Metal organic framework material as well as preparation method and application thereof

Abstract

The invention discloses a metal organic framework material as well as a preparation method and application thereof. The metal organic framework material is formed by connecting a secondary building unit Zn4O and a six-connection organic ligand with a structure shown in a formula 1 through a coordinate bond, and the metal organic framework material is of a nia type crystallographic topological structure. The invention designs and synthesizes a novel MOF material which is not interspersed in structure, ultrahigh in specific surface area (up to 10917 m < 2 > / g), ultrahigh in porosity (up to 91.8%) and high in gravimetric methane adsorption capacity, and has good industrial application value.

Description

Technical Field

[0001] This invention relates to a metal-organic framework material. Background Technology

[0002] Metal-Organic Frameworks (MOFs) are crystalline porous materials composed of organic ligands and inorganic building blocks. Their highly tunable pore size, designable pore environment, and ultra-high specific surface area make them promising for applications in energy gas storage (such as methane and hydrogen storage), gas separation, catalysis, and sensing. As a result, the design and synthesis of MOF materials with ultra-high porosity and specific surface area has become a new research hotspot.

[0003] Currently, cutting-edge scientific research mainly focuses on increasing ligand chain length through network synthesis strategies or increasing topological complexity through ligand mixing strategies to effectively increase porosity and specific surface area. However, further fundamental improvements in material properties face two main challenges: First, when achieving a certain theoretical porosity through simple ligand growth, interpenetration occurs during actual synthesis, significantly reducing the actual specific surface area. Second, when using complex, multi-component ligands to construct MOFs, phase separation during synthesis imposes stringent requirements on synthesis conditions, and the introduction of multiple members and nodes reduces structural stability, severely limiting large-scale industrial applications. Existing design strategies cannot simultaneously achieve both stability and high performance.

[0004] Currently, the design of MOFs with ultra-high porosity and specific surface area has reached a bottleneck, and further performance improvements cannot be achieved through existing design strategies. While simple ligand growth can effectively increase the porosity and specific surface area of ​​MOF materials, it can lead to interpenetration of the structure to some extent, thereby reducing the actual specific surface area and stability. Introducing complex, multi-component ligands into MOF construction inevitably results in phase separation and decreased stability during the synthesis process, thus limiting their true industrial application in large-scale mass production. Although significant breakthroughs have been achieved in current MOF materials, there is still room for improvement in the storage performance of energy gases such as methane and hydrogen, requiring new design strategies and technologies to further enhance their performance.

[0005] Therefore, how to design MOF materials with higher porosity, larger specific surface area, and more stability through simple topology selection to achieve higher energy gas storage applications remains an unsolved systemic challenge.

[0006] To address the above issues, there is an urgent need to provide a method for synthesizing and activating metal-organic framework materials based on simple topology, in order to prepare metal-organic framework materials with ultra-high specific surface area and porosity. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to overcome the defects of the prior art, such as the lack of a simple and efficient topology selection strategy, the easy mixing of products due to multiphase synthesis, and the pore blockage and performance degradation caused by structural interpenetration. The present invention provides a method for the synthesis and activation of metal-organic framework materials based on simple topology, which can achieve ultra-high specific surface area and porosity and has high methane storage capacity.

[0008] The present invention solves the above-mentioned technical problems through the following technical solution:

[0009] This invention provides a metal-organic framework material, which is formed by connecting secondary building units Zn4O with six-linked organic ligands of the structure shown in Formula 1 through coordination bonds; the metal-organic framework material has a nia-type crystallographic topology.

[0010] .

[0011] In this invention, the Zn4O secondary building unit has an octahedral geometry, in which four Zn(II) ions are located on the equatorial plane of the octahedron and are connected by μ4-O atoms to form a six-coordinate node.

[0012] In this invention, the six-linked organic ligand is triangular prism-shaped with six-directional linking sites, and each linking site is coordinated with a Zn4O secondary building unit through a carboxylate group.

[0013] In this invention, the Zn4O secondary building blocks and the organic ligands are periodically arranged in three-dimensional space to form a nia-type topological network.

[0014] In this invention, the metal-organic framework material has a three-dimensional hierarchical pore structure, including a rhomboid main channel (3.3) extending along the c-axis. 2 ×3.8 nm 3 ) and cubic octahedral secondary perforated cages distributed on plane ab (2.9 2 ×1.8 nm 3 ).

