Organic ligand, metal organic framework material, preparation method of metal organic framework material and application of metal organic framework material in aspect of adsorbing natural gas

Abstract

The invention relates to the technical field of natural gas adsorption, in particular to an organic ligand, a metal organic framework material, a preparation method of the metal organic framework material and application of the metal organic framework material in natural gas adsorption. The organic ligand has a structural formula as shown in a formula (I): # imgabs0 # (I). The organic framework material disclosed by the invention has good chemical stability and can be recycled for a long time; and compared with most of common adsorption materials in the market, such as activated carbon, the natural gas adsorption performance is more excellent. Meanwhile, the synthesis conditions are mild, the cost is low, and certain commercial application potential is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of natural gas adsorption, and in particular to an organic ligand, a metal organic framework material and a preparation method thereof, and an application thereof in adsorbing natural gas. Background Art

[0002] Natural gas has a very high carbon-to-hydrogen ratio, and its combustion efficiency is generally higher than that of traditional fossil fuels such as oil and coal. In addition, the byproducts of natural gas combustion are water and carbon dioxide, which is a clean fuel that is good for the environment. At present, there are three main ways to store natural gas: liquefied natural gas, compressed natural gas and adsorbed natural gas. Among them, liquefied natural gas is liquefied by ultra-low temperature. This method requires a lot of energy to maintain a low temperature environment and has the risk of leakage. Compressed natural gas is compressed at a pressure of more than 80 to 100 bar. This technology has high requirements for the pressure resistance and safety performance of the container. The above two methods require a lot of energy, are complicated to operate and have safety hazards. The above problems limit the transportation and use of natural gas. Adsorbed natural gas is to use adsorbents to adsorb and store natural gas under normal temperature and low pressure (30 to 80 bar). Traditional adsorbents include molecular sieves and activated carbon. The adsorption capacity of molecular sieves for natural gas is 100cm 3 / cm 3 This is far below the U.S. Department of Energy's requirements for the development of adsorbents; and the pore structure and pore size of activated carbon are difficult to adjust, so the development of materials with high adsorption capacity for natural gas has important significance and development prospects for energy utilization.

[0003] Metal-organic framework materials (MOFs) are crystalline materials with high specific surface area and regular pores, which are assembled by metal ions or metal clusters and organic ligands connected by coordination bonds. They can have an infinitely repeated network structure on a three-dimensional scale. The structure of MOFs and the size and shape of the pores can be changed by adjusting the structure of organic ligands and the diversity of metal ions. The surface of the pores can also be further modified to regulate the physical and chemical properties of MOFs. These regulated MOFs can be used in the fields of gas storage and separation, drug delivery, catalysis, etc. Methane, the main component of natural gas, has a strong interaction with the internal surface of the pores of MOFs. At present, a considerable number of MOFs materials have been used for the adsorption and storage of natural gas, but the adsorption capacity of natural gas by MOFs materials disclosed in the prior art still has room for further improvement. Therefore, it is of great significance to synthesize MOFs with higher natural gas adsorption capacity. Summary of the invention

[0004] In order to solve the above problems in the prior art, the present invention provides an organic ligand, a metal organic framework material and a preparation method thereof and its application in the adsorption of natural gas. The synthesis conditions of the material are mild and the cost is low. When used as a natural gas adsorbent, it has the advantages of high adsorption and long life.

[0005] Based on this, the present invention has the following technical solutions:

[0006] In a first aspect, the present invention provides an organic ligand of a metal organic framework material, wherein the organic ligand has a structural formula (I):

[0007]

[0008] In a second aspect, the present invention provides a method for preparing an organic ligand of the metal organic framework material, comprising:

[0009] S1: Mix 2,6-dibromoazulene, 3.5-dimethoxycarbonylphenylboronic acid, a catalyst, a first solvent and a weak base under a nitrogen atmosphere to obtain a first mixed solution, and subject the first mixed solution to a coupling reaction at 95 to 105° C.; after the reaction, purify to obtain an ester derivative of azulene.

[0010] In the present invention, the structural formula of the ester derivative of azulene is

[0011]

[0012] Preferably, the first solvent comprises a mixture of 1,4-dioxane and water.

[0013] S2: The ester derivative of azulene obtained in S1, the second solvent and a strong base are mixed to obtain a second mixed solution, and the second mixed solution is subjected to a hydrolysis reaction at 95 to 105°C.

[0014] Preferably, the second solvent comprises a mixture of 1,4-dioxane, ethanol and water.

[0015] Preferably, the catalyst comprises tetrakis(triphenylphosphine)palladium; more preferably, based on the molar amount of bromine in 2,6-dibromoazulene, the amount of the catalyst is 3 to 8 mol%.

