Metal organic framework material as well as preparation method and application thereof in methane adsorption

Abstract

The invention discloses two metal organic framework materials Zr-TTB-1 and Zr-TTB-2, a preparation method of the two metal organic framework materials, and an application of the two metal organic framework materials in methane adsorption. The preparation method comprises the following steps: firstly, synthesizing an organic ligand TTB containing a five-membered thiophene ring by taking 1, 3, 5-tri (thiophene-2-yl) benzene as a raw material under specific and appropriate conditions, and then preparing two stable metal organic framework materials from the organic ligand TTB and Zr6 metal clusters under specific and appropriate conditions. The synthesis and preparation method is simple in route, easy to operate, low in cost and suitable for efficient methane adsorption and storage.

Description

Technical Field

[0001] The invention relates to the field of new materials, and in particular to two metal organic framework materials and preparation methods thereof and applications in methane adsorption. Background Art

[0002] In recent decades, the excessive use of traditional fossil fuels has led to a sharp increase in carbon dioxide emissions in the atmosphere, and people are constantly looking for sustainable, low-carbon energy.

[0003] Natural gas (NG), which mainly consists of methane, is considered a key transition fuel for achieving carbon neutrality goals due to its wide availability, low cost and low carbon-to-hydrogen ratio.

[0004] The traditional compressed natural gas (CNG) method requires a multi-stage compressor to charge high-pressure natural gas, as well as a thick tank wall that can withstand high tank pressure. In addition, this method also has a high risk of explosion. Liquefied natural gas (LNG) is currently a more common commercial method, with relatively simple storage conditions and a higher safety factor, but the problem of evaporating gas needs to be solved urgently. The adsorbed natural gas (ANG) method has attracted much attention due to its advantages such as simple operation and ease of use. However, when adsorbing a large amount of natural gas, ANG usually requires a long buffer time to cool down.

[0005] Recently, the coupling of LNG regasification and ANG buffering process, referred to as LNG-ANG coupled system, has been considered as a promising alternative to solve the above problems. Through the coupling process, on the one hand, the adsorbent can adsorb the gasified natural gas in the LNG process for reuse; on the other hand, the adsorption heat generated by the ANG process can be transferred to the LNG regasification process to achieve efficient natural gas storage at low temperature. Undoubtedly, the design and use of excellent adsorbents are crucial in the entire coupled system.

[0006] Metal-organic frameworks (MOFs) are porous framework materials composed of metal ions or clusters and organic ligands. MOFs have the characteristics of high porosity, high specific surface area and easily controllable pore structure, and have attracted more and more attention from researchers as gas adsorbents.

[0007] Chen Banglin and Yaghi's research group reported a series of MOF materials based on structural design and regulation for the adsorption and storage of methane, such as the classic USTA-110 and MOF-905 (Adv. Mater. 2018, 30, 1704792; J. Am. Chem. Soc. 2016, 138, 10244).

[0008] However, the regulation of methane adsorption performance based on LNG-ANG (liquefied natural gas-adsorbed natural gas combined system) has rarely been reported.

[0009] In addition, zirconium-based metal organic frameworks are one of the most widely studied MOF-based adsorbents due to their high chemical and mechanical stability, and have high skeleton density, making them an ideal volumetric methane adsorption material. However, the structural design and regulation of zirconium-based MOFs for methane adsorption have been rarely reported.

[0010] Therefore, designing and regulating the LNG-ANG-related methane adsorption performance of Zr-based metal-organic frameworks has important practical significance. Summary of the invention

[0011] In view of the above technical problems and the shortcomings in the art, the present invention provides two metal organic framework materials and preparation methods thereof and applications in methane adsorption. The two metal organic framework materials have novel structures, simple synthesis, excellent properties, different porosities and specific surface areas, among which Zr-TTB-2 has excellent volumetric methane working capacity.

