Microporous metal-organic framework material by fluorine functionalization treatment and preparation method and application thereof

Abstract

The application discloses a microporous metal organic framework material treated by fluorine functionalization, a preparation method and application thereof, and preparation of the microporous metal organic framework material comprises the following steps: dissolving a mixture of a Ni salt and H2 p F2-bdp) in an organic solvent, adding an HCl solution, transferring into a reactor, sealing the reactor, and then transferring into an oven for heating reaction at 100-150 DEG C for 30-60 h; after cooling to room temperature, yellow microcrystalline powder is obtained, and the microporous metal organic framework material [Ni p F2-bdp) is obtained through post-treatment, namely, the preparation is completed. The framework material of the application can be used for separating C2H4 / C2H6 mixed gas due to the adsorption difference of C2H4 and C2H6, and presents adsorption inversion separation characteristics; the separation selectivity of C2H4 is significantly improved through the fluorine functionalization strategy, and the adsorption capacity of C2H4 is large, so the framework material is a solid physical adsorbent with multiple characteristics.

Description

Technical Field

[0001] The present invention relates to the technical field of petrochemical gas separation and purification, and in particular to a microporous metal organic framework material treated by fluorine functionalization, and a preparation method and application thereof. Background Art

[0002] Currently, C2H4 is mainly obtained from the steam cracking of naphtha and ethane (C2H6), and then further purified by repeated low-temperature distillation cycles under harsh conditions. Due to the very similar molecular size and volatility of C2H4 / C2H6, separation of C2H4 / C2H6 is very difficult and is one of the most energy-intensive processes. Generally speaking, the separation of C2H4 / C2H6 mixtures can be achieved by using C2H4-selective or C2H6-selective adsorbents. Compared with the developed C2H4-selective adsorbents, the use of C2H6-selective adsorbents provides a more energy-efficient strategy because it can produce high-purity C2H4 through a single separation process.

[0003] Metal-organic frameworks (MOFs) are a class of crystalline porous materials with a defined composition and structure, formed by the self-assembly of metal nodes and organic ligands. Due to their tunable pore size, high surface area, and ease of functionalization, they are rapidly developing and have become highly promising adsorbent materials for the separation and purification of low-carbon hydrocarbon gases.

[0004] Metal-organic frameworks (MOFs) are an emerging class of customizable porous materials that have been extensively studied as adsorbents for gas separation / purification due to their high structural modularity and rich functionality. To achieve a MOF with C2H6 selectivity, it is necessary to minimize the framework's interaction with C2H4 while maximizing its interaction with C2H6, which is very difficult and challenging. This is because typical functional sites, especially open metal sites, interact more strongly with C2H4 than with C2H6.

[0005] The present invention relates to a microporous MOF, namely [Ni(p-F2-bdp)], which improves the ethylene / ethane reversal separation selectivity through a fluorine functionalization strategy, and is used for the efficient separation of C2H4 / C2H6. Compared with C2H4 molecules, the three exposed aromatic ring surfaces in [Ni(p-F2-bdp)] can form more and stronger CH···π interactions with C2H6 molecules. Under the fluorine functionalization strategy, C2H6 molecules can also form more CH-F hydrogen bonds with F ions, further improving the reversal separation selectivity for C2H4. The present invention not only clearly establishes a rich aromatic ring surface, so that it has a stronger CH···π interaction with the C2H6 molecule, and improves the adsorption reversal separation selectivity of C2H4 / C2H6 through the CH-F hydrogen bonds formed by the fluorine functionalization strategy as a general method for achieving efficient separation of C2H4 / C2H6, but also significantly improves the yield of polymerization-grade C2H4. Considering that there is currently no systematic approach to develop high-performance porous materials for C2H4 / C2H6 separation, this work opens the door to a more rational realization of higher-performance porous materials for this industrially very important gas separation in the future. Summary of the Invention

[0006] In order to overcome the shortcomings of traditional C2H4 / C2H6 separation, the present invention provides a microporous metal-organic framework material treated with fluorine functionalization, a preparation method and application thereof. The microporous metal-organic framework material of the present invention has a large adsorption capacity for ethylene at room temperature and pressure and a high selectivity for C2H4 / C2H6 separation.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] A method for preparing a microporous metal-organic framework material through fluorine functionalization treatment comprises dissolving a mixture of Ni salt and H2(p-F2-bdp) in an organic solvent, adding an HCl solution, and transferring the mixture to a reactor. The reactor is sealed and then transferred to an oven for heating at 100-150°C for reaction for 30-60 hours. After cooling to room temperature, a yellow microcrystalline powder is obtained, which is then post-treated to obtain the microporous metal-organic framework material [Ni(p-F2-bdp)], thereby completing the preparation.

