JHUNG, Sung-Hwa (5-1104 Cheongsol APT, Sahmcheon-dong Seo-gu, Daejeon 302-743, KR)
HWANG, Young-Kyu (110-101 Daerimdoore APT, Shinseong-dong Yuseong-gu, Daejeon 305-720, KR)
CHAE, HEE-K (802-603 Hyundai APT, Gwanjang-dong Gwanjin-gu, Seoul 143-754, KR)
CHOI, Jae-Yong (636-11 Hwajeong-dong, Dong-gu, Ulsan 682-090, KR)
CHANG, Jong-San (103-204 Yudeungmaheul APT, Taepyung-dong Joong-gu, Daejeon 301-779, KR)
JHUNG, Sung-Hwa (5-1104 Cheongsol APT, Sahmcheon-dong Seo-gu, Daejeon 302-743, KR)
HWANG, Young-Kyu (110-101 Daerimdoore APT, Shinseong-dong Yuseong-gu, Daejeon 305-720, KR)
CHAE, HEE-K (802-603 Hyundai APT, Gwanjang-dong Gwanjin-gu, Seoul 143-754, KR)
CHOI, Jae-Yong (636-11 Hwajeong-dong, Dong-gu, Ulsan 682-090, KR)
[CLAIMS]
[Claim l]
A method of preparing a porous zinc-based carboxylate coordination polymer compound with large surface area comprising:
(1) mixing a zinc precursor, a carboxylic acid compound or a mixture thereof, and a solvent to prepare a reactant mixture ; and
(2) irradiating microwaves in a range of 0.3-300 GHz to the reactant mixture, thereby heating to 20 to 120 ° C
[Claim 2]
The method of claim 1, wherein the zinc-based carboxylic acid coordination polymer compound has a BET surface area (S BET )
more than 3000 m'/g- [Claim 3]
The method of claim 1, wherein the carboxylic acid compound is selected from the group consisting of benzene dicarboxylic acid, naphthalene dicarboxylic acid, benzene tricarboxylic acid, naphthalene tricarboxylic acid, pyridine dicarboxylic acid, bipyridyl dicarboxylic acid, formic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, hexane dioic acid, heptane dioic acid, cyclohexyl dicarboxylic acid, and a salt thereof. [Claim 4l The method of claim 1, wherein the solvent is at least one selected from the group consisting of N, N-dimethyIformamide (DMF), N, N-diethylformamide (DEF), alcohols, ketones and hydrocarbons . [Claim 5]
The method of claim I 1 wherein the zinc-based carboxylate coordination polymer compound has a cubic structure .
[Claim 6]
The method of claim 3, wherein the carboxylic acid compound is terephthalic acid or 2 , 6-naphthalene dicarboxylic acid.
[Claim 7]
The method of claim 6, wherein the carboxylic acid compound is terephthalic acid.
[Claim 8] The method of claim 7, wherein the zinc-based carboxylate coordination polymer compound has nitrogen adsorption capacity more than 900 cc/g when the relative pressure of nitrogen is 0.5 (P/P 0 =0.5) at liquid nitrogen temperature, or has crystal sizes below 10 μm. [Claim 9]
The method of claim 1, wherein a batch mode reactor or a continuous mode reactor is used. [Claim lθ] The method of claim 1, wherein the porous zinc-based carboxylate coordination polymer compound has a thin film or a membrane form .
[Claim ll] The method of claim 10, wherein the porous zinc-based carboxylate coordination polymer compound in a thin film or membrane form is prepared by immersing a substrate made of alumina, silica, ITO glass, silicon or a polymer, or a substrate of which surface is treated with such material in a reactant mixture.
[Claim 12]
The method of claim 11, wherein the substrate is deposited with a noble metal selected from the group consisting of gold, silver and platinum on its upper surface. [Claim 13]
A porous zinc-based carboxylate coordination polymer compound with large surface area prepared by the method according to any one of Claims 1 to 12.
