Metal organic structure and method for producing same

Abstract

The purpose of the present invention is to provide a method for producing, at a high yield, an MOF having an RHO-type topological structure and having high gas adsorbability. One embodiment of the present invention relates to a metal organic structure comprising a metal ion that is a zinc cation and a ligand that is a 2-ethylimidazole (2-EtIm) or an anion of a monocarboxylic acid, the metal organic structure having an RHO-type topological structure in which a part of the 2-EtIm anion is substituted with an anion of a monocarboxylic acid. Another aspect of the invention relates to a method of manufacturing a metal organic structure having the foregoing features.

Description

Technical Field

[0001] The present invention relates to a metal organic structure and a method for producing the same. Background Art

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

[0003] For example, Non-Patent Document 1 describes the synthesis of Zn(2-EtIm) having an RHO topological structure by mechanochemical reaction. 2 The RHO-type topology of the MOF is composed of a metal ion as a zinc cation and a ligand as an anion of 2-ethylimidazole (2-EtIm).

[0004] [Prior art literature]

[0005]

Non-patent literature

[0006] [Non-patent document 1] PJ Beldon et al., Angew. Chem. Int. Ed. Vol. 49, p. 9640-9643 (2010) Summary of the invention

[0007] [Problems to be solved by the invention]

[0008] As mentioned above, it is known to produce Zn(2-EtIm) with RHO-type topology by mechanochemical reaction. 2 However, in the case of the conventional method, there is a problem of low yield due to the low solubility of the zinc compound as a raw material in the organic solvent. In addition, there is room for improvement in the gas adsorption of MOF produced by the conventional method.

[0009] Therefore, the object of the present invention is to provide a method for producing MOFs of RHO type topology with high gas adsorption in high yield.

[0010]

Methods to solve the problem

[0011] The present inventors have studied various methods for solving the above-mentioned problems. The present inventors have found that when manufacturing MOF by mechanochemical reaction, by adding monocarboxylic acid to zinc compound and 2-ethylimidazole as raw materials, an RHO-type topological structure MOF having a structure in which a part of 2-ethylimidazole is replaced by monocarboxylic acid can be obtained with high yield. The present inventors have completed the present invention based on the above-mentioned findings.

[0012] That is, the present invention includes the following aspects and embodiments.

[0013] (Implementation 1) A metal organic structure is composed of a metal ion as a zinc cation and a ligand as an anion of 2-ethylimidazole (2-EtIm) or a monocarboxylic acid, and has an RHO type topology structure in which a part of the 2-EtIm anion is replaced by the anion of the monocarboxylic acid.

[0014] (Embodiment 2) According to the metal organic structure described in Embodiment 1, the monocarboxylic acid is benzoic acid or acetic acid.

[0015] (Embodiment 3) According to the metal organic structure described in Embodiment 1 or 2, the existence ratio of the anion of the monocarboxylic acid in the ligand is in the range of 1 to 20 mol% relative to the total number of moles of the ligand.

[0016] (Embodiment 4) The method for producing a metal organic structure according to any one of Embodiments 1 to 3, comprising a mechanochemical reaction step of subjecting a zinc compound, 2-ethylimidazole (2-EtIm) and a monocarboxylic acid to a mechanochemical reaction in the presence of a solvent.

[0017] (Embodiment 5) A method according to Embodiment 4, wherein the mechanochemical reaction comprises mixing the raw materials using a ball mill.

[0018] [Effects of the invention]

[0019] According to the present invention, a method for producing a MOF having an RHO type topology structure with high gas adsorption in high yield can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The powder X-ray diffraction pattern of the product of Example 1 is shown. The horizontal axis represents the 2θ value (°), and the vertical axis represents the intensity (au). In addition, 100 rpm, 200 rpm, 300 rpm, 400 rpm or 500 rpm represents the rotation speed of the planetary ball mill during production. RHO type, ANA type or ZnO represents the RHO type Zn (2-EtIm) calculated 2 、ANA type Zn(2-EtIm) 2 Simulation results of X-ray diffraction patterns obtained with ZnO.