[0009] The organic ligand H2(p-F2-bdp) in the present invention is named 4,4'-(2,5-difluoro-1,4-phenylene)bis(1H-pyrazole) in Chinese and has a CAS number of 2044270-06-4. The bdp in the organic ligand H2(p-F2-bdp) is a group composed of a benzene ring in the middle of the molecular structure of 4,4'-(2,5-difluoro-1,4-phenylene)bis(1H-pyrazole) and two pyrazole groups in the para position. The inorganic metal ion Ni 2+The process of obtaining [Ni(p-F2-bdp)] from H2(p-F2-bdp) and organic ligand H2(p-F2-bdp) in a hydrothermal environment is that the H at the -NH position of the pyrazole group in the ligand H2(p-F2-bdp) is replaced by Ni.

[0010] Further, the Ni salt is nickel nitrate, and the molar ratio of the Ni salt to H2(p-F2-bdp) is 2.5-3.5:1, preferably 2.8-3.0:1.

[0011] Further, the organic solvent is DMF, and the volume of the solvent is 70-90 L / mol based on the amount of substance of H2(p-F2-bdp).

[0012] Further, the molar ratio of the HCl solution to H2(p-F2-bdp) is 0.5-1.0:1, preferably 0.6-0.8:1.

[0013] Further, the temperature of the heating reaction is 110-120 DEG C, and the heating reaction time is 40-50 h.

[0014] Further, the post-treatment is that the reaction solution is filtered, the obtained filter cake is washed with DMF and acetone for several times, and then dried to obtain the metal organic framework material [Ni(p-F2-bdp)].

[0015] Further, the present application recommends that the mixture of Ni(NO3)2·6H2O and H2(p-F2-bdp) is dissolved in DMF and HCl, and then is subjected to ultrasonic treatment before being put into an oven for heating, and the ultrasonic treatment is generally 20-30 min. The present application also recommends that the mixture solution of Ni(NO3)2·6H2O and H2(p-F2-bdp) is constantly stirred during the ultrasonic treatment to prevent insufficient dissolution.

[0016] The present application also provides the application of the microporous metal organic framework material in adsorbing and separating C2H4 / C2H6 in a mixed gas.

[0017] The metal salt for preparing the microporous metal organic framework material of the present application is Ni(NO3)2·6H2O, and the organic ligand is H2(p-F2-bdp), and due to the suitable pore size and fluorinated functional sites, the crystallographically independent Ni 2+ ions are coordinated by four pyrazole groups and four N atoms to form a typical square planar geometry, and the three exposed aromatic ring surfaces can form more and stronger C-H···π interactions with C2H6 molecules. It is worth noting that the Ni 2+ ions are only extended through the pyrazole (pz) groups to form a one-dimensional [Ni(Pz)2] nThe C2H6 molecules are further connected by the bdp linker to construct a three-dimensional neutral open framework with a similar one-dimensional rhombic channel. Under the fluorine functionalization strategy, the C2H6 molecules can further form more CH-F hydrogen bonds with F ions, and the separation selectivity of the reverse separation of C2H4 is further improved. The adsorption difference of the framework material to C2H4 and C2H6 can be used for separating the C2H4 / C2H6 mixed gas, and the adsorption reverse separation characteristic is presented, the separation selectivity to C2H4 is higher, and the adsorption capacity of C2H4 is larger, so the solid physical adsorbent with the two characteristics is relatively excellent.

[0018] Compared with the prior art, the present application has the following beneficial effects:

[0019] (1) The metal-organic framework material of the present application is based on inorganic metal ions Ni 2+ , inorganic anions NO3 - and organic ligands H2(p-F2-bdp) to obtain the microporous metal-organic framework material [Ni(p-F2-bdp)] under a hydrothermal environment. The metal-organic framework material of the present application establishes a rich aromatic ring surface, so that it has a stronger carbon hydrogen···π interaction with the C2H6 molecules. A three-dimensional neutral open framework with a similar one-dimensional rhombic channel is constructed, and the CH-F hydrogen bond formed by the fluorine functionalization strategy improves the adsorption reverse separation selectivity of C2H4 / C2H6, which is a general method for realizing the efficient separation of C2H4 / C2H6, and also significantly improves the yield of polymerization grade C2H4.