[Claim 14] A storage material that adsorbs or stores gases by employing the porous zinc-based carboxylate coordination polymer compound with large surface area prepared by the method according to any one of Claims 1 to 12. [Claim 15] The storage material of claim 14, wherein the gas is selected from the group consisting of hydrogen, nitrogen, oxygen, carbon dioxide, methane, ethane, natural gas, acetic acid, LPG or mixtures thereof . |
A NEW PREPARATION METHOD OF POROUS COORDINATION POLYMER COMPOUNDS COMPOSED OF ZINC ION AND CARBOXYLATES
[Technical Field]
The present invention relates to a method of preparing a porous zinc-based carboxylate coordination polymer, and more particularly, to a novel method of preparing λ metal-organic framework' (hereinafter, refers to abbreviated MOF; Nature, 423, 705, 2003), a zinc-based carboxylate coordination compound, of which its surface area and gas adsorption capacity are very much improved by performing a reaction of preparing the MOF through heating by employing microwaves instead of conventional electrical heating as heat sources for the preparation reaction.
[Background Art]
The metal-organic framework compound is a kind of a coordination polymer resulting from crystal engineering. In 1971, G. M. Schmidt first used the term, λ Crystal Engineering' for an organic solid compound obtained from researching the photochemistry for unsaturated hydrocarbon compounds including cinnamic acid. For past 30 years since then, the crystal engineering has been the central concept of modern chemistry in the fields of not only the synthesis for organic and
inorganic compounds, but also the properties and application of the compounds (Chemical Reviews, 101, 1629, 2001) . The subject material for the crystal engineering may be various, e.g., from simple organic material up to an organometallic compound, a coordination compound and a biochemical material, and its binding form may include not only a covalent bond, an ionic bond and a coordinated bond, but also a hydrogen bond and a van der Waals bond, and thus the crystal engineering can deserve to be the center of synthesis chemistry. Initially, solid-state organic chemists including D. Y. Curtin, I. C. Paul and G. R. Desiraju in the University of Illinois at Urbana-Champaign, United States have formed mainstream in that field, but since mid 1990s, many inorganic chemists including R. Robson in Australia, M. J. Zaworotko and 0. M. Yaghi in United States, and M. Fujita and S. Kitagawa in Japan participated in the field, and finally a coordination polymer such as an inorganic coordination polymer became the fastest- growing field of the crystal engineering recently (Chem. Eng. Commun. 4, 500, 2002). The coordination polymer chemistry became a chemical field greatly coming into notice in recent years, since it is easy to bringing design concept from top-down to bottom-up in the chemistry due to the properties of the coordination compound and the compound easily grows to a crystal, and thus it can unravel a crystal structure. The compound is composed
of a metal salt and a ligand. The ligand includes from simple hydrocarbons including an electron donor such as oxygen, nitrogen or sulfur atom to various organic material, other coordination compound, a biomolecule material including an amino acid, and an organic metal and an inorganic material. The metal also includes various forms from a simple ion to a complex metal cluster, and the kind of the metal is mainly a transition metal, but also includes various elements in the periodic table, such as an alkali metal or a rare earth metal. The coordinated structure formed from the metal ion part and the organic ligand may be simple molecule form, but also be linear first structure, planar secondary structure and complex 3 -dimensional structure through self-assembly, and accordingly, the research for the compound is captivated like useful application obtained in an organic polymer (Angewandte Chemie- International Edition 43, 2334, 2004) . Accordingly, the coordination chemistry is coming into notice in a bottom-up design form that a porous material or structure in desired form is disrupted in top-down manner thereby reassembling to a proper central metal ion and a ligand, but the design is not easily achieved in a real reaction. For example, when the central metal ion of the coordination compound in tetrahedron binding form is bound to 4 , 4 ' -bipyridine, an organic ligand, a diamond-like hexagonal structure can be formed. However, when the hexagonal shapes are all chair form, the coordination
compound has diamond-like structure, and when the hexagonal shapes are in a mixture of chair form and boat form, the coordination compound has hexagonal diamond form known as Lonsdaleite. Accordingly, coordination polymers having different structure and property can be formed (Nature, 423, 705, 2003) .