[0016] Preferably, the method for preparing the organic ligand of the metal organic framework material comprises:

[0017] S1: Add 2,6-dibromoazulene and 3,5-dimethoxycarbonylphenylboronic acid to a mixed solution of 1,4-dioxane and water, then add tetrakis(triphenylphosphine)palladium under a nitrogen atmosphere, and then add a weak base, and carry out a coupling reaction at 95-105° C. for more than 12 hours; after the reaction, dilute the reaction solution with water, extract with dichloromethane, wash the obtained organic layer with water, dry with anhydrous sodium sulfate, and purify by column chromatography to obtain an ester derivative of azulene;

[0018] S2: adding the ester derivative of azulene obtained in S1 to a mixed solvent of dioxane, ethanol and water, and then adding a strong base, and performing a hydrolysis reaction at 95-105°C for 15-20 hours; after the reaction, removing all solvents, dissolving the product in water again, and adjusting the pH value to 2-3, filtering, washing and drying the precipitated solid in turn, and the obtained solid is the organic ligand.

[0019] Preferably, in S1, the molar ratio of 2,6-dibromoazulene to 3,5-dimethoxycarbonylphenylboronic acid is 1:(2-2.5); and / or the volume ratio of 1,4-dioxane to water is (3.5-4.5):1.

[0020] Preferably, in S2, the volume ratio of dioxane, ethanol and water is (1-2):(1-2):(1-2).

[0021] In the present invention, the weak base that can be used in S1 includes one or more of potassium carbonate, potassium phosphate, potassium acetate, cesium carbonate and sodium carbonate, and the added amount is at least 3 times the molar amount of bromine element in 2,6-dibromoazulene.

[0022] The strong base that can be used in S2 includes potassium hydroxide and / or sodium hydroxide, etc., and the ester is hydrolyzed by adding the strong base; the amount of the strong base added is 8 to 12 times the molar amount of the bromine element in 2,6-dibromoazulene.

[0023] In a third aspect, the present invention provides a metal organic framework material (hereinafter also referred to as "Azu-MOF"), which is a three-dimensional crystalline porous material assembled by the organic ligands and copper ions through coordination bonds.

[0024] Preferably, the metal organic framework material has a topological structure of (4,4)-connected NbO configuration.

[0025] More preferably, in the metal-organic framework material, two adjacent copper ions are bridged by four carboxyl groups, and each copper ion is coordinated with a water molecule to form a paddle-shaped secondary structural unit, and the secondary structural unit is constructed by bridging organic ligands to obtain a three-dimensional periodic network structure; the molecular formula of the secondary structural unit is Cu2(COO)4(H2O)2.

[0026] Preferably, there are two types of cage-like cavities in the structure of the metal organic framework material: one is a cavity with a diameter of The spherical cavity on the left and right is composed of 6 secondary structural units and 12 ligands; the other is an olive-shaped cavity with a size of It is composed of 12 secondary structural units and 6 ligands.

[0027] In a fourth aspect, the present invention provides a method for preparing the metal organic framework material, comprising:

[0028] S3: The organic ligand, copper nitrate trihydrate and N,N-dimethylformamide are mixed, and then a mixture of 1,4-dioxane and water is added, and an acid is added as a regulator to obtain a third mixed solution; the third mixed solution is kept sealed at 70-80° C. for 1-2 days.

[0029] In the present invention, dioxane is used as a non-polar solvent, water is used as a coordinating small molecule, and together with DMF, the synthesis rate of MOF is regulated to obtain crystals of better quality; acid is used as a regulator to suppress the rate of MOF during the crystallization process, which is helpful to obtain MOF with better crystallinity. The acid used can be concentrated hydrochloric acid and / or nitric acid, etc.; the concentration of nitric acid is 3 to 4M.

[0030] In the specific implementation process, the amount of acid is adjusted according to the amount of N,N-dimethylformamide. Specifically, the amount of N,N-dimethylformamide and the acid is in the following manner: 1 to 2 drops of the acid are added per milliliter of N,N-dimethylformamide.

[0031] Preferably, the mass ratio of the organic ligand to copper nitrate trihydrate is (0.5-1):(1-2).

[0032] Preferably, in S3, the volume ratio of 1,4-dioxane to water is 1:(1.5-2.5).

[0033] S4: After taking out the reaction solution obtained in S3, the supernatant is removed and washed with dry DMF to obtain dark blue crystal particles, which are the metal organic framework material.

[0034] In a fifth aspect, the present invention provides application of the metal organic framework material in adsorbing natural gas.