[0020] (2) The microporous metal-organic framework material of the present application for improving the reverse separation selectivity of ethylene / ethane by the fluorine functionalization strategy can be used for separating the C2H4 / C2H6 mixed gas due to the adsorption difference of the material to C2H4 and C2H6, and presents the adsorption reverse separation characteristic, the separation selectivity to C2H4 is higher, and the adsorption capacity of C2H4 is larger. The material can be reused after multiple desorption / adsorption, and has great potential in industrial application. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 Fig. 1 is an XRD pattern of the microporous MOF material prepared in Example 1 and a simulated MOF material.

[0022] Figure 2 Fig. 2 is a nitrogen adsorption / desorption isotherm of the microporous MOF material prepared in Example 1 at 77K.

[0023] Figure 3 Fig. 3 is a C2H6 / C2H4 adsorption curve diagram of the microporous MOF material prepared in Example 1.

[0024] Figure 4This is the IAST selectivity diagram of the C2H4 / C2H6 mixed gas of the microporous MOF material prepared in Example 1 at 296K.

[0025] Figure 5 This is the Qst curve of the microporous MOF material prepared in Example 1 for C2H6 / C2H4 gas at 296K. DETAILED DESCRIPTION

[0026] The technical solution of the present invention will be further described in detail below through specific embodiments in conjunction with the accompanying drawings.

[0027] In the present invention, unless otherwise specified, all equipment and raw materials can be purchased from the market or are commonly used in the industry. The methods in the following embodiments, unless otherwise specified, are all conventional methods in the art.

[0028] Example 1

[0029] 0.14 mmol of Ni(NO₃)₂·6H₂O and 0.05 mmol of H₂(p-F₂-bdp) were dispersed by oscillation in 4 mL of N,N-dimethylformamide and 20 μL of 2 M HCl solution (Solution A). Solution A was sonicated for 20 minutes while stirring. Solution A was added to a glass bottle, sealed with a cap, and placed in an oven preheated at 120°C for 60 minutes. The vial was heated at 120°C for 48 hours. After the reaction, a yellow microcrystalline powder was obtained by filtration. The powder was rinsed three times with N,N-dimethylformamide and acetone, and then dried in vacuo at 80°C to obtain a microporous MOF material.

[0030] The purity of the microporous MOF material prepared in Example 1 was first verified by powder X-ray diffraction. The XRD pattern of the microporous MOF material is as follows: Figure 1 As shown, it can be seen that the XRD characterization results of the microporous MOF material are consistent with the simulation.

[0031] The fitting XRD pattern of MOF material is obtained as follows:

[0032] 1) Powder Preparation: 0.14 mmol of Ni(NO₃)₂·6H₂O and 0.05 mmol of H₂(p-F₂-bdp) were dispersed in 4 mL of N,N-dimethylformamide and 20 μL of 2 M HCl solution by oscillation. The resulting mixture was sonicated in an ultrasonicator while stirring for 20 minutes. The mixture was then added to a sealed glass bottle and placed in an oven preheated at 120°C for 60 minutes. The vial was heated at 120°C for 48 hours. After the reaction, the yellow microcrystalline powder was filtered and rinsed three times with N,N-dimethylformamide and acetone. The solvent was then exchanged with N,N-dimethylformamide and acetone at least four times over two days. The microporous MOF material powder was then dried in vacuo at 80°C.

[0033] 2) Fitting XRD pattern of MOF material: The powder obtained in step 1) was subjected to XRD simulation to obtain fitting XRD results.

[0034] Then, the specific surface area of ​​the microporous MOF material prepared in Example 1 was characterized by using N2 adsorption-desorption isotherm at 77K, as shown in FIG. Figure 2 As shown in the figure, under the conditions of 77K and 1 bar, the adsorption capacity of the material for N2 is 431.88 (cm 3 / g STP), the curve is a type I adsorption isotherm, showing the characteristics of microporous materials, and the calculated BET specific surface area is 1196.19 m 2 / g.

[0035] pass Figure 1 and Figure 2 As a result, it can be seen that the microporous MOF material synthesized in Example 1 is [Ni(p-F2-bdp)].

[0036] The gas separation ability of the microporous MOF material of Example 1 was tested. Before the gas adsorption separation ability test, the guest solvent in the skeleton was removed by activation treatment: first, the newly synthesized microporous MOF material product powder sample was subjected to at least 4 solvent exchanges with N,N-dimethylformamide and acetone respectively within two days, and then the temperature was raised to 150°C on a Micromeritics ASAP 2020 instrument at a heating rate of 2°C / min and vacuumed for 24 hours until the exhaust rate was 4 mm Hg / min before measurement.

