KR101616078B1 - Manufacturing method of chromium-based metal organic frameworks - Google Patents

Abstract

The present invention relates to a method for producing a chromium salt, comprising: grinding a chromium salt to obtain a chromium salt milled product; Mixing the chromium salt mill with an organic ligand to obtain a chromium salt-organic ligand mixture; And a step of grinding the chromium salt-organic ligand mixture to obtain a chromium salt-organic ligand pulverized product, wherein a high specific surface area of not less than 4,100 m < 2 > / g and a high yield of not less than 90% The present invention provides a method of manufacturing a chromium-based metal organic structure that can drastically reduce the purification process.

Description

TECHNICAL FIELD [0001] The present invention relates to a method for producing a chromium-based metal organic structure,

The present invention relates to a process for preparing a chromium-based metal organic structure, and more particularly, to a process for preparing a chromium-based metal organic structure having a high BET surface area and a high yield without further purification .

Metal Organic Frameworks (MOFs) are metal complexes in which metal ion clusters connected by a metal ion or an oxygen atom are connected to an organic ligand by a coordination bond to form a crystalline porous material having primary, secondary and three dimensional skeletons to be. Basically, the metal organic structure has a wide specific surface area and pore volume, exhibits regular pore structure and high metal content. In addition, the metal organic structure can be subjected to various post treatment and functionalization on the organic ligand constituting the structure. Based on these excellent physicochemical characteristics, various applications such as energy storage, catalyst, adsorption of carbon dioxide, hydrogen storage and separation, Research is being conducted.

In most MOFs, all metal ions are coordinately saturated by organic ligands during the synthesis process. However, in the case of some MOF materials, some metal ions are partially bound to the solvent molecules or water molecules during the synthesis process. If this is removed by a simple heat treatment and vacuum treatment, the coordination bonds (Lewis acid) unsaturated open metal sites (CUS) are formed.

In particular, when MOF having a large specific surface area is used as a catalyst, it is important in catalytic applications because of its large active sites, and they have been reported to have excellent performance as a gas adsorption / separation and Lewis acid catalyst. On the other hand, most MOF materials have relatively low stability to heat, moisture and acid / base, which is still an important challenge to be solved in the industrial application of MOF materials.

Of the MOFs presently reported for synthesis, chromium (III) terephthalate, which exhibits excellent moisture stability, has thermal and chemical stability, and has a large specific surface area (3900 to 4300 m 2 / g) and a large cell volume (702,000 Å ³ ) MIL-101 (Materials of Institute Lavoisier 101) is attracting attention as a (III) terephthalate-based MOF material.

MIL-101 (Cr) is generally prepared by hydrothermal synthesis (HTS) and is synthesized in a narrow temperature range of 200 to 220 ° C for about 8 hours under acidic conditions with a hydrogen ion concentration (pH) As an alternative to synthesis time reduction, microwave-assisted synthesis has been reported.

On the other hand, in the case of MIL-101 (Cr) which forms MOF based on H ₂ BDC (1,4-benzenedicarboxylic acid) ligand, H ₂ BDC is not soluble in water Since the H ₂ BDC ligand not participating in the formation of the structure is recrystallized and present as an impurity in and out of the MIL-101 (Cr) pores, there is a limitation in obtaining a BET specific surface area of at least 3,200 m 2 / g and a high pore volume.

As a method to solve this problem, it has been reported that the BET specific surface area is greatly increased from 2200 to 4230 m 2 / g and the pore volume is increased from 1.13 to 2.15 ml / g according to various purification steps after the synthesis of MIL-101 (Cr) There have been reported results of ultrasonication using dimethylformamide (DMF) as a solvent to shorten the purification time. However, such a purification process is not only complicated, but also consumes much in terms of time and energy, and therefore, there is a limit to industrially apply it in a large amount.

Therefore, in order to solve such a complicated and costly purification process, a synthesis alternative study to prevent the recrystallization of H ₂ BDC ligand, which is a fundamental problem, is desperately required rather than research and development on the purification process performed after MOF synthesis.

Accordingly, in the present invention, the Cr salt is pulverized and mixed with an organic ligand (H ₂ BDC), and the mixture of chromium salts and organic ligands thus mixed is re-pulverized (secondary pulverization) DGC) can solve the above-described problems, and the present invention has been completed on the basis thereof.