[0021] Figure 2The powder X-ray diffraction pattern of the product of Example 2 is shown. The horizontal axis represents the 2θ value (°), and the vertical axis represents the intensity (au). In addition, 100 rpm, 200 rpm, 300 rpm, 400 rpm or 500 rpm represents the rotation speed of the planetary ball mill during production. RHO type, ANA type or ZnO represents the RHO type Zn (2-EtIm) calculated 2 、ANA type Zn(2-EtIm) 2 Simulation results of X-ray diffraction patterns obtained with ZnO.

[0022] Figure 3 The powder X-ray diffraction pattern of the product of Example 3 is shown. The horizontal axis represents the 2θ value (°), and the vertical axis represents the intensity (au). In addition, 100 rpm, 200 rpm, 300 rpm, 400 rpm or 500 rpm represents the rotation speed of the planetary ball mill during production. RHO type, ANA type or ZnO represents the RHO type Zn (2-EtIm) calculated 2 、ANA type Zn(2-EtIm) 2 Simulation results of X-ray diffraction patterns obtained with ZnO.

[0023] Figure 4 The powder X-ray diffraction pattern of the product of Example 4 is shown. The horizontal axis represents the 2θ value (°), and the vertical axis represents the intensity (au). In addition, 100 rpm, 200 rpm, 300 rpm, 400 rpm or 500 rpm represents the rotation speed of the planetary ball mill during production. RHO type, ANA type or ZnO represents the RHO type Zn (2-EtIm) calculated 2 、ANA type Zn(2-EtIm) 2 Simulation results of X-ray diffraction patterns obtained with ZnO.

[0024] Figure 5 The abundance ratio of RHO-type MOF relative to the total weight of the product in Examples and Comparative Examples is shown. The horizontal axis is the rotation speed (rpm) of the planetary ball mill during production, and the vertical axis is the abundance ratio (weight %) of RHO-type MOF.

[0025] Figure 6 The N of the products of Examples 1 to 4 and Comparative Examples 1 to 4 was measured. 2 Adsorption-desorption isotherms determined by N 2 The horizontal axis is the rotation speed (rpm) of the planetary ball mill during manufacturing, and the vertical axis is N 2 Determination of adsorption-desorption isotherms, N 2 N when relative pressure is 50% 2 Adsorption capacity (mL (STP) g -1 ). DETAILED DESCRIPTION

[0026] Hereinafter, preferred embodiments of the present invention will be described in detail.

[0027] <1: Metal-organic structures>

[0028] Another aspect of the present invention relates to a metal organic structure (MOF). The MOF of this embodiment is composed of a metal ion that is a cation of zinc (Zn) and a ligand that is an anion of 2-ethylimidazole (2-EtIm) or a monocarboxylic acid, and has an RHO-type topological structure in which a portion of the 2-EtIm anion is replaced by an anion of the monocarboxylic acid.

[0029] Zn(2-EtIm) composed of Zn and 2-EtIm 2 MOFs can form various topological structures. Among them, Zn(2-EtIm) 2 The pore capacity of MOF is large. It is also known that there is a certain correlation between the pore capacity of MOF and gas adsorption. Therefore, the MOF of this method having a RHO type topological structure can have a high gas adsorption compared with MOFs having other topological structures.

[0030] In the MOF of the present embodiment, a part of the 2-EtIm anion is replaced by an anion of a monocarboxylic acid. The monocarboxylic acid is preferably benzoic acid, acetic acid or formic acid, more preferably benzoic acid or acetic acid, and further preferably benzoic acid. By replacing a part of the 2-EtIm anion with an anion of a monocarboxylic acid, a MOF having large pores due to the template effect of the monocarboxylic acid can be prepared. In particular, in the case of a monocarboxylic acid having a bulky group such as benzoic acid, the template effect of the monocarboxylic acid becomes more significant, and a MOF having larger pores can be formed.

[0031] The MOF of this embodiment preferably has a presence ratio of the anion of the monocarboxylic acid in the ligand in the range of 1 to 20 mol% relative to the total molar number of the ligand, more preferably in the range of 3 to 20 mol%, and further preferably in the range of 3 to 12 mol%. Since the presence ratio of the anion of the monocarboxylic acid in the ligand is within the above range, the MOF of the present invention can have high gas adsorption.