[0037] The gases used for gas separation capability testing are C2H4 and C2H6, the temperature is 296K, and can be stabilized by a low-temperature thermostat. The test pressure is 0-1 bar. The gases used and their purities include: N2 (>99.999%), He (99.999%), C2H4 (99.99%), and C2H6 (99.99%). The N,N-dimethylformamide used for exchange is HPLC-grade N,N-dimethylformamide produced by Alfa Aesar, and the acetone used for exchange is HPLC-grade acetone produced by Alfa Aesar.

[0038] Gas adsorption test was performed using Micromeritics ASAP 2020 fully automatic adsorption instrument, and the adsorption isotherm obtained was as follows: Figure 3 As shown in the figure, it can be seen that at 296K and 1 bar, the adsorption capacity of ethylene is as high as 107.92 cm 3 / g, and the adsorption capacity for ethane is 136.44 cm 3 / g.

[0039] The pure component isotherm data of C2H4 and C2H6 at 296 K were fitted in Origin according to the dual-site Langmuir-Freundlich isotherm model, and the results are shown in Table 1. Figure 4 According to the IAST calculation, the C2H6 / C2H4 (50 / 50, v / v) IAST selectivity can be as high as 2.04 at 296 K, 1 bar. It can be seen that the MOF material is excellent in both gas adsorption capacity and separation selectivity.

[0040] In order to further explore the size of the interaction force between C2H4 and C2H6 gas molecules, the isosteric heat of adsorption (Q st ) generated by the interaction between the skeleton and the gas molecules was calculated by simulation to explain, as shown in Figure 2. Figure 5 From the figure, it can be seen that the Qst value of the MOF material for C2H6 (23.11 kJ / mol) is higher than that for C2H4 (21.93 kJ / mol) when the coverage is close to zero, which indicates that the affinity of the MOF for C2H6 is stronger than that for C2H4, further proving that the material has excellent C2H4 / C2H6 separation selectivity.

[0041] Example 2

[0042] Example 2 Preparation of microporous MOF material Repeat Example 1, the only difference is that "the reaction temperature is replaced by 100℃, that is, the mixed solution is heated at 100℃ for 48h", the rest is the same, finally the microporous MOF material is prepared. The MOF material prepared in Example 2 is characterized by XRD, and the XRD curve is consistent with the simulation, but at 296K, 1bar, the adsorption capacity of ethane is only 102cm 3 / g, and the adsorption capacity of ethylene is only 87cm 3 / g.

[0043] The adsorption performance of the microporous MOF material of Example 2 is not ideal, and the reason is that the decrease of temperature will reduce the coordination of nickel ions with organic ligands, and then affect the material performance.

[0044] Example 3 (the ratio of ligand to salt is different from Example 1)

[0045] Example 3 Preparation of microporous MOF material Repeat Example 1, the only difference is that "the amount of Ni(NO3)2·6H2O is replaced by 0.1mmol", the rest is the same, finally the microporous MOF material is prepared. The MOF material prepared in Example 3 is characterized by XRD, and the XRD curve has many impurity peaks around 30°, which shows that the microporous MOF material of Example 3 is not pure, and the possible reason is that the ligand and the salt do not react completely.

[0046] Comparative Example 1

[0047] Comparative Example 1 Preparation of Microporous MOF Material Example 1 was repeated, with the only difference being that "4 mL of N,N-dimethylformamide was replaced by 4 mL of deionized water" and the other conditions remained unchanged. Finally, a yellow-green product was obtained by filtration and drying. XRD testing showed that the desired material was not synthesized. Analysis showed that the reason might be that nickel ions could not coordinate with the ligands in the environment of deionized water and HCl.

[0048] Comparative Example 2

[0049] Comparative Example 2 The preparation of microporous MOF material was repeated in Example 1, with the only difference being that "Ni(NO3)2·6H2O" was replaced with an equal molar amount of "Zn(NO3)2·6H2O". XRD characterization of the product of Comparative Example 2 revealed the presence of impurity peaks, which was considered to be because the atomic radius of zinc was larger than that of nickel atoms and could not coordinate to form MOF.

[0050] Comparative Example 3

[0051] Comparative Example 3 Preparation of Microporous MOF Material Example 1 was repeated, with the only difference being that "4 mL N,N-dimethylformamide" was replaced with "4 mL". The other conditions remained unchanged. The product was filtered, washed, dried, and characterized. XRD characterization of the product showed many impurity peaks and insufficient purity, which may be due to the poor coordination of the ligand and nickel ions in the acetonitrile and HCl system.

