090] The XRD pattern of the MOF product obtained in Example 32 is as Figure 19 shown, and its structure diagram is as Figure 1 shown in f, which proves that another Zn-based MOF material with fatty acid as the second ligand has been successfully synthesized by the method of the present invention.

[0091] Application Example The gas separation ability of the Zn2(atz)2ipa material obtained in Example 1 in CH4 / N2 separation was evaluated. According to the corresponding adsorption isotherms, at 298 K and 273 K, Zn2(atz)2ipa-(kg) exhibited significant adsorption capacity for CH4 at an absolute pressure of 1 bar, reaching 18.3 and 28.3 cm³ / g, respectively (see Figure 20 a and 20b). As the temperature increased, the decrease in adsorption capacity indicated that the above gas adsorption was mainly physical adsorption. In contrast, the adsorption capacity for N2 was relatively low, being 4.8 and 8.6 cm³ / g at the same pressure and temperature, almost 4 times lower than that of CH4. This demonstrated the potential of the material for CH4 / N2 separation. The high CH4 adsorption capacity originated from the strong affinity between the pore walls and CH4 molecules, and regeneration could 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 Figure 20 c), highlighting its excellent stability towards regeneration.

[0092] Based on the collected adsorption data, the isosteric heat of adsorption Qst of Zn2(atz)2ipa was calculated, and the data was fitted using the virial equation, as well as the selectivity for CH4 in the presence of N2. At 1 bar, the CH4 selectivity of Zn2(atz)2ipa in an equimolar CH4 / N2 mixture was approximately 6.2 and 7.7, and the isosteric heat of adsorption of Zn2(atz)2ipa for CH4 was 28.0 kJ / mol, indicating its applicability in CH4 separation. The excellent adsorption performance and selectivity, combined with a green, scalable, and cost-effective synthesis and regeneration process, make Zn2(atz)2ipa an ideal candidate material for industrial waste gas adsorption.

[0093] At 298 K and 101 kPa, gas separation experiments were carried out using a fixed-bed breakthrough device. The sample prepared in Example 1 was loaded into a quartz glass column, and an equimolar gas mixture of CH4 / N2 (50 / 50, volume / volume) was passed through the column. It could be seen from the breakthrough curve that the release time of CH4 was 4.7 minutes later than that of N2 (see Figure 20 d), confirming its preferential adsorption on Zn2(atz)2ipa-(kg). Considering the actual conditions for methane recovery, gas mixtures with lower concentrations (i.e., CH4 / N2 = 30 / 70 and 15 / 85) were also introduced. The time difference in the release of CH4 and N2 increased to 6.2 minutes (see Figure 20e-f), The penetration results show that even at low CH4 concentrations, the Zn2(atz)2ipa sample can completely separate the CH4 / N2 binary mixture. The above 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.

[0094] The embodiments described above are only descriptions of the preferred embodiments of the present invention and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A large-scale water-based preparation process for zinc-based MOF materials, characterized in that: The steps include: Prepare a mixture solution of zinc salt and anion regulator; prepare a solution of first ligand 1,2,4-triazole and its derivatives; prepare a second ligand aqueous solution, add a base, and prepare a mixed solution of the second ligand and the base; The three solutions were mixed and added into a reactor. After the reaction was completed, they were filtered and separated, washed with deionized water, and dried to obtain a zinc-based metal organic framework material.

2. The large-scale water-based preparation process of zinc-based MOF materials according to claim 1, characterized in that: The anion regulator is one of formate, acetate or trifluoroacetate ions.

3. 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.

4. The large-scale water-based preparation process of zinc-based MOF materials according to claim 1, characterized in that: 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 acids or polycarboxylic acids, heterocyclic monocarboxylic acids or polycarboxylic acids, carbonic acid, aliphatic monocarboxylic acids or polycarboxylic acids, etc., and other positions of the main chain, aromatic ring or heterocyclic ring can be independently selected from one or more of hydrogen, hydroxyl, nitro, amino, methyl, ether and halide groups.

5. The large-scale water-based preparation process of zinc-based MOF materials according to claim 1, characterized in that: The molar ratio of the second ligand to the base is 1:(2-5); the molar ratio of the second ligand to the anion regulator is 1:(1-6).

6. 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 to first mix the mixture solution of zinc salt and anion regulator with the solution of the first ligand 3-amino-1,2,4-triazole and its derivatives, and then add the mixture solution of the second ligand and base.

7. 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 to first mix the solution of 3-amino-1,2,4-triazole and its derivatives and the mixed solution of the second ligand and the base, and then add the mixed solution of the zinc salt and the anion regulator.

8. The large-scale water-based preparation process of zinc-based MOF materials according to claim 6, characterized in that: The reaction conditions are: 20-80°C for 1-12 hours.

9. The large-scale water-based preparation process of zinc-based MOF materials according to claim 7, characterized in that: The reaction conditions are: reaction at 20-80°C for 5-120 minutes.

10. Use of the zinc-based MOF material according to any one of claims 1 to 9 in the separation of CH4 and N2.

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