[0015] In this invention, the specific surface area of ​​the metal-organic framework material is 9000-11000 m². 2 / g, for example 10917 m 2 / g.

[0016] In this invention, the pore volume of the metal-organic framework material is 4.5-5.0 cm³.3 / g, for example 4.57 cm 3 / g.

[0017] In this invention, the porosity of the metal-organic framework material is 82.0-92.0%, for example 91.8%.

[0018] In this invention, the peak positions and corresponding crystal planes of the powder X-ray (synchrotron radiation) diffraction of the metal-organic framework material are: 1.39°, (100) crystal plane; 1.67°, (101) crystal plane; 2.43°, (110) crystal plane.

[0019] In this invention, the single-crystal structure data of the metal-organic framework material obtained by single-crystal X-ray (synchrotron radiation) diffraction are as follows:

[0020] .

[0021] In this invention, the thermogravimetric analysis of the metal-organic framework material shows that it decreases to 90% of its original mass at around 400°C and to 75% of its original mass at around 800°C.

[0022] This invention also provides a method for preparing a metal-organic framework material, comprising the following steps:

[0023] The metal-organic framework material is obtained by heating the compound with the structure shown in Formula 1 and the zinc salt in a polar solvent.

[0024] In this invention, the zinc salt can be hydrated zinc nitrate, such as zinc nitrate tetrahydrate (Zn(NO3)2⋅4H2O) or zinc nitrate hexahydrate (Zn(NO3)2⋅6H2O).

[0025] In this invention, the polar solvent may be an amide solvent, preferably N,N-dimethylformamide (DMF) or N,N-diethylformamide (DEF), such as DMF.

[0026] In this invention, the molar ratio of the compound with the structure shown in Formula 1 to the zinc salt can be 1:(14-18), for example 1:16.

[0027] In this invention, the molar / volume ratio of the zinc salt to the polar solvent can be 1:(20-26), for example 1:23.

[0028] In this invention, the reaction temperature can be 80-90℃, for example 85℃.

[0029] In this invention, the reaction time can be 1-3 days, for example 2 days.

[0030] In this invention, the preparation method of the metal-organic framework material may further include the following post-processing steps: washing, drying, and activation.

[0031] In this invention, the washing process can be gradient washing.

[0032] In this invention, the gradient washing can be performed by washing with different solvents in descending order of polarity, such as DMF, ethyl acetate, acetone, dichloromethane, and n-hexane in sequence.

[0033] In this invention, the amount of each solvent used in the gradient washing can be 10-20 mL, for example, 15 mL.

[0034] In this invention, the gradient washing time can be 3-12 days, for example 10 days.

[0035] In this invention, the gradient washing can be performed 3-7 times per day, for example, 5 times.

[0036] In this invention, the drying process may be supercritical carbon dioxide drying.

[0037] In this invention, the activation can be gas removal under vacuum, for example, gas removal under a vacuum pressure of 15 mTorr.

[0038] In this invention, the activation pressure can be 5-15 mTorr, for example 15 mTorr.

[0039] In this invention, the activation temperature can be 100-120℃, for example, 100℃.

[0040] The present invention also provides metal-organic framework materials prepared by the preparation method of the metal-organic framework materials described above.

[0041] The present invention also provides an application of the metal-organic framework material as described above or the metal-organic framework material prepared by the method described above in gas storage and gas adsorption.

[0042] The present invention also provides the application of metal-organic framework materials as described above or metal-organic framework materials prepared by the preparation method of metal-organic framework materials as described above in the adsorption or storage of methane, hydrogen, nitrogen or argon.

[0043] The significant advantages of this invention are as follows: By selecting the crystallographic topology of Nia, using octahedral Zn₄O secondary building blocks and triangular prism-shaped organic ligands with six-directional connections, this invention designs and synthesizes a structure with non-intersecting components and an ultra-high BET specific surface area (up to 10⁹¹⁷ m²). 2A novel MOF material with high porosity (up to 91.8%) and high gravimetric methane adsorption capacity can effectively overcome the problems of structural interpenetration and phase separation existing in the existing methods, and has high industrial application value.