[0032] The MOF of this embodiment is generally represented by the following formula (I):

[0033] Zn(2-EtIm x MCA y ) 2

[0034] In formula (I), 2-EtIm is a ligand as an anion of 2-ethylimidazole, and MCA is a ligand as an anion of a monocarboxylic acid. x is preferably in the range of 0.8 to 0.99, more preferably in the range of 0.8 to 0.97, and further preferably in the range of 0.88 to 0.97. y is preferably in the range of 0.01 to 0.2, more preferably in the range of 0.03 to 0.2, and further preferably in the range of 0.03 to 0.12. The MOF of this embodiment represented by formula (I) can have high gas adsorption.

[0035] The gas adsorption of MOF in this embodiment can be measured, for example, by measuring the N 2 Adsorption isotherm, calculation of N 2 N when relative pressure is 50% 2 The MOF of this method is evaluated by the adsorption amount. 2 N when relative pressure is 50% 2 The adsorption capacity is usually 180mL (STP) g -1 Above, especially in the range of 180 to 410 mL (STP) g -1 within the range.

[0036] <2: Method for producing metal organic structure>

[0037] Another aspect of the invention relates to a method for making the metal-organic structure of one aspect of the invention.

[0038] The method of this scheme includes a mechanochemical reaction step. This step includes subjecting a zinc compound, 2-ethylimidazole (2-EtIm) and a monocarboxylic acid to a mechanochemical reaction in the presence of a solvent. In this specification, a mechanochemical reaction refers to a chemical reaction in which a mechanical stress such as crushing is applied to a raw material to change the crystal structure of the raw material.

[0039] The zinc compound used in this process is preferably zinc oxide or zinc hydroxide, more preferably zinc oxide. The zinc compound exemplified above can be used to improve reactivity by using the solvent exemplified below. Therefore, by using the zinc compound exemplified above to implement this process, a mechanochemical reaction can be effectively performed to obtain a MOF of one embodiment of the present invention.

[0040] The monocarboxylic acid used in this process is preferably the compound exemplified above as a ligand. The presence of the monocarboxylic acid in the mechanochemical reaction system can promote the decomposition of the raw material zinc compound, while on the other hand, the decomposition of the product MOF is not promoted. Therefore, by adding the monocarboxylic acid exemplified above to implement this process, it is possible to obtain a MOF of one embodiment of the present invention as a product in high yield while promoting the decomposition of the raw material zinc compound.

[0041] The solvent used in this process is preferably a water-miscible organic solvent, more preferably N,N-dimethylformamide, methanol, N,N-diethylformamide or ethanol, and further preferably N,N-dimethylformamide or methanol. The above-exemplified solvent can dissolve the raw material 2-ethylimidazole (2-EtIm) and / or monocarboxylic acid. Therefore, by using the above-exemplified solvent to implement this process, a mechanochemical reaction can be effectively carried out to obtain a MOF of one embodiment of the present invention.

[0042] In this process, the mechanochemical reaction preferably includes a step of mixing the raw materials using a ball mill. In the case of the present embodiment, the rotation speed of the ball mill is preferably 50 rpm or more, more preferably in the range of 50 to 800 rpm, and further preferably in the range of 100 to 500 rpm. In addition, the time for mixing by the ball mill is preferably 1 hour or more, more preferably in the range of 1 to 3 hours. By implementing this process under the above conditions, a mechanochemical reaction can be effectively carried out to obtain a MOF of one embodiment of the present invention.

[0043] As described above, as described in detail, the MOF of one embodiment of the present invention can have a large pore capacity and high gas adsorption by having an RHO-type topology in which a part of the ligand 2-EtIm anion is replaced by the anion of a monocarboxylic acid. Therefore, the MOF of one embodiment of the present invention can be applied to gas adsorption materials in a gas adsorption system, a gas separation system, or a gas storage system. In addition, the manufacturing method of one embodiment of the present invention can obtain the MOF of one embodiment of the present invention having the characteristics described above with a high yield. Therefore, the manufacturing method of one embodiment of the present invention can effectively provide materials suitable for the above-mentioned exemplified uses.

[0044] [Example]

[0045] Hereinafter, the present invention will be described in more detail using examples, but the technical scope of the present invention is not limited to these examples.

