Method for producing metal-organic framework

Abstract

To provide a method for producing ZIF-8 having a large particle diameter, a high specific surface area and a high pore volume.SOLUTION: A process for the preparation of a metal-organic framework comprising Zn and 2-methylimidazole ligands, wherein the Zn source of the aqueous solutions is Zn sulfate or Zn acetate and the concentration of the aqueous ammoniacal solutions is ≥ 0. 7mol / l and ≤ 1. 2mol / l when the Zn source is Zn sulfate and ≥ 0. 7mol / l and ≤ 2. 0mol / l when the Zn source is Zn acetate SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a method for producing a metal-organic framework. [Background technology]

[0002] Metal organic frameworks can be produced by various methods. For example, known methods for producing a metal organic framework containing zinc and a 2-methylimidazole ligand (hereinafter also referred to as "ZIF-8") include a method of adding an aqueous solution containing a strong base such as sodium hydroxide to an aqueous solution containing zinc sulfate and 2-methylimidazole (Patent Document 1), a method of adding triethylamine to an aqueous solution containing zinc nitrate and 2-methylimidazole (Non-Patent Document 1), and a method of stirring zinc oxide and 2-methylimidazole in a solid phase (Patent Document 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2014-523898 [Patent Document 2] International Publication No. 2020 / 230820 [Non-Patent Document 1] Dalton Trans.,41,5458-5460(2012) Summary of the Invention [Problem to be solved by the invention]

[0004] With the method described in Patent Document 1, it was difficult to obtain ZIF-8 with a large particle size. Furthermore, because the synthesis was performed in an aqueous system, the obtained ZIF-8 had to be filtered, which required a long time. Furthermore, since NaOH was used, there was a possibility that Na would remain in the product. Furthermore, with the method described in Non-Patent Document 1, the zinc concentration was low, resulting in poor productivity. Furthermore, the particle size of the obtained ZIF-8 was small, requiring separation by centrifugation or the like, which caused problems with purification and handling. On the other hand, with the method described in Patent Document 2, it was difficult to obtain a high specific surface area and pore volume. [Means for solving the problem]

[0005] The method for producing a metal organic framework comprising zinc and a 2-methylimidazole ligand according to the present disclosure comprises mixing an aqueous solution comprising zinc and 2-methylimidazole with an aqueous ammonia solution to obtain a suspension, wherein the zinc source is zinc sulfate or zinc acetate, and the concentration of the aqueous ammonia solution is 0.7 mol / L or more and 1.2 mol / L or less when the zinc source is zinc sulfate, and 0.7 mol / L or more and 2.0 mol / L or less when the zinc source is zinc acetate. [Effects of the Invention]

[0006] According to the present disclosure, a production method can be provided that allows for a short filtration time and for obtaining ZIF-8 with a large particle size. DETAILED DESCRIPTION OF THE INVENTION

[0007] The manufacturing method according to the present disclosure will be described below.

[0008] The method for producing a metal organic framework comprising zinc and a 2-methylimidazole ligand according to the present disclosure comprises mixing an aqueous solution comprising zinc and 2-methylimidazole with an aqueous ammonia solution to obtain a suspension, wherein the zinc source is zinc sulfate or zinc acetate, and the concentration of the aqueous ammonia solution is 0.7 mol / L or more and 1.2 mol / L or less when the zinc source is zinc sulfate, and 0.7 mol / L or more and 2.0 mol / L or less when the zinc source is zinc acetate.

[0009] The metal organic framework (ZIF-8) containing zinc and a 2-methylimidazole ligand has a structure in which the 2-methylimidazole ligand is coordinated to a zinc ion. The 2-methylimidazole ligand includes 2-methylimidazole and its anion, preferably the anion of 2-methylimidazole.

[0010] First, an aqueous solution containing zinc and 2-methylimidazole is prepared. In this specification, the aqueous solution refers to a solution containing water (HO) as a solvent, and may also contain other water-soluble liquids.

[0011] Here, the zinc may exist in the aqueous solution as zinc ions or as a salt with a counter anion, and preferably exists in the aqueous solution as zinc ions.

