Metal-organic framework and method for producing the same

Abstract

To provide a metal-organic framework that has an RHO-type topology and exhibits high gas adsorption and desorption performance, and means for producing the metal-organic framework in a high yield.SOLUTION: One embodiment of the present invention relates to a metal-organic framework having an RHO-type topology, which includes zinc (Zn) as a metal and benzimidazole (BzIm) and 4-methylimidazole (4-MeIm) as ligands. Another embodiment of the present invention relates to a method for producing a metal-organic framework having the above characteristics.SELECTED DRAWING: Figure 12

Description

[Technical Field]

[0001] The present invention relates to a metal-organic framework and a method for producing the same. [Background technology]

[0002] Metal-organic frameworks (hereinafter also referred to as "MOFs") are crystalline porous materials composed of metals and organic ligands. The pore size, surface shape, and other properties of MOFs can be designed at the molecular level by selecting the combination of metals and organic ligands used. MOFs are expected to be used in gas storage materials, heterogeneous catalysts, and conductive materials, for example.

[0003] For example, Non-Patent Document 1 discloses the solvothermal synthesis of RHO-type Zn(BzIm)2 (ZIF-11), where BzIm represents benzimidazole.

[0004] Non-Patent Document 2 discloses the mechanochemical synthesis of RHO-type Zn(BzIm)2 (ZIF-11) using rccc-MeMeCH2 as a template.

[0005] Non-Patent Document 3 discloses the production of layered Zn(BzIm)2 (ZIF-7-III), a dense phase that is stable at high temperatures. [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] KS Park et al., “Exceptional chemical and thermal stability of zeolitic imidazolate frameworks,” PNAS, vol. 103, no. 27, p.10186-10191 (2006) [Non-patent document 2] I. Brekalo et al., "Exploring the Scope of Macrocyclic "Shoe-last" Templates in the Mechanochemical Synthesis of RHO Topology Zeolitic Imidazolate Frameworks (ZIFs)," molecules, 25, 633 (2020) [Non-patent document 3] P. Zhao et al., “Phase Transitions in Zeolitic Imidazolate Framework 7: The Importance of Framework Flexibility and Guest-Induced Instability,” Chem. Mater., 26, p.1767-1769 (2014) Summary of the Invention [Problem to be solved by the invention]

[0007] Zn(BzIm)2 can have RHO type (Figure 1), layered (Figure 2 and Non-Patent Document 3), and SOD type topologies. Of these, the RHO type is known to have the largest pore volume and excellent gas adsorption capacity.

[0008] In Non-Patent Document 1, single-phase RHO-type Zn(BzIm)2 was obtained by liquid phase synthesis. In liquid phase synthesis, Zn was converted into zinc ions (Zn 2+ ) and is easily reactive because it has passed through a completely dissolved state. 2+ remains dissolved in the solution, so ZnO and other impurities are less likely to be mixed in. 2+ The concentration of Zn(BzIm)2 is only equivalent to 6.4 mmol / L, which means that 156 L of DEF solvent is required per mol of Zn. As a result, the yield of RHO-type Zn(BzIm)2 is only 0.1 wt% or less based on the solvent and raw materials.

[0009] In Non-Patent Document 2, RHO-type Zn(BzIm)2 was obtained by mechanochemical synthesis using rccc-MeMeCH2 as a template. However, since rccc-MeMeCH2 is not commercially available, a synthesized product was used. Using such a template increases the manufacturing cost.

[0010] In addition, the RHO-type Zn(BzIm)2 has a narrow pore window, and there is room for improvement in the gas adsorption / desorption rate.

[0011] Therefore, an object of the present invention is to provide a MOF having an RHO topology with high gas adsorption / desorption properties and a means for producing the MOF in high yield. [Means for solving the problem]

[0012] The present inventors have investigated various means for solving the above problems. In the production of MOFs, the present inventors performed mechanochemical synthesis by replacing part of the BzIm in the raw materials zinc compound and benzimidazole (BzIm) with 4-methylimidazole (4-MeIm). As shown in Figure 3, 4-MeIm (B), which has less steric hindrance than BzIm (A), has high solubility and diffusibility and is more reactive. Furthermore, part of the BzIm in RHO-type Zn(BzIm)2 is replaced with 4-MeIm, which has less steric hindrance, to form RHO-type Zn(BzIm). 2-z (4-MeIm) z When this occurs, the pore windows expand as shown in Figure 4, improving the diffusibility of raw materials and gases inside the product. The present inventors have completed the present invention based on the above findings.