[0046] <I: Fabrication of metal-organic structures>

[0047] [I-1: Reagents]

[0048] Zinc oxide (ZnO): Fujifilm Wako Pure Chemical Industries, Ltd. 0.02μm practical grade 95.0+%

[0049] 2-Ethylimidazole (2-EtIm): Tokyo Chemical Industry Co., Ltd. > 98.0%

[0050] Benzoic acid (BA): Fujifilm Wako Pure Chemical Industries, Ltd. 99.5+%

[0051] Acetic acid (AA): Fujifilm Wako Pure Chemical Industries, Ltd. 99.7+%

[0052] Phosphoric acid (PA): Fujifilm Wako Pure Chemical Industries, Ltd. 85.0+%

[0053] Methanol (MeOH): NAKARAKU CO., LTD., grade 1 grade ≥ 99.0%

[0054] Ethanol (EtOH): Kanto Chemical Co., Ltd. Special Grade 94.8 to 95.8%

[0055] N,N-Dimethylformamide (DMF): Fujifilm Wako Pure Chemical Industries, Ltd., super dehydrated, for organic synthesis 99.5+%

[0056] [I-2: Comparative Example 1-1]

[0057] Add raw materials containing ZnO 1.22g (15mmol), 2-EtIm 2.88g (30mmol) and DMF 3mL and 50g of Φ5mm zirconium oxide balls into a 45mL ball mill container. Install the ball mill container on a planetary ball mill. Set the speed of the planetary ball mill to 100rpm, apply rotation for 3 hours, and mix the raw material mixture. Recover the reaction mixture and remove the zirconium oxide balls from the reaction mixture. Add 50mL of ethanol to the reaction mixture and stir. Centrifuge the reaction mixture at 16000rpm for 15 minutes and remove the supernatant. Repeat the steps of centrifugation and supernatant removal 4 times in total. Dry the recovered precipitate at 60°C for 1 night while reducing the pressure. Powder is obtained by the above treatment.

[0058] [I-3: Comparative Examples 1-2, 1-3, 1-4, 1-5]

[0059] Powders of Comparative Examples 1-2, 1-3, 1-4, or 1-5 were obtained in the same manner as in Comparative Example 1-1 except that the rotation speed of the planetary ball mill was changed to 200, 300, 400, or 500 rpm.

[0060] [I-4: Comparative Example 2-1]

[0061] A powder of Comparative Example 2-1 was obtained in the same manner as in Comparative Example 1-1 except that the amount of 2-EtIm was changed to 3.60 g (37.5 mmol).

[0062] [I-5: Comparative Examples 2-2, 2-3, 2-4, 2-5]

[0063] Powders of Comparative Examples 2-2, 2-3, 2-4, or 2-5 were obtained in the same manner as in Comparative Example 2-1 except that the rotation speed of the planetary ball mill was changed to 200, 300, 400, or 500 rpm.

[0064] [I-6: Comparative Example 3-1]

[0065] A powder of Comparative Example 3-1 was obtained in the same manner as in Comparative Example 1-1 except that the amount of DMF was changed to 6 mL.

[0066] [I-7: Comparative Examples 3-2, 3-3, 3-4, 3-5]

[0067] Powders of Comparative Examples 3-2, 3-3, 3-4 or 3-5 were obtained in the same manner as in Comparative Example 3-1 except that the rotation speed of the planetary ball mill was changed to 200, 300, 400 or 500 rpm.

[0068] [I-8: Comparative Example 4-1]

[0069] A powder of Comparative Example 4-1 was obtained in the same manner as in Comparative Example 1-1 except that DMF was replaced with 3 mL of MeOH.

[0070] [I-9: Comparative Examples 4-2, 4-3, 4-4, 4-5]

[0071] Powders of Comparative Examples 4-2, 4-3, 4-4, or 4-5 were obtained in the same manner as in Comparative Example 4-1 except that the rotation speed of the planetary ball mill was changed to 200, 300, 400, or 500 rpm.

[0072] [I-10: Example 1-1]

[0073] A powder of Example 1-1 was obtained in the same manner as in Comparative Example 1-1 except that 0.916 g (7.5 mmol) of BA was added to the raw material.

[0074] [I-11: Examples 1-2, 1-3, 1-4, 1-5]

[0075] Powders of Examples 1-2, 1-3, 1-4 or 1-5 were obtained in the same manner as in Example 1-1 except that the rotation speed of the planetary ball mill was changed to 200, 300, 400 or 500 rpm.