[0012] The zinc source of the aqueous solution is zinc sulfate or zinc acetate. By using these zinc salts as the zinc source, the crystallinity of the metal organic framework is improved.

[0013] The aqueous solution can be obtained by mixing the zinc source, 2-methylimidazole, and water. The mixing method is not particularly limited, and examples thereof include the following mixing methods. Aqueous zinc solution and aqueous 2-methylimidazole solution are prepared separately and then mixed. A zinc aqueous solution is prepared, and then the zinc aqueous solution is mixed with solid 2-methylimidazole. A 2-methylimidazole aqueous solution is prepared, and then the 2-methylimidazole aqueous solution is mixed with a solid zinc source. A solid zinc source and solid 2-methylimidazole are mixed with water.

[0014] The zinc concentration in the aqueous solution is preferably 0.25 mol / L to 2.00 mol / L, more preferably 0.75 mol / L to 1.25 mol / L, where "zinc in the aqueous solution" includes not only zinc ions dissolved in the solution but also undissolved zinc in zinc salts.

[0015] The concentration of 2-methylimidazole in the aqueous solution is preferably 0.50 mol / l or more and 4.00 mol / l or less, more preferably 1.50 mol / l or more and 2.50 mol / l or less.

[0016] The molar ratio of 2-methylimidazole to zinc in the aqueous solution (2-methylimidazole / zinc) is preferably 1 or more and 5 or less, more preferably 1 or more and 3 or less.

[0017] The aqueous solution may further contain methanol, which allows the reaction rate to be controlled and increases the particle size of the resulting ZIF-8.

[0018] The volume ratio of water to methanol (water / methanol) in the aqueous solution is preferably 0.25 or more and 4 or less, more preferably 0.5 or more and 2 or less, even more preferably 0.65 or more and 1.5 or less, and particularly preferably 1.

[0019] The timing of adding methanol is arbitrary. For example, methanol may be added simultaneously with water, or after zinc, 2-methylimidazole, and water are mixed.

[0020] Separately, prepare an aqueous ammonia solution.

[0021] The concentration of the aqueous ammonia solution is 0.7 mol / L or more and 1.2 mol / L or less when the zinc source is zinc sulfate, and 0.7 mol / L or more and 2.0 mol / L or less when the zinc source is zinc acetate. By setting the concentration of the aqueous ammonia solution to 0.7 mol / L or more, the productivity of ZIF-8 is improved. Furthermore, by setting the concentration of the aqueous ammonia solution to 1.2 mol or less (in the case of zinc sulfate) or 2.0 mol / L or less (in the case of zinc acetate), the particle size of the obtained ZIF-8 is increased.

[0022] When the zinc source is zinc sulfate, the concentration of the aqueous ammonia solution may be preferably 0.8 mol / L or more, more preferably 0.9 mol / L or more, and may be preferably 1.1 mol / L or less.

[0023] When the zinc source is zinc acetate, the concentration of the aqueous ammonia solution may be preferably 0.8 mol / L or more, more preferably 1.0 mol / L or more, and may be preferably 1.8 mol / L or less.

[0024] The molar ratio of 2-methylimidazole in the aqueous solution containing zinc and 2-methylimidazole to ammonia in the aqueous ammonia solution (2-methylimidazole / ammonia) is preferably 0.25 or more and 2 or less, more preferably 0.5 or more and 2 or less, and even more preferably 0.65 or more and 1.5 or less.

[0025] Next, the aqueous solution containing zinc and 2-methylimidazole is mixed with the aqueous ammonia solution to obtain a suspension. The aqueous solution containing zinc and 2-methylimidazole may be a suspension, or may be suspended by adding aqueous ammonia to a non-suspended aqueous solution. This mixing produces ZIF-8.

[0026] The aqueous solution and the aqueous ammonia solution may be mixed by any method. Preferably, the aqueous solution and the aqueous ammonia solution are mixed by adding the aqueous ammonia solution to the aqueous solution. The aqueous ammonia solution may be added by, for example, dropwise addition or pouring, and is preferably added by dropwise addition.

