JP7099419B2 - Metal-organic framework - Google Patents

Description

The present invention relates to metal-organic structures.

A metal-organic framework (MOF), which is a porous compound, is a material also called a porous coordination polymer (PCP). The MOF has a high surface area coordination network structure formed by the interaction of a metal with an organic ligand.

In recent years, various researches and developments have been carried out on such metal-organic frameworks.

For example, Non-Patent Document 1 discloses an aluminum organic structure (CAU-10) in which an Al ³⁺ ion and an isophthalic acid ion as a ligand are coordinated.

H. Reinsch et al. , "Structures, Structure Chemicals, and Nonlinear Optical Properties of a New Series of Highly Double Aluminum MOFs", Chem. Mater. , 2013, 25, 17-26.

The MOF can adsorb water vapor, and therefore, it is considered to be used as a hygroscopic material for adsorption type heat pumps, humidity control systems and the like used in automobiles, houses, manufacturing equipment and the like.

When MOF is used as a hygroscopic material, it is important that water vapor can be adsorbed at a low relative humidity and that the range of humidity difference between the adsorption humidity and the desorption humidity is narrow.

However, the MOFs reported so far are often unable to adsorb water vapor at a low relative humidity or have a wide range of humidity difference between the adsorption humidity and the desorption humidity. Therefore, when such MOFs are used as moisture absorbing materials for adsorption heat pumps, the heat output may be inadequate, and these MOFs are used as moisture absorbing materials for humidity control systems. In some cases, the dehumidifying performance may be insufficient.

Therefore, the present invention has been made in view of the above circumstances, and provides a MOF capable of adsorbing water vapor at a low relative humidity and narrowing the range of the humidity difference between the adsorption humidity and the desorption humidity. The purpose is.

As a result of diligent studies, the present inventor has found that the above problems can be solved by the following means.

Aluminum ion Al ³⁺ and
A metal-organic framework composed of a ligand coordinated to the aluminum ion Al ³⁺ .
The ligand consists of an isophthalate ion as a first ligand and a pyrazole-3,5-dicarboxylic acid ion as a second ligand, and has a first ligand and a second ligand. A metal-organic framework in which the molar ratio of coordinates is 1st ligand: 2nd ligand = 98-90: 2-10.

According to the MOF of the present invention, it is possible to achieve both the adsorption of water vapor at a low relative humidity and the narrowing of the range of the humidity difference between the adsorption humidity and the desorption humidity.

FIG. 1 is a diagram showing water vapor adsorption isotherms of MOFs of Example 1 and Comparative Examples 3 and 4. FIG. 2 is an X-ray diffraction diagram summarizing the data of Examples 1 to 3 and Comparative Examples 3 and 4. FIG. 3 is a diagram showing water vapor adsorption isotherms of MOFs of Examples 1 to 3 and Comparative Examples 1 and 4. FIG. 4 is a diagram showing differential values of the amount of water vapor adsorbed by MOFs of Examples 1 to 3 and Comparative Examples 1 and 4.

The present invention will be described below with reference to the drawings. The forms shown below are examples of the present invention, and the present invention is not limited to the forms shown below.

《Metal-organic framework》
The metal-organic framework of the present invention comprises an aluminum ion Al ³⁺ and a ligand coordinated to the aluminum ion Al ³⁺ , wherein the ligand is an isophthalate ion as a first ligand and an isophthalate ion. It consists of pyrazole-3,5-dicarboxylic acid ion as a second ligand, and the molar ratio of the first ligand to the second ligand is the first ligand: the second coordination. It is a metal-organic structure having a child = 98 to 90: 2 to 10.

The reason why the metal-organic framework of the present invention can both adsorb water vapor at a low relative humidity and narrow the range of the humidity difference between the adsorption humidity and the desorption humidity is not always clear. Infer as follows.

According to the diligent research of the present inventor, as a conventional MOF, for example, CAU-10 in which Al ³⁺ ion disclosed in Non-Patent Document 1 and isophthalate ion as a ligand are coordinated (the present). (Corresponding to the MOF of Comparative Example 3 of the disclosure), as shown in FIG. 1, the range of the humidity difference between the adsorption humidity and the desorption humidity is narrow, but the relative humidity for adsorbing water vapor is about 13%. It shows a high value.

On the other hand, MOF-303 in which isophthalate ion, which is a ligand of CAU-10, was replaced with pyrazole-3,5-dicarboxylate ion having two carboxy groups (in MOF of Comparative Example 4 of the present disclosure). As shown in FIG. 1, the relative humidity for adsorbing water vapor is lower than that in the case of CAU-10, but the range of the humidity difference between the adsorption humidity and the desorption humidity is the isotherm of water vapor adsorption. Since the line has two stages, it can be seen that it is significantly wider than the case of CAU-10.