[0052] Comparative Example 4

[0053] Comparative Example 4 Preparation of Microporous MOF Material Example 1 was repeated, with the only difference being that "Ni(NO3)2·6H2O" was replaced with an equal molar amount of "NiCl2·6H2O" and the other conditions remained unchanged, and finally a MOF material was obtained.

[0054] The XRD curve of the MOF material in Comparative Example 4 is consistent with the simulation, but the adsorption capacity of ethane and ethylene at 296K and 1 bar is too low, which is 77 cm 3 / g and 66cm 3 / g. The reason may be that the presence of chloride ions hinders the coordination of nickel atoms and ligands, and the hydrogen bond force is reduced, so the absorbed ethylene is greatly reduced.

[0055] Comparative Example 5

[0056] Comparative Example 5 Preparation of Microporous MOF Material Example 1 was repeated, except that the "H2(p-F2-bdp)" ligand was replaced with an equal molar amount of 4,4'-(1,4-phenyl)bis(4H-1,2,4-triazole), the CAS number of which is 681004-60-4, and the other conditions remained unchanged, to finally obtain a MOF material.

[0057] The XRD curve of the MOF material in comparative example 5 is consistent with the simulation, but the adsorption capacity of ethane and ethylene at 296K and 1 bar is too low, which is 50 cm 3 / g and 34cm 3 / g, the reason may be that the structure of the btz ligand is too long, and the prepared MOF material is not conducive to the formation of a certain adsorption channel.

[0058] Comparative Example 6

[0059] Comparative Example 6 Preparation of Microporous MOF Material Repeat Example 1, the only difference is that "Ni(NO3)2·6H2O" is replaced by an equal molar amount of "Ca(NO3)2·4H2O", and the other conditions remain unchanged, and finally a MOF material is obtained.

[0060] XRD characterization of the MOF material product in Comparative Example 6 showed that there were many impurity peaks and the purity was insufficient. It was considered that Ca was not properly coordinated with the ligand.

[0061] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent transformation made to the above embodiment based on the technical essence of the present invention still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for preparing a microporous metal organic framework material by fluorine functionalization treatment, characterized in that Ni salt and H2( p -F2-bdp) mixture was dissolved in an organic solvent, HCl solution was added, and the mixture was transferred to a reactor. The reactor was sealed and then transferred to an oven for heating at 100-150°C for 30-60h. After cooling to room temperature, a yellow microcrystalline powder was obtained, which was post-treated to obtain the microporous metal organic framework material [Ni( p -F2-bdp)], the preparation is completed; the H2 ( p -F2-bdp) is 4,4'-(2,5-difluoro-1,4-phenylene)bis(1H-pyrazole); The Ni salt is nickel nitrate, and the Ni salt is mixed with H2( p -F2-bdp) has a molar ratio of 2.5-3.5:1; The organic solvent is DMF.

2. The method for preparing a microporous metal organic framework material by fluorine functionalization treatment according to claim 1, characterized in that Ni salt and H2( p -F2-bdp) in an amount ratio of 2.8-3.0:

1.

3. The method for preparing a microporous metal organic framework material by fluorine functionalization treatment according to claim 1, characterized in that The volume of the organic solvent is expressed as H2( p -F2-bdp) was calculated to be 70-90 L / mol.

4. The method for preparing a microporous metal organic framework material by fluorine functionalization treatment according to claim 1, characterized in that HCl solution and H2( p -F2-bdp) is 0.5-1.0:

1.

5. The method for preparing a microporous metal organic framework material by fluorine functionalization treatment according to claim 4, characterized in that HCl solution and H2( p -F2-bdp) is 0.6-0.8:

1.

6. The method for preparing a microporous metal organic framework material by fluorine functionalization treatment according to claim 1, characterized in that The temperature of the heating reaction is 110-120° C., and the heating reaction time is 40-50 hours.

7. The method for preparing a microporous metal organic framework material by fluorine functionalization treatment according to claim 1, characterized in that The post-treatment is as follows: filtering the reaction solution, washing the obtained filter cake with DMF and acetone for several times, and drying to obtain the metal organic framework material [Ni( p -F2-bdp)].

8. A microporous metal-organic framework material prepared by the method according to any one of claims 1 to 7.

9. Use of the microporous metal organic framework material according to claim 8 in adsorption inversion separation of C2H4 / C2H6 mixed gas.

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