[0076] [I-12: Example 2-1]

[0077] The powder of Example 2-1 was obtained in the same manner as in Example 1-1 except that DMF was replaced with 3 mL of MeOH.

[0078] [I-13: Examples 2-2, 2-3, 2-4, 2-5]

[0079] Powders of Example 2-2, 2-3, 2-4 or 2-5 were obtained in the same manner as in Example 2-1 except that the rotation speed of the planetary ball mill was changed to 200, 300, 400 or 500 rpm.

[0080] [14: Example 3-1]

[0081] A powder of Example 3-1 was obtained in the same manner as in Comparative Example 1-1 except that 0.450 g (7.5 mmol) of AA was added to the raw material.

[0082] [15: Examples 3-2, 3-3, 3-4 and 3-5]

[0083] Powders of Examples 3-2, 3-3, 3-4 or 3-5 were obtained in the same manner as in Example 3-1 except that the rotation speed of the planetary ball mill was changed to 200, 300, 400 or 500 rpm.

[0084] [16: Example 4-1]

[0085] The powder of Example 4-1 was obtained in the same manner as in Example 3-1 except that DMF was replaced with 3 mL of MeOH.

[0086] [I-17: Examples 4-2, 4-3, 4-4, 4-5]

[0087] Powders of Examples 4-2, 4-3, 4-4 or 4-5 were obtained in the same manner as in Example 4-1 except that the rotation speed of the planetary ball mill was changed to 200, 300, 400 or 500 rpm.

[0088] [I-18: Comparative Example 5-1]

[0089] A powder of Comparative Example 5-1 was obtained in the same manner as in Comparative Example 1-1 except that 0.865 g (7.5 mmol) of PA was added to the raw material.

[0090] [I-19: Comparative Examples 5-2, 5-3, 5-4, 5-5]

[0091] Powders of Comparative Examples 5-2, 5-3, 5-4 or 5-5 were obtained in the same manner as in Comparative Example 5-1 except that the rotation speed of the planetary ball mill was changed to 200, 300, 400 or 500 rpm.

[0092] [I-20: Comparative Example 6-1]

[0093] A powder of Comparative Example 6-1 was obtained in the same manner as in Comparative Example 5-1 except that DMF was changed to 3 mL of MeOH.

[0094] [I-21: Comparative Examples 6-2, 6-3, 6-4, 6-5]

[0095] Powders of Comparative Examples 6-2, 6-3, 6-4, or 6-5 were obtained in the same manner as in Example 6-1 except that the rotation speed of the planetary ball mill was changed to 200, 300, 400, or 500 rpm.

[0096] <II: Crystal structure analysis of metal-organic structures>

[0097] The powders of the products obtained in Comparative Examples 1-1 to 6-5 and Examples 1-1 to 4-5 were subjected to X-ray diffraction measurement. The measuring apparatus and measuring conditions are as follows.

[0098] Measuring device: RINT RAPID II (RIGAKU CORPORATION)

[0099] Measurement conditions: voltage 50V, current 100mA, collimator diameter φ0.3, sample angle ω5°

[0100] For RHO-type Zn(2-EtIm) as a well-known MOF 2 (reported as MAF-6) and ANA Zn(2-EtIm) 2 (reported as MAF-5 or ZIF-14) and ZnO as raw materials, the X-ray diffraction patterns were simulated by calculation and compared with the powder X-ray diffraction patterns of the products of Comparative Examples and Examples. The powder X-ray diffraction patterns of the products of Examples 1, 2, 3 and 4 are shown in Figure 1 , 2 , 3 and 4. In each figure, the horizontal axis represents the 2θ value (°) and the vertical axis represents the intensity (au). In addition, in each figure, 100 rpm, 200 rpm, 300 rpm, 400 rpm or 500 rpm represents the rotation speed of the planetary ball mill during production. For RHO type, ANA type or ZnO, the calculation of RHO type Zn (2-EtIm) is shown. 2 、ANA type Zn(2-EtIm) 2 Simulation results of X-ray diffraction patterns obtained for ZnO.

