Method for producing three-dimensional porous coordination polymer

Abstract

[Problem] To enable production of SIFSIX-3-Cu or an analog thereof with high stability and reproducibility. [Solution] The present disclosure relates to a method for producing a three-dimensional porous coordination polymer represented by the chemical formula: [M(μ-SiF6)(μ-pyr*)2]. A first method according to the present disclosure comprises: preparing a first two-dimensional coordination polymer represented by the chemical formula [M(μ-SiF6)(μ-pyr*)(pyr*)2]; and mixing the first two-dimensional coordination polymer and a solvent containing an alcohol. A second method according to the present disclosure comprises: preparing a second two-dimensional coordination polymer represented by the chemical formula [M(μ-SiF6)(μ-pyr*)(H2O)2]; and reacting the second two-dimensional coordination polymer with pyr*. Here, M is one or more divalent metal atoms capable of forming an octahedral hexacoordinate (OC-6) structure, and pyr* is pyrazine, a derivative thereof, or a mixture thereof.

Description

Method for producing three-dimensional porous coordination polymer

[0001] The present disclosure relates to a method for producing a three-dimensional porous coordination polymer. Specifically, the present disclosure relates to a novel method for producing SIFSIX-3-Cu or its analogs. Note that SIFSIX-3-Cu has the chemical formula [Cu(μ-SiF ６ )(μ-pyr) ２ (where pyr represents pyrazine) and is a three-dimensional porous coordination polymer represented by the formula.

[0002] In order to stop the increase in the concentration of CO ２ in the atmosphere associated with the use of fossil fuels, the development of technologies for recovering CO ２ is an urgent issue. Although CO ２ recovery technologies using acid-base reactions or chemisorption with alkaline aqueous solutions are being studied, the development of physical adsorption materials that can recover CO ２ with less energy is strongly desired.

[0003] Porous coordination polymers (PCPs) composed of combinations of metals and organic molecules have attracted attention as new highly designable physical adsorption materials, and research on the adsorption and separation of CO ２ is being actively conducted.

[0004] Among the various PCPs developed for CO ２ adsorption, a PCP called SIFSIX-3-Cu has been reported to be particularly excellent in CO ２ adsorption performance at low pressure (Non-Patent Document 1), and its application to the direct recovery (DAC) of extremely low-concentration CO ２ in the air is expected.

[0005] However, it has been pointed out that this material has poor stability and its structure can collapse in the presence of a large amount of water vapor (Non-Patent Document 2).

[0006] O. Shekhah et al. “Made-to-order metal-organic frameworks for trace carbon dioxide removal and air capture” Nature Communications volume 5, Article number: 4228 (2014)David G. Madden et al. “Flue-gas and direct-air capture of CO2 by porous metal-organic materials” Phil. Trans. R. Soc. A 2017, 375, 20160025K. Uemura et al. “Syntheses, Crystal Structures and Adsorption Properties of Ultramicroporous Coordination Polymers Constructed from Hexafluorosilicate Ions and Pyrazine” Eur. J. Inorg. Chem. 2009, 2329.

[0007] The inventors further investigated SIFSIX-3-Cu produced according to Non-Patent Document 1. As a result, this porous coordination polymer is H ２ When exposed to CO vapor, the CO ２ We found that the adsorption performance can be significantly impaired. Furthermore, this porous coordination polymer is H ２ We also found that the stability against steam was not reproducible.

[0008] Therefore, the present disclosure aims to enable the production of SIFSIX-3-Cu or its analogues with high stability and reproducibility. Here, "analogue" means a compound in which at least a portion of pyr (pyrazine) in SIFSIX-3-Cu is substituted with a pyrazine derivative, and / or a compound in which other metal atoms are used instead of or in addition to Cu, as will be described later.

[0009] The inventors diligently investigated the reasons why conventional SIFSIX-3-Cu lacked stability and reproducibility. They hypothesized that the instability was due to trace structural defects. With the aim of reducing the amount of such structural defects, the inventors established a new synthesis method that constructs the skeleton in two steps, replacing the previously reported one-step synthesis method.

[0010] Embodiments of the present invention are, for example, as follows: [1] Chemical formula [M(μ-SiF ６ ) (μ-pyr ＊ ) ２ A method for producing a three-dimensional porous coordination polymer represented by the chemical formula [M(μ-SiF ６ ) (μ-pyr ＊ ) (pyr ＊ ) ２ The process includes preparing a first two-dimensional coordination polymer represented by ] and mixing the first two-dimensional coordination polymer with an alcohol-containing solvent, wherein M is one or more divalent metal atoms capable of forming an octahedral hexa-coordination (OC-6) structure, and the pyr ＊ A method for producing a compound, wherein the compound is pyrazine or a derivative thereof or a mixture thereof, and the alcohol is at least one selected from the group consisting of methanol, ethanol, and 2-propanol. [2] Chemical formula [M(μ-SiF ６ ) (μ-pyr ＊ ) ２ A method for producing a three-dimensional porous coordination polymer represented by the chemical formula [M(μ-SiF ６ ) (μ-pyr ＊ ) (H ２ O) ２ The process involves preparing a second two-dimensional coordination polymer represented by ] and then using the second two-dimensional coordination polymer to pyr ＊ The process includes reacting with, where M is one or more divalent metal atoms capable of forming an octahedral hexa-coordinate (OC-6) structure, and the pyr ＊A method for producing pyrazine or a derivative thereof or a mixture thereof. [3] The method for producing according to [1] or [2], wherein M comprises at least one metal atom selected from the group consisting of Fe, Co, Ni, Zn, and Cu. [4] The method for producing according to any one of [1] to [3], wherein M comprises Cu. [5] The pyr ＊ A manufacturing method according to any one of [1] to [4], wherein at least a portion of the is represented by the following general formula. In the formula, R ２ , R ３ , R ５ and R ６ Each is independently selected from the group consisting of a hydrogen atom, a methyl group, a fluoromethyl group, an amino group, a hydroxyl group, a mercapto group, and a halogen atom. [6] The first two-dimensional coordination polymer is M(NO ３ ) ２ or its hydrate or M (BF ４ ) ２ Or its hydrate, (NH ４ ) ２ (SiF ６ ) and the aforementioned pyr ＊ The method for producing the polymer described in [1] by mixing the following: [7] The second two-dimensional coordination polymer is M(NO ３ ) ２ or its hydrate or M (BF ４ ) ２ Or its hydrate, (NH ４ ) ２ (SiF ６ ) and the aforementioned pyr ＊ and an excess amount of H ２ The method for producing [2], which is synthesized by mixing in a solvent containing O. [8] The method for producing [7], wherein the solvent further comprises an alcohol selected from the group consisting of methanol, ethanol, and 2-propanol.