[0027] The temperature at which the aqueous solution and the aqueous ammonia solution are mixed is preferably 5°C or higher and 40°C or lower, more preferably 10°C or higher and 30°C or lower, and even more preferably 15°C or higher and 25°C or lower.

[0028] It is preferable to mix the aqueous solution and the aqueous ammonia solution while suspending them, which makes it easier to obtain ZIF-8 particles with large particle sizes and also reduces particle size variations.

[0029] The rate of addition of the aqueous ammonia solution is preferably 50 ml / min or more and 500 ml / min or less, more preferably 50 ml / min or more and 300 ml / min or less.

[0030] The zinc concentration in the suspension is preferably 0.20 mol / l or more and 0.35 mol / l or less, and more preferably 0.25 mol / l or more and 0.30 mol / l or less.

[0031] The process then preferably includes filtering, washing and drying the suspension.

[0032] Filtration may be performed by conventional filtration methods, such as pressure filtration, vacuum filtration, and flat filtration, and industrially, flat filtration is preferred. According to the manufacturing method of the present disclosure, ZIF-8 with large particle size and uniformity can be obtained, so that the filtration time can be shortened.

[0033] The washing is preferably carried out using the solvent of the aqueous solution. Specifically, the washing solvent is, for example, water, methanol, or a mixture thereof, with water being preferred. The washing may be carried out simultaneously with the filtration. By carrying out reslurry washing and rinsing, the by-product ammonium salt can be washed away.

[0034] Drying is preferably carried out at a high temperature under reduced pressure, preferably at 60°C or higher, more preferably at 80°C or higher and 200°C or lower, and even more preferably at 80°C or higher and 150°C or lower.

[0035] The median particle size of the obtained ZIF-8 is preferably 10 μm or more, more preferably 15 μm or more, even more preferably 20 μm or more, for example, 40 μm or more. The median particle size may be, for example, 200 μm or less or 100 μm or less. Here, the median particle size can be measured using a laser diffraction particle size analyzer. [Example]

[0036] Example 1 A 10 L glass flask was charged with 2.4 L of methanol, 1.2 L of pure water, and 400 g (4.87 mol) of 2-methylimidazole, and dissolved to obtain an aqueous solution of 2-methylimidazole. Next, a solution of 700 g (2.43 mol) of zinc sulfate heptahydrate and 1.2 L of pure water was added to the resulting 2-methylimidazole aqueous solution. Next, 4.9 L of aqueous ammonia (1.6%, 1.0 M) was added dropwise over 30 minutes, and the mixture was stirred at room temperature (25°C) for 1 hour to obtain a white suspension. The resulting white suspension was subjected to vacuum filtration using a filter equipped with a Buchner funnel to obtain a filter cake. The filtration was carried out with a retention particle size of 1 μm and a filtration area of ​​267 cm. 2 A quantitative filter paper (185 mm diameter) was used. It took 17 minutes to filter 10 L of water. The filter cake was then washed twice with 10 L of pure water to obtain a separated cake. Each 10 L washing took 20 minutes. The separated cake was a crystalline solid. The solid was dried in a tray dryer at 100°C under vacuum for 24 hours to obtain ZIF-8. The dry weight was 527 g, and the yield based on zinc was 95%. The formation of ZIF-8 was confirmed by powder X-ray diffraction (PXRD).

[0037] Example 2 A 50 L glass flask was charged with 12 L of methanol, 6 L of pure water, and 2,000 g (24.3 mol) of 2-methylimidazole, and dissolved to obtain an aqueous solution of 2-methylimidazole. Next, a solution of 3,500 g (12.2 mol) of zinc sulfate heptahydrate and 6 L of pure water was added to the resulting 2-methylimidazole aqueous solution. Next, 24.3 L of aqueous ammonia (1.6%, 1.0 M) was added dropwise over 60 minutes, followed by stirring and reaction at room temperature (25°C) for 1 hour, yielding a white suspension. The resulting white suspension was subjected to vacuum filtration using a filter equipped with a Buchner funnel to obtain a filter cake. The filtration was carried out with a retention particle size of 1 μm and a filtration area of ​​707 cm. 2 A 300mm diameter quantitative filter was used. It took 37 minutes to filter 48 L. The filter cake was then washed and filtered twice with 50 L of pure water to obtain a separated cake. Each 50 L washing and filtration took 42 minutes. The separated cake was a crystalline solid. The solid was dried in a tray dryer at 100°C under vacuum for 24 hours to obtain ZIF-8. The dry weight was 2,622 g, and the yield based on zinc was 95%. The formation of ZIF-8 was confirmed by powder X-ray diffraction (PXRD).