Of the coordination polymer compounds, when an organic ligand is used as carboxylic acid or carboxylic acid/electron donor ligand, the compound particularly also refers to 'Metal- Organic Frameworks (MOF) ' . In such a case, more complex and delicate three-dimensional coordination polymer can be designed depending on the environment of coordination bond for metal simplified by employing the concept of secondary building unit, and the shape of the ligand. Specifically, MOF is differently sorted with a coordination polymer compound, and is actively studied as a novel form of an organic zeolite in inorganic chemistry or solid chemistry since the MOF provides thermal stability until about 400 ° Cwith its backbone structure being not disrupted through strong interaction (δE (Zn-O) = 360 kJ/mol) between the ligand of carboxylic acid and the metal cluster compound such as Zn 4 O even when guest molecules in their pores are removed, and the MOF has excellent resistance against various chemicals like a zeolite and is porous. This field became international research theme in recent years (Nature, 423, 705, 2003) as a MOF-5 compound
is known in 1999 by Yaghi (Nature, 402, 276, 1999), since the MOF has larger surface area than that of a zeolite or an activated carbon in addition to the zeolite's properties, and its porosity and surface area can be controlled according to the organic ligand. Recently, various kinds of MOF were synthesized by using various ligands, and particularly, there were IRMOF (iso-reticular MOF) (US Patent No. 6,930,193) wherein the term 'iso-reticular' means 'having the same network topology' , and IRMOF- 8 prepared by using naphthalene dicarboxylic acid as a ligand. Concerning a zinc-based carboxylic acid coordination compound, hundreds of research articles have been published in recent years, and the structures of several tens of kinds for the compound are known. These materials have large a surface area and a pore in molecular size or even in nano size, and thus can be used in not only an adsorbent, a gas storage material, a sensor, a catalyst and a catalyst support, but also in capturing guest molecules smaller than the pore size or separating molecules larger than the pore size. The most important properties in employing these materials by porosity are a surface area and a pore volume, etc. For example, in case of storing hydrogen, the stored quantity depends on the surface area of the porous material (Nature, 414, 353, 2001), and the stored quantity of methane is also directly proportional to the surface area (Journal of Porous Materials 4, 53, 1998). Accordingly, it is
very important for commercial application to increase the surface area of the MOF.
Until now, these materials are prepared in various ways, but are typically prepared through solvent diffusion at near ambient temperature, or solvothermal synthesis using an organic material as a solvent (Microporous Mesoporous Materials 73, 15, 2004) . In case of the solvent diffusion, it takes at least one week and the yield is very low. In solvothermal synthesis, suitable organic material is used as a solvent, and generally, crystallization process is undergone under an autogenous pressure at a synthesis temperature above the boiling point of the solvent or mixed solution. That is, those materials could be obtained after reactants were put into a pressure reactor and the reactor was sealed, and then crystallization time usually passed for a couple of days at high temperature. The electrical heating employing the heat of a resistor was usually employed as a heat source for synthesis at high temperature. That is, the precursor materials composed of a metal salt, an organic ligand compound and an organic solvent were mixed well, put into a pressure reactor, and then the reactor was completely sealed and thereafter, heated by employing an electrical heater in order to proceed with synthesis. Alternatively, the precursor materials were put into a pressure vessel, and then the vessel was put into an electrical oven, etc. controllable at constant temperature in
order to proceed with synthesis. However, those synthesis methods are very inefficient method since nucleation or crystallization processes are very slow, thereby usually requiring at least several days of reaction time in obtaining a complete crystalline MOF compound, and thus energy for process is excessively consumed; and the reaction must be progressed only in batch mode (US Patent No. 6,930,193). Accordingly, the existing inefficient method of synthesizing a porous MOF has an obstacle for industrial application due to the high production costs. Further, such a typical synthesis method has its limitation in the surface area and adsorption capacity of the synthesized compound, and thus has a problem in industrial application.
Furthermore, in order to provide the applicability as a sensor and an optoelectronic functional device in addition to the synthesis, it is necessary that a MOF membrane and a thin film having uniform particle size and thickness be prepared. However, the existing preparation method for a MOF membrane and a thin film comprises a complex procedure that a prepared organic/inorganic hybrid was supported in a polymer to prepare a simple composite (Advanced Materials, 17, 80, 2005) , and the prepared organic/inorganic hybrid was secondarily dissolved in a solvent to prepare a membrane; and the method cannot be easily applied to an insoluble organic/inorganic hybrid. In addition, a method of preparing a MOF membrane by employing a
substrate made of gold to which an organic functional group is attached is reported, but the method has a trouble in requiring attaching the organic functional group to a substrate and recrystallizing (Journal of the American Chemical Society, 127, 13744, 2005) .