[0011] According to this disclosure, it becomes possible to manufacture SIFSIX-3-Cu or its analogues with high stability and reproducibility.

[0012] Figure 1 is a schematic diagram illustrating a conventional manufacturing method of SIFSIX-3-Cu. Figure 2 is a conceptual diagram illustrating a schematic comparison between the conventional manufacturing method and the novel manufacturing method according to the present invention. In Figure 2, M is Cu and pyr ＊ This shows an example where the material is pyr. Figure 3 is a schematic diagram illustrating the first manufacturing method according to the present invention. Figure 4 is a schematic diagram illustrating the second manufacturing method according to the present invention. Figure 5 is a schematic diagram illustrating a modified example of the second manufacturing method according to the present invention. Figure 6 shows the estimated mechanism of structural change due to hydrolysis of 3D-PCP synthesized by the conventional method. Figure 7 shows the results of PXRD (powder X-ray diffraction) measurements for the comparative example and the example. Figure 8 shows the results of TGA (thermogravimetric analysis) measurements for the comparative example and the example. Figure 9 shows the CO2 in the comparative example. ２ and H ２ The results of the O adsorption measurement are shown. Figure 10 shows the CO adsorption measurement according to the example. ２ and H ２ The results of the O adsorption measurement are shown. Figure 11 shows the CO adsorption measurement for a comparative example. ２ and H ２ The results of the O adsorption measurement are shown. Figure 12 shows the CO adsorption measurement according to the example. ２ and H ２ The results of the O adsorption measurement are shown. Figure 13 shows the N in comparative examples and examples. ２ The results of the adsorption measurement are shown. Figure 14 shows the CO2 in the comparative example. ２ and H ２ Figure 15 shows the results of oxyhydrogen (O) adsorption measurements. Figure 16 shows the results of acetone adsorption measurements for the comparative example and the example. Figure 17 shows the results of PXRD (powder X-ray diffraction) measurements after hydrolysis treatment of 3D-PCP obtained by the conventional method. Figure 18 is a scheme diagram showing an example of the change in stability due to the structural regeneration process.

[0013] The following describes in detail a method for producing a three-dimensional porous coordination polymer according to one aspect of the present invention. When referring to drawings or chemical formulas, the same reference numerals or symbols are used for components that exhibit similar or identical functions, and redundant explanations are omitted.

[0014] The present invention relates to the chemical formula [M(μ-SiF) ６ ) (μ-pyr ＊ ) ２ This invention relates to a novel method for producing a three-dimensional porous coordination polymer represented by ]. Here, M represents one or more divalent metal atoms capable of forming an octahedral hexa-coordination (OC-6) structure, and pyr ＊ represents pyrazine or its derivatives or mixtures thereof. M is Cu and pyr ＊ If M is pyrazine (pyr), the above three-dimensional porous coordination polymer is SIFSIX-3-Cu. ＊ If the compound contains a pyrazine derivative, the above three-dimensional porous coordination polymer is an analog of SIFSIX-3-Cu. In the following text, analogs of SIFSIX-3-Cu may also be simply referred to as SIFSIX-3-Cu.

[0015] As described above, M represents one or more divalent metal atoms capable of forming an octahedral hexa-coordinate (OC-6) structure. For example, M is at least one metal atom selected from the group consisting of Fe, Co, Ni, Zn, and Cu. From the viewpoint of DAC performance, it is more preferable for M to contain Cu. Furthermore, from the viewpoint of stability, it is also preferable for M to contain Ni.

[0016] As described above, M may contain two or more metal atoms. For example, if M contains two types of metal atoms, in the above three-dimensional porous coordination polymer, some of the metal sites occupied by the first metal atom may be replaced by the second metal atom. In this case, the above three-dimensional porous coordination polymer has the chemical formula [(M １ ｘ M ２ １－ｘ ) (μ-SiF ６ ) (μ-pyr ＊ ) ２ It can be expressed as follows: Here, M １ is the first metal atom, M ２x is the second metal atom, and 0.5 ≤ x < 1. Although not explicitly stated, a similar formula can be derived when M contains three or more types of metal atoms. When M contains two or more types of metal atoms, it is preferable that M contains Cu and Ni.

[0017] pyr ＊ As mentioned above, pyrazine is pyrazine or its derivatives or mixtures thereof. Pyrazine derivatives will be explained in detail later. Here, pyr ＊ The term "mixture" refers to the "μ-pyr" in the above-mentioned three-dimensional porous coordination polymer. ＊ This means that a portion of the pyrazine or its derivatives that mainly constitute the 'part' is substituted by other pyrazine derivatives or pyrazines.

[0018] Figure 1 shows a conventional manufacturing method for SIFSIX-3-Cu. As shown in Figure 1, in the conventional manufacturing method, SIFSIX-3-Cu is CuSiF ６ ・H ２ It is synthesized in one step using O and pyr. As shown in Figure 1, the resulting SIFSIX-3-Cu is a three-dimensional porous coordination polymer (3D-PCP). In the following, 3D-PCP produced by the conventional method may be represented as "1a".

[0019] Figure 2 is a conceptual diagram illustrating a schematic comparison between a conventional manufacturing method and the novel manufacturing method according to the present invention. Note that here, pyr ＊ It is simply shown as pyr.

[0020] As shown in the upper part of Figure 2, in the conventional manufacturing method, 3D-PCP is manufactured in one step. In contrast, in the manufacturing method according to the present invention, as shown in the lower part of Figure 2, a two-dimensional coordination polymer (2D-CP) is first prepared. Then, these 2D-CPs are crosslinked with pyrazine (or its derivative) to obtain a three-dimensional porous coordination polymer (3D-PCP). Note that in Figure 2, M is Cu and pyrazine ＊ The case where is pyr is shown as an example. In addition, in the following, 3D-PCPs manufactured by this method may be represented by "1b" or "1c".

