Metal-organic framework materials, methods of making and use in methane adsorption

Abstract

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

Description

Technical Field

[0001] This invention relates to the field of new materials, specifically to two metal-organic framework materials, their preparation methods, and their applications in methane adsorption. Background Technology

[0002] In recent decades, the overuse of traditional fossil fuels has led to a sharp increase in carbon dioxide emissions into the atmosphere, prompting people to continuously search for sustainable, low-carbon energy sources.

[0003] Natural gas (NG) is primarily composed of methane and is considered a key transitional fuel for achieving carbon neutrality due to its widespread availability, low cost, and low C-H ratio.

[0004] Traditional compressed natural gas (CNG) methods require a multi-stage compressor to fill high-pressure natural gas and a thick tank wall capable of withstanding high pressure. Furthermore, this method carries a high risk of explosion. Liquefied natural gas (LNG) is currently a more common commercial method, with relatively simple storage conditions and a high safety factor, but the problem of evaporated gas needs to be addressed. Adsorbed natural gas (ANG) methods have attracted considerable attention due to their ease of operation and use. However, when adsorbing large amounts of natural gas, ANG typically requires a long buffer time to cool down.

[0005] Recently, the coupling of liquefied natural gas regasification and ANG buffer processes, referred to as the LNG-ANG coupled system, has been considered a promising alternative for solving the aforementioned problems. Through this coupling process, on the one hand, the adsorbent can adsorb the natural gas regasified during the LNG process for reuse; on the other hand, the adsorption heat generated in the ANG process can be transferred to the LNG regasification process, enabling efficient natural gas storage at low temperatures. Undoubtedly, the excellent design and use of the adsorbent 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 possess characteristics such as high porosity, high specific surface area, and easily tunable pore structures, making them increasingly attractive to 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, there are few reports on the regulation of methane adsorption performance based on LNG-ANG (liquefied natural gas-adsorbed natural gas combined system).

[0009] In addition, zirconium-based metal organic frameworks are one of the widely studied MOF-based adsorbents due to high chemical and mechanical stability, and have high framework density, which is an ideal volumetric methane adsorbent. However, there is almost no report on the structure design and regulation of zirconium-based MOFs for methane adsorption.

[0010] Therefore, it is of important practical significance to design and regulate the LNG-ANG related methane adsorption performance of zirconium-based metal organic frameworks. SUMMARY

[0011] In view of the above technical problems and deficiencies in the field, the present application provides two kinds of metal organic framework materials, a preparation method thereof and application thereof in methane adsorption. The two kinds of metal organic framework materials are novel in structure, simple in synthesis, excellent in properties, have different porosities and specific surface areas, and Zr-TTB-2 has excellent volumetric methane working capacity.

[0012] The specific technical solutions are as follows:

[0013] [1] A metal organic framework material Zr-TTB-1 is formed by substitution coordination connection of an organic ligand TTB and a Zr6 metal cluster;

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

[0015]

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

[0017]

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

[0019]

[0020] [2] A metal organic framework material Zr-TTB-2 is formed by substitution coordination connection of an organic ligand TTB and a Zr6 metal cluster;

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

[0022]

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

[0024]

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

[0026]

[0027] Both of the metal organic framework materials of the application are formed by the coordination connection of the organic ligand TTB and Zr6 metal cluster (Zr6 cluster), and the forming process can be referred to Figure 1 . In the coordination process, the organic ligand is connected with the Zr6 metal cluster by the same structure substitution of O-C-O in the Zr6 metal cluster through the carboxyl group.

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

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

[0030] (1) Under the condition of anhydrous and anaerobic, 1,3,5-tris (thiophene-2-yl) benzene is added into tetrahydrofuran, and butyllithium is added at-75 to-80℃, and after fully mixed reaction at-80℃ to room temperature, carbon dioxide gas is introduced at-75 to-80℃ and continuously stirred for a period of time, then the reaction is quenched by hydrochloric acid, and dichloromethane is extracted, the obtained organic phase is washed with saturated brine, dried with anhydrous sodium sulfate, and the organic solvent is rotary evaporated to obtain the organic ligand TTB with the chemical structure as shown below:

[0031]

[0032] (2) The organic ligand TTB and ZrOCl2 are added into mixed solution I or mixed solution II for solvothermal reaction to obtain the metal organic framework material Zr-TTB-1 of [1] or the metal organic framework material Zr-TTB-2 of [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 application 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 suitable conditions, so that the two materials have different porosities, specific surface areas and pore environments through interpenetration control. In the LNG-ANG coupling system, the volumetric methane working capacity of Zr-TTB-2 is excellent, and it has multiple cycle use ability.

