JP2016098212A - Metal complex, gas adsorbent and gas separation device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a novel metal complex capable of being used as a gas adsorbent and a gas separation device using the same.SOLUTION: There is provided a metal complex having a unit structure of the following formula (I). Cu(BF)L(I), where L is an organic ligand represented by the following general formula (II), R, R, Rand Rare same or different and represent a hydrogen atom, an alkyl group which may have a substituent or a halogen atom, Rand Ras well as Rand Rtogether represent an alkylene group, an oxyalkylene group or an alkenylene group which may have a substituent, n is 1 or 2, R, R, Rand Rare same or different and represent a hydrogen atom, an alkyl group which may have a substituent or a halogen atom or Rand Ras well as Rand Rtogether represent an alkylene group, an oxyalkylene group or an alkenylene group which may have a substituent.SELECTED DRAWING: None

Description

  The present invention relates to a metal complex, and more particularly, to a metal complex including a metal ion, a counter ion, and a neutral organic ligand. The present invention relates to an adsorbent comprising such a metal complex, and a gas separation apparatus using the adsorbent.

  So far, various adsorbents have been developed in fields such as deodorization and exhaust gas treatment. Activated carbon is a representative example, and is widely used in various industries such as air purification, desulfurization, denitration, and removal of harmful substances by utilizing the excellent adsorption performance of activated carbon. In recent years, the demand for nitrogen has increased for semiconductor manufacturing processes, etc., and as a method for producing such nitrogen, a method of producing nitrogen from air by pressure swing adsorption method or temperature swing adsorption method using molecular sieve charcoal is used. Has been. Molecular sieve charcoal is also applied to various gas separation and purification such as hydrogen purification from methanol cracked gas.

  When separating mixed gas by pressure swing adsorption method or temperature swing adsorption method, generally, molecular sieve charcoal or zeolite is used as the separation adsorbent, and separation is performed by the difference in the equilibrium adsorption amount or adsorption rate. . However, when separating the mixed gas based on the difference in the amount of equilibrium adsorption, the conventional adsorbents cannot selectively adsorb only the gas to be removed, so the separation factor becomes small, and the size of the apparatus is inevitable. . In addition, when separating the mixed gas based on the difference in adsorption speed, only the gas to be removed can be adsorbed depending on the type of gas, but it is necessary to perform adsorption and desorption alternately, and in this case, the apparatus still has to be large. I didn't get it.

  On the other hand, polymer metal complexes that cause a dynamic structural change due to an external stimulus have been developed as adsorbents that give better adsorption performance. When this novel dynamic structural change polymer metal complex is used as a gas adsorbent, a unique phenomenon has been observed in which gas adsorption or desorption occurs at a certain pressure. In addition, a phenomenon has been observed in which the adsorption / desorption start pressure varies depending on the type of gas.

  When this phenomenon is applied to, for example, an adsorbent in a pressure swing adsorption type gas separation apparatus, very efficient gas separation is possible. In addition to reducing the time required for pressure change, the energy required for adsorbent regeneration can be reduced, which contributes to a reduction in running cost. Furthermore, since it can contribute to miniaturization of the gas separation device, it is possible to increase cost competitiveness when selling high-purity gas as a product, of course, even when high-purity gas is used inside its own factory Since the cost required for the equipment that requires high purity gas can be reduced, the manufacturing cost of the final product can be reduced.

  Examples of the application of a dynamic structural change polymer metal complex as a separating material include (1) a metal complex having an interdigitated integrated structure, and (2) a metal complex having a two-dimensional lattice stacked integrated structure (Patent Documents) 1, see Patent Document 2), and (3) metal complexes having an interpenetrating integrated structure are known.

However, for practical use, it is necessary to further improve the separation performance, and in particular, it is required to suitably control the adsorption and desorption start pressure of the adsorbent. For example, [Cu (BF ₄ ) ₂ (bpy) ₂ ] _n is known as a typical example of a metal complex having the above-described two-dimensional lattice stacked type integrated structure (see Patent Document 3). However, since this metal complex has a low desorption initiation pressure and requires a large amount of energy to recover the adsorbed gas and regenerate the adsorbent, development of a metal complex that can be desorbed at a pressure close to normal pressure is required. .

JP 2003-275531 A JP 2003-278997 A JP-A-2005-232222

  An object of the present invention is to provide a novel metal complex and to provide a gas adsorbent having excellent properties using the metal complex. Another object of the present invention is to provide a gas separation device in which a gas adsorbent having the above characteristics is housed.