[0021] As will be described in detail in the following examples, the 3D-PCP produced by the production method according to the present invention has significantly higher stability against H ２ O vapor compared to 3D-PCP produced by the conventional method. Regarding the reason, the present inventors speculate as follows.

[0022] That is, it is considered that the cause of the instability of 3D-PCP produced by the conventional method is due to trace structural defects. As can be seen from FIG. 2, 3D-PCP has a structure in which two-dimensional sheets are crosslinked by pyrazine (or a derivative thereof). Here, pyrazine (or a derivative thereof) is a small molecule with a short crosslinking distance compared to, for example, 4,4'-bipyridine. Therefore, once a structural defect site is generated when 3D-PCP is constructed, it is extremely difficult for it to be automatically repaired due to the restriction of the diffusion of molecules in the ultrafine pores. In contrast, in the production method according to the present invention, once 2D-CP is prepared and then 3D-PCP is constructed. In this case, due to the large number of accessible spaces in 2D-CP, structural defects can be repaired relatively easily. As a result, the structural defects are also reduced in the finally obtained 3D-PCP. Therefore, the 3D-PCP obtained by the production method according to the present invention is structurally robust and the stability against H ２ O vapor is also significantly improved.

[0023] Hereinafter, the specific method for synthesizing 3D-PCP via 2D-CP will be described in more detail.

[0024] (First production method) FIG. 3 is a schematic diagram schematically showing the first production method according to the present invention. As shown in FIG. 3, in this method, as the first two-dimensional coordination polymer (hereinafter also referred to as "2D-CP-pyr ６ )(μ-pyr ＊ )(pyr ＊ ) ２ ] represented by the chemical formula [M(μ-SiF ＊ ] is used. Here, M represents one or more divalent metal atoms capable of forming an octahedral six-coordinate (OC-6) structure, and pyr＊ represents pyrazine or its derivative or a mixture thereof.

[0025] 2D-CP-pyr shown in FIGURE 3 ＊ can be synthesized, for example, by the method partially described in Non-Patent Document 3. In Non-Patent Document 3, there is no description or suggestion regarding the production of 3D-PCP from 2D-CP-pyr. ＊

[0026] In Non-Patent Document 3, when M is Cu, Cu(BF ＩＩ ) ４ ·xH ２ O is used. However, the inventors have found that Cu(NO ２ ) ＩＩ ·3H ３ O can also be used as the Cu source when M is Cu. In this case, from the perspective of raw material cost, it is more preferable to use Cu(NO ２ ) ２ ·3H ３ O. ２ ·3H ２ O.

[0027] The production of 2D-CP-pyr ＊ is typically carried out under concentrated conditions using a small amount of solvent. As this solvent, it is preferable to use H ２ O or a mixed solvent containing H ２ O. The amount of the solvent is preferably 300 times or less in molar ratio to the M ＩＩ source. If the amount of this solvent is excessively large, the yield may decrease or a mixture with the second two-dimensional coordination polymer described later may occur. The production of 2D-CP-pyr ＊ may also be carried out by solid-phase synthesis or semi-solid-phase synthesis. Thus, 2D-CP-pyr ＊ can be synthesized using a relatively small amount of solvent. Therefore, the method via 2D-CP-pyr ＊ is also particularly excellent in realizing large-scale synthesis by scaling up.

[0028] 2D-CP-pyr ＊It has a two-dimensional sheet-like structure, and its upper and lower coordination sites are single-seat pyr ＊ It is capped by this 2D-CP-pyr ＊ When mixed with an alcohol-containing solvent, pyr ＊ A portion of the alcohol is eluted, and a three-dimensional structure of 3D-PCP with cross-linked two-dimensional sheets is obtained. At least one alcohol selected from the group consisting of methanol, ethanol, and 2-propanol (isopropyl alcohol) is preferably used as the alcohol. The solvent may contain only the alcohol, or it may be a mixed solvent of the alcohol and another solvent.

[0029] As described above, in the first manufacturing method, M represents one or more divalent metal atoms capable of forming an octahedral hexa-coordinate (OC-6) structure. Examples of M are as previously explained. When M contains two or more types of metal atoms, the first two-dimensional coordination polymer is, for example, a polymer with the chemical formula [(M １ ｘ M ２ １－ｘ ) (μ-SiF ６ ) (μ-pyr ＊ ) (pyr ＊ ) ２ It can be represented by ].

[0030] The first two-dimensional coordination polymer is, for example, M(NO ３ ) ２ or its hydrate or M (BF ４ ) ２ Or its hydrate, (NH ４ ) ２ (SiF ６ ) and the aforementioned pyr ＊ It can be synthesized by mixing and . When M is Cu, Cu ＩＩ For example, Cu(NO) ３ ) ２ 3H ２ O or Cu (BF ４ ) ２ ・xH ２ O can be used. If M is Fe, then Fe ＩＩ For example, Fe(NO)３ ) ２ 6H ２ O or Fe (BF ４ ) ２ 6H ２ O can be used. If M is Co, then Co ＩＩ For example, Co(NO) ３ ) ２ 6H ２ O or Co(BF) ４ ) ２ 6H ２ O can be used. If M is Ni, then Ni ＩＩ For example, Ni(NO) ３ ) ２ 6H ２ O or Ni(BF) ４ ) ２ 6H ２ O can be used. If M is Zn, then Zn ＩＩ As a source, for example, Zn (NO ３ ) ２ 6H ２ O or Zn (BF ４ ) ２ ・xH ２ O can be used. If M contains two or more types of metal atoms, they may be mixed and used as appropriate.

[0031] (Second manufacturing method) Figure 4 is a schematic diagram showing the second manufacturing method according to the present invention. As shown in Figure 4, in this method, 2D-CP is given the chemical formula [M(μ-SiF ６ ) (μ-pyr ＊ ) (H ２ O) ２ The second two-dimensional coordination polymer represented by ] (hereinafter referred to as "2D-CP-H ２ The term "O" is used. Here, M represents one or more divalent metal atoms capable of forming an octahedral hexa-coordinate (OC-6) structure, and pyr ＊ This represents pyrazine or its derivatives or mixtures thereof.

[0032] Figure 4 shows 2D-CP-H ２O can be synthesized, for example, by the method partially described in Non-Patent Document 3 above. Note that in Non-Patent Document 3, 2D-CP-H ２ There is no mention or suggestion of manufacturing 3D-PCP from O.