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

[0037]

[0038] Specifically, 1,3,5-tris(thiophen-2-yl)benzene can be obtained by commercial means or the prior art, for example, 1,3,5-tris(thiophen-2-yl)benzene can be prepared according to the prior art document Chem. Asian J. 2017, 12, 2202-2206.

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

[0040] In step (1), the molar ratio of 1,3,5-tris(thiophen-2-yl)benzene to butyllithium can be 0.8-2:6.

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

[0042] In step (1), the carbon dioxide gas can be introduced in excess. For example, the amount of carbon dioxide gas introduced can 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 1:0.1-0.3.

[0047] In step (2), the amount ratio of the organic ligand to DMF can be 30 mg: 2-4 mL;

[0048] In step (2), the temperature of the solvothermal reaction can be 125-135°C, and the time can be 24-48 h.

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

[0050] The preparation method provided by the application first synthesizes the organic ligand TTB containing a five-membered sulfur heterocycle from 1,3,5-tris(thiophene-2-yl)benzene under specific and suitable conditions, and then prepares a stable metal-organic framework material from the Zr6 metal cluster under specific and suitable conditions. The synthesis and preparation method route is simple, easy to operate, and low in cost.

[0051] The two metal-organic framework materials can efficiently adsorb methane, realizing natural gas storage and transportation. Preferably, the metal-organic framework material is activated before being used for methane adsorption, and the activation operation can include vacuum heating the metal-organic framework material at 115-125 DEG C for more than 6h.

[0052] Under the LNG-ANG condition, the volume methane adsorption capacity of the metal-organic framework material Zr-TTB-2 can reach 255cm 3 (STP)cm -3 , which is more than twice (115cm 3 (STP)cm -3 ) of its interpenetrated counterpart Zr-TTB-1 under the same condition. The difference in methane adsorption performance of the two materials is due to the different porosities and specific surface areas caused by interpenetration regulation. In addition, Zr-TTB-2 has excellent performance in repeated use, which shows its potential in practical application.

[0053] [4] Application of the metal-organic framework material Zr-TTB-1 of [1] or the metal-organic framework material Zr-TTB-2 of [2] in methane adsorption. Further, 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: adsorbing methane by using the metal-organic framework material Zr-TTB-1 of [1] and / or the metal-organic framework material Zr-TTB-2 of [2]. Further, the methane adsorption method can adopt 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 can be loaded in the liquefied natural gas-adsorbed natural gas combined system.

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

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

[0057] 1. The present application 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 has simple route, easy operation, high yield and low cost.

[0059] 3. The preparation method of the metal organic framework material is simple and suitable for large-scale synthesis. The porosity and specific surface area can be adjusted by a simple acid adjusting agent (acetic acid or trifluoroacetic acid), so that the target-oriented metal organic framework can be obtained.

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

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

[0062] Figure 1 The figure is a schematic diagram of the organic ligand TTB and Zr6 metal cluster (Zr6 cluster) substituted coordination connection to form two kinds of metal organic framework materials.

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

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

[0065] Figure 4 The figure is a comparison diagram of the methane adsorption performance of the two kinds of metal organic framework materials in Example 3.

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

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

[0068] Example 1

[0069] Synthesis of organic ligand TTB:

[0070]

[0071] TTB (2.6 g, yield 90%) was obtained. The hydrogen nuclear magnetic result is as follows: 1 H NMR (600 MHz, DMSO-d6), δ = 8.02 (s, 3H), 7.88 (d, J = 6.0 Hz, 3H), 7.79 (d, J = 6.0 Hz, 3H).

[0072] Example 2

[0073] Synthesis of metal-organic frameworks (MOFs):

[0074] TTB (40 mg) and ZrOCl2(80 mg) obtained in Example 1 were taken in a 15 mL Pyrex vial, and 4 mL DMF and 2 mL HOAc were added. After ultrasonicating until the solution was clear, the solution was placed in an oven at 130 °C for solvothermal reaction for 24 h. After being cooled to room temperature, the mother liquor was removed by centrifugation, and the MOF was washed twice with fresh DMF. Then the MOF was soaked in DMF for two days, during which fresh DMF was replaced three times, and then the MOF was soaked in acetone for two days, during which fresh acetone was replaced three times. The metal-organic framework was obtained by vacuum drying at 60 °C, and was named Zr-TTB-1, with a yield of 90%.

[0075] When the adjusting agent 2 mL HOAc was replaced by 0.7 mL TFA, the metal-organic framework Zr-TTB-2 was obtained, and other processing steps were unchanged.

[0076] Example 3

[0077] The two MOFs obtained in Example 2 were activated by vacuum heating at 120 °C for 6 h for PXRD test, and the results are shown in Figure 2, which are basically consistent with the peak positions of the simulated PXRD curve (Simulated line), indicating that the designed MOFs are successfully prepared and have high phase purity.