[0013] That is, the present invention includes the following aspects and embodiments. (Embodiment 1) A metal-organic framework having an RHO topology, comprising zinc (Zn) as a metal and benzimidazole (BzIm) and 4-methylimidazole (4-MeIm) as ligands. (Embodiment 2) The metal organic structure according to embodiment 1, wherein the molar ratio of 4-MeIm to the total of BzIm and 4-MeIm (4-MeIm / (BzIm+4-MeIm)) is in the range of 0.11 to 0.53. (Embodiment 3) A gas adsorption / desorption material comprising an adsorption / desorption material, the adsorption / desorption material comprising the metal organic framework according to embodiment 1 or 2, wherein the metal organic framework contains 90 mol % or more of RHO topology relative to the total substance amount of the metal organic framework. (Embodiment 4) A method for producing a metal organic framework according to embodiment 1 or 2, comprising: a mechanochemical reaction step of mechanochemically reacting a zinc compound, BzIm, and 4-MeIm in the presence of a solvent; and a heating step after the mechanochemical reaction step, wherein the relationship between the amount of 4-MeIm charged and the heating temperature is adjusted to be within the range of a square with vertices at (x, y) = (12.5, 80), (50, 80), (50, 130), and (12.5, 100) in an xy graph showing the relationship between the amount of 4-MeIm charged (x mol%) and the heating temperature (y °C). Embodiment 5: The method of embodiment 4, wherein the solvent is N,N-diethylformamide (DEF). Embodiment 6: The method of embodiment 4 or 5, wherein the zinc compound is zinc oxide (ZnO). [Effects of the Invention]

[0014] The present invention makes it possible to provide a MOF having an RHO topology with high gas adsorption / desorption properties and a means for producing the MOF in high yield. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a diagram showing a schematic structure of RHO-type Zn(BzIm) 2 . [Figure 2] FIG. 1 is a diagram showing a schematic structure of layered Zn(BzIm)2. [Figure 3] FIG. 1 shows schematic diagrams of the structures of BzIm (A) and 4-MeIm (B). [Figure 4]FIG. 1 is a diagram showing a schematic structure of RHO-type Zn(BzIm)2-z(4-MeIm)z. [Figure 5] 1 is a graph showing X-ray diffraction patterns of the powder products of Comparative Examples 1-1, 1-5, and 1-6 and Examples 1-2 to 1-4. The horizontal axis represents the 2θ value (°), and the vertical axis represents the intensity (au). x represents the amount (mol%) of 4-MeIm charged relative to the amount (mol%) of the entire ligand (BzIm and 4-MeIm) (hereinafter referred to as "amount (mol%) of 4-MeIm charged"). Note that RHO-type, layered, and ACO-type represent the results of simulations of calculated X-ray diffraction patterns for RHO-type Zn(BzIm)2, layered Zn(BzIm)2, and ACO-type Zn(BzIm)2, respectively. [Figure 6] 1 is a graph showing X-ray diffraction patterns of the products of Comparative Examples 2-1, 2-5, and 2-6 and Examples 2-2 to 2-4. The horizontal axis represents the 2θ value (°), and the vertical axis represents the intensity (au). x represents the amount of 4-MeIm charged (mol%). Note that RHO-type, layered, and ACO-type represent the results of simulations of calculated X-ray diffraction patterns for RHO-type Zn(BzIm)2, layered Zn(BzIm)2, and ACO-type Zn(BzIm)2, respectively. [Figure 7] 1 is a graph showing X-ray diffraction patterns of the products of Comparative Examples 3-1 to 3-3, 3-5, and 3-6 and Example 3-4. The horizontal axis represents the 2θ value (°), and the vertical axis represents the intensity (au). x represents the amount of 4-MeIm charged (mol%). Note that RHO-type, layered, and ACO-type represent the results of simulations of calculated X-ray diffraction patterns for RHO-type Zn(BzIm)2, layered Zn(BzIm)2, and ACO-type Zn(BzIm)2, respectively. [Figure 8] 1 is a graph showing the crystal structure of the product produced as a function of the amount of 4-MeIm charged (mol%) (horizontal axis) and the heating temperature (°C) (vertical axis). ○ indicates RHO type, × indicates layered, and △ indicates ACO type. [Figure 9]1 is a graph showing N adsorption / desorption isotherms for the products of Comparative Examples 1-5 and 1-6 and Examples 1-2 to 1-4. The horizontal axis represents the relative N pressure (%), and the vertical axis represents the amount of N adsorbed (mL(STP) g). x represents the amount of 4-MeIm charged (mol%). [Figure 10] 1 is a graph showing N adsorption / desorption isotherms for the products of Comparative Examples 2-5 and 2-6 and Examples 2-2 to 2-4. The horizontal axis represents the relative N pressure (%), and the vertical axis represents the amount of N adsorbed (mL(STP) g). x represents the amount of 4-MeIm charged (mol%). [Figure 11] 1 is a graph showing N adsorption / desorption isotherms for the products of Comparative Examples 3-1 to 3-3, 3-5, and 3-6 and Example 3-4. The horizontal axis represents the relative N pressure (%), and the vertical axis represents the N adsorption amount (mL(STP) g). x represents the amount of 4-MeIm charged (mol%). [Figure 12] This graph shows the crystal structure of the product produced at each heating temperature, relative to the amount of 4-MeIm charged (mol%) (horizontal axis) versus the amount of N2 adsorption (mL(STP) g-1) at a relative N2 pressure of 50% (vertical axis). ◯ indicates RHO type, × indicates layered, and △ indicates ACO type. DETAILED DESCRIPTION OF THE INVENTION