Accordingly, the present inventors continuously tried to prepare a porous MOF having uniform particle size, of which gas adsorption capacity is greatly improved due to the increase of the surface area and the pore volume, and at last completed the present invention with achieving the above object by applying microwaves as heat sources instead of the conventional electrical heating.
Therefore, the present invention provides a novel method of preparing a porous MOF, and particularly, a method of preparing a porous MOF of which surface area, pore volume and gas adsorption capacity are greatly improved.
[Disclosure] [Technical Problem] In preparing a porous MOF, the present inventors attempted to develop a preparation method by which energy consumption can be diminished and be environmentally effective by finishing the synthesis in a short reaction time through heating by microwaves. Further, the present inventors also attempted to develop a novel preparation method by which the
surface area, pore volume and gas adsorption capacity of the porous MOF are greatly improved. Furthermore, the present inventors attempted to develop a method of preparing a MOF thin film directly through only one time heating by microwaves, not multi-step process. Accordingly, the object of the present invention lies in developing a method of preparing a MOF that can be used in various applications and has large surface area in fast, economical and environmentally effective manner.
[Technical Solution]
Accordingly, the present invention provides a method of preparing a porous metal carboxylate coordination polymer compound (MOF) efficiently, and in particular, a method of a porous MOF of which particle sizes are uniform, the surface area and pore volume are greatly increased, and thus has very excellent gas adsorbing ability, characterized in that the method utilizes microwaves as heat sources of the solvothermal reaction.
The present invention also provides a method of preparing a porous metal carboxylate coordination polymer compound (MOF) comprising the following steps, and in particular, a method of a porous MOF of which BET surface area (S BET ) is more than 3000 m'/g, and particle sizes are below 10 μm and uniform:
(1) mixing a zinc precursor, a carboxylic acid compound or a mixture thereof, and a solvent to prepare a reactant mixture ; and
(2) irradiating microwaves in a range of 0.3-300 GHz to the reactant mixture, thereby heating to 20 to 120 ° C
A porous MOF prepared by the preparation method according to the present invention can be in the form of powder, a thin film or a membrane.
A porous organic/inorganic hybrid in the form of a thin film or a membrane can be easily prepared by immersing a substrate in the reactant mixture, and then irradiating microwaves thereby heating.
Further, the present invention provides a metal carboxylate coordination polymer compound having large BET
surface area (S BET ) more than 3000 m'/g, and excellent gas adsorption ability, prepared by the preparation method according to the present invention. Herein, the metal carboxylate coordination polymer compound may be a zinc-based carboxylate coordination polymer compound. The present invention also provides a storage material that adsorbs or stores gases by employing the zinc-based carboxylate coordination polymer compound.
[Advantageous Effects]
The preparation method according to the present invention provides a porous MOF of which particle sizes are uniform, surface area and pore volume are greatly increased, and thus has very excellent gas adsorbing ability.
[Description of Drawings]
The above and other features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which:
FIG. 1 is an X-ray diffraction pattern concerning a porous zinc-based carboxylate coordination polymer compound according to an exemplary embodiment of the present invention, and (a) represents an X-ray diffraction pattern of Zn-BDC obtained by simulation with X-ray crystallography and (b) represents an X-ray diffraction pattern of Zn-BDC obtained by Example 1;
FIG. 2 is a scanning electron microscope photograph of Zn-BDC obtained by Example 1; and FIG. 3 is a scanning electron microscope photograph of Zn-NDC obtained by Example 5.
[Mode for Invention]
Hereinafter, the present invention will be described in more detail.
The present invention is characterized by applying microwaves instead of electrical heating generally used as a heat source for high temperature reaction, wherein the microwave having a frequency in a range of approximately 300 MHz-300 GHz can be employed in heating reactants, however, the microwave having a frequency of 2.45 GHz or 0.915 GHz that is frequently used industrially is convenient and efficient.