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

[0079] Table 1

[0080]

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

[0082] Table 2

[0083]

[0084] The activated two MOFs were used for 77K nitrogen adsorption-desorption test, and the results are shown in Figure 3 , which shows that Zr-TTB-1 is microporous and Zr-TTB-2 is mesoporous through interpenetration regulation.

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

[0086] The metal-organic framework material Zr-TTB-2 with better performance was subjected to multiple methane adsorption experiments, and the results are shown in Figure 5 , which shows that the three-round methane adsorption capacity remains basically unchanged, indicating that Zr-TTB-2 has excellent recycling performance.

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

Claims

1. A metal-organic framework material Zr-TTB-1, characterized in that, It is formed by the substitution coordination linking of the organic ligand TTB with the Zr6 metal cluster; The organic ligand has the following chemical structure: The Zr6 metal clusters have the following chemical structures: The single-crystal structure data of the metal-organic framework material Zr-TTB-1 are shown below: Molecular formula C 60 H 38 O 32 S8Zr6; Molecular weight 2074.70; Temperature 273.15K; Wavelength Crystal system: cubic; Space group: Unit cell parameters α = β = γ = 90°; Unit cell volume Z = 6; density 1.181 g / cm³ 3 Absorption coefficient 0.714 mm -1 F(000) = 6132.0; Crystal size: 0.15 × 0.15 × 0.1 mm 3 Data collection range: 3.138°–58.592°.

2. The metal-organic framework material Zr-TTB-2, characterized in that, It is formed by the substitution coordination linking of the organic ligand TTB with the Zr6 metal cluster; The organic ligand has the following chemical structure: The Zr6 metal clusters have the following chemical structures: The single-crystal structure data of the metal-organic framework material Zr-TTB-2 are shown below: Molecular formula C 56 H 28 O 32 S8Zr6; Molecular weight 2016.58; Temperature 273.15K; Wavelength Crystal system: cubic; Space group: Unit cell parameters α = β = γ = 90°; Unit cell volume Z = 3; density 0.589 g / cm³ 3 ; Absorption coefficient 0.366 mm -1 F(000) = 2964.0; Crystal size: 0.15 × 0.15 × 0.1 mm 3 Data collection range: 1.582°–60.772°.

3. A method for preparing a metal-organic framework material, characterized in that, Including the following steps: (1) Under anhydrous and oxygen-free conditions, 1,3,5-tris(thiophene-2-yl)benzene was added to tetrahydrofuran, and butyllithium was added at -75 to -80°C. After thorough mixing and reaction at -80°C to room temperature, carbon dioxide gas was introduced at -75 to -80°C and the reaction was continuously stirred for a period of time. The reaction was then quenched with hydrochloric acid and extracted with dichloromethane. The resulting organic phase was washed with saturated brine, dried over anhydrous sodium sulfate, and the organic solvent was evaporated to obtain the organic ligand TTB with the following chemical structure: (2) Add the organic ligand TTB and ZrOCl2 to mixed solution I or mixed solution II for a solvothermal reaction to obtain the metal-organic framework material Zr-TTB-1 as described in claim 1 or the metal-organic framework material Zr-TTB-2 as described in claim 2; The mixed solution I is a mixed solution of DMF and HOAc; The mixed solution II is a mixture of DMF and TFA.

4. The preparation method according to claim 3, characterized in that, In step (1): Add 1,3,5-tris(thiophene-2-yl)benzene to tetrahydrofuran at a ratio of 1-2 g: 100 mL. The molar ratio of 1,3,5-tris(thiophen-2-yl)benzene to butyllithium is 0.8 to 2:6; Butyllithium is added in solution form, wherein the solvent is n-hexane; the concentration of butyllithium in the n-hexane solution is 2-3M; Excessive carbon dioxide gas was introduced; The temperature of the continuously stirred reaction is -80℃ 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 to 0.6; In the mixed solution II, the volume ratio of DMF to TFA is 1:0.1 to 0.3; The ratio of the organic ligand to DMF is 30 mg: 2-4 mL; The solvothermal reaction is carried out at a temperature of 125–135°C for a duration of 24–48 h.

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

7. The application 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 application 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 co-processing system.

9. A method for methane adsorption, characterized in that, include: Methane is adsorbed using the metal-organic framework material Zr-TTB-1 as described in claim 1 and / or the metal-organic framework material Zr-TTB-2 as described in claim 2.

10. The methane adsorption method according to claim 9, characterized in that, The methane adsorption method employs a liquefied natural gas-adsorbed natural gas co-processing system, wherein the liquefied natural gas-adsorbed natural gas co-processing system is loaded with the metal-organic framework material Zr-TTB-1 and / or the metal-organic framework material Zr-TTB-2.

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