[0016] Preferred embodiments of the present invention will now be described in detail.

[0017] <1: Metal-organic structure> One aspect of the present invention relates to a metal-organic framework (MOF), which is a metal-organic framework having an RHO topology and containing zinc (Zn) as a metal and benzimidazole (BzIm) and 4-methylimidazole (4-MeIm) as ligands.

[0018] Zn(BzIm)2 MOFs containing Zn and BzIm can have various topologies, such as RHO type (ZIF-11), layered type (ZIF-7-III), and SOD type. Among them, ZIF-11 has a large gas adsorption capacity. However, ZIF-11 is difficult to obtain in high purity because it competes with ZIF-7-III, which does not have micropores. Furthermore, ZIF-11 has narrow pore windows, which slows the diffusion of gases such as nitrogen (N2).

[0019] In ZIF-11, 4-MeIm was added to BzIm as a ligand to give Zn(BzIm). 2-z (4-MeIm) z When synthesized, the layered crystal structure becomes unstable, making it easier to obtain the RHO type. Furthermore, the pore window expands as part of the BzIm is replaced by 4-MeIm. As a result, the gas adsorption capacity can be further increased and gas diffusivity can also be improved.

[0020] In ZIF-11, the competing product ZIF-7-III interacts with the benzene rings of BzIm in the structure by facing each other. However, this interaction is lost when part of the BzIm is replaced with 4-MeIm. As a result, the substitution with 4-MeIm destabilizes the layered structure, favoring the formation of the RHO type.

[0021] In the MOF of this embodiment, the molar ratio of 4-MeIm to the sum of BzIm and 4-MeIm in the ligand (4-MeIm / (BzIm+4-MeIm)) is not limited as long as the MOF of this embodiment can have an RHO topology, but is usually in the range of 0.11 to 0.53, and in one embodiment, in the range of 0.25 to 0.50. By ensuring that the molar ratio of BzIm to 4-MeIm in the ligand is within the above range, the MOF of this embodiment can have an RHO topology and high gas adsorption / desorption properties.

[0022] The MOF of this embodiment typically has the following formula (I): Zn(BzIm) 2-z (4-MeIm) z In formula (I), BzIm is benzimidazole as a ligand, and 4-MeIm is 4-methylimidazole as a ligand. From formula (I), the molar ratio of Zn as the metal to the total of BzIm and 4-MeIm as ligands (Zn:(BzIm+4-MeIm)) is 1:2. In formula (I), z is not limited as long as it is greater than 0 and less than 2 based on the molar ratio of 4-MeIm to the total of BzIm and 4-MeIm in the ligands described above, but is typically in the range of 0.22 to 1.06, and in one embodiment, in the range of 0.50 to 1.00. The MOF of this embodiment represented by formula (I) can have high gas adsorption / desorption properties.

[0023] The gas adsorption / desorption properties of the MOF of this embodiment can be evaluated, for example, by measuring the N adsorption isotherm of the MOF. The gas adsorption properties of the MOF of this embodiment can be evaluated, for example, by calculating the N adsorption amount at a relative N pressure of 50%. The N adsorption amount of the MOF of this embodiment at a relative N pressure of 50% is usually 180 mL(STP) g -1 In one embodiment, 180 mL (STP) g -1 ~320mL(STP)·g -1 The range is.