[0038] Example 3 In a 10 L glass flask, 361 g (4.4 mol) of 2-methylimidazole and 483 g (2.2 mol) of zinc acetate dihydrate were added and dissolved in a mixture of 2.2 L of methanol and 2.2 L of pure water to obtain an aqueous solution of 2-methylimidazole and zinc acetate dihydrate. Next, 3.7 L of aqueous ammonia (2.1%, 1.2 M) was added dropwise to the obtained aqueous solution of 2-methylimidazole and zinc acetate dihydrate over 30 minutes, and the mixture was stirred at room temperature (25°C) for 1 hour to obtain a white suspension. The obtained white suspension was subjected to vacuum filtration using a filter equipped with a Buchner funnel to obtain a filter cake. The filtration was carried out with a retention particle size of 1 μm and a filtration area of ​​267 cm. 2A quantitative filter paper (185 mm diameter) was used. It took 13 minutes to filter 8 L. The filter cake obtained was then washed and filtered twice with 10 L of pure water to obtain a separated cake. Each 10 L washing and filtration took 20 minutes. The separated cake was a crystalline solid. The solid was dried in a tray dryer at 100°C under vacuum for 24 hours to obtain ZIF-8. The dry weight was 420 g, and the yield based on zinc was 84%. The formation of ZIF-8 was confirmed by powder X-ray diffraction (PXRD).

[0039] Example 4 In a 50 L glass flask, 2,289 g (27.9 mol) of 2-methylimidazole and 3,060 g (13.9 mol) of zinc acetate dihydrate were dissolved in a mixture of 14 L of methanol and 14 L of pure water to obtain an aqueous solution of 2-methylimidazole and zinc acetate dihydrate. Next, 23.3 L of aqueous ammonia (2.1%, 1.2 M) was added dropwise to the resulting aqueous solution of 2-methylimidazole and zinc acetate dihydrate over 60 minutes, and the mixture was stirred at room temperature (25°C) for 1 hour to obtain a white suspension. The resulting white suspension was subjected to vacuum filtration using a filter equipped with a Buchner funnel to obtain a filter cake. The filtration was carried out with a retention particle size of 1 μm and a filtration area of ​​707 cm. 2 A 300mm diameter quantitative filter was used. It took 17 minutes to filter 50 L of the mixture. The filter cake was then rinsed twice with 50 L of pure water to obtain a separated cake. Each 50 L rinse took 15 minutes. The separated cake was a crystalline solid. The solid was dried in a tray dryer at 100°C under vacuum for 24 hours to obtain ZIF-8. The dry weight was 2,624 g, and the yield based on zinc was 83%. The formation of ZIF-8 was confirmed by powder X-ray diffraction (PXRD).

[0040] Example 5 A 10 L glass flask was charged with 2.7 L of methanol, 1.4 L of pure water, and 451 g (5.5 mol) of 2-methylimidazole, and dissolved to obtain an aqueous solution of 2-methylimidazole. Next, a solution of 790 g (2.75 mol) of zinc sulfate heptahydrate and 1.4 L of pure water was added to the resulting 2-methylimidazole aqueous solution. Next, 4.6 L of aqueous ammonia (2.1%, 1.2 M) was added dropwise over 30 minutes, and the mixture was stirred at room temperature (25°C) for 1 hour to obtain a white suspension. The resulting white suspension was subjected to vacuum filtration using a filter equipped with a Buchner funnel to obtain a filter cake. The filtration was carried out with a retention particle size of 1 μm and a filtration area of ​​267 cm. 2 A quantitative filter paper (185 mm diameter) was used. Filtration of 10 L took 20 minutes. The filter cake obtained was then washed and filtered twice with 10 L of pure water to obtain a separated cake. Each 10 L washing and filtration took 40 minutes. The separated cake was a crystalline solid. The solid was dried in a tray dryer at 100°C under vacuum for 24 hours to obtain ZIF-8. The dry weight was 598 g, and the yield based on zinc was 96%. The formation of ZIF-8 was confirmed by powder X-ray diffraction (PXRD).