Accordingly, one aspect of the present invention is to provide a method of making a chromium-based metal organic structure having a high BET surface area and a high yield without requiring a separate purification process.

According to another aspect of the present invention, there is provided a method of manufacturing a chromium-based metal organic structure, comprising: grinding a chromium salt to obtain a chromium salt milled product; Mixing the chromium salt mill with an organic ligand to obtain a chromium salt-organic ligand mixture; And re-grinding the chromium salt-organic ligand mixture to obtain a chromium salt-organic ligand pulverized product.

In one embodiment of the present invention, the method may further comprise heating the crushed salt of chromium salt-organic ligand in an autoclave to obtain a chromium salt-organic ligand compound.

In another embodiment of the present invention, the method may further comprise cooling the chromium salt-organic ligand compound and washing it with deionized water.

In another embodiment of the present invention, the method may further comprise drying the washed chromium salt-organic ligand compound.

In another embodiment of the present invention, the chromium salt crushed material may have an average diameter of 40 to 60 mu m.

In another embodiment of the present invention, the average diameter of the organic ligands of the Cr salt-organic ligand may be 4 to 6 탆.

In still another embodiment of the present invention, the step of mixing the Cr salt with the organic ligand to obtain the Cr salt-organic ligand mixture comprises reacting the Cr salt with the organic ligand in a molar ratio of 1: 1 to 1: 1.2 It can be mixed.

In another embodiment of the present invention, the organic ligand may be 1,4-benzenedicarboxylic acid.

In another embodiment of the present invention, the chromium-based metal organic structure may have a BET surface area of 4100 to 5900 m 2 / g.

In another embodiment of the present invention, the autoclave may include water (H ₂ O) and hydrofluoric acid (HF) solutions.

In another embodiment of the present invention, heating the crushed salt of the chromium salt-organic ligand in the autoclave is carried out by placing the crushed salt of the chromium salt-organic ligand on the Teflon support provided in the autoclave and having a plurality of through- And may be performed.

In another embodiment of the present invention, the heating may be performed at 215 to 225 ° C for 11 to 13 hours.

In another embodiment of the present invention, the heating may be performed at 220 DEG C for 12 hours.

The method for producing a chromium-based metal organic structure according to the present invention uses a dry gel conversion method in which a chromium salt and an organic ligand are placed in an autoclave and a high-temperature steam is contacted, unlike a conventional hydrothermal synthesis method, The organic ligand is permeated into the chromium salt by minimizing the contact between the organic ligand and the water vapor through the process of mixing the crushed chromium salt pulverized material with the organic ligand to re-pulverize the resulting chromium salt-organic ligand mixture, , It is possible to maximize the BET surface area of the chromium-based metal organic structure to be produced and to increase the production yield of the chromium-based metal organic structure with high purity at the same time. It has excellent advantages.

In addition, the present invention has the advantage that a high purity chromium-based metal organic structure can be mass produced and applied on an industrial scale by drastically reducing the complex purification process required in the existing hydrothermal synthesis method.

Figure 1 shows the structure of the metal organic structure MIL-101.
FIGS. 2 and 3 schematically illustrate a method for producing a chromium-based metal organic structure MIL-101 by a DGC synthesis method according to an embodiment of the present invention.
FIG. 4 shows weight changes of DGC-MIL-101, which is a chromium-based metal organic structure produced according to the present invention, and HTS-MIL-101, which is a metal organic structure produced by a conventional synthesis method, according to temperature changes.
5 (a) is an SEM photograph of HTS-MIL-101, which is a metal organic structure produced by a conventional hydrothermal synthesis method, and needle-shaped impurities can be identified. 5 (b) and 5 (c) are SEM photographs of DGC-MIL-101, a chromium-based metal organic structure produced by the process according to the present invention, respectively. The molar ratios of the chromium salt and the organic ligand H ₂ BDC ((B) Cr: H ₂ BDC = 1: 1, (c) Cr: H ₂ BDC = 1: 1.2).
FIG. 6 shows a photograph of the reactor used in the production process of the present invention. FIG. 6 (b) shows the reaction after the reaction was carried out at 220 ° C. for 12 hours before the reaction.
FIG. 7 is a graph showing an XRD analysis pattern of the substrates used in the MIL-101 synthesis, wherein (a) is a micronized H ₂ BDC, (b) is a micronized chromium salt (Cr (NO ₃ ) ₃ .9H ₂ O) (c) is obtained by pulverizing chromium salt and H ₂ BDC in a single process, (d) crushing chromium salt firstly, mixing with H ₂ BDC and then pulverizing the mixture again, and (e) (d) is rehydrated by exposure to excess water for 10 minutes, and (f) is a sample exposed to water vapor for 24 hours ((a) and (d) Strength was reduced by 70%).
8 is an SEM photograph before and after pulverizing H ₂ BDC.
9 is a graph showing IR spectra before and after pulverizing H ₂ BDC.
10 shows XRD patterns (A) and IR spectra (B) of HTS-MIL-101 and DGC-MIL-101 before and after purification.
11 is an XRD pattern (A) and an SEM photograph (B) of DGC-MIL-101 according to the amount of hydrofluoric acid (HF) used in the production method according to the present invention.