[0044] This invention precisely resolved the structures of a series of novel MOFs using high-resolution single-crystal X-ray (synchrotron radiation) diffraction and powder X-ray (synchrotron radiation) diffraction techniques. A series of high-surface-area MOF materials were activated using a highly efficient solvent exchange method with polar gradients combined with supercritical carbon dioxide drying technology. Characterization through 77 K nitrogen adsorption isotherm testing confirmed the accessible pores and high specific surface area of ​​the materials. Adsorption tests of methane at 200 bar pressure (achieving a methane adsorption capacity of 0.975 g / g) at various temperatures demonstrated the high gravimetric methane adsorption capacity of the materials. Simulation of the material adsorption process using the giant canonical model Carlo (GCMC) method yielded experimental results, theoretically confirming the material's performance. Attached Figure Description

[0045] Figure 1 This is the crystal structure diagram of MOF-2021.

[0046] Figure 2 This is a schematic diagram of the hole structure and hole dimensions of MOF-2021.

[0047] Figure 3 This is an optical microscope image of MOF-2021.

[0048] Figure 4 Thermogravimetric analysis diagram of MOF-2021. Detailed Implementation

[0049] The present invention will be further illustrated by way of embodiments below, but the present invention is not limited to the scope of the embodiments described herein.

[0050] Synthesis of the six-linked organic ligand H6TTP:

[0051] ,

[0052] Synthesis of 2,3,6,7,14,15-hexabromoanthracene (3)

[0053] Anthracene (2 g, 1.24 g, 4.87 mmol), iron filings (0.0353 g, 1.06 mmol), and anhydrous chloroform (50 mL) were added to a three-necked round-bottom flask. Bromine (1.52 mL, 29.7 mmol) was then added to the flask via syringe. The reaction mixture was then refluxed for 2 hours under nitrogen protection (using a balloon). After cooling the reaction solution to 25 °C, excess bromine was quenched with a saturated sodium thiosulfate aqueous solution, and the organic layer changed from orange to colorless. The organic phase was separated, washed twice with distilled water and once with saturated brine, dried over anhydrous magnesium sulfate, and the solvent was removed by rotary evaporation under reduced pressure. The resulting product was dried under vacuum to obtain an off-white powder (3.15 g, yield 89.0%). The product purity exceeded 90% and could be used without further purification. ¹H NMR (400 MHz, deuterated chloroform) δ 7.62 (s, 6H), 5.23 (s, 2H).

[0054] ,

[0055] The step of synthesizing hexaacetate via palladium-catalyzed coupling reaction

[0056] Compound 3 (0.727 g, 1.0 mmol), Cs₂CO₃ (6.84 g, 21.0 mmol), and boric acid / boronic acid ester (10.0 mmol) were added to a three-necked round-bottom flask and dissolved in anhydrous tetrahydrofuran (80 mL). The reaction mixture was bubbled with nitrogen for 0.5 h, followed by the addition of Pd(PPh₃)₂Cl₂ (0.211 g, 0.3 mmol). The reaction mixture was stirred at 70 °C for 48 h. After the reaction was complete, the solvent was removed under vacuum, and the residue was redissolved in dichloromethane and filtered through diatomaceous earth. The dark brown filtrate was concentrated under vacuum, and the crude product was purified by silica gel column chromatography using a 40:1 dichloromethane / ethyl acetate eluent. The purified product 4 was dried under vacuum overnight at 80 °C.

[0057] The steps for synthesizing hexacarboxylic acid H6TTP via hydrolysis reaction

[0058] In a round-bottom flask connected to a condenser, hexatriester 4 (1.0 mmol), KOH (3.37 g, 60.0 mmol), and a mixed solvent of tetrahydrofuran (75 mL) and methanol (75 mL) were added. The reaction mixture was refluxed at 80 °C for 24 hours. After the reaction was complete, the system was adjusted to acidity with 2 M hydrochloric acid aqueous solution (approximately 40 mL), at which point a white solid precipitated. After removing the organic solvent under vacuum, the aqueous phase was extracted three times with ethyl acetate until no organic product remained in the aqueous phase. The combined ethyl acetate solutions were washed twice with distilled water and once with saturated brine, dried over anhydrous sodium sulfate, and the solvent was removed by rotary evaporation. The final product 1 was dried under vacuum overnight at 85 °C to obtain pure H6TTP. 1 ¹H NMR (400 MHz, deuterated dimethyl sulfoxide) δ 12.99 (s, 6H), 8.00–7.59 (m, 66H), 7.29 (s, 12H), 6.20 (s, 2H).