[0041] Example 6 In a 10 L glass flask, 361 g (4.4 mol) of 2-methylimidazole and 483 g (2.2 mol) of zinc acetate dihydrate were added and dissolved in a mixture of 2.2 L of methanol and 2.2 L of pure water to obtain an aqueous solution of 2-methylimidazole and zinc acetate dihydrate. Next, 2.5 L of aqueous ammonia (3.0%, 1.8 M) was added dropwise to the obtained aqueous solution of 2-methylimidazole and zinc acetate dihydrate over 30 minutes, and the mixture was stirred at room temperature (25°C) for 1 hour to obtain a white suspension. The obtained white suspension was subjected to vacuum filtration using a filter equipped with a Buchner funnel to obtain a filter cake. The filtration was carried out with a retention particle size of 1 μm and a filtration area of ​​267 cm. 2A quantitative filter paper (185 mm diameter) was used. It took 18 minutes to filter 7 L. The filter cake obtained was then washed and filtered twice with 10 L of pure water to obtain a separated cake. Each 10 L washing and filtration took 25 minutes. The separated cake was a crystalline solid. The solid was dried in a tray dryer at 100°C under vacuum for 24 hours to obtain ZIF-8. The dry weight was 420 g, and the yield based on zinc was 84%. The formation of ZIF-8 was confirmed by powder X-ray diffraction (PXRD).

[0042] (Comparative Example 1) A 10 L glass flask was charged with 2.7 L of methanol, 1.4 L of pure water, and 451 g (5.49 mol) of 2-methylimidazole, and dissolved to obtain an aqueous solution of 2-methylimidazole. Next, a solution of 790 g (2.75 mol) of zinc sulfate heptahydrate and 1.4 L of pure water was added to the resulting 2-methylimidazole aqueous solution. Next, 3 L of aqueous ammonia (3.0%, 1.8 M) was added dropwise over 30 minutes, and the mixture was stirred at room temperature (25°C) for 1 hour to obtain a white suspension. The resulting white suspension was subjected to vacuum filtration using a filter equipped with a Buchner funnel to obtain a filter cake. The filtration was carried out with a retention particle size of 1 μm and a filtration area of ​​707 cm. 2 A 300mm diameter quantitative filter was used. It took 3 hours to filter 9 L. The filter cake was then washed and filtered twice with 10 L of pure water to obtain a separated cake. Each 10 L washing and filtration took 2 hours. The separated cake was a viscous solid. The resulting viscous solid was dried in a tray dryer at 100°C under vacuum for 24 hours to obtain ZIF-8. The dry weight was 577 g, and the yield based on zinc was 92%. The formation of ZIF-8 was confirmed by powder X-ray diffraction (PXRD).

[0043] (Comparative Example 2) A 500 ml glass flask was charged with 163 ml of methanol, 82 ml of pure water, and 26.8 g (0.326 mol) of 2-methylimidazole, and dissolved to obtain an aqueous solution of 2-methylimidazole. Next, a solution of 47 g (0.163 mol) of zinc sulfate heptahydrate and 82 ml of pure water was added to the resulting 2-methylimidazole solution. Next, 105 ml of aqueous ammonia (5.4%, 3.1 M) was added dropwise over 30 minutes, followed by stirring at room temperature (25°C) for 1 hour to obtain a white suspension. Since the resulting white suspension could not be filtered, it was centrifuged at 6,000 rpm for 10 minutes. The supernatant was removed, and the sediment was immersed in 500 ml of pure water for 2 hours to wash, followed by the same centrifugation procedure. The same procedure was repeated, and after removing the supernatant, the precipitated viscous solid was taken out and dried in vacuum at 100 °C for 24 hours. The dry weight was 37 g, and the yield based on zinc was 94%. The formation of ZIF-8 was confirmed by powder X-ray diffraction (PXRD).