[0012] The specific technical solutions are as follows:

[0013] [1] The metal organic framework material Zr-TTB-1 is formed by substitutional coordination between the organic ligand TTB and the Zr6 metal cluster;

[0014] The organic ligand has the chemical structure shown below:

[0015]

[0016] The Zr6 metal cluster has the chemical structure shown below:

[0017]

[0018] The single crystal structure data of the metal organic framework material Zr-TTB-1 is as follows:

[0019]

[0020] [2] The metal organic framework material Zr-TTB-2 is formed by substitutional coordination between the organic ligand TTB and the Zr6 metal cluster;

[0021] The organic ligand has the chemical structure shown below:

[0022]

[0023] The Zr6 metal cluster has the chemical structure shown below:

[0024]

[0025] The single crystal structure data of the metal organic framework material Zr-TTB-2 is as follows:

[0026]

[0027] The two metal organic framework materials of the present invention are formed by substitution and coordination connection between organic ligand TTB and Zr6 metal clusters. The formation process can be seen in Figure 1 In the process of substitution coordination, the organic ligand forms a coordination connection with the Zr6 metal cluster by using its carboxyl group to replace OCO in the Zr6 metal cluster with the same structure.

[0028] In the present invention, the metal organic framework material Zr-TTB-1 is a microporous material, and the metal organic framework material Zr-TTB-2 is a mesoporous material.

[0029] [3] A method for preparing a metal organic framework material, comprising the steps of:

[0030] (1) Under anhydrous and oxygen-free conditions, 1,3,5-tri(thiophen-2-yl)benzene is added to tetrahydrofuran, butyl lithium is added at -75 to -80°C, carbon dioxide gas is introduced at -75 to -80°C and stirred for a period of time after sufficient mixing and reaction at -80°C to room temperature, and then the reaction is quenched with hydrochloric acid, extracted with dichloromethane, and the obtained organic phase is washed with saturated brine, dried over anhydrous sodium sulfate, and the organic solvent is spin-dried to obtain an organic ligand TTB having the following chemical structure:

[0031]

[0032] (2) adding the organic ligand TTB and ZrOCl2 to the mixed solution I or the mixed solution II to carry out a solvothermal reaction to obtain the metal organic framework material Zr-TTB-1 described in [1] or the metal organic framework material Zr-TTB-2 described in [2];

[0033] The mixed solution I is a mixed solution of DMF (N,N-dimethylformamide) and HOAc (acetic acid);

[0034] The mixed solution II is a mixed solution of DMF and TFA (trifluoroacetic acid).

[0035] The present invention first designs and synthesizes a novel organic ligand containing a five-membered sulfur heterocycle, and then synthesizes two stable metal organic framework materials under specific and appropriate conditions. Through interlacing and regulation, the two materials have different porosities, specific surface areas and pore environments. In the LNG-ANG coupling system, Zr-TTB-2 has excellent volumetric methane working capacity and can be used multiple times in cycles.

[0036] In step (1), 1,3,5-tri(thiophen-2-yl)benzene is a material disclosed in the prior art, and has the chemical structure shown below:

[0037]

[0038] Specifically, 1,3,5-tri(thiophene-2-yl)benzene can be obtained through commercial channels or existing technologies. For example, 1,3,5-tri(thiophene-2-yl)benzene can be prepared by referring to the existing technical document Chem. Asian J. 2017, 12, 2202-2206.

[0039] In step (1), 1,3,5-tri(thiophen-2-yl)benzene can be added to tetrahydrofuran at a ratio of 1-2 g:100 mL.

[0040] In step (1), the molar ratio of 1,3,5-tri(thiophen-2-yl)benzene to butyl lithium may be 0.8 to 2:6.

[0041] In step (1), butyl lithium can be added in the form of a solution, wherein the solvent can be n-hexane. Further, the concentration of butyl lithium in the n-hexane solution of butyl lithium can be 2-3M.

[0042] In step (1), the carbon dioxide gas may be introduced in excess. For example, the amount of carbon dioxide gas introduced may be 100 equivalents.

[0043] In step (1), the temperature of the continuous stirring reaction can be -80°C to room temperature.

[0044] In some embodiments, in step (2), the mass ratio of ZrOCl2 to the organic ligand is not less than 2:1.

[0045] In step (2), in the mixed solution I, the volume ratio of DMF to HOAc can be 1:0.4-0.6.