As a metal material that is a component of MOF, any metal may be used, and in particular, a transition metal likely to form coordinate bonds is suitable. Zinc is most suitable among transition metals. As a metal source, not only metal itself but also any compounds thereof may be used. An organic material as a component of MOF also refers to a linker, and any organic material having a carboxylate anion may be used. For directing a stable MOF, a polydentate organic material, such a bidentate or a tridentate one, having two or more position capable of forming a coordinate bond is advantageous. As the organic material, not only a neutral material, and an anion material such as a carboxylate anion, e.g., terephthalate, naphthalenedicarboxylate, benzenetricarboxylate, glutarate, succinate, etc., but also a cation material may be used as long as there is a position to form a coordination bond. For a carboxylate anion, in addition to an anion having an aromatic ring such as terephthalate, not only an anion of linear carbonic acid but also an anion having a non-aromatic
ring such as cyclohexyl dicarboxylate may be used. Further, an organic material not only having a position to be coordinated but also potentially having a position to be coordinated in a reaction condition may be also used. That is, the organic acid such as terephthalic acid can be bound with a metal component to form terephthalate after reaction. The representative example of the organic material to be used includes an organic acid selected from the group consisting of benzene dicarboxylic acid, naphthalene dicarboxylic acid, benzene tricarboxylic acid, naphthalene tricarboxylic acid, pyridine dicarboxylic acid, bipyridyl dicarboxylic acid, formic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, hexane dioic acid, heptane dioic acid or cyclohexyl dicarboxylic acid, and an anion thereof. Further, at least one of organic material can be used in combination.
For synthesizing the MOF, a suitable solvent is needed in addition to a metal component and an organic material. The solvent includes N,N-dimethylformamide (DMF), N, N- diethylformamide (DEF), alcohols such as methanol, ethanol or propanol, ketones such as acetone or methylethyl ketone, and hydrocarbons such as hexane, heptane or octane. Of these solvents, DMF and DEF are suitable.
A guest material may be further used. The guest material may be the same as or different from the solvent. However, it is convenient to use the same guest material as the solvent.
Two or more solvents or guest material may be used in combination.
A reaction temperature according to the present invention is substantially not limited, but a temperature higher than 20 ° Cis suitable, and a temperature in a range of 20 ° Cto 200 ° C may be used, but a temperature in a range of 20 ° Cto 120 ° Cis more suitable. If the temperature is too low, the reaction speed is ineffectively slow. If the temperature is too high, it is likely to result in nonporous material, and it is likely to incorporate impurities due to too fast reaction speed.
Further, the construction of a reactor is uneconomical since the pressure inside the reactor becomes too high.
The pressure of the reactor is substantially not limited. However, it is simple that synthesis is performed under the autogenous pressure of reactants at a reaction temperature.
Further, the reaction may be performed under high pressures by adding an inert gas such as nitrogen or helium.
The reaction can be preformed in batch mode or continuous mode. A batch mode reactor is suitable for producing small amount of MOF due to low productivity per time, and a continuous mode reactor is suitable for mass production though it costs high for investment in equipment. One minute to 8 hours of the reaction time is suitable for the batch mode. If the reaction time is too long, impurities are likely to be incorporated, and particles grow thereby rendering it not easy
to make small particles. If the reaction time is too short, the conversion of the reaction is low. Accordingly, 1 minute to 1 hour of the reaction time is more suitable. The suitable retention time in a continuous mode reactor is approximately 1 minute to 1 hour. If the retention time is too long, a product having low productivity and small surface area is obtained. If the retention time is too short, the conversion of the reaction is low and thus the yield is low. One minute to 30 minutes of the retention time are more suitable. The reactants can be agitated during the batch mode reaction. The suitable agitation speed is 100 to 1000 rpm, but the reaction can be performed without agitation. Rather, no agitation is simple and easy to apply in the construction and operation of the reactor. It is preferable, however, not necessary to elevate the uniformity or solubility of reactants, or irradiate microwave at the pretreated state so that crystal nucleus may be generated partially since the reaction employing microwave occurs very fast. If the reaction by microwave starts immediately at no-pretreated state, the reaction is slow, impurities are incorporated, or the uniformity of particle sizes becomes low, but the process becomes simple. Pretreatment can be performed by treating reactants with ultrasonic waves or agitating vigorously, and the pretreatment temperature may be between room temperature and reaction
temperature. If the temperature is too low, the pretreatment effect is very weak, and if the temperature is too high, it is likely to generate impurities, as well as to complicate the pretreatment equipment. The suitable pretreatment time is above 1 minute and within 5 hours. If the time is too short, the pretreatment effect is very weak, and if the time is too long, the pretreatment efficiency may become low. Ultrasonic waves are more effective for performing pretreatment in terms of the pretreatment time and the uniformity of reactants . Further, in addition to the MOF crystal, a membrane and a thin film can be prepared by immersing a substrate in a reactant mixture of the step (1) , and heating it through irradiating microwaves. The substrate includes alumina, silicon, a glass, ITO glass, a polymer, and a surface-treated substrate thereof. The substrate, on the upper surface of which a noble metal such as gold, silver and platinum is deposited, may be used.