That is, according to the present invention, the following is provided.
(1) A metal complex having a unit structure of the following formula (I).
Cu (BF ₄ ) ₂ L ₂ (I)
(In the formula, L represents the following general formula (II);
An organic ligand represented by
R ¹ , R ² , R ³ and R ⁴ are the same or different and each represents a hydrogen atom, an optionally substituted alkyl group or a halogen atom, or R ¹ and R ² , R ³ and R ⁴ are An alkylene group, an oxyalkylene group or an alkenylene group which may have a substituent together;
n is 1 or 2,
R ⁵ , R ⁶ , R ⁷ and R ⁸ are the same or different and each represents a hydrogen atom, an optionally substituted alkyl group or a halogen atom, or R ⁵ and R ⁶ , R ⁷ and R ⁸ are The alkylene group, the oxyalkylene group, or the alkenylene group which may have a substituent together is shown. )
(2) The metal complex according to (1), wherein the organic ligand L is 1,2-bis (4-pyridyl) ethyne or 1,4-bis (4-pyridyl) butadiyne.
(3) The metal complex according to (1) or (2), wherein the organic ligand L is 1,2-bis (4-pyridyl) ethyne.
(4) An adsorbent comprising the metal complex according to any one of (1) to (3).
(5) The adsorbent is carbon dioxide, hydrogen, carbon monoxide, oxygen, nitrogen, hydrocarbon having 1 to 4 carbon atoms, rare gas, hydrogen sulfide, ammonia, sulfur oxide, nitrogen oxide, siloxane, water vapor or The adsorbent according to (4), which is an adsorbent for adsorbing organic vapor.
(6) A pressure swing type gas separator using the gas adsorbent according to (4) or (5).

  According to the present invention, a metal complex that can be desorbed at a pressure closer to normal pressure can be provided. Moreover, it becomes possible to manufacture the gas separation apparatus which accommodates the gas adsorbent which consists of a metal complex of this invention inside.

  The metal complex of the present invention can be applied to various uses by utilizing the special properties relating to gas adsorption / desorption. For example, when the present invention is applied to an adsorbent in a pressure swing adsorption type gas separation apparatus, the gas adsorbent of the present invention can be used to perform very efficient gas separation. In addition to reducing the time required for pressure change, the energy required for adsorbent regeneration can be reduced, which contributes to a reduction in running cost. Furthermore, since it can contribute to miniaturization of the gas separation device, it is possible to increase cost competitiveness when selling high-purity gas as a product, of course, even when high-purity gas is used inside its own factory Since the cost required for the equipment that requires high purity gas can be reduced, the manufacturing cost of the final product can be reduced.

3 is a powder X-ray diffraction pattern of the metal complex obtained in Synthesis Example 1. FIG. The horizontal axis represents the diffraction angle (2θ), and the vertical axis represents the diffraction intensity (Intensity) indicated by cps (Counts per Second). It is an adsorption-desorption isotherm at -5 degreeC of the carbon dioxide measured by the capacity | capacitance method about the metal complex obtained by the synthesis example 1, and the metal complex obtained by the comparative example 1. FIG.

The metal complex of the present invention is a compound having a unit structure represented by the following formula (I).
Cu (BF ₄ ) ₂ L ₂ (I)
(In the formula, L represents the following general formula (II);
An organic ligand represented by
R ¹ , R ² , R ³ and R ⁴ are the same or different and each represents a hydrogen atom, an optionally substituted alkyl group or a halogen atom, or R ¹ and R ² , R ³ and R ⁴ are An alkylene group, an oxyalkylene group or an alkenylene group which may have a substituent together;
n is 1 or 2,
R ⁵ , R ⁶ , R ⁷ and R ⁸ are the same or different and each represents a hydrogen atom, an optionally substituted alkyl group or a halogen atom, or R ⁵ and R ⁶ , R ⁷ and R ⁸ are The alkylene group, the oxyalkylene group, or the alkenylene group which may have a substituent together is shown. )

  The raw material for synthesize | combining the compound represented by Formula (I) is illustrated.

One of the raw materials is a copper (II) salt, and examples of the counter ion of the copper (II) ion include monovalent anions, but those having BF ₄ ⁻ are preferable.