Before describing the invention in more detail, it is to be understood that the words or words used in the specification and claims are not to be construed in a conventional or dictionary sense, It should be interpreted as meaning and concept consistent with the technical idea of the present invention. Therefore, the constitution of the embodiments described in the present specification is merely a preferred example of the present invention, and does not represent all the technical ideas of the present invention, so that various equivalents and variations And the like.

Hereinafter, preferred embodiments of the present invention will be described in detail so that those skilled in the art can easily carry out the present invention. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail.

The present invention relates to a process for the production of chromium-based metal organic structures (MOFs), and in particular has excellent water stability, thermal and chemical stability, a wide BET surface area (3900 to 4300 m 2 / g) and a large cell volume ³ ) terephthalate based MOF material (hereinafter also referred to as "chromium-based metal organic structure" Such a metal organic structure is specifically referred to as MIL-101 (Materials of Institute Lavoisier 101).

MIL-101 (Cr) is a transition metal, and chromium (Cr (Ⅲ)) metal and terephthalic acid is 1,4-benzene dicarboxylic acid (1,4-benzenedicarboxylic acid) to the starting materials for synthesis, Cr ₃ (F / OH ) - (H ₂ O) ₂ O [(O ₂ C) -C ₆ H ₄ - (CO ₂ )] ₃ n H ₂ O (n is an integer of 1 to 25).

Fig. 1 shows a schematic three-dimensional structure of this MIL-101. That is, as shown in FIG. 1, a trivalent chromium ion trimer having an octahedral structure forms a corner, and six terephthalate anions are connected in both directions to form a supertetrahedron (ST) building Thereby forming a building unit. These STs are three-dimensionally bonded to form a zeolite MTN structure and are composed of two mesoporous cages of 29 to 34 angstroms connected via two micropore windows ranging from 12 to 16 angstroms. ).

In addition, the MIL-101 (Cr) material has a stable structure and it is possible to carry noble metal (Pd, Pt, Au, etc.) nanoparticles in the structure and a large amount of unsaturated coordination Cr (Ⅲ) ㏖ / g), and it is one of the MOF materials which are most attracted attention as heterogeneous catalysts and supports, showing various functional groups introduced with various electrons and showing excellent activity and selectivity in various catalytic reactions.

The present inventors have newly developed a method for producing MIL-101 having a high BET (Brunauer, Emmett, and Teller) surface area at a high purity and a high yield without a complicated purification process, unlike the conventional hydrothermal synthesis (HTS) .

This manufacturing method is basically based on a dry-gel conversion (DGC) synthesis method and a two-stage grinding process.

In 1990 DGC synthesis method was first reported by a team of Prof. Xu as a new synthesis method of zeolite. This synthesis method has been studied in the synthesis of zeolite with new composition and structure as a method of synthesizing zeolite by contacting amorphous aluminosilicate gel with high temperature and high pressure steam.

In recent years, ZIF-8 and MIL-100 (Fe) have been prepared by applying DGC synthesis method to MOF. This synthesis method can reduce the synthesis time and is evaluated as an environmentally friendly synthesis method.

The present inventors have combined the DGC synthesis method with a synthetic precursor pulverizing process to limit the recrystallization of H ₂ BDC generated in a large amount of water due to water contact under high temperature and high pressure conditions, (Cr) having a high specific surface area and reproducibility of 90% or more.