From the X-ray diffraction results, when the isophthalic acid of CAU-10 is replaced with pyrazole-3,5-dicarboxylic acid ion, the X-ray diffraction peak of MOF-303 type can be seen. Therefore, CAU-10 It is considered that MOF-303 and MOF-303 have different pore structures. Here, in MOF-303, since the region having a nitrogen atom and the region not having a nitrogen atom derived from the pore structure are clearly separated, it is considered that the water vapor adsorption isotherm has two stages. Therefore, in the present invention, the humidity difference between the adsorption humidity and the desorption humidity is obtained by substituting the isophthalic acid of CAU-10 with pyrazole-3,5-dicarboxylic acid ion to the extent that the pore structure of CAU-10 does not collapse. While narrowing the range of, it is made hydrophilic so that it adsorbs water vapor even at low humidity.

Further, as an expression of the effect of the present invention, for example, the water vapor adsorption amount at a relative humidity of 0 to 20% is 100%, the humidity when the water vapor adsorption amount is 70% is the adsorption humidity, and the water vapor adsorption amount is 30. The adsorption humidity of the MOF of the present disclosure is 11.5% or less, 11.2% or less, 11.0% or less, 10.5% or less, or 9.5%, when the humidity in the case of% is desorption humidity. It may be less than or equal to%, and may be more than 8.0%. The difference between the adsorption humidity and the desorption humidity (adsorption humidity-desorption humidity) is 3.0% or less, 2.9% or less, 2.5% or less, 2.0% or less, 1.5% or less, or It may be 1.0% or less, and may be 0.5% or more.

Hereinafter, each component constituting the MOF of the present invention will be described in detail.

<Metal ions>
The metal ion used in the MOF of the present invention is an aluminum ion (Al ³⁺ ). In the MOF of the present invention, aluminum ions are coordinated with six oxygen atoms to form an octahedral structure of AlO ₆ .

The octahedron of AlO ₆ contains [Al (COO) ₂ OH] _∞ having a spiral structure with shared vertices in a cis type, and may form, for example, a CAU-10 type MOF, or a trans type vertex. It may contain a shared linear [Al (COO) ₂ OH] _∞ and form, for example, a MIL-53 type MOF.

The aluminum ion source is not particularly limited as long as it contains an aluminum atom, but is selected from the group consisting of, for example, aluminum chloride, aluminum nitrate, and aluminum sulfate from the viewpoint of high solubility in water and a polar solvent. At least one may be used. Further, as the aluminum ion source, the hydrate of the compound of these aluminum ion sources described above can also be used. More specifically, as hydrates of such aluminum ion source compounds, for example, aluminum hexahydrate (AlCl _{3.6H 2} O) and aluminum nitrate nine hydrate (Al (NO ₃ ) _3.9 H). ₂ O), aluminum sulfate 14-18 hydrate (Al ₂ (SO ₄ ) _{3.14-18H 2} O) and the like, but are not limited thereto.

で表されるイソフタル酸を用いてよい。 <First ligand>
The first ligand used in the MOF of the present disclosure is an isophthalate ion. The first ligand source is the following equation.

Isophthalic acid represented by may be used.

で表されるピラゾール－３，５－ジカルボン酸を用いてよい。 <Second ligand>
The second ligand used in the MOF of the present disclosure is pyrazole-3,5-dicarboxylic acid ion. The second ligand source is the following equation.

Pyrazole-3,5-dicarboxylic acid represented by may be used.

In the MOF of the present invention, the molar ratio of the first ligand to the second ligand is 1st ligand: 2nd ligand = 98 to 90: 2 to 10. In other words, the first ligand is 90 to 98 mol% and the second ligand is 10 to 2 mol% with respect to the entire ligand.

<< Manufacturing method of metal-organic framework >>
The metal-organic structure of the present invention can be produced, for example, by using a hydrothermal synthesis method or a solvothermal synthesis method.

More specifically, the metal of the present invention is reacted by heating a raw material solution containing an aluminum ion source as a metal ion source, a first ligand source, a second ligand source, and a solvent. Organic structures can be produced.

Here, the concentration of aluminum ions contained in the raw material solution is not particularly limited, and is, for example, 10 mmol / L or more, 25 mmol / L or more, 50 mmol / L or more, 75 mmol / L or more, 100 mmol / L or more with respect to the solvent. , 125 mmol / L or more, 150 mmol / L or more, 175 mmol / L or more, 200 mmol / L or more, 225 mmol / L or more, 250 mmol / L or more, or 300 mmol / L or more, and 500 mmol / L or less, 400 mmol / L or more. Hereinafter, it may be 300 mmol / L or less, or 250 mmol / L or less.