[0033] In Non-Patent Document 3, Cu ＩＩ As a source, Cu(BF ４ ) ２ ・xH ２ O is used. However, the inventors of the present invention have developed 2D-CP-H ２ In the synthesis of O, Cu ＩＩ As a source, Cu (NO ３ ) ２ 3H ２ It has been found that O can be used. From the perspective of raw material cost, Cu (NO ３ ) ２ 3H ２ Using O is preferable.

[0034] 2D-CP-H ２ The production of O typically involves an excess amount of H ２ This is carried out under dilution conditions using a solvent containing O. Note that in Non-Patent Document 3, H is used as this solvent. ２ Although O is used alone, the inventors of this invention use H ２ It has been found that using a mixed solvent of O and an alcohol is particularly preferable. In this case, it is preferable to use at least one alcohol selected from the group consisting of methanol, ethanol, and 2-propanol. Note that the H in the above solvent ２ If the amount of oxygen is excessively low, 2D-CP-pyr is produced as a byproduct. ＊ Sometimes these can end up mixed together unintentionally.

[0035] 2D-CP-H ２ O has a two-dimensional sheet-like structure, and its upper and lower coordination sites are H ２ It is capped with O. This 2D-CP-H ２ O to pyr ＊Further reaction yields a 3D-PCP with a three-dimensional structure in which the two-dimensional sheet is crosslinked. This reaction is carried out, for example, in a solvent containing alcohol. In this case, at least one selected from the group consisting of methanol, ethanol, and 2-propanol is preferably used as the alcohol. The solvent may contain only the alcohol, or it may be a mixed solvent of the alcohol and another solvent.

[0036] As described above, in the second manufacturing method, M represents one or more divalent metal atoms capable of forming an octahedral hexa-coordinate (OC-6) structure. Examples of M are the same as those previously explained. When M contains two or more types of metal atoms, the second two-dimensional coordination polymer is, for example, a polymer with the chemical formula [(M １ ｘ M ２ １－ｘ ) (μ-SiF ６ ) (μ-pyr ＊ ) (H ２ O) ２ It can be represented by ].

[0037] The second two-dimensional coordination polymer is, for example, M(NO ３ ) ２ or its hydrate or M (BF ４ ) ２ Or its hydrate, (NH ４ ) ２ (SiF ６ ) and the aforementioned pyr ＊ and an excess amount of H ２ It can be synthesized by mixing in a solvent containing O. ＩＩ The specific example of the source is the same as that described earlier for the first manufacturing method. As mentioned above, the second manufacturing method is 2D-CP-H ２ O and pyr ＊ This process includes a step of reacting with 2D-CP-H. ２ O and 2D-CP-pyr ＊ A mixture of pyr ＊ The process may involve a reaction with 2D-CP-pyr. ＊This can be prepared, for example, by the method described earlier in relation to the first manufacturing method. ＊ The reaction step is carried out, for example, in a solvent containing alcohol. In this case, as before, at least one selected from the group consisting of methanol, ethanol, and 2-propanol is preferably used as the alcohol.

[0038] Here, the inventors have found that 3D-PCP synthesized by conventional methods is H ２ The structure after decay by O is 2D-CP-H ２ O and 2D-CP-pyr ＊ We have newly discovered that this mixture is a mixture of [unclear]. In addition, the inventors have discovered that this mixture is pyr ＊ By reacting with it, 3D-PCP can be regenerated, and this regenerated 3D-PCP differs from 3D-PCP synthesized by conventional methods, H ２ We also discovered that it has extremely high stability against O. Specifically, the inventors hydrolyzed 3D-PCP synthesized by the conventional method to produce 2D-CP-H ２ O and 2D-CP-pyr ＊ Prepare a mixture of and and then pyr ＊ We discovered that by reacting it with [a specific substance], we could manufacture 3D-PCPs that exhibit excellent stability.

[0039] Figure 5 is a schematic diagram showing a modified example of the second manufacturing method according to the present invention. In Figure 5, M is Cu and pyr ＊ The method for synthesizing 3D-PCPs with the above-mentioned structural reconstruction is described using the case where pyr is used as an example.

[0040] Figure 6 shows the estimated mechanism of structural change due to hydrolysis of 3D-PCP synthesized by the conventional method. As shown in Figure 6, 3D-PCP synthesized by the conventional method becomes two-dimensional through hydrolysis, resulting in 2D-CP-H ２ O and 2D-CP-pyr ＊ It is presumed that the mixture has changed into one containing approximately equal amounts of the two substances.

[0041] In the first and second manufacturing methods described above, pyr ＊At least some of these are compounds represented by the following general formulas, for example. In the formula, R ２ , R ３ , R ５ and R ６ Each of these is independently selected from the group consisting of a hydrogen atom, a methyl group, a fluoromethyl group, an amino group, a hydroxyl group, a mercapto group, and a halogen atom.

[0042] In the above formula, R ２ , R ３ , R ５ and R ６ When all atoms are hydrogen atoms, it corresponds to pyr. From the perspective of pore size in 3D-PCP, R ２ , R ３ , R ５ and R ６ The substituent represented by is preferably not too large in size. ＊ Specific examples include the following. Note that these are merely examples, and it is of course possible to use other pyrazine derivatives. Furthermore, as mentioned above, mixtures of these may also be used.

[0043]

[0044] As explained earlier with reference to Figure 2, the lack of stability in 3D-PCP is thought to be due to structural defects that occur during manufacturing. When a pyrazine derivative is used instead of pyrazine, the size of the crosslinking molecules in 3D-PCP becomes larger, thus further restricting the diffusion of molecules in the ultrafine pores. Therefore, when using conventional methods, structural defects are more likely to occur. In contrast, the method according to the present invention can avoid such problems. That is, the method according to the present invention is also useful when a pyrazine derivative is used instead of pyrazine. When a pyrazine derivative is used, for example, it becomes possible to impart functionality to 3D-PCP due to the presence of functional groups.