[0035] At present, patent research related to adsorption gas storage mainly focuses on the development of high-efficiency adsorbents and devices. Conventional room-temperature adsorption gas storage technology mainly focuses on the adsorption storage and application of gas under ambient conditions, which has not yet met the requirements of industrial application. The above-mentioned metal organic framework material and its preparation method and application provided by the present invention have mild synthesis conditions and low cost. When used as a natural gas adsorbent, it has the advantages of high adsorption and long life.

[0036] The specific surface area of ​​the metal organic framework material Azu-MOF for natural gas adsorption of the present invention can reach 2000-2500m 2 / g, and its pore volume is between 0.8 and 1.2 cm 3 / g. The synthesized metal organic framework material has good thermal stability and a simple preparation process. The material has a high room temperature natural gas adsorption capacity, far exceeding the US Department of Energy's target (180cm 3 / cm 3 ), and is easy to desorb.

[0037] At the same time, the methane adsorption of this MOF is much higher than that of coconut shell charcoal, one of the high specific area activated carbons sold on the market. Its volume adsorption capacity under 159K / 8bar is 1.8 times that of coconut shell charcoal.

[0038] Preferably, the method for adsorbing natural gas using the metal organic framework material comprises: activating the metal organic framework material, and then adsorbing natural gas at room temperature and 0 to 80 bar; the activation comprises replacing N,N-dimethylformamide in the metal organic framework material with a third solvent; preferably, the third solvent comprises one or a mixture of low boiling point solvents such as acetone, dichloromethane, methanol, ethanol, chloroform and tetrahydrofuran.

[0039] In the present invention, the organic framework material can be widely used in scenarios such as BOG treatment in LNG receiving stations / satellite stations, natural gas recovery in marginal gas fields, and gas storage in distributed energy systems.

[0040] Based on this, the technical solution of the present invention has the following beneficial effects:

[0041] 1. The organic framework material described in the present invention has good chemical stability and can be recycled for a long time.

[0042] 2. The organic framework material described in the present invention is porous and has better natural gas adsorption performance than most common adsorption materials on the market, such as activated carbon.

[0043] 3. The organic framework material provided by the present invention has mild synthesis conditions, low cost and certain commercial application potential. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0045] Figure 1 It is a characterization diagram of the organic ligand H4L in Example 1 provided by the present invention.

[0046] Figure 2 It is a ball-and-stick model structure diagram of the metal organic framework material Azu-MOF in Example 2 provided by the present invention.

[0047] Figure 3 This is the X-ray powder diffraction result of the metal organic framework material Azu-MOF in Example 2 provided by the present invention.

[0048] Figure 4 It is a nitrogen adsorption curve diagram of the metal organic framework material Azu-MOF in Example 2 provided by the present invention.

[0049] Figure 5 This is the cyclic stability test result of the metal organic framework material Azu-MOF in Example 2 provided by the present invention.

[0050] Figure 6 This is a methane storage test diagram of the metal organic framework material Azu-MOF under LNG-ANG working conditions in Example 2 provided by the present invention.

[0051] Figure 7 This is the adsorption test curve of methane by the metal organic framework material Azu-MOF at 298K in Example 2 provided by the present invention. DETAILED DESCRIPTION

[0052] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0053] Unless otherwise specified, the various raw materials used in the examples and comparative examples are commercially available conventional raw materials, and the technical means used are conventional means well known to those skilled in the art.

[0054] Example 1

[0055] This embodiment provides an organic ligand H4L, and its preparation method comprises the following steps:

[0056] 2,6-dibromoazulene and 3,5-dimethoxycarbonylphenylboronic acid are added in a molar ratio of 1:2.2 to a mixed solution of 1,4-dioxane and water in a volume ratio of 4:1, followed by adding 5 mol% of tetrakis(triphenylphosphine)palladium as a catalyst under a nitrogen atmosphere, and then adding 4 mol equivalents of potassium carbonate, and reacting for at least 12 hours at 95-105 degrees. After the reaction is completed, the reaction solution is diluted with water, extracted with dichloromethane, and the obtained organic layer is washed with water, dried with anhydrous sodium sulfate, and purified by column chromatography to obtain an ester derivative of azulene.

[0057] The obtained product is added to a mixed solvent of dioxane, ethanol and water in a ratio of 1:1:1, and then 10 molar equivalents of potassium hydroxide are added thereto, and the mixture is reacted at 100 degrees for 15 to 20 hours. When the reaction is completed, all solvents are removed and the product is dissolved in water again, and the pH value is adjusted to 2 to 3 by adding hydrochloric acid. The precipitated solid is filtered and washed with distilled water until the filtrate is neutral, and the organic ligand H4L is obtained after the solid is dried.