[0024] <2:Method for producing metal-organic framework> Another aspect of the present invention relates to a method for producing the metal-organic framework of the aspect of the present invention.

[0025] The method of this embodiment includes a mechanochemical reaction step. This step involves mechanochemically reacting a zinc compound with benzimidazole (BzIm) and 4-methylimidazole (4-MeIm) in the presence of a solvent. As used herein, mechanochemical reaction refers to applying mechanical stress, such as grinding, to a raw material, typically a solid, to change the crystalline structure of the raw material and promote a chemical reaction. Therefore, in the mechanochemical reaction of the present invention, a chemical reaction is promoted by applying mechanical stress, such as by stirring or mixing, to a raw material containing a zinc compound that is not dissolved in a solvent.

[0026] The zinc compound used in this step is not limited to, but may be, for example, zinc oxide (ZnO), zinc hydroxide (Zn(OH)), or a mixture thereof, and in one embodiment, zinc oxide. The reactivity of the zinc compounds exemplified above can be improved by using the solvents exemplified below. Therefore, by carrying out this step using the zinc compounds exemplified above, the mechanochemical reaction can be efficiently carried out, and the MOF of one embodiment of the present invention can be obtained.

[0027] The amounts of benzimidazole (BzIm) and 4-methylimidazole (4-MeIm) charged are usually twice the amount of zinc. The amount of 4-MeIm charged is adjusted so that the molar ratio of 4-MeIm to the total of BzIm and 4-MeIm (4-MeIm / (BzIm+4-MeIm)) is in the range of 0.125 to 0.500, and in one embodiment, in the range of 0.250 to 0.500. By adjusting the amount of 4-MeIm charged to the above range, Zn(BzIm) 2-z (4-MeIm) z has an RHO-type topology.

[0028] The 4-MeIm content (molar ratio) in an MOF according to one embodiment of the present invention and the amount (molar ratio) of 4-MeIm charged in a method for producing an MOF according to another embodiment of the present invention generally have a similar relationship, within an error range of about 10%. This is because, in the synthesis method of the present invention, BzIm and 4-MeIm are highly reactive and are almost entirely incorporated into the MOF upon contact with ZnO, and the MOF once produced is stable and BzIm and 4-MeIm do not elute, resulting in a MOF containing BzIm and 4-MeIm in approximately the same ratio as the charged amounts.

[0029] The solvent used in this step is a liquid compound that can dissolve the starting ligands BzIm and 4-MeIm and serves as a reaction site for Zn with BzIm and 4-MeIm in the mechanochemical reaction. Examples of solvents include, but are not limited to, cyclohexane, N,N-dimethylformamide (DMF), N,N-diethylformamide (DEF), methanol, ethanol, or a mixture of two or more of these. In one embodiment, the solvent is DEF. The solvents listed above are capable of dissolving the starting materials BzIm and 4-MeIm. Therefore, by performing this step using the solvents listed above, the mechanochemical reaction can be efficiently carried out to obtain the MOF of one embodiment of the present invention.

[0030] The amount of solvent used in this step is not limited, but is typically 20% to 60% by weight, and in one embodiment, 30% to 50% by weight, based on the total weight of the raw materials. By using a solvent amount within this range in this step, the MOF of one aspect of the present invention can be obtained without using a large amount of solvent, improving production efficiency.

[0031] In this step, the mechanochemical reaction can be carried out by mixing the raw materials using a mortar. The mixing time in the mortar is usually 20 minutes or more, and in one embodiment, it is in the range of 20 minutes to 3 hours, for example, in the range of 30 minutes to 2 hours. Furthermore, the mixing temperature in the mortar is usually in the range of 0°C to 50°C, and in one embodiment, it is in the range of 10°C to 30°C. By carrying out this step under the above conditions, the mechanochemical reaction can be efficiently carried out, and an MOF of one aspect of the present invention can be obtained.

[0032] In this step, the mechanochemical reaction may be carried out by mixing the raw materials using a ball mill. In this embodiment, the rotation speed of the ball mill is not limited, but is usually 50 rpm or higher, and in one embodiment, in the range of 50 rpm to 800 rpm. The mixing time using the ball mill is usually 1 hour or longer, and in one embodiment, in the range of 1 hour to 3 hours. The mixing temperature using the ball mill is usually in the range of 0°C to 100°C, and in one embodiment, in the range of 10°C to 50°C. By carrying out this step under the above conditions, the mechanochemical reaction can be efficiently carried out, and an MOF of one aspect of the present invention can be obtained.