[0046] In step (2), in the mixed solution II, the volume ratio of DMF to TFA can be 1:0.1 to 0.3.

[0047] In step (2), the usage ratio of the organic ligand and DMF may be 30 mg: 2-4 mL;

[0048] In step (2), the temperature of the solvent thermal reaction can be 125 to 135° C., and the time can be 24 to 48 hours.

[0049] In step (2), after the solvothermal reaction is completed, the following post-treatment operation can be performed: the solid product is washed and soaked with DMF and then soaked with acetone, and then vacuum dried to obtain a metal organic framework material. Furthermore, the vacuum drying temperature can be 55-65°C.

[0050] The preparation method provided by the present invention first uses 1,3,5-tri(thiophene-2-yl)benzene as a raw material to synthesize an organic ligand TTB containing a five-membered sulfur heterocycle under specific and appropriate conditions, and then prepares a stable metal organic framework material with a Zr6 metal cluster under specific and appropriate conditions. The synthesis and preparation method of the present invention has a simple route, is easy to operate, and has low cost.

[0051] The two metal organic framework materials of the present invention can efficiently adsorb methane and realize natural gas storage and transportation. The metal organic framework materials of the present invention are preferably activated before being used for methane adsorption, and the activation operation may include vacuum heating the metal organic framework materials at 115-125°C for more than 6 hours.

[0052] Under LNG-ANG conditions, the volumetric methane adsorption capacity of the metal-organic framework Zr-TTB-2 can reach 255 cm 3 (STP)cm -3 , which is more than twice that of its intercalated counterpart Zr-TTB-1 under the same conditions (115 cm 3 (STP)cm -3 ). The different methane adsorption performance of the two materials is attributed to the different porosities and specific surface areas caused by intercalation regulation. In addition, Zr-TTB-2 has excellent performance in multiple cycles, demonstrating its potential in practical applications.

[0053] [4] Use of the metal organic framework material Zr-TTB-1 according to [1] or the metal organic framework material Zr-TTB-2 according to [2] in methane adsorption. Furthermore, the metal organic framework material Zr-TTB-1 or the metal organic framework material Zr-TTB-2 is particularly suitable for a liquefied natural gas-adsorbed natural gas combined system.

[0054] [5] A methane adsorption method, comprising: using the metal organic framework material Zr-TTB-1 described in [1] and / or the metal organic framework material Zr-TTB-2 described in [2] to adsorb methane. Furthermore, the methane adsorption method may use a liquefied natural gas-adsorbed natural gas combined system, and the metal organic framework material Zr-TTB-1 and / or the metal organic framework material Zr-TTB-2 may be loaded in the liquefied natural gas-adsorbed natural gas combined system.

[0055] In the application described in [4] and the methane adsorption method described in [5], the conditions of the liquefied natural gas-adsorbed natural gas combined system can be set as follows: 159K, 6 bar; 298K, 5 bar.

[0056] Compared with the prior art, the present invention has the following beneficial effects:

[0057] 1. The present invention creatively synthesizes a novel organic ligand TTB containing a five-membered thiophene ring.

[0058] 2. The preparation method of the organic ligand containing a five-membered thiophene ring provided by the present invention has a simple route, easy operation, high yield and low cost.

[0059] 3. The preparation method of the metal organic framework material provided by the present invention is simple and suitable for large-scale synthesis. The porosity and specific surface area can be adjusted by a simple acid regulator (acetic acid, trifluoroacetic acid) to obtain a target-oriented metal organic framework.

[0060] 4. The metal organic framework material provided by the present invention has a high volumetric methane working capacity and has high practical application value.

[0061] 5. The metal organic framework material provided by the present invention has a stable structure and crystal form after long-term storage, which is convenient for long-term use. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Figure 1 It is a schematic diagram of the organic ligand TTB of the present invention and the Zr6 metal cluster (Zr6 cluster) forming two metal organic framework materials through substitution coordination connection.

[0063] Figure 2 The powder X-ray diffraction (PXRD) patterns of the two metal organic framework materials in Example 3 and the comparison with the simulated PXRD (Simulated line).

[0064] Figure 3 This is a nitrogen adsorption-desorption curve diagram of the two metal organic framework materials in Example 3.