[0058] Its representation diagram is shown in Figure 1 , hydrogen spectrum data: 1 H NMR(600MHz,DMSO-d6)δ13.47(s,4H),8.76(s,2H),8.54(d,J=10.2Hz,2H), 8.53(s,1H),8.46(s,1H),8.45(s,2H),7.99(s,2H),7.56(d,J=10.2Hz,2H).

[0059] Example 2

[0060] This embodiment provides a metal organic framework material Azu-MOF, and the preparation method thereof comprises the following steps:

[0061] Copper nitrate trihydrate (60 mg) and the organic ligand H4L (30 mg) in Example 1 are added to a 40 mL glass bottle, and N, N-dimethylformamide (10 mL) is added. After ultrasonic dissolution, 5 mL of H2O and 2.5 mL of 1,4-dioxane are added. After mixing evenly, 10 to 20 drops of concentrated hydrochloric acid are added. The glass bottle is sealed and placed in a 75 ° C forced air drying oven for 2 days, taken out and cooled to room temperature. The supernatant is removed and washed with dry DMF to obtain a dark blue crystalline solid, which is the metal organic framework material.

[0062] The obtained blue crystalline solid was characterized by the ball-and-stick model structure. Figure 2The X-ray powder diffraction results are shown in Figure 3 The nitrogen adsorption curve is shown in Figure 4 shown.

[0063] Example 3

[0064] This embodiment provides a metal organic framework material Azu-MOF, and the preparation method thereof includes:

[0065] 2,6-dibromoazulene and 3,5-dimethoxycarbonylphenylboronic acid were added in a molar ratio of 1:2 to a mixed solution of 1,4-dioxane and water in a volume ratio of 4.5:1, followed by adding 8 mol% of tetrakis(triphenylphosphine)palladium as a catalyst under a nitrogen atmosphere, and then adding 3 mol equivalents of potassium phosphate, and reacting at 95-105 degrees for more than 12 hours. After the reaction, the reaction solution was diluted with water, extracted with dichloromethane, and the obtained organic layer was washed with water, dried with anhydrous sodium sulfate, and purified by column chromatography to obtain an ester derivative of azulene.

[0066] The obtained product is added to a mixed solvent of dioxane, ethanol and water in a ratio of 1:1:1, and then 10 molar equivalents of sodium hydroxide are added thereto, and the mixture is reacted at 100 degrees for 15 to 20 hours. When the reaction is completed, all solvents are removed and the product is dissolved in water again, and the pH value is adjusted to 2 to 3 by adding hydrochloric acid. The precipitated solid is filtered and washed with distilled water until the filtrate is neutral, and the organic ligand H4L is obtained after the solid is dried.

[0067] Copper nitrate trihydrate (60 mg) and the organic ligand H4L (40 mg) obtained above were added to a glass bottle, and N,N-dimethylformamide (10 mL) was added. After ultrasonic dissolution, 5 mL of H2O and 3 mL of 1,4-dioxane were added, and 10 to 20 drops of concentrated hydrochloric acid were added after mixing evenly. The glass bottle was sealed and placed in a 75°C forced air drying oven for reaction for 2 days, then taken out and cooled to room temperature. The supernatant was removed and washed with dry DMF to obtain a dark blue crystalline solid, which was the metal organic framework material.

[0068] Experimental example

[0069] The natural gas adsorption performance of the metal organic framework Azu-MOF obtained in Examples 2 to 3 was tested.

[0070] The specific steps include:

[0071] (a) The metal organic framework material synthesized in Example 2 was cleaned with acetone, and then immersed in 5 mL of acetone for three days, and the acetone was replaced every 12 hours. The blue solid with acetone was added to an adsorption tube, the acetone was gradually blown dry with nitrogen, and then dried at 100° C. under vacuum conditions for 6 hours to obtain an activated sample.

[0072] (b) The activated samples were transferred to a high-pressure adsorption instrument to test the adsorption and desorption performance of the metal organic framework for natural gas at room temperature at 159K and 0-10bar and at 298K and 0-80bar. Figures 5 to 7 As shown in the figure, the metal organic framework material synthesized by the present invention has a good adsorption capacity for natural gas at room temperature and 65 bar. The adsorption capacity at 65 bar is 180 cm 3 / cm 3 These results indicate that the metal-organic framework material has certain stability and porosity, and has potential for application in natural gas adsorption and storage.

[0073] At the same time, the experimental results show that the metal organic framework materials prepared in Example 3 and Example 2 have comparable effects on natural gas adsorption and storage.