[0033] The mechanochemically reacted raw materials are then subjected to a heating step. In this heating step, the relationship between the amount of 4-MeIm charged and the heating temperature is adjusted so that it falls within the range of a rectangle with vertices (x, y) = (12.5, 80), (50, 80), (50, 130), and (12.5, 100) in an xy graph showing the relationship between the amount of 4-MeIm charged (x mol%) and the heating temperature (y °C). In other words, the heating temperature can be changed depending on the amount of 4-MeIm charged. By adjusting the heating temperature to fall within the above range depending on the amount of 4-MeIm charged, Zn(BzIm) 2-z (4-MeIm) z has an RHO-type topology.

[0034] As described in detail above, the MOF of one aspect of the present invention has a RHO-type topology in which a part of the ligand BzIm is substituted by 4-MeIm, so that it can have a large pore volume and high gas adsorption / desorption properties. Furthermore, by expanding the pore window, a large amount of gas adsorption / desorption can be achieved at high speed. Therefore, the MOF of one aspect of the present invention can be used as a gas adsorption / desorption material, and the gas adsorption / desorption material can be applied to a gas adsorption / desorption system, a gas separation system, or a gas storage system. The gas adsorption / desorption material of one aspect of the present invention contains the MOF of one aspect of the present invention, and the MOF contains a RHO-type topology at 90 mol% or more, in one embodiment 95 mol% or more, and in one embodiment 99 mol% or more based on the total amount of substances of the MOF. In one embodiment, the gas adsorption / desorption material containing the MOF of one aspect of the present invention contains the MOF of one aspect of the present invention, and the MOF contains the RHO-type topology in a single phase. Here, the single phase means that all of the MOF of one aspect of the present invention exists in a RHO-type topology. In addition, the production method of one aspect of the present invention can obtain the MOF of one aspect of the invention having the characteristics described above in a high yield. Therefore, the production method of one aspect of the present invention can efficiently provide a material applicable to the uses exemplified above.

Example

[0035] Hereinafter, the present invention will be described more specifically using examples. However, the technical scope of the present invention is not limited to these examples.

[0036] <I: Production of Metal-Organic Framework> [Reagents] Zinc oxide (ZnO): FUJIFILM Wako Pure Chemical Corporation 0.02 μm Practical Grade 95.0+% Benzimidazole (BzIm): Tokyo Chemical Industry Co., Ltd. >98.0% 4-Methylimidazole (4-MeIm): Tokyo Chemical Industry Co., Ltd. >98.0% Ethanol (EtOH): Kanto Chemical Co., Inc. Special Grade 94.8% - 95.8% N,N-Diethylformamide (DEF): Tokyo Chemical Industry Co., Ltd. >98.0%

[0037] [Comparative Example 1-1] (1) ZnO (12.2 g, 150 mmol), BzIm (35.4 g, 300 mmol), and DEF (30 mL) were added to an agate mortar. (2) The mixture was mixed in an agate mortar for 30 minutes, and then transferred to a 100 mL PTFE container. (3) The PTFE container was placed in a pressure-resistant stainless steel outer cylinder and heated at 80°C for 48 hours. (4) EtOH (50 mL) was added to the contents, stirred, and centrifuged at 16,000 rpm for 15 minutes, and the supernatant was removed. (5)(4) was repeated a total of four times. (6) The collected precipitate was dried overnight at 60°C under reduced pressure to obtain a powder.

[0038] [Example 1-2] A powder was obtained in the same manner as in Comparative Example 1-1, except that BzIm (35.4 g, 300 mmol) was changed to BzIm (31.0 g, 262.5 mmol) and 4-MeIm (3.08 g, 37.5 mmol).

[0039] [Examples 1-3] A powder was obtained in the same manner as in Comparative Example 1-1, except that BzIm (35.4 g, 300 mmol) was changed to BzIm (26.6 g, 225 mmol) and 4-MeIm (6.16 g, 75 mmol).

[0040] [Examples 1-4] A powder was obtained in the same manner as in Comparative Example 1-1, except that BzIm (35.4 g, 300 mmol) was changed to BzIm (17.7 g, 150 mmol) and 4-MeIm (12.3 g, 150 mmol).