[0065] Figure 4 This is a comparison chart of the methane adsorption performance of the two metal organic framework materials in Example 3.

[0066] Figure 5 This is a performance diagram of multiple methane adsorption cycles of the metal organic framework material Zr-TTB-2 in Example 3. DETAILED DESCRIPTION

[0067] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0068] Example 1

[0069] Synthesis method of organic ligand TTB:

[0070]

[0071] Weigh 2g of 1,3,5-tri(thiophene-2-yl)benzene in a 250mL flask with a branch, replace the system with a nitrogen atmosphere, introduce 200mL of anhydrous tetrahydrofuran (THF) under anhydrous and oxygen-free conditions, and place it in a low-temperature bath at -78°C. Slowly drop 15mL of butyl lithium n-hexane solution with a butyl lithium concentration of 2.5M. After the addition is completed, stir at -78°C for 30min. Then transfer the system to room temperature and stir for 4h to complete the lithiation reaction, and the system gradually becomes a turbid liquid. Transfer the system to -78°C again, continuously pass carbon dioxide (CO2) gas, turn off the low-temperature refrigeration, and stir overnight. Quench the reaction with 2M hydrochloric acid, extract twice with dichloromethane, combine the organic phases and wash with saturated brine, then dry the organic phase with anhydrous sodium sulfate, spin dry the organic solvent, and obtain the product TTB (2.6g, yield 90%), hydrogen nuclear magnetic results: 1 H NMR (600MHz, DMSO-d6), δ = 8.02 (s, 3H), 7.88 (d, J = 6.0Hz, 3H), 7.79 (d, J = 6.0Hz, 3H).

[0072] Example 2

[0073] Synthesis methods of metal organic framework materials (MOFs):

[0074] Take TTB (40 mg) and ZrOCl2 (80 mg) prepared in Example 1 into a 15 mL Pyrex vial, and then add 4 mL DMF and 2 mL HOAc. After ultrasonication until the solution is clear, place it in a 130°C oven for solvent thermal reaction for 24 hours. After cooling to room temperature, centrifuge to remove the mother liquor and wash twice with new DMF. Then soak it in DMF for two days, replacing new DMF three times during this period, and then soak it in acetone for two days, replacing new acetone three times during this period. Vacuum drying at 60°C to obtain a metal organic framework material, named Zr-TTB-1, with a yield of 90%.

[0075] When the regulator 2mL HOAc is replaced with 0.7mL TFA, the metal organic framework material Zr-TTB-2 can be obtained, and the other processing steps remain unchanged.

[0076] Example 3

[0077] The two MOFs obtained in Example 2 were heated and activated at 120°C in vacuum for 6 h for PXRD testing. Figure 2, which are basically consistent with the peak positions of the simulated PXRD curves (Simulated lines), indicating that the designed MOF was successfully prepared with high phase purity.

[0078] The single crystal structure data of the metal organic framework material Zr-TTB-1 is shown in Table 1.

[0079] Table 1

[0080]

[0081] The single crystal structure data of the metal organic framework material Zr-TTB-2 is shown in Table 2.

[0082] Table 2

[0083]

[0084] The two activated MOFs were used for nitrogen adsorption and desorption tests at 77K. The results are shown in Figure 3 , showing that through intercalation regulation, Zr-TTB-1 is microporous and Zr-TTB-2 is mesoporous.

[0085] The methane adsorption performance results of the two MOFs (Zr-TTB-1 and Zr-TTB-2) are shown in Figure 4 Under LNG-ANG conditions (159K, 6 bar; 298K, 5 bar), the volumetric methane adsorption capacity of the metal organic framework material Zr-TTB-2 is 255 cm 3 (STP)cm -3 , which is more than twice that of its intercalated counterpart Zr-TTB-1 (115 cm 3 (STP)cm -3 ).

[0086] Several methane adsorption experiments were conducted on the metal organic framework material Zr-TTB-2 with good performance. Figure 5 As shown, the methane adsorption capacity remained basically unchanged in three rounds, indicating that Zr-TTB-2 has excellent recyclability.