The organic ligand L in the formula (I) is represented by the following general formula (II);
It is represented by
In the formula, R ¹ , R ² , R ³ and R ⁴ are the same or different and each represents a hydrogen atom, an optionally substituted alkyl group or a halogen atom, or R ¹ and R ² , R ³ and R ⁴ together represents an alkylene group, an oxyalkylene group or an alkenylene group which may have a substituent;
n is 1 or 2;
R ⁵ , R ⁶ , R ⁷ and R ⁸ are the same or different and each represents a hydrogen atom, an optionally substituted alkyl group or a halogen atom, or R ⁵ and R ⁶ , R ⁷ and R ⁸ are The alkylene group, the oxyalkylene group, or the alkenylene group which may have a substituent together is shown.

  The alkyl group preferably has 1 to 5 carbon atoms. As examples of the alkyl group, a linear or branched alkyl group such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, or a pentyl group is a halogen atom. Examples of are fluorine atom, chlorine atom, bromine atom and iodine atom. Examples of the substituent that the alkyl group may have include an alkoxy group (methoxy group, ethoxy group, n-propoxy group, isopropoxy group, n-butoxy group, isobutoxy group, tert-butoxy group, etc. ), Amino group, aldehyde group, epoxy group, acyloxy group (acetoxy group, n-propanoyloxy group, n-butanoyloxy group, pivaloyloxy group, benzoyloxy group, etc.), alkoxycarbonyl group (methoxycarbonyl group, ethoxycarbonyl) Group, n-butoxycarbonyl group, etc.), carboxylic anhydride group (—CO—O—CO—R group) (R is an alkyl group having 1 to 5 carbon atoms) and the like. When the alkyl group has a substituent, the number thereof is preferably 1 to 3, and more preferably 1.

3-6 are preferable and, as for carbon number of the said alkylene group, 3-4 are more preferable. When the alkylene group has 3 to 6 carbon atoms, R ¹ and R ² , R ³ and R ⁴ , R ⁵ and R ⁶ , R ⁷ and R ⁸ together with the carbon atom to which they are bonded are 5 ˜8-membered ring (cyclopentane, cyclohexane, cycloheptane, cyclooctane).

3-6 are preferable and, as for the total number of atoms of carbon of the said oxyalkylene group and oxygen, 3-4 are more preferable. When the total number of carbon atoms and oxygen atoms in the alkylene group is 3 to 6, as the oxyalkylene group, —O—CH ₂ —O—, —CH ₂ —O—CH ₂ —, —O—CH ₂ —CH _{2 -O -, - O-CH 2} -CH 2 -CH 2 -, - CH 2 -O-CH 2 -CH 2 -, - O-CH 2 -CH 2 -CH 2 -CH 2 -, - O-CH _{2 -CH 2 -CH 2 -CH 2 -CH} 2 - and the like.

3-6 are preferable and, as for carbon number of the said alkenylene group, 3-4 are more preferable. When the alkylene group has 3 to 6 carbon atoms, R ¹ and R ² , R ³ and R ⁴ , R ⁵ and R ⁶ , R ⁷ and R ⁸ together with the carbon atom to which they are bonded are 5 -8-membered ring (cyclopentene, cyclohexene (when having one double bond) or benzene (when having two double bonds), cycloheptane, cyclooctane).

  Examples of the substituent that the alkylene group, oxyalkylene group, and alkenylene group may have include an alkoxy group (methoxy group, ethoxy group, n-propoxy group, isopropoxy group, n-butoxy group, isobutoxy group). Group, tert-butoxy group, etc.), amino group, aldehyde group, epoxy group, acyloxy group (acetoxy group, n-propanoyloxy group, n-butanoyloxy group, pivaloyloxy group, benzoyloxy group, etc.), alkoxycarbonyl group (Methoxycarbonyl group, ethoxycarbonyl group, n-butoxycarbonyl group, etc.), carboxylic anhydride group (—CO—O—CO—R group) (R is an alkyl group having 1 to 5 carbon atoms) and the like. It is done.

  As the organic ligand (II), 1,2-bis (4-pyridyl) ethyne or 1,4-bis (4-pyridyl) butadiyne is preferable, and 1,2-bis (4-pyridyl) ethyne is more preferable. .