The concentrations of the first ligand and the second ligand contained in the raw material solution are not particularly limited, and are, for example, 10 mmol / L or more, 20 mmol / L or more, and 30 mmol with respect to the solvent. / L or more, 40 mmol / L or more, 50 mmol / L or more, 60 mmol / L or more, 70 mmol / L or more, 80 mmol / L or more, 90 mmol / L or more, 100 mmol / L or more, 150 mmol / L or more, or 200 mmol / L or more. It may be 300 mmol / L or less, 250 mmol / L or less, or 200 mmol / L or less.

Further, the compounding ratio of the first ligand source and the second ligand source is within the above-mentioned peculiar abundance ratio range to obtain the first ligand and the second ligand. If possible, there is no particular limitation.

For example, with respect to the total amount (mol) of the first ligand source and the second ligand source, the first ligand source is more than 0 mol% and less than 100 mol%, and 5 mol% or more and 85 mol% or less. , Or 10 mol% or more and 80 mol% or less, and the second ligand source may be blended in an amount of more than 0 mol% and less than 90 mol%, 5 mol% or more and 85 mol% or less, or 10 mol% or more and 80 mol% or less.

Examples of the solvent include, but are not limited to, N, N-dimethylformamide (DMF), N, N-diethylformamide (DEF), formic acid, acetic acid, methanol, ethanol, water and mixtures thereof.

At the time of heating, the raw material solution may be placed in an arbitrary sealed container, or the raw material solution may be refluxed.

The heating temperature is not particularly limited and is not particularly limited, and may be, for example, 100 ° C. or higher or 120 ° C. or higher from the viewpoint of enhancing reactivity, and 150 ° C. or higher from the viewpoint of preventing steam leakage during the reaction. It may be as follows.

The heating time is not particularly limited and can be appropriately adjusted according to the heating temperature. The heating time is, for example, 6 hours or more, 10 hours or more, 12 hours or more, 18 hours or more, 24 hours or more, 30 hours or more, 36 hours or more, 42 hours or more, 48 hours from the viewpoint of completely completing the reaction. It may be 54 hours or more, 60 hours or more, and 96 hours or less, 84 hours or less, 72 hours or less, 60 hours or less, 48 hours or less, 24 hours or less, 12 hours or less, or 10 hours or less. It's okay.

Further, after the reaction is completed, the obtained product may be appropriately post-treated.

As a post-treatment, for example, the resulting product may be filtered. Further, if necessary, a poor solvent or the like may be added to the filtrate obtained by filtration, heated at room temperature or appropriately to disperse the filtrate, and then filtered again. Here, the poor solvent may be a solvent in which the target MOF is difficult to dissolve, and for example, water, acetonitrile, hexane, ethanol, or the like may be used. The temperature for heating may be, for example, 40 ° C. or higher, 50 ° C. or higher, 60 ° C. or higher, 70 ° C. or higher, or 80 ° C. or higher, and 100 ° C. or lower, 90 ° C. or lower, or 80 ° C. or lower. It's okay. The heating time in the case of heating may be, for example, 1 hour or more, 2 hours or more, 6 hours or more, 10 hours or more, or 12 hours or more, and may be 24 hours or less, or 16 hours or less.

Further, the desired MOF can be obtained by appropriately drying the filter mass obtained by filtration or re-filtration. Here, the drying may be performed under normal pressure or under reduced pressure, but it is preferable to perform drying under reduced pressure from the viewpoint of improving efficiency. The temperature for drying may be, for example, 20 ° C or higher, 25 ° C or higher, 40 ° C or higher, 50 ° C or higher, or 60 ° C or higher, and 100 ° C or lower, 90 ° C or lower, 80 ° C or lower, or 60 ° C. It may be below ° C. The drying time in the case of drying may be, for example, 1 hour or more, 2 hours or more, 6 hours or more, 10 hours or more, or 12 hours or more, and may be 24 hours or less, or 16 hours or less.

《Adsorption heat pump》
The metal-organic framework of the present invention can be used as a hygroscopic material in, for example, an adsorption type heat pump. In this case, the adsorption type heat pump flows water vapor between the water storage unit that stores water as an operating medium, the hygroscopic material holding unit that holds the hygroscopic material, and the water storage unit and the hygroscopic material holding unit. It has a water vapor flow path to make it. In such an adsorption type heat pump, the water reservoir may be used as both an evaporator and a condenser, the water reservoir may be used as an evaporator, and the water vapor may be condensed by a separate condenser. Such adsorption type heat pumps can be used for cooling and heating in automobiles, houses, manufacturing equipment and the like.