[0041] [Comparative Example 1-5] A powder was obtained in the same manner as in Comparative Example 1-1, except that BzIm (35.4 g, 300 mmol) was changed to BzIm (8.86 g, 75 mmol) and 4-MeIm (18.5 g, 225 mmol).

[0042] [Comparative Example 1-6] A powder was obtained in the same manner as in Comparative Example 1-1, except that BzIm (35.4 g, 300 mmol) was changed to 4-MeIm (24.6 g, 300 mmol).

[0043] [Comparative Example 2-1] A powder was obtained in the same manner as in Comparative Example 1-1, except that the heating temperature was changed to 100°C.

[0044] [Example 2-2] A powder was obtained in the same manner as in Example 1-2, except that the heating temperature was changed to 100°C.

[0045] [Example 2-3] A powder was obtained in the same manner as in Example 1-3, except that the heating temperature was changed to 100°C.

[0046] [Example 2-4] A powder was obtained in the same manner as in Example 1-4, except that the heating temperature was changed to 100°C.

[0047] [Comparative Example 2-5] A powder was obtained in the same manner as in Comparative Example 1-5, except that the heating temperature was changed to 100°C.

[0048] [Comparative Example 2-6] A powder was obtained in the same manner as in Comparative Example 1-6, except that the heating temperature was changed to 100°C.

[0049] [Comparative Example 3-1] A powder was obtained in the same manner as in Comparative Example 1-1, except that the heating temperature was changed to 130°C.

[0050] [Comparative Example 3-2] In Comparative Example 3-2, a powder was obtained in the same manner as in Example 1-2, except that the heating temperature was changed to 130°C.

[0051] [Comparative Example 3-3] In Comparative Example 3-3, a powder was obtained in the same manner as in Example 1-3, except that the heating temperature was changed to 130°C.

[0052] [Example 3-4] In Example 3-4, a powder was obtained in the same manner as in Example 1-4, except that the heating temperature was changed to 130°C.

[0053] [Comparative Example 3-5] In Comparative Example 3-5, a powder was obtained in the same manner as in Comparative Example 1-5, except that the heating temperature was changed to 130°C.

[0054] [Comparative Example 3-6] In Comparative Example 3-6, a powder was obtained in the same manner as in Comparative Example 1-6, except that the heating temperature was changed to 130°C.

[0055] <II: Evaluation of Metal-Organic Framework> [Analysis of Product] 1. X-ray Diffraction Measurement: Confirmation of Crystal Structure of Product (MOF) X-ray diffraction measurements were performed on the powders obtained in the comparative examples and examples, respectively. The measuring apparatus and measuring conditions are shown below. · Measuring apparatus: RINT RAPID II (Rigaku Corporation) · Measuring conditions: Voltage 50V, Current 100mA, Collimator diameter φ0.3, Sample angle ω5°

[0056] X-ray diffraction patterns were simulated for RHO-type Zn(BzIm)2, layered Zn(BzIm)2, and ACO-type Zn(4-MeIm)2, and compared with the products. Figure 5 shows the X-ray diffraction patterns of the products of Comparative Examples 1-1, 1-5, and 1-6 and Examples 1-2 to 1-4. Figure 6 shows the X-ray diffraction patterns of the products of Comparative Examples 2-1, 2-5, and 2-6 and Examples 2-2 to 2-4. Figure 7 shows the X-ray diffraction patterns of the products of Comparative Examples 3-1 to 3-3, 3-5, and 3-6 and Example 3-4.

[0057] From Figure 5, it was found that when the heating temperature was 80°C, when the amount of 4-MeIm charged was 0 mol% to 50.0 mol%, RHO-type products (Comparative Example 1-1 and Examples 1-2 to 1-4) were obtained, and when the amount of 4-MeIm charged was 75.0 mol% or more, ACO-type products (Comparative Examples 1-5 to 1-6) were obtained.

[0058] From Figure 6, it was found that when the heating temperature was 100°C, when the amount of 4-MeIm charged was 0 mol%, a layered and RHO-type mixture (Comparative Example 2-1) was obtained, when the amount of 4-MeIm charged was 12.5 mol% to 50.0 mol%, an RHO-type product (Example 2-2 to Example 2-4) was obtained, and when the amount of 4-MeIm charged was 75.0 mol% or more, an ACO-type product (Comparative Examples 2-5 to 2-6) was obtained.

