JP4741789B2 - Synthesis method of polymer complex with adsorption performance - Google Patents

Description

  The present invention relates to a method for producing a polymer complex exhibiting adsorption performance.

  It has recently been clarified that polymer complexes composed of organic ligands and metal ions having two or more coordination sites have various higher-order structures and adsorb various substances (( Non-patent document 1), (see non-patent document 2)). In general, adsorbents such as activated carbon and zeolite are widely used for gas storage using their adsorption performance, gas separation using the difference in adsorption capacity depending on the type of gas, or water purification by liquid phase adsorption, etc. In recent years, with the growing awareness of the environment, adsorption and storage of gases that are clean energy sources such as methane and hydrogen have been studied, and this polymer complex is expected to be applied to similar industrial applications (( Non-patent document 1), (see non-patent document 2)).

  However, polymeric metal complexes are a very new type of material shortly after its existence was discovered. Therefore, it can be said that the synthesis method is a groping stage, and almost none has been industrialized.

  As a method of synthesizing a polymer metal complex, a method in which a metal solution and a ligand solution are carefully mixed and a complex is formed at the interface over a long period of several days to several weeks has been reported in academic literature. (See (Patent Document 1) and (Non-Patent Document 3)).

However, this method requires improvement for implementation on an industrial scale where the yield is not so good and takes a very long time. In addition, as another method, methods of mixing raw materials in a solvent and heating have been reported, but all are small-scale synthesis methods at the laboratory level, and the solvent is often highly toxic and expensive. However, it has disadvantages such as complicated operation and is difficult to apply industrially. For example, a method for synthesizing a porous polymer complex [Cu (bpy) (BF ₄ ) ₂ (H ₂ O) ₂ (bpy)] _n (bpy represents 4,4′-bipyridyl) having a high gas adsorption capacity The following methods are known (Non-Patent Document 4). That is, a method in which bpy is dissolved in acetonitrile and mixed with an aqueous copper salt solution under heating, and after removing the microcrystals that have come out, ether vapor is diffused into the solution and further concentrated to obtain the target substance. It is. This method is difficult to put into practical use because of the cost and safety of the solvent used and the complicated process.

  In addition to the lack of know-how as described above, it is difficult to study the production method of polymer complexes. Often it is not possible to obtain. This is a major difference from the production of general organic substances. In the case of a general organic synthesis reaction, there are usually various solvents that can be used. For example, in the industrially important Friedel-Crafts reaction, various solvents such as halogen solvents, aromatic solvents having a low electron density, and nitromethane can be used as the solvent. In addition, with regard to the reaction concentration, except for extremely high and low concentrations, generally there is considerable tolerance even though there are some differences in the reaction rate, such as fast and slow reaction rates or by-products. Patent Document 5).

  On the other hand, in the synthesis of a polymer complex, a higher-order structure that exhibits a function is formed by self-assembly of a metal salt and an organic ligand as raw materials. Even if the raw materials are exactly the same, the higher-order structure itself is not uniquely determined, and a variety of structures can be created. If the reaction conditions are changed even slightly, the assembly mode changes and the target product changes. (See (Non-Patent Document 6) and (Non-Patent Document 7)). Therefore, the synthesis method of similar compounds cannot be diverted, and a method for producing a novel polymer complex often has to be searched by hand.

In addition, when a polymer complex is used as a functional chemical such as an adsorbent, it can function even when the same kind of compound can be synthesized as in the case of functional chemicals such as liquid crystals and electronic materials. There are many cases where very bad things can be made. That is, when producing a polymer complex having an adsorption function, production know-how is important because slight differences in higher-order structures and trace amounts of impurities due to differences in production processes greatly affect the adsorption characteristics.
JP 2000-117100 A Susumu Kitagawa, Integrated Metal Complex, Kodansha Scientific, 2001, pp. 192-223 Naoshi Okawa, Tsubasa Ito, Science of Integrated Metal Complexes, Chemistry Dojin, 2003, pages 135-143 Carlucci L. , Et al. , J. et al. Chem. Soc. , Dalton Trans. , (2000) 3821 Blake A. , Et al. , J. et al. Chem. Soc. , Dalton Trans. , (1997) 913 Olah G. A. “Friedl-Crafts and related reactions”, Vol. I, pp. 298-305, Inter Science Publishers, New York (1963) Carlucci L. , Et al. , J. et al. Chem. Soc. Dalton Trans. , (1994) 2397 Carlucci L. , Et al. , J. et al. Am. Chem. Soc. , (1995) 4562