《Humidity control system》
The metal-organic framework of the present invention can be used as a hygroscopic material in, for example, a humidity control system. The humidity control system in this case is supplied to the hygroscopic material holding part that holds the hygroscopic material, the air supply flow path for supplying the air containing water vapor to the hygroscopic material holding part, and the hygroscopic material holding part. It has an air take-out flow path for taking out the air from the hygroscopic material holding part. Such a humidity control system can be used for dehumidification or humidity control in automobiles, houses, manufacturing equipment and the like.

The present invention will be described in more detail with reference to the examples shown below. However, the scope of the present invention is not limited to the examples.

<< Synthesis of Metal-Organic Framework (MOF) >>
Metal-organic frameworks (MOFs) of Examples and Comparative Examples were synthesized using the reagents shown in Table 1.

<Example 1>
(1) 869 mg (3.60 mmol) of AlCl _{3.6H 2} O as a metal source and 568 mg (3.42 mmol) of H as a first ligand source in a 25 ml PTFE container (HUT-25, San-ai Kagaku). ₂ BDC, 31 mg (0.18 mmol) H ₂ PzDC · H ₂ O as the second ligand source, and 3 mL DMF and 12 mL water as the solvent were added.
(2) The PTFE container was placed in a pressure-resistant stainless steel outer cylinder (HUS-25, San-ai Kagaku) and heated at 120 ° C. for 48 hours.
(3) The precipitate of the product was filtered, washed 3 times with 10 mL DMF and 3 times with 10 mL of ethanol, and then the precipitate was collected by filtration again.
(4) The MOF of Example 1 was obtained by heating at 60 ° C. overnight while reducing the pressure to 10 ^-1 Pa or less and drying.

<Example 2>
Except for the addition of 538 mg (3.24 mmol) of H ₂ BDC as the first ligand source and 63 mg (0.36 mmol) of H ₂ PzDC · H ₂ O as the second ligand source. The MOF of Example 2 was obtained in the same manner as in Example 1.

<Example 3>
Performed except that 478 mg (2.88 mmol) of H ₂ BDC was added as the first ligand source and 125 mg (0.72 mmol) of H ₂ PzDC · H ₂ O was added as the second ligand source. The MOF of Example 3 was obtained in the same manner as in Example 1.

<Comparative Example 1>
Performed except that 419 mg (2.52 mmol) of H ₂ BDC was added as the first ligand source and 188 mg (1.08 mmol) of H ₂ PzDC · H ₂ O was added as the second ligand source. The MOF of Comparative Example 1 was obtained in the same manner as in Example 1.

<Comparative Example 2>
Performed except that 359 mg (2.16 mmol) of H ₂ BDC was added as the first ligand source and 251 mg (1.44 mmol) of H ₂ PzDC · H ₂ O was added as the second ligand source. The MOF of Comparative Example 2 was obtained in the same manner as in Example 1.

<Comparative Example 3>
The comparison was made in the same manner as in Example 1 except that 598 mg (3.60 mmol) of H ₂ BDC was added as the ligand source in place of the first ligand source and the second ligand source. The MOF of Example 3 was obtained.

<Comparative Example 4>
The comparison was made in the same manner as in Example 1 except that 627 mg (3.6 mmol) of H ₂ PzDC was added as the ligand source in place of the first ligand source and the second ligand source. The MOF of Example 4 was obtained.

"evaluation"
<X-ray diffraction measurement (confirmation of MOF crystal structure)>
X-ray diffraction measurements were performed on the MOFs synthesized in each Example and Comparative Example. The measuring device and measuring conditions are shown below:
・ Measuring device: RINT RAPID II (Rigaku Co., Ltd.)
-Measurement conditions: voltage 50V, current 100mA, collimator diameter φ0.3, sample angle ω5 °.

Moreover, the X-ray diffraction pattern of the MOF of each Example and the comparative example obtained by measurement is shown in FIG.

< ^{1 1} H-NMR measurement (MOF composition analysis)>
After decomposing the MOFs synthesized in each Example and Comparative Example, the ¹ H-NMR spectrum of the solution was measured, and the ratio of each ligand contained in the MOF was determined from the integral ratio. The decomposition conditions, measuring devices and measuring conditions are shown below:
・ Decomposition conditions: MOF is decomposed with 5 wt% sodium hydroxide (NaOH) heavy water ₍ D2O) solution. ・ Measuring device: JNM-AL400 (JEOL Ltd.)
-Measurement conditions: Measure the ¹ H-NMR spectrum of the solution using sodium 3- (trimethylsilyl) propionate-d ₄ (TSP-d ₄ ) as an internal standard.