[0059] From Figure 7, it was found that when the heating temperature was 130°C, when the amount of 4-MeIm charged was 0 mol% to 12.5 mol%, a layered product (Comparative Examples 3-1 to 3-2) was obtained, when the amount of 4-MeIm charged was 25 mol%, a mixture of layered and RHO types (Comparative Example 3-3) was obtained, when the amount of 4-MeIm charged was 50 mol%, an RHO type product (Example 3-4) was obtained, and when the amount of 4-MeIm charged was 75.0 mol% or more, an ACO type product (Comparative Examples 3-5 to 3-6) was obtained.

[0060] FIG. 8 shows the crystal structure of the product produced depending on the amount of 4-MeIm charged and the heating temperature.

[0061] Figure 8 reveals the following. When the amount of 4-MeIm added was 0 mol%, a heating temperature of 80 °C yielded the RHO-type product. At a heating temperature of 100 °C, a mixture of layered and RHO-type products was obtained. At a heating temperature of 130 °C, a layered product was obtained. On the other hand, when part of the BzIm was replaced with 4-MeIm, the RHO-type product was obtained even at heating temperatures of 100 °C and 130 °C. Thus, the temperature range for RHO-type formation was extended to the higher temperature range. This is because layered Zn(BzIm)2 interacts with the benzene rings of BzIm facing each other. However, substituting part of the BzIm with 4-MeIm eliminates this interaction. Therefore, substitution with 4-MeIm destabilizes the layered crystal structure, favoring the formation of the RHO-type. Furthermore, when the amount of 4-MeIm added was 75 mol% or more, an ACO-type product was obtained. This is thought to be because too much 4-MeIm destabilizes the RHO type, and the ACO type, which is a stable crystal structure of Zn(4-MeIm)2, becomes dominant. Therefore, in order to produce the RHO type, it was found that in the xy graph showing the relationship between the amount of 4-MeIm charged (x mol%) and the heating temperature (y °C), it was necessary to adjust the amount so that it falls within the range of a square with vertices at (x, y) = (12.5, 80), (50, 80), (50, 130), and (12.5, 100), as shown in Figure 8.

[0062] The molar ratio of the layered product to the RHO-type product ((RHO-type / (layered+RHO-type))×100) was calculated from the peak intensities in the X-ray diffraction patterns of Comparative Example 2-1 and Comparative Example 3-3, and was found to be 71 mol% in Comparative Example 2-1 and 60 mol% in Comparative Example 3-3.

[0063] 2. 1 H-NMR measurement: composition analysis of MOFs The products of the Examples and Comparative Examples were decomposed and dissolved in a heavy solvent. 1 The H-NMR spectrum was measured, and the ratio of BzIm and 4-MeIm contained in the MOF was calculated from the integral ratio of the spectrum. The decomposition conditions, measurement device, and measurement conditions used in this measurement are shown below. Decomposition conditions: The product was decomposed in a 10% by weight solution of bisulfate (D2SO4) in heavy water (D2O). Measurement equipment: INOVA300 (Agilent Technologies)

[0064] Table 1 shows the products of the examples and comparative examples. 1 RHO-type Zn(BzIm) determined from H-NMR spectrum 2-z (4-MeIm) z The composition is shown below.

[0065] [Table 1]

[0066] Regarding the product that has been confirmed to be RHO type based on the results of X-ray diffraction, 1 The results of H-NMR confirmed that the compound contained 4-MeIm. In Examples 1-2 to 1-4, 2-2 to 2-4, and 3-4, the compound was an RHO-type Zn(BzIm) in which part of the BzIm in the RHO-type Zn(BzIm)2 was replaced with 4-MeIm. 2-z (4-MeIm) z It is believed that this has been achieved.

[0067] 3. N2 adsorption isotherm measurement: evaluation of pore volume of MOF The products of the examples and comparative examples were pretreated, and then the N adsorption isotherms were measured. The N adsorption amounts at a relative N pressure of 50% were also compared. The pretreatment equipment, pretreatment conditions, measurement equipment, and measurement conditions used in this measurement are shown below. Pretreatment device: BELPREP vacII (Microtrac BEL Co., Ltd.) Pretreatment conditions: Vacuum degree <10 -2 Pa, heated at 160°C for 6 hours Measuring device: BELSORPmax (Microtrac BEL Co., Ltd.) Measurement conditions: Temperature 77K, N2 adsorption amount measured at N2 relative pressure 0% to 99%