The production process of the metal complex of the present invention is preferably carried out in a solution state by dissolving a copper salt and an organic ligand in a solvent in order to produce the compound represented by the formula (I). As a solvent for dissolving the copper salt, good results can be obtained by using a proton solvent such as water or alcohol. Protonic solvent such as water or alcohol, to dissolve well copper salts, further copper ion and BF4 @ ^- copper salt stabilized by coordination bond and a hydrogen bond to suppress a rapid reaction with the ligand This suppresses side reactions. Examples of the alcohol include aliphatic monohydric alcohols such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol and 2-butanol, and aliphatic dihydric alcohols such as ethylene glycol. Methanol, ethanol, 1-propanol, 2-propanol, and ethylene glycol are preferable in that they are inexpensive and have high copper salt solubility. These alcohols may be used alone or in combination.

  It is also preferable to use a mixture of water and the alcohol as a solvent. The mixing ratio of water and alcohols is arbitrary from 1: 100 to 100: 1 (volume ratio). From the viewpoint of improving the solubility of the ligand, the mixing ratio of the alcohols is preferably 30% or more (volume ratio) in the total solvent.

  Moreover, it is also possible to mix and use organic solvents other than alcohol with the mixed solvent of water, alcohol, or water-alcohol. The organic solvent to be mixed is a solvent miscible with water, and examples thereof include acetonitrile, tetrahydrofuran, acetone, 1,4-dioxane, dimethylformamide, dimethyl sulfoxide and the like. These may be used singly or in combination of two or more. Of these, acetonitrile, acetone, 1,4-dioxane, dimethylformamide, and dimethyl sulfoxide give good results. The mixing ratio of the organic solvent is 50% or less, preferably 30% or less in the total solvent.

  On the other hand, as a solvent for dissolving the organic ligand, alcohol solvents such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol and ethylene glycol, acyclic and cyclic such as ether and tetrahydrofuran Aliphatic ethers, ketones such as acetone, esters such as ethyl acetate, aliphatic nitriles such as acetonitrile, halogenated solvents such as dichloromethane, aromatic solvents such as benzene and toluene, formamides such as dimethylformamide, dimethyl sulfoxide The sulfoxides such as can be widely exemplified. These may be used singly or in combination of two or more. In terms of cost and solubility, methanol, ethanol, 2-propanol, acetonitrile, acetone and the like are preferable.

  The method of mixing the copper salt solution and the organic ligand system solution may add the ligand solution to the copper salt solution or vice versa. In addition, the mixing is not necessarily performed in a solution. For example, a method of adding a solid ligand to a copper salt solution and simultaneously adding a solvent, or after charging a reaction vessel with a copper salt, the ligand solid Alternatively, various methods are possible as long as the reaction finally occurs substantially in a solvent, such as injecting a solution and further injecting a solution for dissolving the copper salt. However, the method of dropping and mixing the copper salt solution and the ligand solution is industrially the most convenient and preferable.

  The concentration of the solution is 40 mmol / L to 4 mol / L, preferably 40 mmol / L to 2 mol / L for the copper 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 lower concentration, the target product can be obtained, but the production efficiency may be lowered. Further, at a concentration higher than this, there is a possibility that the adsorption capacity is lowered.

  The reaction temperature is -20 to 120 ° C, preferably 25 to 90 ° C. If it is carried out at a temperature lower than this, the solubility of the raw material may be lowered. Although it is possible to carry out the reaction at a higher temperature using an autoclave or the like, the yield is difficult to improve for the energy cost such as heating.

  The mixing ratio of the copper salt and the organic ligand used in the reaction of the present invention is in the range of 3: 1 to 1: 5, preferably 1.5: 1 to 1: 3. In other ranges, the yield of the target product decreases, and unreacted raw materials remain, making it difficult to take out the target product.

  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 raw material can be separated by filtration and drying to produce a target substance with high purity.

The metal complex of the present invention obtained as described above is a two-dimensional lattice-integrated type tertiary in which a two-dimensional lattice in which an organic ligand is coordinated to a copper ion is laminated, and BF ₄ ⁻ is present between the layers. Form the original structure.

  Since the three-dimensional structure in the metal complex of the present invention can be changed in the synthesized crystal, the structure and size of the pores change with the change. The conditions for changing the structure depend on the type of substance to be adsorbed, the adsorption pressure, and the adsorption temperature. That is, in addition to the difference in the interaction between the pore surface and the substance (the strength of the interaction is proportional to the magnitude of the Lennard-Jones potential of the substance), the degree of structural change differs depending on the adsorbing substance, and thus the adsorbed substance Depending on the type, the adsorption start pressure varies and high selectivity is exhibited. Further, the adsorption start pressure varies depending on the adsorption temperature. After the adsorbed substance is desorbed, it returns to its original structure, so the pore size also returns.