[0044] (Comparative Example 3) In a 10 L glass flask, 361 g (4.4 mol) of 2-methylimidazole and 483 g (2.2 mol) of zinc acetate dihydrate were added and dissolved in a mixture of 2.2 L of methanol and 2.2 L of pure water to obtain an aqueous solution of 2-methylimidazole and zinc acetate dihydrate. Next, 2.0 L of aqueous ammonia (3.8%, 2.25 M) was added dropwise to the obtained aqueous solution of 2-methylimidazole and zinc acetate dihydrate over 30 minutes, and the mixture was stirred at room temperature (25°C) for 1 hour to obtain a white suspension. The obtained white suspension was subjected to vacuum filtration using a filter equipped with a Buchner funnel to obtain a filter cake. The filtration was carried out with a retention particle size of 1 μm and a filtration area of ​​267 cm. 2A quantitative filter paper (185 mm diameter) was used. It took 40 minutes to filter 7 L. The filter cake obtained was then washed and filtered twice with 10 L of pure water to obtain a separated cake. Each 10 L washing and filtration took 45 minutes. The separated cake was a crystalline solid. The solid was dried in a tray dryer at 100°C under vacuum for 24 hours to obtain ZIF-8. The dry weight was 420 g, and the yield based on zinc was 84%. The formation of ZIF-8 was confirmed by powder X-ray diffraction (PXRD).

[0045] Comparative Example 4 A 10 L glass flask was charged with 2.7 L of methanol, 1.4 L of pure water, and 451 g (5.49 mol) of 2-methylimidazole, and dissolved to obtain an aqueous solution of 2-methylimidazole. Next, a solution of 790 g (2.75 mol) of zinc sulfate heptahydrate and 1.4 L of pure water was added to the resulting 2-methylimidazole aqueous solution. Next, 3 L of aqueous sodium hydroxide (7.4%, 1.85 M) was added dropwise over 30 minutes, and the mixture was stirred at room temperature (25°C) for 1 hour to obtain a white suspension. The resulting white suspension was subjected to vacuum filtration using a filter equipped with a Buchner funnel to obtain a filter cake. The filtration was carried out with a retention particle size of 1 μm and a filtration area of ​​707 cm. 2 A quantitative filter paper (300φ) was used. It took 80 minutes to filter 9 L. The filter cake was then washed and filtered twice with 10 L of pure water to obtain a separated cake. Each 10 L washing and filtration required 2 hours. The separated cake was a viscous solid. The solid was dried in a tray dryer at 100°C under vacuum for 24 hours to obtain ZIF-8. The dry weight was 600 g, and the yield based on zinc was 96%. The formation of ZIF-8 was confirmed by powder X-ray diffraction (PXRD). 0.1% Na was detected as an impurity.

[0046] (Comparative Example 5) A 5-L glass flask was charged with 2.5 L of purified water and 81 g (0.99 mol) of 2-methylimidazole, and dissolved to obtain an aqueous solution of 2-methylimidazole. Next, 100 g (0.99 mol) of triethylamine was added dropwise to the resulting 2-methylimidazole solution over 10 minutes to deprotonate it. Next, a solution of 36.7 g (0.123 mol) of zinc nitrate hexahydrate in 2.5 L of purified water was added to the deprotonated 2-methylimidazole solution, and the mixture was stirred at room temperature (25°C) for 10 minutes to obtain a white suspension. Since the resulting white suspension could not be filtered, it was centrifuged at 6,000 rpm for 10 minutes. The supernatant was removed, and the precipitate was immersed in 5 L of purified water for 12 hours to wash, followed by the same centrifugation procedure. The same procedure was repeated, and after removing the supernatant, the precipitated solid was dried at 150°C under vacuum for 24 hours to obtain crystals. The Zn content of the obtained crystals was low at 23.6% (purity 82.1%), and TG / DTA analysis suggested the presence of residual 2-imidazole. Therefore, the crystals were further dried at 350°C under vacuum for 24 hours. The yield was 27.6 g, a 98.5% yield. Powder X-ray diffraction (PXRD) confirmed that the crystals were not fully crystallized. The formation of ZIF-8 was confirmed by powder X-ray diffraction (PXRD).