[0068] Figure 9 shows the N adsorption / desorption isotherms for the products of Comparative Examples 1-5 and 1-6 and Examples 1-2 to 1-4. Figure 10 shows the N adsorption / desorption isotherms for the products of Comparative Examples 2-5 and 2-6 and Examples 2-2 to 2-4. Figure 11 shows the N adsorption / desorption isotherms for the products of Comparative Examples 3-1 to 3-3, 3-5, and 3-6 and Example 3-4. Note that in Comparative Examples 1-1 and 2-1, the N adsorption measurement took a very long time, and the liquid nitrogen required to maintain the measurement temperature (77 K) evaporated, making it difficult to obtain the N adsorption isotherms. Figure 12 shows the relationship between the amount of 4-MeIm charged (mol%) (horizontal axis) and the N adsorption amount (mL(STP) g) at a N relative pressure of 50%. -1 The graph shows the crystal structure of the product produced at each heating temperature in relation to the 4-MeIm content (vertical axis). Table 2 also shows the synthesis conditions (4-MeIm charge amount, heating temperature), the crystal structure of the product, the 4-MeIm content, and the N adsorption amount for each example and comparative example.

[0069] [Table 2]

[0070] For the products of Comparative Examples 1-1 and 2-1, the time required for N2 adsorption measurement was very long, and N2 adsorption isotherms could not be obtained. This is thought to be because the RHO-type Zn(BzIm)2 has a narrow pore window, and N2 diffusion within the pores is very slow.

[0071] On the other hand, Zn(BzIm) has the same RHO-type crystal structure, but with part of BzIm replaced with 4-MeIm. 2-z (4-MeIm) z For the products of Examples 1-2 to 1-4, 2-2 to 2-4, and 3-4 (shown by circles in Figure 12), N adsorption isotherms could be obtained. This is presumably because the pore window was enlarged by substituting a portion of BzIm with 4-MeIm, improving the diffusivity of N.

[0072] In Comparative Example 3-3 (overlap of circles and crosses in FIG. 12), RHO-type Zn(BzIm) 2-z (4-MeIm) zIn addition, layered Zn(BzIm) without pores for gas adsorption 2-z (4-MeIm) z was produced, and the amount of N2 adsorption decreased accordingly.

[0073] In addition, in Comparative Examples 1-5 to 1-6, 2-5 to 2-6, and 3-5 to 3-6 (△ in FIG. 12), ACO-type Zn(BzIm) 2-z (4-MeIm) z was produced, and showed a smaller N2 adsorption amount than the RHO type.

[0074] These results confirmed that by synthesizing RHO-type Zn(BzIm)2 by replacing part of the BzIm with 4-MeIm, it becomes easier to obtain the RHO-type product, and that by replacing part of the BzIm with 44-MeIm, the pore window is enlarged, improving the gas adsorption capacity and diffusivity.

[0075] The present invention is not limited to the above-described embodiments, but includes various modifications. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those including all of the described configurations. Furthermore, it is possible to add, delete, and / or replace part of the configuration of each embodiment with other configurations.

Claims

1. A metal-organic framework having an RHO-type topology, comprising zinc (Zn) as a metal and benzimidazole (BzIm) and 4-methylimidazole (4-MeIm) as ligands.

2. 2. The metal organic structure according to claim 1, wherein the molar ratio of 4-MeIm to the total of BzIm and 4-MeIm (4-MeIm / (BzIm+4-MeIm)) is in the range of 0.11 to 0.

53.

3. A gas adsorption / desorption material comprising an adsorption / desorption material, The adsorption / desorption material comprises the metal organic framework according to claim 1 or 2, The metal organic framework contains an RHO topology in an amount of 90 mol % or more relative to the total amount of substances of the metal organic framework. Gas adsorption / desorption material.

4. a mechanochemical reaction step of mechanochemically reacting a zinc compound, BzIm, and 4-MeIm in the presence of a solvent; and Heating process after mechanochemical reaction process Including, The relationship between the amount of 4-MeIm charged and the heating temperature is adjusted so as to be within the range of a rectangle having vertices at (x, y) = (12.5, 80), (50, 80), (50, 130), and (12.5, 100) in an xy graph showing the relationship between the amount of 4-MeIm charged (x mol %) and the heating temperature (y °C). The method for producing the metal organic framework according to claim 1 or 2.

5. 5. The method of claim 4, wherein the solvent is N,N-diethylformamide (DEF) and the zinc compound is zinc oxide (ZnO).

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