  Although the said adsorption mechanism is presumption, even if it does not follow the said mechanism, if the requirements prescribed | regulated by this invention are satisfied, it will be included in the technical scope of this invention.

  In the metal complex of the present invention, the accumulation structure of the metal complex and the size of the pores change depending on the type of the substance to be adsorbed, the adsorption pressure or the adsorption temperature. Reach the maximum adsorption amount instantly. The starting pressure of adsorption varies depending on the type of substance to be adsorbed or the adsorption temperature.

  Examples of the gas to be adsorbed include various gases, such as carbon dioxide, hydrogen, carbon monoxide, oxygen, nitrogen, C 1-4 hydrocarbons (methane, ethane, ethylene, acetylene, etc.), rare gases ( Helium, neon, argon, krypton, xenon, etc.), hydrogen sulfide, ammonia, sulfur oxide, nitrogen oxide, siloxane (hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, etc.), water vapor, organic vapor, etc. it can. The organic vapor means a vaporized organic substance that is liquid at normal temperature and pressure. Examples of such organic substances include alcohols such as methanol and ethanol; amines such as trimethylamine; aldehydes such as acetaldehyde; aliphatic hydrocarbons having 5 to 16 carbon atoms; aromatic hydrocarbons such as benzene and toluene; acetone And ketones such as methyl ethyl ketone; halogenated hydrocarbons such as methyl chloride and chloroform.

  Furthermore, since the metal complex of the present invention can selectively adsorb various gases by controlling the adsorption pressure, carbon dioxide, hydrogen, carbon monoxide, oxygen, nitrogen, hydrocarbons having 1 to 4 carbon atoms. (Methane, ethane, ethylene, acetylene, etc.), noble gases (helium, neon, argon, krypton, xenon, etc.), hydrogen sulfide, ammonia, sulfur oxide, nitrogen oxide, siloxane (hexamethylcyclotrisiloxane, octamethylcyclohexane) Tetrasiloxane and the like, and is also preferable as a separating material for separating water vapor or organic vapor, and in particular, pressure swing adsorption method using methane and carbon dioxide, hydrogen and carbon dioxide, nitrogen and carbon dioxide or carbon dioxide in the air. And suitable for separation by temperature swing adsorption method. The organic vapor means a vaporized organic substance that is liquid at normal temperature and pressure. Examples of such organic substances include alcohols such as methanol and ethanol; amines such as trimethylamine; aldehydes such as acetaldehyde; aliphatic hydrocarbons having 5 to 16 carbon atoms; aromatic hydrocarbons such as benzene and toluene; acetone And ketones such as methyl ethyl ketone; halogenated hydrocarbons such as methyl chloride and chloroform.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples. Analysis and evaluation in the following examples and comparative examples were performed as follows.

(1) Measurement of powder X-ray diffraction pattern Using an X-ray diffractometer, a range of diffraction angle (2θ) = 5 to 50 ° was scanned at a scanning speed of 1 ° / min, and measured by a symmetric reflection method. Details of the measurement conditions are shown below.
<Analysis conditions>
Apparatus: RINT2400 manufactured by Rigaku Corporation
X-ray source: CuKα (λ = 1.5418Å) 40 kV 200 mA
Goniometer: Vertical goniometer Detector: Scintillation counter Step width: 0.02 °
Slit: Divergent slit = 0.5 °
Receiving slit = 0.15mm
Scattering slit = 0.5 °

(2) Measurement of adsorption / desorption isotherm The measurement was performed by a volume method using a high-pressure gas adsorption amount measuring device. Details of the measurement conditions are shown below.
<Analysis conditions>
Apparatus: BELSORP-HP manufactured by Nippon Bell Co., Ltd.
Equilibrium waiting time: 500 seconds

<Synthesis Example 1>
A 100 mL (40 mmol / L) aqueous solution of copper (II) tetrafluoroborate was prepared under a nitrogen atmosphere, and 100 mL (80 mmol / L) of a methanol solution of 1,2-bis (4-pyridyl) ethyne was stirred at 60 ° C. ) Was added dropwise over 3 hours. After completion of dropping, a small amount of powder was collected by suction filtration to obtain a filtrate. The filtrate was concentrated, and the precipitated powder was collected by suction filtration and then dried at 100 ° C. and 50 Pa for 8 hours to obtain 0.937 g (yield 39%) of the desired metal complex.