FIGS. 2 and 3 schematically illustrate a method for preparing MIL-101, a chromium-based metal organic structure, by DGC synthesis according to an embodiment of the present invention. That is, the left upper end of FIG. 2 represents an autoclave reactor in which water and a solution of HF are contained in the bottom, and a plate-shaped support is placed in the autoclave. The support is made of polytetrafluoroethylene (PTFE), that is, Teflon. The support is in the form of a plate having a plurality of through holes. The support has a plurality of through holes having a thickness of about 5 mm and a diameter of about 1 mm Respectively. These through holes serve as passages for water vapor present in the autoclave, as described below. On the other hand, the volume-pressure graph shown in the upper right corner of FIG. 2 shows that there is a liquid-vapor two phase region in which water existing in the autoclave exists at the same time.

The method for producing a chromium-based metal organic structure MIL-101 according to an embodiment of the present invention comprises the steps of: crushing a chromium salt to obtain a chromium salt milled product; Mixing the chromium salt mill with an organic ligand to obtain a chromium salt-organic ligand mixture; And grinding the chromium salt-organic ligand mixture to obtain a chromium salt-organic ligand mill, wherein the chromium salt-organic ligand mill is further heated in an autoclave to obtain a chromium salt-organic ligand compound step; And cooling and cleaning the chromium salt-organic ligand compound with deionized water.

Unlike the conventional MIL-101 hydrothermal synthesis method and simple dry gel conversion method, the production method according to the present invention is characterized in that after crushing the chromium salt which is the precursor of MIL-101, the crushed chromium salt forms the structure of MIL-101 And then the mixture of the mixed chromium salt and the organic ligand is pulverized again.

That is, the existing hydrothermal synthesis method involves a simple mixing process of chromium, an organic ligand, a hydrofluoric acid solution and water. When the organic ligand is in direct contact with water, recrystallization is promoted so that the organic ligand is impurities And a very complicated purification process was required to remove these impurities. Further, even if the purification process is carried out, there is a problem that the BET surface area is low and the yield is not high.

However, in the dry gel conversion method according to the present invention, the high-temperature and high-pressure steam is brought into contact with the chromium-organic ligand mixture, the crushed chromium salt and the organic ligand are mixed, The residue of impurities formed by recrystallization of the organic ligand can be minimized. That is, when the organic ligand mixed with the crushed chromium salt (about 50 탆 in diameter) is pulverized again and the diameter of the organic ligand becomes about 5 탆, the crushed organic ligand penetrates into the chromium salt The direct contact with water vapor is blocked and thus the organic ligand reacts with the chromium salt before recrystallization by moisture and eventually produces a high purity chromium-based metal organic structure with low impurity content. Also, since the recrystallized organic ligand is easily removed even by washing with water for 2 to 3 times, the purity of the finally produced chromium-based metal organic structure becomes very high, and accordingly the production yield is increased accordingly.

The chromium salt of the present invention may be selected from a variety of trivalent chromium salts such as chromium nitrate and chromium phosphate. However, the present inventors used chromium niobate hydrate (Cr (NO ₃ ) ₃ .9H ₂ O).

In the present invention, an autoclave is used to produce MIL-101. In the bottom of the autoclave, a 47% diluted HF solution and a small amount of water are contained, and a Teflon support is placed in the autoclave. The chromium salt-organic ligand mixed powder is placed on the Teflon support, and the autoclave is operated for a predetermined time to synthesize the metal organic structure. The Teflon substrate supports the synthesis of metal organic structures under high temperature and pressure conditions, and has strong corrosion resistance under strong acid conditions. Particularly, as described above, a plurality of through holes are formed in the Teflon support to help moisture contained in the bottom of the autoclave evaporate to reach the chromium salt and the organic ligand.

Meanwhile, the metal organic structure washed by the above-mentioned method can be used in various fields by drying at 80 ° C for about 12 hours by using a vacuum dryer.

The particle size of the chromium salt milled product is suitably about 40 to 60 탆 in average diameter. This particle size can be obtained by milling at 20 Hz for about 30 minutes using MM200, a ball milling device from Retsch.

Further, the organic ligands of the Cr salt-organic ligand pulverized product are pulverized until the average diameter becomes about 4 to 6 탆. Such a particle size can be obtained by pulverizing at 20 Hz for about 15 minutes using the ball mill apparatus.