Further, the present invention provides a storage material that adsorbs or stores gases by employing the zinc- based carboxylic acid coordination polymer compound prepared by the preparation method according to the present invention, since the above-mentioned polymer compound has very large surface area and large pore volume, and thus adsorbs much gas. The gases include, however, are not limited to, an oxidizing gas, an inert gas and a hydrocarbon, and in particular,
hydrogen, nitrogen, oxygen, carbon dioxide, methane, ethane, natural gas, acetic acid, LPG or mixtures thereof.
Hereinafter, the present invention will be described in non-limiting examples below in more detail.
Example 1. Zn-BDC-I
Zinc nitrate tetrahydrate (Zn (NO 3 ) 2 • 4H 2 O) and 1,4 -benzene dicarboxylic acid (C 6 H 4 -I, 4- (CO 2 H) 2 ; hereinafter, abbreviated to BDC) were dissolved in N, N-diethylformamide (DEF) to obtain a reactant mixture. The mixture was put into a glass tube, and the tube was sealed. Then, the tube was irradiated with a microwave at 2.45 GHz in a microwave reactor (CEM, Discover), and maintained for 14 minutes at 80 ° Cfor crystallization. Subsequently, the tube was cooled to 25 ° C and crystalline solid was separated from working solution. The solid was washed three times with 1 mi of DMF, and then was dried in air to obtain Zn-BDC, a kind of MOF-5. The X-ray diffraction pattern and scanning electron microscope (SEM) photograph for Zn-BDC obtained as above were shown in FIGS Ib and 2, respectively. The results of a powder X-ray diffraction are almost the same as those of the simulation by X-ray crystallography (FIG Ia), from the SEM photograph in FIG 2, it can be seen that each face of a single crystal in cubic shape has a size of about 1 μm . The detailed reaction condition is summarized in table 1 below.
Example 2 . Zn-BDC-2
This example was performed in the same manner as in Example 1 except that the reaction temperature in Example 1 was maintained at 105 °C instead of 80 ° C From the X-ray diffraction analysis and the electronic microscope photograph, it can be seen that Zn-BDC very similar to Example 1 was obtained. The detailed reaction condition is summarized in table 1 below.
Example 3. Zn-BDC-3
Zinc nitrate tetrahydrate (Zn(NO 3 ) 2 • 4H 2 O) and 1,4 -benzene dicarboxylic acid (C 6 H 4 -1, 4- (CO 2 H) 2 ; abbreviated to BDC) were dissolved according to the reactant composition described in table 1 below in N,N-diethylformamide (DEF) to obtain a reactant mixture. A continuous mode reactor was employed instead of the batch mode reactor in Example 2. The continuous mode reactor was 2 -stage reactor in tube shape, and Korean Patent Application No. 2005-0063515 describes this concept by the present inventors . The retention time was each 5 minutes per respective reactors totaling 10 minutes, and the microwave irradiation and the reaction temperature were performed in the same manner as in Example 2. From the X-ray diffraction analysis and the electronic microscope photograph, it can be seen that Zn-BDC very similar to Example 1 was obtained. The detailed reaction condition is summarized in table 1 below.
Example 4 . Zn-BDC-4
This example was performed in the same manner as in Example 3 except that a continuously stirred continuous reactor was employed instead of the tube type continuous reactor. Korean Patent Application No. 2005-0064629 describes this concept of the continuously stirred continuous reactor by the present inventors . The retention time was set by controlling the speed of the reactants flew into the reactor so that it may be 5 minutes in total. From the X-ray diffraction analysis and the electronic microscope photograph, it can be seen that Zn-BDC very similar to Example 1 was obtained. The detailed reaction condition is summarized in table 1 below.