[0045] SIFSIX-3-Cu or its analogues produced by the first or second manufacturing method described above are H ２It exhibits excellent stability against O vapor. Specifically, it is stable against CO at 100 kPa and 298 K immediately after synthesis. ２ Adsorption amount S １ And, H ２ CO at 100 kPa and 298 K after exposure to O vapor ２ Adsorption amount S ２ The ratio to is typically S ２ / S １ The condition ≥ 0.9 is satisfied, preferably S ２ / S １ The value ≥0.95 is satisfied. Furthermore, as will be explained in the examples, in SIFSIX-3-Cu manufactured according to Non-Patent Document 1, S ２ / S １ It is at most around 0.8, and typically below 0.5. １ and S ２ The measurement method will be explained in detail in the examples. Note that in the following, S ２ / S １ The percentage of this value is sometimes referred to as the stability index (st%).

[0046] SIFSIX-3-Cu or its analogues produced by the first or second manufacturing method described above are also excellent in terms of BET specific surface area determined from nitrogen adsorption isotherms. Specifically, this BET specific surface area is typically 250 m². ２ g －１ The above is the most common, preferably 270m ２ g －１ That concludes the explanation. Furthermore, for SIFSIX-3-Cu manufactured according to Non-Patent Document 1, the BET specific surface area is 230 m². ２ g －１ This is the extent of the improvement. As mentioned above, this improvement in BET specific surface area is presumed to be due to a reduction in structural defects by the new synthesis method.

[0047] <Synthesis of Materials> All reagents and solvents used below are commercially available and were used in their raw state without further purification. Note that below, pyr ＊ As a typical example, we used Pyr.

[0048] (Comparative Example 1: Direct Synthesis by Conventional Method) SIFSIX-3-Cu(3D-PCP) was synthesized based on the conventional method described in Non-Patent Document 1. Specifically, Cu(SiF) in MeOH (100 mL) ６ )・xH ２ A solution of O (2.47 g; 12.0 mmol) was added to a solution of pyr (4.80 g; 60.0 mmol) in MeOH (100 mL) with vigorous stirring. After stirring the mixture at room temperature for 3 days, the resulting precipitate was collected by centrifugation, washed with MeOH (5 × 200 mL), and dried at room temperature under dynamic vacuum to obtain a blue [Cu(μ-SiF ６ ) (μ-pyr) ２ [Compound 1a; 2.93 g] was obtained.

[0049] (Example 1: Two-step synthesis by the first manufacturing method) First, as the first 2D-PCP, [Cu(μ-SiF ６ ) (μ-pyr) (pyr) ２ ], Cu ＩＩ The source was synthesized using a method that improved upon Non-Patent Document 3.

[0050] That is, Cu(NO ３ ) ２ 3H ２ O (2.91 g; 12.0 mmol) and (NH ４ ) ２ (SiF ６ ) (2.14 g; 12.0 mmol) of H ２ Add H2 (2.88 g; 36.0 mmol) to the O (9.0 mL) solution while stirring vigorously. ２ It was added to a 7.5 mL solution of O. After stirring the mixture at room temperature for one day, the resulting precipitate was collected by centrifugation and continuously subjected to H. ２ Wash as quickly as possible with O / MeOH (1:3 (v / v); 3 × 18 mL) and MeOH (3 × 18 mL), dry at room temperature under dynamic vacuum, and a deep blue-violet [Cu(μ-SiF) ６ ) (μ-pyr) (pyr) ２ ] (Compound 2; 3.56 g; yield 66%) was obtained. Note that Cu ＩＩ As a source, Cu (NO ３ ) ２ 3H ２Cu (BF) instead of O ４ ) ２ ・xH ２ A similar compound 2 was obtained using O. However, Cu ＩＩ As a source, CuCl ２ ・2H ２ O or CuSO ４ ・5H ２ When oxygen (O) was used, a different compound from compound 2 was produced.

[0051] Next, SIFSIX-3-Cu(3D-PCP) was synthesized using the obtained 2D-PCP (compound 2). Specifically, first, compound 2 (483 mg; 1.00 mmol) was dispersed in MeOH (10.0 mL). After stirring the suspension at room temperature for 3 days, the resulting precipitate was collected by centrifugation, washed with MeOH (5 × 10 mL), and dried at room temperature under dynamic vacuum to obtain a blue [Cu(μ-SiF ６ ) (μ-pyr) ２ [Compound 1b; 423 mg] was obtained.

[0052] Furthermore, without isolating the above 2D-PCP (compound 2), copper, SiF ６ Furthermore, it was also possible to obtain 3D-PCP (compound 1b) starting from a pyr source. Specifically, Cu(NO ３ ) ２ 3H ２ O (4.84 g; 20.0 mmol) and (NH ４ ) ２ (SiF ６ ) (3.57 g; 20.0 mmol) of H ２ Add H(4.80 g; 59.9 mmol) of pyr (15.0 mL) to the O (15.0 mL) solution while stirring vigorously. ２ It was added to a solution of O (12.5 mL). After stirring the mixture at room temperature for 1 day, the resulting deep blue-violet precipitate was collected by centrifugation, washed sequentially with H2O / MeOH (1:3 (v / v); 3 × 30 mL) and MeOH (3 × 30 mL), and redispersed in MeOH (200 mL). After stirring the suspension at room temperature for 3 days, the resulting precipitate was collected by centrifugation, washed with MeOH (5 × 200 mL), and dried at room temperature under dynamic vacuum to obtain a blue [Cu(μ-SiF ６ ) (μ-pyr)２ [Compound 1b; 5.15 g] was obtained.

[0053] (Example 2: Two-step synthesis by the second manufacturing method) First, as the second 2D-PCP, [Cu(μ-SiF ６ ) (μ-pyr) (H ２ O) ２ ], Cu ＩＩ The compound was synthesized using a method that improved upon Non-Patent Document 3 regarding the source and solvent.

[0054] That is, H ２ Cu(NO) in O / MeOH (1:1 (v / v); 100 mL) ３ ) ２ 3H ２ O (2.90 g; 12.0 mmol) and (NH ４ ) ２ (SiF ６ A solution of (2.14 g; 12.0 mmol) was added to a solution of pyr (2.88 g; 36.0 mmol) in MeOH (100 mL) while vigorously stirring. After stirring the mixture at room temperature for 1 day, the resulting precipitate was collected by centrifugation and H ２ Wash continuously with O / MeOH (1:3 (v / v); 3 × 200 mL) and MeOH (3 × 200 mL), dry at room temperature under dynamic vacuum, and obtain a pale blue [Cu(μ-SiF ６ ) (μ-pyr) (H ２ O) ２ ] (Compound 3; 3.23 g; yield 84%) was obtained. Note that Cu ＩＩ As a source, Cu (NO ３ ) ２ 3H ２ Cu (BF) instead of O ４ ) ２ ・xH ２ A similar compound 3 was obtained using O. However, Cu ＩＩ As a source, CuCl ２ ・2H ２ O or CuSO ４ ・5H ２ When oxygen (O) was used, a compound different from compound 3 was produced.