[0047] (Comparative Example 6) A 500 ml glass flask was charged with 120 ml of methanol, 60 ml of purified water, and 20 g (0.244 mol) of 2-methylimidazole, and dissolved to obtain an aqueous solution of 2-methylimidazole. Next, a solution of 36.2 g (0.122 mol) of zinc nitrate hexahydrate and 60 ml of purified water was added to the resulting 2-methylimidazole solution. Next, 284 ml of aqueous ammonia (1.6%, 0.86 M) was added dropwise over 30 minutes, followed by stirring at room temperature (25 °C) for 1 hour to obtain a white suspension. The resulting white suspension was filtered under reduced pressure using a filter equipped with a Buchner funnel to obtain a filter cake. The resulting filter cake was then washed twice with 500 ml of purified water and filtered to obtain a separated cake. The separated cake was then dried in a tray dryer at 100 °C under vacuum for 24 hours to obtain ZIF-8. The dry weight was 24 g, and the yield based on zinc was 87%. Powder X-ray analysis (PXRD) confirmed that the product was not sufficiently crystallized.

[0048] (Comparative Example 7) A 500 ml glass flask was charged with 120 ml of methanol, 60 ml of purified water, and 20 g (0.244 mol) of 2-methylimidazole, and dissolved to obtain an aqueous solution of 2-methylimidazole. Next, a solution of 16.6 g (0.122 mol) of zinc chloride and 60 ml of purified water was added to the resulting 2-methylimidazole solution. Next, 284 ml of aqueous ammonia (1.6%, 0.86 M) was added dropwise over 30 minutes, followed by stirring at room temperature (25 °C) for 1 hour to obtain a white suspension. The resulting white suspension was filtered under reduced pressure using a filter equipped with a Buchner funnel to obtain a filter cake. The resulting filter cake was then washed twice with 500 ml of purified water and filtered to obtain a separated cake. The separated cake was then dried in a tray dryer at 100 °C under vacuum for 24 hours to obtain ZIF-8. The dry weight was 25 g, and the yield based on zinc was 91%. Powder X-ray analysis (PXRD) confirmed that the product was not sufficiently crystallized.

[0049] (Comparative Example 8) 1.35 g (16.6 mmol) of zinc oxide, 2.73 g (33.3 mmol) of 2-methylimidazole and 8 ml of pure water were added to a rotary high-speed mixer with a capacity of 30 ml, and a solid-phase reaction was carried out while stirring at 16,000 revolutions per minute for 15 minutes. The solid after the reaction was filtered, washed with pure water, and a solid was obtained. The obtained solid was dried in a shelf dryer at 100 °C under vacuum for 24 hours to obtain ZIF-8. The dry weight was 5.4 g (theoretical yield: 3.7 g). The formation of ZIF-8 was confirmed by powder X-ray analysis (PXRD).

[0050] (Evaluation) <Particle size> The particle sizes of the ZIF-8 obtained in each example and each comparative example were measured using ethanol as the measurement solvent with a commercially available laser diffraction particle size distribution measuring device (Mastersizer 3000 manufactured by Malvern Panalytical).

[0051] <Zn content> The Zn contents of the ZIF-8 obtained in each example and each comparative example were measured using chelometric titration analysis.