Example 5. Zn-NDC-I
Zinc nitrate tetrahydrate (Zn (NO 3 ) 2 • 4H 2 O) and 2,6- naphthalene dicarboxylic acid (Ci 0 H 6 -2 , 6- (CO 2 H) 2 ; abbreviated to NDC) were dissolved according to the reactant composition described in table 1 below in N,N-diethylformamide (DEF) to obtain a reactant mixture. The reactant mixture was irradiated with a microwave at 2.45 GHz in the same reactor as in Example 1, and maintained for 10 minutes at 65 ° C From the X-ray diffraction analysis for material which was obtained by separating, washing and drying in the same manner as in Example 1, it can be seen that crystalline material in cubic
shape was obtained. From the electron microscope photograph (FIG 3), it can be seen that cubic crystals in very small cubic shape of which each face is about 3 μm were obtained.
Example 6. Zn-BDC-thin film
Zinc nitrate tetrahydrate (Zn (NO 3 ) 2 • 4H 2 O) and 1,4 -benzene dicarboxylic acid (C 6 H 4 -I, 4- (CO 2 H) 2 ; abbreviated to BDC) were dissolved according to the reactant composition described in table 1 below in N,N-diethylformamide (DEF) to obtain a reactant mixture. The mixture was put into a glass tube, an alumina substrate was further put into the tube, and the tube was sealed. Then, the tube was irradiated with a microwave at 2.45 GHz in a microwave reactor (CEM, Discover), and maintained for 14 minutes at 80 ° Cfor crystallization. Subsequently, the tube was cooled to 25 °Q and crystalline thin film was separated from working solution. The crystalline thin film was washed three times with 10 mi of DMF, and then was dried in air to obtain Zn-BDC, a kind of MOF-5. The results of the X-ray diffraction for Zn-BDC thin film obtained as above almost corresponded with the pattern (FIG Ia) derived by analyzing single crystal obtained according to a conventional preparation method through electric heating.
Comparative example 1
Zn-BDC was prepared in the same manner as in Example 1, but in similar manner to Method 3 among the preparation method of IRMOF-I in Examples of US Patent No. 6930193. In other words, a typical electrical oven was employed instead of microwaves as a heat sources for obtaining high temperature, and the reaction time was 20 hours instead of 14 minutes. From the X-ray diffraction pattern, it can be seen that the same crystalline material as in Example 1 was obtained, but from the electron microscope photograph, it can be seen that MOF having large particle size, of which each face has particle
sizes in a range of about 50 to 100 μm was obtained and its porosity and adsorption capacity were much lower than that of Example 1.
Table 1
Example 7. Analysis for porosity and adsorption capacity
The surface area, the pore volume and the gas adsorption capacity were evaluated for the MOF prepared in Examples 1 to 4 and Comparative example 1. After removing the solvent and guest present in pores under vacuum, the MOF prepared in Examples 1 to 4 and Comparative example 1 was analyzed for the surface area, the pore volume, the nitrogen adsorption capacity and hydrogen adsorption capacity by volumetry, and the results including the analysis method are summarized in table 2 below. In comparison with the comparative example, the surface area and the pore volume were improved by at least 30% at minimum over the MOF synthesized by electrical heating, and the hydrogen adsorption capacity was improved by at least 60% at minimum. Accordingly, it can be seen that the MOF of which surface area, pore volume and adsorption capacity are greatly improved can be obtained when employing microwaves instead of the electrical heating as heat sources in synthesizing MOF.
Table 2
[industrial Applicability]
As described above in detail, when employing microwaves as heat sources in preparing a porous zinc-based carboxylic acid coordination compound according to the present invention, the decrease in preparation time, the energy saving and the decrease in a reactor capacity, etc. can be achieved, and accordingly the method of preparing the porous zinc-based carboxylic acid coordination compound according to the present invention can be advantageous environmentally and economically. In particular, a zinc-based carboxylic acid coordination compound in small particles of which the length of one side is
below 10 μxa and the surface area and the adsorption capacity are greatly improved can be easily prepared through the synthesis by microwaves. These zinc-based carboxylic acid coordination compound can be used in preparing a catalyst, a catalyst support, an adsorbent, a gas storage material, an ion exchanger and a nano reactor and nano material, and particularly small particles thereof can be used in not only a catalyst having excellent activity but also a sensor, optoelectronic material and medical material .