  An object of the present invention is to solve the above-mentioned problems in organic synthesis and to provide a method capable of producing a polymer complex exhibiting adsorption performance on an industrial scale in a short time and with a simple process.

  As a result of intensive research to solve the above-mentioned problems, the present inventors mixed a polymer complex having adsorption performance with an aqueous solution of a metal salt and an alcoholic solution of an organic ligand. The reaction has led to the completion of a simple synthesis method.

That is, the present invention is a method for synthesizing a polymer complex comprising a metal ion and an organic ligand, wherein an aqueous solution is used as a solvent for the metal salt containing the metal ion, and an alcohol is used as the solvent for the organic ligand. Obtained by measuring the nitrogen adsorption isotherm at 77 K , characterized in that the reaction is carried out in a solution system with the concentration increase in the receiving vessel of the solute of the added solution being 1000 mmol / L / h or less. This is a method for synthesizing a polymer complex having an adsorption performance that results in an adsorption amount of 200 mL (STP) / g or more . That is , this method is a production method in which an aqueous solution of a metal salt and an alcoholic solution of an organic ligand are mixed while controlling the mixing amount per hour.

The polymer complex synthesized in the present invention is a compound represented by the following formula (1).
[XY ₂ Z ₂ (H ₂ O) _m ] _n (1)
(Wherein, X represents a divalent transition metal ion, Y represents a monovalent anion, and Z represents an organic ligand having two coordination sites. M is 0, 1 or 2.)
The raw material for synthesize | combining the compound represented by Formula (1) is illustrated.

One of the raw material is a metal salt, is a compound represented by XY _2. Here, X is a transition metal ion, and examples include divalent transition metal ions such as iron, cobalt, nickel, copper, and zinc ions. In terms of ease of forming the complex, cobalt, nickel, copper, and zinc ions are preferable, and nickel and copper ions are more preferable. Y is a monovalent anion, and examples thereof include acid group ions of strong acids such as Cl ⁻ , Br ⁻ , BF ₄ ⁻ , PF ₆ ⁻ , CF ₃ SO ₃ ⁻ and CF ₃ CO ₂ ⁻ . BF ₄ ⁻ , PF ₆ ⁻ , CF ₃ SO ₃ ⁻ , CF ₃ CO ₂ ⁻ , and more preferably BF ₄ ⁻ , PF ₆ ⁻ , and CF ₃ SO ₃ ⁻ are mentioned in terms of ease of forming the complex.

Furthermore, another type of raw material is Z. Here, Z is an organic ligand, which is a ligand having two coordination sites at relatively distant positions in the molecule, that is, 4,4′-bipyridyl and 4-pyridyl at both ends of the molecule. A ligand having one group at a time, that is, a ligand of ABA (A = 4-pyridyl group) type. Here, B is —CH ₂ —, —CH═CH— (cis and trans), —CO—NH—, 1,4-phenylene and substituted phenylene, 1,3-phenylene and substituted phenylene, 2,5- Examples include thiophenyl and substituted products thereof, 2,7-fluorenyl and substituted products thereof, 1,4-diethynylbenzene, and the like. 4,4′-bipyridyl and 1,4-bis (4-pyridyl) benzene, 1,4-
Bis (4-pyridyl) thiophene and 1,4-bis (4-pyridyl) acetylene are preferable, and 4,4′-bipyridyl is preferable in terms of easy availability as a general-purpose product.