<Measurement of water vapor absorption / desorption (evaluation of water vapor absorption / desorption characteristics of MOF)>
After pretreatment for each MOF synthesized in each Example and Comparative Example, the water adsorption isotherm was measured, and when the water adsorption amount at relative humidity of 0 to 20% was set to 100%, the water adsorption amount became 30%. Humidity (desorption humidity) and humidity (adsorption humidity) at which the amount of water adsorbed is 70% were determined. The pretreatment device, pretreatment conditions, measuring device and measurement conditions are shown below:
・ Pretreatment device: BELPREP-vacII (Microtrack Bell Co., Ltd.)
・ Pretreatment conditions: Vacuum degree < ^10-2 Pa, heated at 130 ° C for 6 hours ・ Measuring device: BELSORP-max (Microtrac Bell Co., Ltd.)
-Measurement conditions: Measure the amount of water vapor adsorbed at a temperature of 20 ° C and a relative humidity of 0 to 85%.

The water vapor adsorption isotherms of the MOFs synthesized in each of the measured examples and comparative examples are shown in FIGS. 1, 3 and 4.

The composition analysis results of the MOFs synthesized in each Example and Comparative Example are shown in Table 2 below.

<< Consideration of results >>
As shown in FIG. 2, in Examples 1 to 3, an X-ray diffraction pattern similar to that in Comparative Example 3 was obtained. On the other hand, in Comparative Examples 1 and 2, in addition to the diffraction line similar to that of Comparative Example 3, a new diffraction line was observed at about 9 °, which is the same as that of Comparative Example 4. This means that the amount of H ₂ PzDC / H ₂ O charged is 20 mol% or less (that is, the second ligand) with respect to the total amount of H ₂ BDC and H ₂ PzDC / H ₂ O which are the ligand sources. When a certain pyrazole-3,5-dicarboxylic acid ion is 10 mol% or less of the total ligand), it dissolves in CAU-10 type MOF, but the amount of H2 _PzDC / _H2O charged is 30 mol. If it is% or more, it is considered that MOF-303 type MOF was generated.

Further, as shown in Table 2, in the system in which BDC ² -is replaced with PzDC ^2- (Examples 1 to 3 and Comparative Examples 1 to ₂ ), when the amount of H2 PzDC / _H2O charged is 20 mol%. The amount of substitution by PzDC ^2- is 10 mol%. Considering that the angle between the two carboxyl groups in isophthalic acid is 117 ° and the angle between the two carboxyl groups in pyrazole-3,5 dicarboxylic acid is 149 °, this result is a ligand. If the angle between the carboxyl groups of the source is 120 ° or less on average (calculated by BDC ² : PzDC ^2- = 90: 10), the structure of CAU-10 type is considered to be stable. Here, in a system in which BDC ² -is replaced with PzDC ^2- , the content of PzDC ^2- tends to be lower than the amount of H2 _PzDC / _H2O added. It is considered that this is because the solubility in water is lower in H ₂ BDC than in H ₂ PzDC / H ₂ O.

Further, as shown in FIGS. 3 and 4, in Examples 1 to 3 (substitution amount of BDC ^2- by ^PzDC 2-2 to 10 mol%), the rise of water vapor adsorption shifts to the low humidity side as compared with Comparative Example 3. Was. It is considered that this is because the inside of the pores of MOF became hydrophilic by substituting a part of BDC ^2- with PzDC ^2- . On the other hand, Comparative Example 4 ( ^PzDC 2-100%) shows two stages of water vapor adsorption at relative humidity of about 0% and about 10%. Therefore, the amount of water vapor adsorbed at a relative humidity of about 10% becomes small.

That is, it was suggested that the MOF of the present invention can both adsorb water vapor at a low relative humidity and narrow the range of the humidity difference between the adsorption humidity and the desorption humidity.

Claims (1)

Aluminum ion Al ³⁺ and
A metal-organic framework composed of a ligand coordinated to the aluminum ion Al ³⁺ .
The ligand consists of an isophthalate ion as a first ligand and a pyrazole-3,5-dicarboxylic acid ion as a second ligand, and has a first ligand and a second ligand. A metal-organic framework in which the molar ratio of coordinates is 1st ligand: 2nd ligand = 98-90: 2-10.

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