[0087] In addition, it should be understood that after reading the above description of the present invention, those skilled in the art may make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the claims attached to this application.

Claims

1. Metal-organic framework material Zr-TTB-1, characterized in that: It is formed by substitution coordination connection between organic ligand TTB and Zr6 metal cluster; The organic ligand has the chemical structure shown below: The Zr6 metal cluster has the chemical structure shown below: The single crystal structure data of the metal organic framework material Zr-TTB-1 is as follows:

2. Metal-organic framework material Zr-TTB-2, characterized in that: It is formed by substitution coordination connection between organic ligand TTB and Zr6 metal cluster; The organic ligand has the chemical structure shown below: The Zr6 metal cluster has the chemical structure shown below: The single crystal structure data of the metal organic framework material Zr-TTB-2 is as follows:

3. A method for preparing a metal organic framework material, characterized in that: Includes steps: (1) Under anhydrous and oxygen-free conditions, 1,3,5-tri(thiophen-2-yl)benzene is added to tetrahydrofuran. Butyl lithium was added at -75 to -80°C, and after fully mixing and reacting at -80°C to room temperature, carbon dioxide gas was introduced at -75 to -80°C and the reaction was continued with stirring for a period of time, and then the reaction was quenched with hydrochloric acid, and extracted with dichloromethane. The obtained organic phase was washed with saturated brine, dried over anhydrous sodium sulfate, and the organic solvent was spin-dried to obtain an organic ligand TTB having the following chemical structure: (2) adding the organic ligand TTB and ZrOCl2 to the mixed solution I or the mixed solution II to carry out a solvothermal reaction to obtain the metal organic framework material Zr-TTB-1 according to claim 1 or the metal organic framework material Zr-TTB-2 according to claim 2; The mixed solution I is a mixed solution of DMF and HOAc; The mixed solution II is a mixed solution of DMF and TFA.

4. The preparation method according to claim 3, characterized in that: In step (1): Add 1,3,5-tri(thiophen-2-yl)benzene to tetrahydrofuran at a ratio of 1-2 g:100 mL; The molar ratio of 1,3,5-tri(thiophen-2-yl)benzene to butyl lithium is 0.8 to 2:6; The butyl lithium is added in the form of a solution, wherein the solvent is n-hexane; the concentration of butyl lithium in the n-hexane solution of butyl lithium is 2 to 3 M; Excessive carbon dioxide gas is introduced; The temperature of the continuous stirring reaction is -80°C to room temperature.

5. The preparation method according to claim 3, characterized in that: In step (2): The mass ratio of ZrOCl2 to the organic ligand is not less than 2:1; In the mixed solution I, the volume ratio of DMF to HOAc is 1:0.4-0.6; In the mixed solution II, the volume ratio of DMF to TFA is 1:0.1-0.3; The usage ratio of the organic ligand and DMF is 30 mg: 2-4 mL; The temperature of the solvent thermal reaction is 125-135° C. and the time is 24-48 hours.

6. The preparation method according to claim 3, characterized in that: In step (2), after the solvothermal reaction is completed, the following post-treatment operation is further performed: the solid product is washed with DMF, soaked in acetone, and then vacuum dried to obtain a metal organic framework material; The vacuum drying temperature is 55-65°C.

7. Use of the metal organic framework material Zr-TTB-1 according to claim 1 or the metal organic framework material Zr-TTB-2 according to claim 2 in methane adsorption.

8. The use according to claim 7, characterized in that: The metal organic framework material Zr-TTB-1 or the metal organic framework material Zr-TTB-2 is used in a liquefied natural gas-adsorbed natural gas combined system.

9. A methane adsorption method, characterized in that: include: The metal organic framework material Zr-TTB-1 according to claim 1 and / or the metal organic framework material Zr-TTB-2 according to claim 2 are used to adsorb methane.

10. The methane adsorption method according to claim 9, characterized in that: The methane adsorption method adopts a liquefied natural gas-adsorbed natural gas combined system, and the metal organic framework material Zr-TTB-1 and / or the metal organic framework material Zr-TTB-2 are loaded in the liquefied natural gas-adsorbed natural gas combined system.

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