[0055] Next, SIFSIX-3-Cu(3D-PCP) was synthesized using the obtained 2D-PCP (compound 3). Specifically, first, compound 3 (324 mg; 1.01 mmol) was dispersed in MeOH (10.0 mL). Pyr (202 mg; 2.53 mmol) was added to this suspension with vigorous stirring. After stirring the mixture at room temperature for 3 days, the resulting precipitate was collected by centrifugation, washed with MeOH (5 × 10 mL), and dried at room temperature under dynamic vacuum to obtain a blue [Cu(μ-SiF ６ ) (μ-pyr) ２ [Compound 1c; 354 ​​mg] was obtained.

[0056] Furthermore, without isolating the above 2D-PCP (compound 3), copper, SiF ６ Furthermore, it was also possible to obtain 3D-PCP (compound 1c) starting from a pyr source. Specifically, H ２ Cu(NO) in O / MeOH (1:1 (v / v); 7.5 mL) ３ ) ２ 3H ２ O (217 mg; 899 μmol) and (NH ４ ) ２ (SiF ６ A solution of (161 mg; 905 μmol) was added to a solution of pyr (218 mg, 2.72 mmol) in MeOH (7.5 mL) while vigorously stirring. After stirring the mixture at room temperature for 1 day, the resulting pale blue precipitate was collected by centrifugation and H ２ The suspension was washed sequentially with O / MeOH (1:3 (v / v); 3 × 15 mL) and MeOH (3 × 15 mL), and then redispersed in MeOH (9.0 mL). Pyr (181 mg; 2.26 mmol) was added to this suspension with vigorous stirring. After stirring the mixture at room temperature for 3 days, the resulting precipitate was collected by centrifugation, washed with MeOH (5 × 9 mL), and dried at room temperature under dynamic vacuum to obtain a blue [Cu(μ-SiF ６ ) (μ-pyr) ２ [Compound 1c; 262 mg] was obtained.

[0057] (Example 3: Large-scale synthesis by the first manufacturing method) Cu(NO ３ ) ２ 3H ２O (87.0 g; 360 mmol) and (NH ４ ) ２ (SiF ６ ) (64.1 g; 360 mmol) of H ２ Add H₂O (86.8 g; 1080 mmol) to the 270 mL solution while stirring vigorously. ２ It was added to a solution of O (225 mL). After stirring the mixture at room temperature for one day, the resulting dark blue-violet precipitate was collected by suction filtration and continuously filtered with H ２ O (50 mL), H ２ Washed with O / MeOH (1:3 (v / v); 500 mL) and MeOH (500 mL), and redispersed in MeOH (500 mL). After stirring the suspension at room temperature for 3 days, the resulting precipitate was collected by suction filtration, washed with MeOH (500 mL), and dried at room temperature under dynamic vacuum to obtain a blue [Cu(μ-SiF ６ ) (μ-pyr) ２ [Compound 1b; 106 g] was obtained.

[0058] (Comparative Example 2; Intentional Introduction of Structural Defects) Using compound 3, a 3D-PCP with intentionally introduced structural defects was prepared. Specifically, first, compound 3 (162 mg; 503 μmol) was dispersed in MeOH (5.0 mL). To this suspension, an insufficient amount of pyr (37 mg; 460 μmol) was added while vigorously stirring. After stirring the mixture at room temperature for 3 days, the resulting precipitate was collected by centrifugation, washed with MeOH (5 × 5 mL), and dried at room temperature under dynamic vacuum to obtain [Cu(μ-SiF ６ ) (μ-pyr) ２ ] (1c ｄｅｆ (164 mg) was obtained.

[0059] <Evaluation> Powder X-ray diffraction (PXRD) patterns due to CuKα emission (λ = 1.54184 Å) were collected in 0.01° increments from 4.00° to 40.00° using a SmartLab (Rigaku) ​​X-ray diffractometer. Thermogravimetric analysis (TGA) was performed using Thermo+EVOTG8120 (Rigaku) ​​and N ２The experiment was carried out under a flow rate of 200 mL / min at a heating rate of 5 K / min. Gas and vapor adsorption isotherms were measured using a BELSORPMAX II (MicrotracBEL) volumetric gas adsorption apparatus with a liquid nitrogen Dewar container (77 K) or a circulating water bath (298 K).

[0060] (PXRD Measurement) Figure 7 shows the results of the PXRD measurement of SIFSIX-3-Cu (3D-PCP) synthesized as described above. Comparison with computer simulations confirmed that SIFSIX-3-Cu was indeed formed in both the example and the comparative example.

[0061] (TGA Measurement) Figure 8 shows the TGA measurement results for SIFSIX-3-Cu(3D-PCP) synthesized as described above. As shown in Figure 8, it was found that both the example and the comparative example have almost identical thermal stability.

[0062] (H ２ (Stability against steam) Regarding the SIFSIX-3-Cu(3D-PCP) synthesized as described above, H ２ To evaluate the stability against O vapor, the following measurements were performed sequentially in this order: (Stage 1) Degassed at 373 K for 3 hours, then degassed at 298 K to remove CO ２ Adsorption measurement (Stage 2): After degassing at 373K for 3 hours, H at 298K. ２ O adsorption measurement (Stage 3): After degassing at 373K for 3 hours, CO2 adsorption measurement at 298K. ２ Adsorption measurement, i.e., CO in step 3 ２ Adsorption measurement is performed in step 2, H ２ This was done after exposure to O vapor.

[0063] Figure 9 shows the results of adsorption measurements for SIFSIX-3-Cu(3D-PCP; compound 1a) synthesized by a conventional manufacturing method. Here, the filled data points indicate the amount of adsorption when the pressure is increased, and the white data points indicate the amount of adsorption when the pressure is decreased.