  Moreover, it is preferable that m in Formula (1) is 2 in the point which contains two water molecules in a structural unit at the point from which a stable and highly functional complex is obtained.

  According to the method of the present invention, a polymer complex exhibiting adsorption performance can be produced on an industrial scale in a short time and with a simple process. That is, the present invention provides an industrially excellent method for producing a polymer complex exhibiting adsorption performance.

  In the method of the present invention, in order to produce the compound represented by the formula (1), it is necessary to dissolve the starting metal salt and the organic ligand in a solvent and carry out the solution. As a solvent for dissolving the metal salt, it is important to use water. Since water is coordinated to the metal salt and is stabilized, when mixed with an organic ligand, water has an effect of suppressing a rapid reaction and reducing side reactions. It is also possible to use an organic solvent mixed with water. The organic solvent to be mixed is a solvent miscible with water, for example, alcohols such as methanol and ethanol, acetonitrile, tetrahydrofuran, acetone, 1,4-dioxane and the like. These may be used singly or in combination of two or more. Of these, alcohols and acetonitrile give good results. The mixing ratio of the organic solvent is 50 mol% or less, preferably 30 mol% or less.

  On the other hand, as the solvent for dissolving the organic ligand, alcohol solvents such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol and ethylene glycol, and acetonitrile are preferable. These may be used singly or in combination of two or more. In terms of cost and solubility, methanol, ethanol, 2-propanol, and acetonitrile are preferable. Alcohols having a high molecular weight such as hexanol can be used, but there is no substantial meaning since the solubility of the organic ligand is reduced and the cost is high. It is also possible to use a small amount of a non-alcohol organic solvent or water mixed with an alcohol solvent or an acetonitrile solvent. For example, polar organic solvents such as acetone, tetrahydrofuran and 1,4-dioxane, and aromatic solvents such as toluene can be used. These may serve as guests for the resulting polymer complex, giving the product good properties. The mixing amount is 0 to 60 mol%, preferably 0 to 40 mol%. Water can also be suitably mixed and used, but if the amount of mixing is too large, the solubility of the organic ligand decreases, so mixing up to about 60 mol% is preferable. More preferably, mixing up to 40 mol% is preferable.

  The method for mixing the aqueous solution of the metal salt and the organic solvent-based solution of the organic ligand may add the ligand organic solution to the aqueous metal salt solution or vice versa. In addition, it is not always necessary to perform the mixing in a solution. For example, a method in which a solid ligand is added to an aqueous metal salt solution and a solvent is added at the same time. Alternatively, various methods are possible as long as the reaction finally occurs substantially in a solvent, such as injecting a solution and then injecting an aqueous solution for dissolving the metal salt. However, the method of dropping and mixing an aqueous solution of a metal salt and an organic solution of a ligand is industrially the most convenient and preferable.

  The concentration of the solution is 40 mmol / L to 4 mol / L, preferably 80 mmol / L to 2 mol / L for the aqueous metal salt solution, and 40 mmol / L to 3 mol / L, preferably 80 mmol / L to the organic solution of the ligand. 1.8 mol / L. Even if the reaction is carried out at a concentration lower than this, the desired product can be obtained, but this is not preferable because the production efficiency is lowered. On the other hand, a concentration higher than this is not preferable because the adsorption ability is lowered.

  The reaction temperature is -20 to 120 ° C, preferably 25 to 90 ° C. If it is performed at a lower temperature than this, the solubility of the raw material is lowered, which is not preferable. Although it is possible to carry out the reaction at a higher temperature using an autoclave or the like, there is no substantial meaning because the yield does not improve for the energy cost such as heating.

  The mixing ratio of the metal salt and the organic ligand used in the reaction of the present invention is in the range of 3: 1 to 1: 3, preferably 2: 1 to 1: 2. In other ranges, the yield of the target product decreases, and unreacted raw materials remain, making it difficult to take out the target product.