On the other hand, the mixing ratio of the chromium salt milled product and the organic ligand is suitably about 1: 1 in the mixing molar ratio used in the conventional synthesis of MIL-101. When the mixing molar ratio of the chromium salt ground product and the organic ligand exceeds 1: 1.2, there is a problem that the residual amount of the recrystallized H ₂ BDC increases.

The organic ligand used in the present invention is generally 1,4-benzenedicarboxylic acid (H ₂ BDC), which is an organic ligand used in the synthesis of MIL-101.

On the other hand, hydrofluoric acid (HF) and water (H ₂ O) are required to produce MIL-101 in addition to chromium salts and organic ligands. The hydrofluoric acid solution uses a commercially available 47% dilution solution, and the hydrofluoric acid acts as a useful mineralizing agent for increasing the crystallinity and promoting the growth of crystals in the MIL-101 synthesis. That is, DGC-MIL-101 prepared without HF exhibits lower crystallinity and pore volume (BET surface area of 2910 m 2 / g) compared to DGC-MIL-101 prepared using HF. As the amount of hydrofluoric acid used increases, the particle size of DGC-MIL-101 steadily increases and crystallinity also tends to improve (FIG. 11). This is also the same result in hydrothermal synthesis.

Heating in the autoclave is carried out at 215 to 225 ° C for 11 to 13 hours. If the synthesis temperature is lower than 215 ° C, sufficient synthesis can not be performed. If the synthesis temperature is higher than 225 ° C, the structure of MIL-101 may collapse. The inventors of the present invention have found that it is appropriate to perform synthesis by heating for 12 hours at 220 DEG C by various experiments.

Upon such heating, MIL-101 particles with dark green and weakly aggregate are obtained.

Since the thus-synthesized chromium-based metal organic structure contains some impurities, it is recovered and washed with distilled water 2-3 times and dried.

The MIL-101 produced through this process is substantially free of recrystallized H ₂ BDC impurities.

The H ₂ BDC is required to produce MIL-101. However, when a general hydrothermal synthesis method is used, H ₂ BDC is recrystallized and is present in the form of a needle-like impurity in the MIL-101 structure. Conventionally, these impurities have been removed through several purification steps. However, in the case of using the DGC synthesis method as in the embodiment of the present invention, the H ₂ BDC impurities are almost completely removed even by a simple two to three washings.

The chromium-based metal organic structure MIL-101 produced by such a production method has a BET surface area of about 4100 to 5900 m 2 / g.

In addition, the yield calculated by comparing the chromium present in the precursor chromium and the chromium present in the produced MIL-101 is close to 90%.

FIG. 4 shows the weight change of DGC-MIL-101, which is a chromium-based metal organic structure produced according to the present invention, and HTS-MIL-101, a metal organic structure produced by a conventional hydrothermal synthesis method. As a result, DGC-MIL-101 showed a rapid weight loss change in the temperature range of 250 to 300 ° C., while HTS-MIL-101 showed 250 to 500 ° C. The weight decreases gradually over a wider temperature range. This is because, when MIL-101 is synthesized by hydrothermal synthesis, a recrystallized needle-like H ₂ BDC ligand exists as an impurity both inside and outside the pores of MIL-101.

FIG. 5 is an electron micrograph of DGC-MIL-101, a chromium-based metal organic structure prepared according to the present invention, and HTS-MIL-101, a metal organic structure prepared by a conventional synthesis method. Referring to FIG. 5, it can be confirmed that needle-shaped H ₂ BDC impurity (dotted line) exists in MIL-101 synthesized by hydrothermal synthesis (upper photograph). However, in the case of MIL-101 prepared according to the present invention (bottom photograph), it is observed that no such H ₂ BDC impurity is present at all. 5 (a) is an SEM photograph of HTS-MIL-101, which is a metal organic structure produced by a conventional hydrothermal synthesis method, and needle-like impurities can be identified. 5 (b) and 5 (c) are SEM photographs of DGC-MIL-101, a chromium-based metal organic structure produced by the process according to the present invention, respectively. The molar ratios of the chromium salt and the organic ligand H ₂ BDC ((B) Cr: H ₂ BDC = 1: 1, (c) Cr: H ₂ BDC = 1: 1.2).