[0064] As can be seen from Figure 9, compound 1a from Comparative Example 1 has CO2 immediately after synthesis. ２ In the adsorption measurement (stage 1), it showed no particular problems. However, the subsequent H２ In the O adsorption measurement (stage 2), a decrease in adsorption amount was observed, particularly during desorption. Furthermore, the subsequent CO ２ In the adsorption measurement (stage 3), CO ２ Almost no adsorption was observed. This result is related to H in stage 2. ２ This suggests that exposure to oxygen vapor has caused the porous structure of compound 1a to collapse.

[0065] Figure 10 shows the results of adsorption measurements for SIFSIX-3-Cu(3D-PCP; compound 1b) synthesized by a manufacturing method according to one aspect of the present invention.

[0066] As can be seen in Figure 10, compound 1b according to Example 1 is CO immediately after synthesis. ２ Adsorption measurement (stage 1), and H ２ CO after exposure to O vapor ２ There was almost no change in behavior between the adsorption measurement (stage 3) and the subsequent H ２ In the O adsorption measurement (stage 2), no decrease in the amount of adsorption during desorption was observed. This result indicates that compound 1b is H ２ This demonstrates that it is extremely stable against exposure to oxygen vapor.

[0067] (Reproducibility) The instability of compound 1a described above was further evaluated using multiple lots. Figure 11 shows the results of adsorption measurements for three lots of SIFSIX-3-Cu(3D-PCP; compound 1a) synthesized by the conventional manufacturing method. Note that Figure 11(a) is the same as Figure 9.

[0068] As shown in Figure 11, the adsorption behavior of compound 1a from Comparative Example 1 varied greatly depending on the manufacturing lot. Specifically, in the example shown in Figure 11(a), H ２ CO after exposure to steam ２ The decrease in adsorption amount was particularly pronounced, but it was moderate in the example shown in Figure 11(b) and small in the example shown in Figure 11(c). This is because 3D-PCP obtained by the conventional manufacturing method is H ２ This means that the stability against exposure to O vapor is not easily reproducible.

[0069] Similar evaluations were performed for compound 1b from Example 1 and compound 1c from Example 2. The results, along with the results for compound 1a from Comparative Example 1, are presented in H ２ CO before and after exposure to O vapor ２ The adsorption amounts were compared and summarized in Table 1 below. In Table 1, the column labeled "1st (pristine)" represents the CO2 adsorbed at 100 kPa and 298 K immediately after synthesis. ２ Adsorption amount S １ This represents the following, and the column labeled "2nd (after H2O sorption)" is H ２ CO at 100 kPa and 298 K after exposure to O vapor ２ Adsorption amount S ２ It represents.

[0070] As can be seen from Table 1, in compound 1a of Comparative Example 1, H ２ Regarding stability against exposure to steam, it can be seen that the reproducibility is low. ２ / S １ At most, it is around 0.8, H ２ It is difficult to say that it is stable against exposure to O vapor. In contrast, in compound 1c according to Example 2, S ２ / S １ It was stable at 0.95 or higher. Furthermore, in compound 1b according to Example 1, S ２ / S １ It was stable at 0.98 or higher. From these results, compound 1b from Example 1 and compound 1c from Example 2 are H ２ It was found to be stable against exposure to O vapor, and its stability exhibited high reproducibility.

[0071] Next, the stability of compound 1b, which was synthesized in large quantities using the method described in Example 3, was evaluated. The results are shown in Figure 13.

[0072] Figure 12 shows the results of adsorption measurements for SIFSIX-3-Cu (3D-PCP; compound 1b) synthesized in large quantities by a manufacturing method according to one aspect of the present invention. As shown in Figure 12, compound 1b obtained by large-scale synthesis also exhibits high stability (st% = 96; S ２ / S １ = 0.96) was confirmed.

[0073] (Evaluation of BET specific surface area) For the 3D-PCPs related to Comparative Example 1 and Example 1, N at 77K ２ Adsorption measurements were performed. The results, along with the calculated BET specific surface area, are shown in Figure 13. Figure 13(a) shows the results for compound 1a according to Comparative Example 1, and Figure 13(b) shows the results for compound 1b according to Example 1.

[0074] As can be seen from Figure 13, the BET specific surface area of ​​compound 1a in Comparative Example 1 is 230 m². ２ g ―１ In contrast, the BET specific surface area of ​​compound 1b according to Example 1 is 283 m². ２ g ―１ This result suggests that 3D-PCP produced by the manufacturing method according to one aspect of the present invention has higher quality in terms of gas adsorption suitability. Regarding compound 1a in Comparative Example 1, high P / P ０ A sharp increase in adsorption was observed in the region. This is presumed to be due to the presence of macropores between particles.

[0075] (Hypothesis Verification Regarding Structural Defects) As stated above, the inventors hypothesize that the differences in stability and reproducibility due to differences in manufacturing methods are due to structural defects. To verify this hypothesis, the following additional experiments were conducted.

[0076] As described above, as Comparative Example 2, a 3D-PCP with intentionally introduced structural defects was prepared. Specifically, in the manufacturing method described in Example 2, the amount of pyrazine (pyr) was reduced to 0.9 times the stoichiometric amount, thereby producing compound 1c ｄｅｆ The following was prepared. And compound 1c obtained in this way ｄｅｆ Regarding this, as explained earlier, CO２ Adsorption measurements were performed. The results are shown in Figure 14.

[0077] As shown in Figure 14, compound 1c related to Comparative Example 2 ｄｅｆ Compound 1a exhibited similar behavior to Compound 1a in Comparative Example 1. This result shows that Compound 1a in Comparative Example 1 exhibited similar behavior to Compound 1c in Comparative Example 2. ｄｅｆ This suggests the presence of structural defect sites similar to those in [location].

[0078] Next, acetone adsorption measurements were performed at 298 K for compound 1a from Comparative Example 1 and compound 1b from Example 1. The results are shown in Figure 15. Note that the P content in this measurement was ０ The pressure is 30.6 kPa. Furthermore, measurements during desorption were omitted for compound 1a.

[0079] As shown in Figure 15, compound 1a showed an increase in acetone adsorption in the low-pressure region. This is presumed to be due to the adsorption of the carbonyl oxygen atom of acetone to an uncoordinated Cu site (i.e., a structural defect site), as schematically shown in the figure. No such increase in adsorption was observed in compound 1b.