  In the reaction of the present invention, it is important to keep the concentration of the metal salt or organic ligand in the reaction solution low when the raw material metal salt and the organic ligand are dissolved in a solvent and mixed. .

  When mixing the raw material metal salt and organic ligand in a solvent, if the concentration of the metal salt or organic ligand in the reaction solution is high, the adsorption performance of the resulting polymer complex may decrease. is there. However, for efficient production, it is preferable that a raw material solution having a concentration as high as possible can be mixed in a short time. However, when a solution having a high concentration of 500 mmol / L or more is used for the reaction, the adsorption performance of the generated polymer complex may be lowered. In order to prevent this, the concentration of the metal ions or organic ligands in the reaction solution may be controlled by controlling the mixing speed. Specifically, it is carried out by the following method.

  The reaction is performed by mixing an aqueous solution of a metal salt and an organic solution of a ligand. In practice, the method of adding the other solution to one solution is easy. At this time, assuming that the solution in the receiving container is X, the dropped substance is A, and the concentration is a, the concentration control in X after a certain time of a is important. Here, assuming that A does not react during the dropping, the concentration of A in X increases as the dropping proceeds. At this time, since a side reaction occurs when the concentration rises rapidly, it is necessary to keep the concentration rise low. As a result of various investigations, it has been found that the increase in the concentration of the added solute in the receiving container may be 1000 mmol / L / h or less, preferably 500 mmol / L / h or less. An example is shown below.

  When 12.5 L of an 800 mmol / L solution is mixed with 6.25 L of an 800 mmol / L solution, assuming that the first dripping amount is yL (where y> 0), (800 × y) / (6. 25 + y) <500, and y <10.4 L / h, and it is understood that the dropping may be performed at a speed of 10.4 L / h or less.

  The meaning that the concentration of the added substance after 1 hour is 500 mmol / L or less is as follows. In an actual reaction vessel, a polymer complex is formed by the reaction between a metal salt and a ligand, and as the molecular weight increases, it becomes a crystal and precipitates, resulting in a decrease in solute concentration. Therefore, if the substance is added dropwise at a slow rate that does not exceed the rate of polymer complex formation, that is, the rate of crystal formation, the added substance will not accumulate in the actual reaction vessel. This means that it is always kept at a low concentration and side reactions can be suppressed. At this time, the concentration of the compound loaded in advance in the receiving container may exceed 500 mmol / L. This is because the reaction occurs when the two kinds of substances are mixed, and therefore, only the concentration of the low concentration substance, that is, the dropped substance in the reaction container needs to be considered.

  The above method means that the substance concentration in the reaction system should be kept low. For example, after a small amount is dropped, the reaction is promoted with a holding time, and then a small amount is dropped again. It does not matter how you said. Alternatively, by adding a small amount of a very concentrated solution or adding a metal salt or ligand solid without dissolving in a solvent and then adding only the solvent, the concentration in the reaction vessel is increased. A method of setting the above values may be used. That is, as long as the reaction is controlled so as to keep the concentration low, the method of addition mixing is not restricted.

  After completion of the reaction, the target polymer complex can be easily obtained by filtering the precipitated powder (crystal). In addition, the yield of the target product can be increased by concentrating the reaction solution under reduced pressure. The concentration under reduced pressure can be performed under various conditions. For example, the temperature range is 10 to 80 ° C., and the energy cost is preferably 20 to 60 ° C.

  The reaction can be carried out using an ordinary glass-lined SUS reaction vessel and a mechanical stirrer. After completion of the reaction, the target substance and the raw material can be separated by filtration, washing with water, and drying to produce a target substance with high purity.

  In the reaction system of the present invention, the process of polymer complex formation is considered to proceed as follows.