[0052] <Specific surface area and pore volume> The specific surface areas and pore volumes of the ZIF-8 obtained in each example and each comparative example were measured using a commercially available gas adsorption analyzer (Autosorb iQ manufactured by Anton Paar Co., Ltd.). ·Measurement conditions Pretreatment: 150 °C for 24 hours Measurement temperature: 87 K (liquid argon) Measurement gas: argon gas <Powder X-ray diffraction (PXRD)> For the ZIF-8 obtained in each example and each comparative example, PXRD measurement was performed using a commercially available X-ray diffractometer (manufactured by Rigaku Corporation, trade name: MniFlex600).

[0053]

Table 1

[0054] [Table 2]

[0055] From the above results, it was confirmed that the manufacturing method of the present disclosure can obtain ZIF-8 with a short filtration time and a large particle size. In addition, the specific surface area and pore volume were also sufficiently large.

[0056] Embodiments of the present disclosure include the following items. [Section 1] A method for producing a metal organic framework containing zinc and a 2-methylimidazole ligand, comprising: mixing an aqueous solution containing zinc and 2-methylimidazole with an aqueous ammonia solution to obtain a suspension; the zinc source of the aqueous solution is zinc sulfate or zinc acetate; The concentration of the aqueous ammonia solution is 0.7 mol / L or more and 1.2 mol / L or less when the zinc source is zinc sulfate, and is 0.7 mol / L or more and 2.0 mol / L or less when the zinc source is zinc acetate. Method for producing metal-organic frameworks. [Section 2] Item 2. The method according to Item 1, wherein the molar ratio of 2-methylimidazole to zinc in the aqueous solution containing zinc and 2-methylimidazole is 1 or more and 5 or less. [Section 3] Item 2. The method according to Item 1, wherein the molar ratio of 2-methylimidazole in the aqueous solution containing zinc and 2-methylimidazole to ammonia in the aqueous ammonia solution is 0.25 or more and 2 or less. [Section 4] Item 1. The method according to Item 1, wherein the aqueous solution containing zinc and 2-methylimidazole further contains methanol. [Section 5] Item 5. The method according to Item 4, wherein the volume ratio of water to methanol in the aqueous solution containing zinc and 2-methylimidazole is 0.25 or more and 4 or less. [Section 6] Item 2. The method according to Item 1, wherein the zinc concentration in the suspension is 0.20 mol / L or more and 0.35 mol / L or less. [Section 7] Item 1. The method of claim 1, further comprising filtering, washing, and drying the suspension. [Section 8] Item 2. The production method according to Item 1, wherein the metal organic framework containing zinc and a 2-methylimidazole ligand is obtained as particles having a median particle size of 10 μm or more.

Claims

1. A method for producing a metal organic framework containing zinc and a 2-methylimidazole ligand, comprising: mixing an aqueous solution containing zinc and 2-methylimidazole with an aqueous ammonia solution to obtain a suspension; the zinc source of the aqueous solution is zinc sulfate or zinc acetate; The concentration of the aqueous ammonia solution is 0.7 mol / L or more and 1.2 mol / L or less when the zinc source is zinc sulfate, and is 0.7 mol / L or more and 2.0 mol / L or less when the zinc source is zinc acetate. Method for producing metal-organic frameworks.

2. 2. The method according to claim 1, wherein the molar ratio of 2-methylimidazole to zinc in the aqueous solution containing zinc and 2-methylimidazole is 1 or more and 5 or less.

3. 2. The method according to claim 1, wherein a molar ratio of 2-methylimidazole in the aqueous solution containing zinc and 2-methylimidazole to ammonia in the aqueous ammonia solution is 0.25 or more and 2 or less.

4. The method according to claim 1, wherein the aqueous solution containing zinc and 2-methylimidazole further contains methanol.

5. 5. The method according to claim 4, wherein the volume ratio of water to methanol in the aqueous solution containing zinc and 2-methylimidazole is 0.25 or more and 4 or less.

6. The method according to claim 1, wherein the zinc concentration in the suspension is 0.20 mol / L or more and 0.35 mol / L or less.

7. The method of claim 1 further comprising filtering, washing, and drying the suspension.

8. The production method according to claim 1, wherein the metal organic framework containing zinc and a 2-methylimidazole ligand is obtained as particles having a median particle size of 10 μm or more.

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