  The result of having measured the powder X-ray-diffraction pattern of the obtained metal complex is shown in FIG.

<Example 1>
For the metal complex obtained in Synthesis Example 1, the adsorption and desorption isotherm of carbon dioxide at −5 ° C. was measured by the volume method. Prior to the measurement, the sample was vacuum-dried at 100 ° C. for 5 hours to remove solvent molecules and the like that may remain in trace amounts. The results are shown in FIG.

<Comparative Example 1>
The adsorption / desorption isotherm of [Cu (BF ₄ ) ₂ (bpy) ₂ ] _n at −5 ° C. was measured by the capacitance method. [Cu (BF ₄ ) ₂ (bpy) ₂ ] _n precursor [Cu (BF ₄ ) ₂ (bpy) ₂ (H ₂ O) ₂ ] _n (Tokyo Chemical Industry Co., Ltd.) was measured at 170 ° C. And dried for 8 hours in a vacuum, and provided with the water removed by coordinating with the metal. The results are shown in FIG.

  FIG. 2 shows that desorption of the metal complex of the present invention is started at a pressure higher than that of the conventional material. By utilizing this feature, it is possible to reduce the energy required for the recovery of the adsorbed gas and the regeneration of the adsorbent compared to the case where a conventional material is used as the adsorbent.

Since the adsorption and desorption of the metal complex of the present invention is started at a higher pressure than before, the adsorbed gas can be recovered with energy saving and the adsorbent can be regenerated. Carbon dioxide, hydrogen, carbon monoxide, oxygen, nitrogen, carbon It is also preferable as an adsorbent for adsorbing hydrocarbons of several to four, rare gas, hydrogen sulfide, ammonia, sulfur oxide, nitrogen oxide, siloxane, water vapor or organic vapor. Furthermore, since the metal complex of the present invention can selectively adsorb various gases by controlling the adsorption pressure, carbon dioxide, hydrogen, carbon monoxide, oxygen, nitrogen, hydrocarbons having 1 to 4 carbon atoms. It is also preferable as a separation material for separating rare gas, hydrogen sulfide, ammonia, sulfur oxide, nitrogen oxide, siloxane, water vapor, organic vapor, etc., and can contribute to miniaturization of the gas separation device. In particular, it is preferable as a separating material such as methane and carbon dioxide, hydrogen and carbon dioxide, nitrogen and carbon dioxide, or carbon dioxide in the air.

Claims (6)

A metal complex having a unit structure of the following formula (I).
Cu (BF ₄ ) ₂ L ₂ (I)
(In the formula, L represents the following general formula (II);
An organic ligand represented by
R ¹ , R ² , R ³ and R ⁴ are the same or different and each represents a hydrogen atom, an optionally substituted alkyl group or a halogen atom, or R ¹ and R ² , R ³ and R ⁴ are An alkylene group, an oxyalkylene group or an alkenylene group which may have a substituent together;
n is 1 or 2,
R ⁵ , R ⁶ , R ⁷ and R ⁸ are the same or different and each represents a hydrogen atom, an optionally substituted alkyl group or a halogen atom, or R ⁵ and R ⁶ , R ⁷ and R ⁸ are The alkylene group, the oxyalkylene group, or the alkenylene group which may have a substituent together is shown. )   The metal complex according to claim 1, wherein the organic ligand L is 1,2-bis (4-pyridyl) ethyne or 1,4-bis (4-pyridyl) butadiyne.   The metal complex according to claim 1 or 2, wherein the organic ligand L is 1,2-bis (4-pyridyl) ethyne.   The adsorbent which consists of a metal complex as described in any one of Claims 1-3.   The adsorbent is carbon dioxide, hydrogen, carbon monoxide, oxygen, nitrogen, hydrocarbon having 1 to 4 carbon atoms, rare gas, hydrogen sulfide, ammonia, sulfur oxide, nitrogen oxide, siloxane, water vapor or organic vapor. The adsorbent according to claim 4, which is an adsorbent for adsorbing.   A pressure swing type gas separation device using the gas adsorbent according to claim 4 or 5.