  First, an oligomer of a complex in which a metal salt and an organic ligand are coordinated is formed. The oligomers slowly gather and become larger while forming an optimal structure, so that the solubility is lowered, and as a result, a complex having a high molecular weight adsorption performance is precipitated. Therefore, a polymer complex having adsorption performance can be produced by selecting an appropriate solvent for oligomer formation. In the method for controlling the concentration of the solute in the reaction solution, the concentration is increased to the complex precipitation concentration through the formation of oligomers at a low concentration by mixing two kinds of raw materials within a predetermined speed range. In this respect, it contributes to the formation of a polymer complex having high adsorption ability. If the concentration of the reaction solution becomes too high, the polymer complex precipitates rapidly without proper oligomer formation, and it is thought that structures with insufficient structure optimization are generated, so control of the solution concentration is very important. It is.

To 100 mL of the 4,4′-bipyridyl solution prepared to a predetermined concentration, 50 mL of a copper (II) borofluoride solution having the same concentration was dropped at a predetermined rate over a predetermined time (specifically in Table 1). Describe the conditions). Thereafter, the mixture was stirred for 2 hours while maintaining the predetermined temperature. Thereafter, filtration was performed to obtain a light blue polymer complex powder. Identification was performed using an infrared spectrometer system 2000 manufactured by PerkinElmer, Inc. and an ATR attachment, and it was confirmed that the substance was the same as the substance synthesized by the method described in (Non-Patent Document 2) (3483, 2606, 1826, 1616, 1599, 1087, 1060, 1046, 1014, 813 cm ⁻¹ ). Further, it was confirmed by elemental analysis that the composition was the same as [Cu (bpy) (BF ₄ ) ₂ (H ₂ O) ₂ (bpy)] _n described in (Non-patent Document 4 ).

  In Example 7, the metal salt solution was dropped into the ligand solution, but in all other cases, the ligand solution was dropped into the metal salt solution. Moreover, Examples 1-3 and 5 performed vacuum concentration at 50 degreeC before filtration. Details of the synthesis method and adsorption characteristics are shown in Table 1.

The adsorption characteristics were evaluated by nitrogen adsorption isotherm measurement at 77K, which is a technique generally used for the evaluation of porous pore structures and the like (Belle soap 36, volume method by Nippon Bell Co., Ltd.). By measurement). The characteristics when the adsorption amount is 200 ml (STP) / g or more are shown as ○, the case when it is 100 ml (STP) / g or more and less than 200 ml (STP) / g, the case when it is less than 100 ml (STP) / g. X.

Claims (6)

A method for synthesizing a polymer complex comprising a metal ion and an organic ligand, represented by the following formula (1), wherein an aqueous solution is used as a solvent for the metal salt containing the metal ion, Nitrogen adsorption isotherm at 77K, characterized in that an alcoholic solution is used as a solvent, and the concentration of the solute of the added solution is 1000 mmol / L / h or less in the receiving vessel, and the reaction is carried out in the solution system. A method for synthesizing a polymer complex having an adsorption performance in which an adsorption amount obtained by measurement is 200 mL (STP) / g or more.
[XY ₂ Z ₂ (H ₂ O) _m ] _n (1)
(Wherein, X is a divalent transition metal ion, Y is a monovalent anion, Z is an organic ligand having two coordination sites, and m is 0, 1 or 2). 2. The method for synthesizing a polymer complex according to claim 1, wherein an organic solvent is contained in an aqueous solution as a solvent for the metal salt containing the metal ion in a mixing ratio of 50 mol% or less . The method for synthesizing a polymer complex according to claim 1 or 2, wherein the alcohol-based solution as a solvent for the organic ligand contains a non-alcoholic organic solvent or water in a mixing ratio of 0 to 60 mol%. . The method for synthesizing a polymer complex according to any one of claims 1 to 3, wherein X in the formula (1) is divalent copper or nickel ion. The method for synthesizing a polymer complex according to claim 1, wherein Z in the formula (1) is 4,4′-bipyridyl or 1,4-bis (4-pyridyl) benzene. The method for synthesizing a polymer complex according to any one of claims 1 to 3, wherein m in the formula (1) is 2.