FIG. 6 shows photographs of the reactor used in the production process of the present invention. FIG. 6 (a) shows the photographs after the reaction was carried out at 220 ° C. for 12 hours before the reaction.

FIG. 7 is a graph showing an XRD analysis pattern of the substrates used in the MIL-101 synthesis, wherein (a) is a micronized H ₂ BDC, (b) is a micronized chromium salt (Cr (NO ₃ ) ₃ .9H ₂ O) (c) is obtained by pulverizing chromium salt and H ₂ BDC in a single process, (d) crushing chromium salt firstly, mixing with H ₂ BDC and then pulverizing the mixture again, and (e) (d) was exposed to water vapor for 24 hours (in the case of (a) and (d) above, the sample (d) was rehydrated by being exposed to excess water for 10 minutes, XRD intensity reduced by 70%).

8 is an SEM photograph before and after pulverizing H ₂ BDC. Referring to FIG. 8, it can be seen that when H ₂ BDC is pulverized, much more amount of Cr ₂ O ₃ penetrates into the chromium salt than before pulverization. 9 is a graph showing IR spectra before and after pulverizing H ₂ BDC. 10 shows XRD patterns (A) and IR spectra (B) of HTS-MIL-101 and DGC-MIL-101 before and after purification.

11 is an XRD pattern (A) and an SEM photograph (B) of DGC-MIL-101 according to the amount of hydrofluoric acid (HF) used in the production method according to the present invention. Referring to FIG. 11, it can be seen that the crystallinity of MIL-101 produced is improved as the amount of hydrofluoric acid increases.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. However, the scope of the present invention is not limited to the following examples.

Examples 1 to 4 and Comparative Examples 1 to 17 use a dry gel conversion method, and Comparative Example 18 uses a hydrothermal synthesis method.

Example 1

200 g of chromium nitrate was crushed finely at 20 Hz for 30 minutes using a ball mill apparatus (Rertsch MM200). The mixture of the crushed chromium nitrate and 1,4-benzenedicarboxylic acid in a molar ratio of 1: 1 was pulverized for 15 minutes using the ball mill, Was placed on a Teflon support in a 30 ml autoclave reactor and 6.25 ml of water and 1.0 ml of a 47% HF solution were added to the bottom of the reactor and synthesized at 220 ° C for 12 hours. After the synthesis, the product was separated, washed twice with distilled water and dried in an oven at 80 ° C for 12 hours to prepare a DGC-MIL-101 metal organic structure.

Example 2

The DGC-MIL-101 metal organic structure was prepared under the same conditions as in Example 1 except that the synthesis time was changed to 14 hours.

Example 3

A DGC-MIL-101 metal organic structure was prepared under the same conditions as in Example 1, and the amount of water present in the autoclave was changed to 3.0 ml.

Example 4

A DGC-MIL-101 metal organic structure was prepared under the same conditions as in Example 1, and the amount of water present in the autoclave was changed to 10.0 ml.

Comparative Examples 1 to 9 and 12 to 17

The DGC-MIL-101 metal organic structure was prepared in a manner similar to that of Example 1, by varying the synthesis conditions as shown in Table 1 below.

Comparative Example 10

140 g of a mixture of finely divided chromium nitrate and 1,4-benzenedicarboxylic acid in a molar ratio of 1: 1 was placed on a Teflon substrate in a 30 ml autoclave reactor, 6.25 ml of water and 1.0 ml of a 47% hydrofluoric acid (HF) solution were added thereto and synthesized at 220 占 폚 for 12 hours. After the synthesis, the product was separated, washed twice with distilled water and dried in an oven at 80 ° C for 12 hours to prepare a DGC-MIL-101 metal organic structure.

Comparative Example 11

A mixture of chromium nitrate and 1,4-benzenedicarboxylic acid in a molar ratio of 1: 1 is pulverized through a single pulverization process, and then 140 g of the pulverized mixture is pulverized into 30 ml of autoclave The solution was placed on a Teflon support in a Klebri reactor and 6.25 ml of water and 1.0 ml of a 47% HF solution were added to the bottom of the reactor and synthesized at 220 ° C for 12 hours. After the synthesis, the product was isolated and washed twice with distilled water and dried at 80 < 0 > C.