[0074] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An organic ligand of a metal organic framework material, characterized in that: The organic ligand has a structural formula (I):

2. The method for preparing the organic ligand of the metal organic framework material according to claim 1, characterized in that: include: S1: Mixing 2,6-dibromoazulene, 3.5-dimethoxycarbonylphenylboronic acid, a catalyst, a weak base and a first solvent under a nitrogen atmosphere to obtain a first mixed solution, and subjecting the first mixed solution to a coupling reaction at 95 to 105° C.; after the reaction is completed, purifying to obtain an ester derivative of azulene; Preferably, the first solvent comprises a mixture of 1,4-dioxane and water; S2: mixing the ester derivative of azulene obtained in S1, a second solvent and a strong base to obtain a second mixed solution, and subjecting the second mixed solution to a hydrolysis reaction at 95 to 105° C.; Preferably, the second solvent comprises a mixture of 1,4-dioxane, ethanol and water.

3. The method for preparing an organic ligand of a metal organic framework material according to claim 2, characterized in that: include: S1: Add 2,6-dibromoazulene and 3,5-dimethoxycarbonylphenylboronic acid to a mixed solution of 1,4-dioxane and water, then add tetrakis(triphenylphosphine)palladium under a nitrogen atmosphere, and then add a weak base, and carry out a coupling reaction at 95-105° C. for more than 12 hours; after the reaction, dilute the reaction solution with water, extract with dichloromethane, wash the obtained organic layer with water, dry with anhydrous sodium sulfate, and purify by column chromatography to obtain an ester derivative of azulene; S2: adding the ester derivative of azulene obtained in S1 to a mixed solvent of dioxane, ethanol and water, and then adding a strong base, and performing a hydrolysis reaction at 95-105°C for 15-20 hours; after the reaction, removing all solvents, dissolving the product in water again, and adjusting the pH value to 2-3, filtering, washing and drying the precipitated solid in turn, and the obtained solid is the organic ligand.

4. The method for preparing an organic ligand of a metal organic framework material according to claim 2 or 3, characterized in that: In S1, the molar ratio of 2,6-dibromoazulene to 3,5-dimethoxycarbonylphenylboronic acid is 1:(2-2.5); and / or the volume ratio of 1,4-dioxane to water is (3.5-4.5):1; In S2, the volume ratio of dioxane, ethanol and water is (1-2):(1-2):(1-2).

5. A metal organic framework material, characterized in that: The invention is a three-dimensional crystalline porous material assembled by the organic ligand described in claim 1 and copper ions through coordination bonds.

6. The metal organic framework material according to claim 5, characterized in that: The metal organic framework material has a topological structure of a (4,4) connected NbO configuration; Preferably, in the metal-organic framework material, two adjacent copper ions are bridged by four carboxyl groups, and each copper ion is coordinated with a water molecule to form a paddle-shaped secondary structural unit, and the secondary structural unit is constructed by bridging organic ligands to obtain a three-dimensional periodic network structure; the molecular formula of the secondary structural unit is Cu2(COO)4(H2O)2.

7. The metal organic framework material according to claim 5 or 6, characterized in that: There are two kinds of cage-like cavities in the structure of the metal organic framework material: one is The spherical cavity on the left and right is composed of 6 secondary structural units and 12 ligands; the other is an olive-shaped cavity with a size of It is composed of 12 secondary structural units and 6 ligands.

8. The method for preparing the metal organic framework material according to claim 4 or 5, characterized in that: include: S3: mixing the organic ligand, copper nitrate trihydrate and N,N-dimethylformamide, and then adding a mixture of 1,4-dioxane and water, and adding an acid as a regulator to obtain a third mixed solution; and keeping the third mixed solution sealed at 70 to 80° C. for 1 to 2 days; Preferably, the mass ratio of the organic ligand to copper nitrate trihydrate is (0.5-1): (1-2); S4: After taking out the reaction solution obtained in S3, the supernatant is removed and washed with dry DMF to obtain dark blue crystal particles, which are the metal organic framework material.

9. Use of the metal organic framework material according to any one of claims 5 to 7 in the adsorption of natural gas.

10. The use of the metal organic framework material in the adsorption of natural gas according to claim 9, characterized in that: The method for adsorbing natural gas using the metal organic framework material of claim 9 comprises: activating the metal organic framework material, and then adsorbing natural gas at room temperature and 0 to 80 bar; the activation comprises replacing N,N-dimethylformamide in the metal organic framework material with a third solvent; Preferably, the third solvent includes one or more of acetone, dichloromethane, methanol, ethanol, chloroform and tetrahydrofuran.

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