[0101] It can be clearly seen from the powder X-ray diffraction pattern of the product of Comparative Example 1 that the product at 100rpm is a mixture of raw materials ZnO and RHO-type MOF (X-ray diffraction pattern not shown). As the rotation speed of the planetary ball mill during manufacturing increases, the peak intensity of ZnO in the X-ray diffraction pattern decreases. Therefore, it is speculated that as the rotation speed of the planetary ball mill during manufacturing increases, the amount of MOF generated increases. On the other hand, when the rotation speed of the planetary ball mill during manufacturing increases to more than 200rpm, the peak intensity of ANA-type MOF in the X-ray diffraction pattern increases. From these results, it can be inferred that when the rotation speed of the planetary ball mill during manufacturing is low, RHO-type MOF is mainly generated, but as the rotation speed increases, the amount of ANA-type MOF generated increases more than the amount of RHO-type MOF generated. The same tendency was also confirmed in the powder X-ray diffraction patterns of the products of Comparative Examples 2, 3 and 4 (X-ray diffraction patterns not shown).

[0102] From the powder X-ray diffraction pattern of the product of Example 1, it can be seen that regardless of the rotation speed of the planetary ball mill during production, the product is a single phase of RHO-type MOF ( Figure 1 In Example 2, when the rotation speed of the planetary ball mill during manufacturing was 100 rpm or 300 rpm, it was confirmed that ZnO slightly existed in the product, but the main phase was RHO type MOF ( Figure 2 In Examples 3 and 4, as the rotation speed of the planetary ball mill increased during the manufacturing process, ANA-type MOF ( Figure 3 and 4 ).

[0103] In the powder X-ray diffraction pattern of the product of Comparative Example 5, a peak belonging to neither the RHO type nor the ANA type was observed (the X-ray diffraction pattern is not shown). In the powder X-ray diffraction pattern of the product of Comparative Example 6, in addition to the peaks observed in Comparative Example 5, a peak of the ANA type MOF was slightly observed as the rotation speed of the planetary ball mill device during production increased (the X-ray diffraction pattern is not shown). From these results, it can be seen that although the decomposition and reaction of ZnO can be promoted by adding PA, for the formation of RHO type MOF, it is preferable to add monocarboxylic acids such as BA and AA.

[0104] The abundance ratios of RHO-type MOF, ANA-type MOF, and ZnO as a raw material were calculated from the peak intensities in the powder X-ray diffraction patterns of the products of Examples and Comparative Examples. Figure 5 The figure shows the abundance of RHO-type MOF relative to the total weight of the products of Examples and Comparative Examples. In the figure, the horizontal axis is the rotation speed (rpm) of the planetary ball mill during production, and the vertical axis is the abundance (weight %) of RHO-type MOF.

[0105] like Figure 5 As shown, in the products of Comparative Examples 1 to 4, although the existence rate of ZnO decreases with the increase in the rotation speed of the planetary ball mill during production, the formation of ANA-type MOF becomes favorable, so the existence rate of RHO-type MOF decreases. In contrast, in the products of Examples 1 to 4, RHO-type MOF is obtained as the main phase under all conditions.

[0106] <III: Evaluation of properties of metal-organic structures>

[0107] [III-1: Evaluation of pore capacity of MOF]

[0108] The products of Examples 1 to 4 and Comparative Examples 1 to 4 were pretreated and the N 2 Adsorption isotherm. In addition, find N 2 N when relative pressure is 50% 2 The pretreatment device, pretreatment conditions, measurement device and measurement conditions used in this measurement are shown below.

[0109] Pretreatment device: BELPREP vacII (Matron Co., Ltd.)

[0110] Pretreatment conditions: vacuum degree <10 -2 Pa, 160℃ heating for 6 hours

[0111] Measuring device: BELSORP max (Masutra Co., Ltd.)

[0112] Measurement conditions: Measurement temperature 77K, N 2 N at relative pressure 0~99% 2 Adsorption

[0113] By measuring the N of the products of Examples 1 to 4 and Comparative Examples 1 to 4 2 Adsorption-desorption isotherms determined by N 2 Adsorption amount Figure 6 In the figure, the horizontal axis is the rotation speed (rpm) of the planetary ball mill during manufacturing, and the vertical axis is N 2 Determination of adsorption-desorption isotherms, N 2 N when relative pressure is 50% 2 Adsorption capacity (mL (STP) g -1 ).