Comparative Example 18-hydrothermal synthesis

1.6 g of Chromium (III) nitrate nonahydrate, 0.64 g of H ₂ BDC, 0.02 g of HF (47%, aq.) And 19.2 ml of water (H ₂ O) were mixed with stirring. The thus-blended mixture was placed on a Teflon support in an autoclave and then heated in a convection oven at a temperature of 220 DEG C for 8 hours. After the hydrothermal reaction was carried out in this manner, the mixture was maintained at 150 ° C for 1 hour and then naturally cooled to room temperature. Through this process, the synthesized material (green solid) was filtered using a 100 μm sieve to remove the crystallized H ₂ BDC, and then the MIL-101 product was separated using a 25 μm filter paper. Subsequently, the MIL-101 product thus separated was washed with 1) water (H ₂ O) 2 to 3 times, 2) immersed in water at 70 ° C for 12 hours, 3) 4) immersing in 0.03M NH ₄ F aqueous solution for 12 hours at 60 ° C, 5) immersion in water at 60 ° C for 12 hours and 6) vacuum drying at 150 ° C for 12 hours .

Table 1 below shows the BET surface area, pore volume, yield and the like of MIL-10 prepared through Examples 1 to 4 and Comparative Examples 1 to 17.

Examples /
Comparative Example
Synthesis condition S _BET
(M < 2 > / g)
S _Langmuir
(M < 2 > / g) V _Pore
(Cm3 / g)
yield
(%)
HF
(Mg) H ₂ O
(Ml)
time
(h) Temperature
(° C) Comparative Example 1 - 6.25 12 220 2910 4356 1.89 78 Comparative Example 2 One 6.25 1/6 220 - - - - Comparative Example 3 One 6.25 1/3 220 - - - - Comparative Example 4 One 6.25 1/2 220 915 1286 0.69 21 Comparative Example 5 One 6.25 One 220 1865 2869 1.64 43 Comparative Example 6 One 6.25 2 220 2249 3460 1.85 64 Comparative Example 7 One 6.25 4 220 2690 4120 1.88 71 Comparative Example 8 One 6.25 8 220 3302 4620 2.15 80 Comparative Example 9 One 6.25 10 220 4130 5808 2.76 86 Comparative Example 10 One 6.25 12 * 220 3492 4758 2.21 64 Comparative Example 11 One 6.25 12 ** 220 3724 5148 2.51 78 Example 1 One 6.25 12 220 4164 5850 2.77 90 Example 2 One 6.25 14 220 4075 5720 2.68 88 Comparative Example 12 One 0 12 220 - - - - Example 3 One 3.0 12 220 4138 5833 2.77 89 Example 4 One 10.0 12 220 4149 5846 2.77 89 Comparative Example 13 One 6.25 12 200 3488 4875 2.18 80 Comparative Example 14 One 6.25 12 240 4033 5630 2.42 88 Comparative Example 15 2 6.25 12 220 4087 5727 2.69 85 Comparative Example 16 4 6.25 12 220 3880 5428 2.41 83 Comparative Example 17 8 6.25 12 220 3150 4410 2.11 81

<Reference> S _BET : BET surface area, S _Langmuir : _Langmuir surface area, V _Pore : Total pore volume, Yield: Calculated as the ratio of Cr of MIL-101 prepared for Cr used in the manufacture of MIL-101, HF: 47 % Aqueous solution, *: when using finely divided chromium salt and H ₂ BDC, **: when using chromium salt and H ₂ BDC as a single process.

Referring to Table 1, it can be seen that MIL-101 is not synthesized at all in the absence of water in the autoclave (Comparative Example 12).

On the other hand, as a result of carrying out the synthesis while changing the amount of water in the autoclave, the BET specific surface area of MIL-101 did not change much (Examples 3 and 4).

The amount of water was fixed to 6.25 ml and the temperature was changed from 220 to 240 캜, and the amount of hydrofluoric acid (HF) was changed to 1 to 8 mg. (Example 1 and Comparative Examples 13 and 14). As a result, it was found that the synthesis conditions of MIL-101 (Cr) having the best physical properties were 6.25 ml of water, 1 mg of 47% of hydrofluoric acid, and a synthesis temperature of 220 캜 (Example 1).

In addition, it was confirmed that the MIL-101 synthesized under the above conditions was simply washed with water to produce a chromium-based metal organic structure having a high BET specific surface area with high yield in a reproducible manner.