[0080] Finally, acetonitrile adsorption measurements were performed at 298 K for compound 1a from Comparative Example 1 and compound 1b from Example 1. The results are shown in Figure 16. Note that the P2 in this measurement was ０ The pressure is 11.8 kPa.

[0081] As shown in Figure 16, compound 1a showed an increase in acetonitrile adsorption in the low-pressure region. This is presumed to be due to the adsorption of nitrogen atoms of acetonitrile to uncoordinated Cu sites (i.e., structural defect sites), as schematically shown in the figure. No such increase in adsorption was observed in compound 1b.

[0082] (Example 4: Regeneration of structurally collapsed 3D-PCP) (Structural collapse by hydrolysis) Compound 1a was synthesized by the conventional method described in Comparative Example 1. Subsequently, the following treatment (measurement) was performed on compound 1a. As a result, structurally collapsed compound 1a (hereinafter referred to as compound 1a ｄｅｃ (Also known as) was prepared. (Stage 1) After degassing at 373K for 3 hours, CO2 was removed at 298K. ２ Adsorption measurement (Stage 2): After degassing at 373K for 3 hours, H at 298K. ２ O adsorption measurement (Stage 3): After degassing at 373K for 3 hours, CO2 adsorption measurement at 298K. ２ Adsorption measurement

[0083] (Compound 1a ｄｅｃ Structural evaluation) Compound 1a obtained as described above ｄｅｃ PXRD (powder X-ray diffraction) measurements were performed on the subject. The results are shown in Figure 17.

[0084] Figure 17 shows the results of PXRD (powder X-ray diffraction) measurements after hydrolysis treatment of 3D-PCP obtained by the conventional method. Upon analysis of these measurement results, the inventors identified compound 1a ｄｅｃ We discovered that the structure matches that of a mixture of two types of 2D-CP (i.e., compound 2 and compound 3). Specifically, by hydrolyzing 3D-PCP obtained by the conventional method, we obtained 2D-CP-H ２ O and 2D-CP-pyr ＊ It was found that a mixture of the above was obtained. In addition, although a similar PXRD pattern is reported in Non-Patent Document 2 mentioned above, it was not attributed to a mixture of two types of 2D-CP (i.e., compound 2 and compound 3).

[0085] (Improved stability through structural regeneration) Next, compound 1a obtained as described above. ｄｅｃA mixture of compound 2 and compound 3 (48.2 mg) was treated with pyr (28.7 mg) in the presence of methanol (1.3 mL). This process was carried out in the same manner as when SIFSIX-3-Cu (3D-PCP) was synthesized using 2D-PCP (compound 3) in Example 2. The 3D-PCP thus obtained was confirmed to have the same structure as SIFSIX-3-Cu by PXRD (powder X-ray diffraction) measurement.

[0086] The 3D-PCP obtained as described above was evaluated for its stability index (st%) in the same manner as previously explained. The results are shown in Figure 18.

[0087] Figure 18 is a scheme diagram showing an example of the change in stability due to the structural regeneration process. As shown in Figure 18, the 3D-PCP regenerated by the method of Example 4 showed an extremely high stability index of over 99%. This suggests that this 3D-PCP has a structure equivalent to compound 1b and / or 1c. On the other hand, attempts were made to improve the stability of the 3D-PCP (compound 1a) obtained by the conventional method by treating it with pyr under methanol, but the stability index was only about 71%, which did not exceed the range of compound 1a.

[0088] In the above examples, compounds 1b and 1c were always stable, so only regeneration from compound 1a was considered. However, it is expected that even if compounds 1b and 1c undergo structural collapse under more severe conditions, structural regeneration may be possible using a similar method.

Claims

1. Chemical formula [M(μ-SiF ６ ) (μ-pyr ＊ ) ２ A method for producing a three-dimensional porous coordination polymer represented by the chemical formula [M(μ-SiF ６ ) (μ-pyr ＊ ) (pyr ＊ ) ２ The process includes: preparing a first two-dimensional coordination polymer represented by ], and mixing the first two-dimensional coordination polymer with an alcohol-containing solvent, wherein M is one or more divalent metal atoms capable of forming an octahedral hexa-coordination (OC-6) structure, and the pyr ＊ A method for producing a substance, wherein the substance is pyrazine or a derivative thereof or a mixture thereof, and the alcohol is at least one selected from the group consisting of methanol, ethanol, and 2-propanol.

2. A method for producing a three-dimensional porous coordination polymer represented by the chemical formula [M(μ-SiF ６ )(μ-pyr ＊ ), comprising: preparing a second two-dimensional coordination polymer represented by the chemical formula [M(μ-SiF ２ )(μ-pyr ６ )(H ＊ O)(H ２ O)]; reacting the second two-dimensional coordination polymer with pyr ２ ; wherein M is one or more divalent metal atoms capable of forming an octahedral six-coordinate (OC-6) structure, and pyr ＊ is pyrazine or a derivative thereof or a mixture thereof.​​ 3. The manufacturing method according to claim 1 or 2, wherein M comprises at least one metal atom selected from the group consisting of Fe, Co, Ni, Zn, and Cu.

4. The manufacturing method according to claim 1 or 2, wherein M contains Cu.

5. The aforementioned pyr ＊ The manufacturing method according to claim 1 or 2, wherein at least a portion of is represented by the following general formula. In the formula, R ２ , R ３ , R ５ and R ６ Each of these is independently selected from the group consisting of a hydrogen atom, a methyl group, a fluoromethyl group, an amino group, a hydroxyl group, a mercapto group, and a halogen atom.

6. The first two-dimensional coordination polymer is M(NO ３ ) ２ or its hydrate or M (BF ４ ) ２ or its hydrate, (NH ４ ) ２ (SiF ６ ) and the aforementioned pyr ＊ The manufacturing method according to claim 1, wherein the product is synthesized by mixing the two.

7. The second two-dimensional coordination polymer is M(NO ３ ) ２ or its hydrate or M (BF ４ ) ２ or its hydrate, (NH ４ ) ２ (SiF ６ ) and the aforementioned pyr ＊ and an excess amount of H ２ The manufacturing method according to claim 2, wherein the synthesis is carried out by mixing in a solvent containing oxygen.

8. The manufacturing method according to claim 7, wherein the solvent further comprises an alcohol selected from the group consisting of methanol, ethanol, and 2-propanol.

Images