[0114] like Figure 6 As shown, compared with the products of Comparative Examples 1 to 4, it was confirmed that the products of Examples 1 to 4 had N 2A tendency of high adsorption capacity. In the case of the products of Comparative Examples 1 to 4, among the products with a rotational speed of 400 rpm or 500 rpm in the planetary ball mill during manufacturing, the presence rate of RHO-type MOF was low ( Figure 5 ), but the N 2 adsorption capacity was not too low. ANA-type MOF has a pore volume about 1 / 2 of that of RHO-type MOF. Therefore, if ANA-type MOF is formed instead of RHO-type MOF, it is speculated that a certain degree of N 2 adsorption capacity will be shown. From these results, it can be speculated that the addition of monocarboxylic acid (especially benzoic acid) promotes the decomposition of ZnO and the formation of RHO-type MOF.

[0115] [III-2: Composition Analysis of MOF]

[0116] The products of Examples 1-4 were decomposed and dissolved in a deuterated solvent. The 1 1H-NMR spectrum of the obtained solution was measured, and the ratios of 2-ethylimidazole and monocarboxylic acid (benzoic acid or acetic acid) contained in the MOF were determined from the integral ratio of the spectrum. The decomposition conditions, measurement device, and measurement conditions used in this measurement are as follows.

[0117] Decomposition conditions: The product was decomposed with a solution of 10 wt% deuterated sulfuric acid (D 2 2SO 4 4) in deuterated water (D 2 2O)

[0118] Measurement device: INOVA300 (Agilent Technologies)

[0119] The composition of RHO-type MOF determined from the 1 1H-NMR spectrum of the products of Examples 1 to 4 is shown in Table 1.

[0120] Table 1

[0121] Example No. Composition formula of RHO-type MOF Example 1-1 Zn(2-EtIm0.91BA0.09)2 Example 1-2 Zn(2-EtIm0.91BA0.09)2 Examples 1-3 Zn(2-EtIm0.92BA0.08)2 Examples 1-4 Zn(2-EtIm0.92BA0.08)2 Examples 1-5 Zn(2-EtIm0.91BA0.09)2 Example 2-1 Zn(2-EtIm0.93BA0.07)2 Example 2-2 Zn(2-EtIm0.89BA0.11)2 Example 2-3 Zn(2-EtIm0.88BA0.12)2 Embodiment 2-4 Zn(2-EtIm0.88BA0.12)2 Embodiment 2-5 Zn(2-EtIm0.92BA0.08)2 Example 3-1 Zn(2-EtIm0.96AA0.04)2 Example 3-2 Zn(2-EtIm0.96AA0.04)2 Example 3-3 Embodiment 3-4 Embodiment 3-5 Example 4-1 Zn(2-EtIm0.96AA0.04)2 Example 4-2 Zn(2-EtIm0.97AA0.03)2 Example 4-3 Example 4-4 Embodiment 4-5

[0122] The monocarboxylic acid added during synthesis becomes a -1-valent organic anion. Therefore, it is speculated that the monocarboxylic acid is introduced into the structure of MOF in the form of replacing a part of 2-ethylimidazole.

[0123] In addition, the present invention is not limited to the above embodiments and also includes various modified examples. For example, the above embodiments are examples described in detail for easy understanding of the present invention and are not used to limit to all the structures necessarily described. In addition, for a part of the structure of each embodiment, other structures can be added, deleted, and / or replaced with other structures.

Claims

1. A metal organic structure, composed of a metal ion and a ligand, wherein the metal ion is a zinc cation, and the ligand is an anion of 2-ethylimidazole (2-EtIm) or an anion of a monocarboxylic acid, wherein the metal organic structure has an RHO type topological structure in which a portion of the 2-EtIm anion is replaced by an anion of the monocarboxylic acid.

2. The metal-organic structure according to claim 1, wherein the monocarboxylic acid is benzoic acid or acetic acid.

3. The metal organic structure according to claim 1, wherein the presence ratio of the anion of the monocarboxylic acid in the ligand is in the range of 1 to 20 mol% relative to the total molar number of the ligand.

4. The method for producing a metal organic structure according to claim 1, comprising the following mechanochemical reaction step: a zinc compound, 2-ethylimidazole (2-EtIm), and a monocarboxylic acid are subjected to a mechanochemical reaction in the presence of a solvent.

5. The method for producing a metal-organic structure according to claim 4, wherein the mechanochemical reaction comprises a step of mixing the raw materials using a ball mill.

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