On the other hand, such experimental results are believed to reflect the limited recrystallization of MIL-101 by limited contact with water vapor during DGC synthesis.

When the chromium salt and H ₂ BDC were simultaneously pulverized in one step, the BET specific surface area was 3724 m 2 / g and the yield was 78% (Comparative Example 11).

When the temperature of the autoclave was increased from 200 to 220 캜, the BET surface area increased from 3488 to 4164 m 2 / g, and the yield increased from 80 to 90% (Comparative Example 13 and Example 1). However, when the autoclave temperature was raised again to 240 ° C, no increase was observed in terms of BET surface area or yield (Comparative Example 14).

On the other hand, when MIL-101 was synthesized by hydrothermal synthesis using Cr salt, it was confirmed that H ₂ BDC impurities were produced in the same manner as the conventional synthesis method. Therefore, H ₂ BDC impurities Can be removed.

On the other hand, MIL-101 synthesized by hydrothermal synthesis method according to Comparative Example 18 and synthesized by the dry gel conversion method of the synthesis of the present invention were purified through various steps such as filtering, water washing and ethanol washing, The results of surface area measurements are shown in Table 2 below.

Purification step BET surface area (m 2 / g) HTS-MIL-101 DGC-MIL-101 One DF + H ₂ O cleaning 1924 4164 2 H ₂ O (70 ° C, 12 hours) 2168 4171 3 EtOH (80 &lt; 0 &gt; C, 24 h) 2534 4188 4 _{0.03M NH 4 F (60 ℃,} 12 hours) 3268 4194 5 H2O (60 DEG C, 12 hours) 3482 4198

<Reference> DF: Double filtration using a 100 μm sieve and 25 μm filter paper

As shown in Table 2, in the case of MIL-101 (HTS-MIL-101) synthesized by the hydrothermal synthesis method, the BET surface area was very low as 1924 (m 2 / g) after double filtration (DF) , It can be seen that the BET surface area gradually increases during several purification steps.

However, in the case of MIL-101 (DGC-MIL-101) synthesized by the dry gel conversion method according to the present invention, it was confirmed that the BET surface area was very high at 4164 (m 2 / g) by double filtration (DF) , Which is much higher than the BET surface area value of 3482 (m &lt; 2 &gt; / g) after purification of HTS-MIL-101 through a five step purification process.

That is, it can be interpreted that MIL-101 is directly synthesized by the dry gel conversion method according to the present invention, and that a very high BET surface area can be obtained by simple water washing.

Claims (8)

Pulverizing a chromium salt to obtain a chromium salt pulverized product;
Mixing the chromium salt mill with an organic ligand 1,4-benzenedicarboxylic acid to obtain a chromium salt-organic ligand mixture;
Re-grinding the chromium salt-organic ligand mixture to obtain a chromium salt-organic ligand pulverization product; And
Heating the crushed salt of chromium salt-organic ligand in an autoclave containing water (H ₂ O) and hydrofluoric acid (HF) solution to obtain a chromium salt-organic ligand compound,
The heating of the chromium salt-organic ligand pulverizer in the autoclave is carried out by placing the chromium salt-organic ligand pulverizer on the Teflon support provided in the autoclave and having a plurality of through-holes formed therein,
A method of making a chromium-based metal organic structure having a BET surface area of 4100 to 5900 m &lt; 2 &gt; / g. The method according to claim 1,
The method further comprises cooling the chromium salt-organic ligand compound and washing with deionized water. The method of claim 2,
The method further comprises drying the washed chromium salt-organic ligand composite. The method according to claim 1,
Wherein the chromium salt milled product has an average diameter of 40 to 60 占 퐉. The method according to claim 1,
Wherein the average diameter of the organic ligands of the chromium salt-organic ligand mill is 4 to 6 占 퐉. The method according to claim 1,
The step of mixing the Cr salt with the organic ligand to obtain a chromium salt-organic ligand mixture comprises mixing the Cr salt with the organic ligand in a molar ratio of 1: 1 to 1: 1.2, &Lt; / RTI &gt; The method according to claim 1,
Wherein the heating is carried out at 215 to 225 DEG C for 11 to 13 hours. The method of claim 7,
Wherein the heating is performed at 220 &lt; 0 &gt; C for 12 hours.

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