[0059] Example 1

[0060] The hexagonal linked organic ligand H6TTP (i.e., the compound with the structure shown in Formula 1) (0.056 mmol) and zinc nitrate tetrahydrate (Zn(NO3)2⋅4H2O) (0.880 mmol) were mixed thoroughly in 20 mL of N,N-dimethylformamide (DMF) and ultrasonically dispersed. The mixture was then placed in an oven at 85 °C for 2 days.

[0061] The obtained product was then subjected to optical microscopy, powder X-ray (synchrotron radiation) diffraction, single-crystal X-ray (synchrotron radiation) diffraction, adsorption site analysis, and nuclear magnetic resonance. 1 Characterization was performed using 1H spectroscopy, a nitrogen adsorption isotherm at 77 K, a methane adsorption isotherm at 200 bar, and thermogravimetric analysis.

[0062] Based on the experimental results, the pore size, porosity, pore volume, geometric specific surface area, adsorption curve, and methane storage performance of the material were calculated using computer simulation methods such as pore size analysis (Zeo++ software), grand canonical Monte Carlo (GCMC) (RASPA software), and molecular dynamics MD (CP2K software).

[0063] The obtained product was washed with 15 mL DMF for 2 days, 3 times a day, and then subjected to gradient exchange with ethyl acetate, acetone, dichloromethane, and n-hexane (15 mL of each washing solvent was used for 2 days, 3 times a day). After drying with supercritical carbon dioxide, the gas was removed under a vacuum of 15 mTorr and activated by heating to 100 °C to obtain MOF-2021 material. Its nitrogen adsorption and high-pressure methane storage performance were tested.

[0064] Example 2

[0065] The experimental procedures and dosages are the same as in Example 1, except that DMF is replaced with diethylformamide (DEF).

[0066] Example 3

[0067] The experimental procedure and dosage are the same as in Example 1, except that zinc nitrate tetrahydrate is replaced with zinc nitrate hexahydrate.

[0068] Example 4

[0069] The experimental procedure and dosage are the same as in Example 1, except that the two-day reaction time is replaced with a one-day reaction time.

[0070] Example 5

[0071] The experimental procedure and dosage are the same as in Example 1, except that the reaction temperature of 85°C is replaced with the reaction temperature of 80°C.

[0072] Example 6

[0073] The experimental procedure and dosage are the same as in Example 1, except that gradient washing is replaced with DMF washing, followed by washing with acetone solvent using Soxhlet extraction, which can be completed in just 3 days.

[0074] Testing instruments, testing conditions, and testing results for the materials:

[0075] optical microscope

[0076] Experimental instrument: Zoom stereo microscope from Chongqing Aote Optical Instrument Co., Ltd.

[0077] Experimental conditions: 298 K crystals dispersed in a clean DMF solution.

[0078] Experimental results: see appendix Figure 3 .

[0079] Powder X-ray (synchrotron radiation) diffraction

[0080] Experimental apparatus: Shanghai Synchrotron Radiation Facility BL-14B beamline. Data acquisition was performed using 2θ scan mode with a step size of 0.004°, a scan rate of 8° per minute, and a wavelength of 0.6895 Å.

[0081] Experimental conditions: Tested at 298 K after activation.

[0082] Experimental results: 2θ (°, 0.6895 Å), a = 32.3461(2) Å, b = 32.3461(2) Å, c = 42.8709(2) Å, peak positions and corresponding crystal planes: 1.39°, diffraction intensity 74866, (100) crystal plane; 1.67°, diffraction intensity 37755, (101) crystal plane; 2.43°, diffraction intensity 17383, (110) crystal plane.

[0083] Single-crystal X-ray (synchrotron radiation) diffraction

[0084] Experimental apparatus: BL-10U2 beamline of Shanghai Synchrotron Radiation Facility (wavelength 0.6888 Å).

[0085] Experimental conditions: Raw data were processed using the Bruker APEX3 software package: first, data integration was performed using the SAINT V8.38A program, followed by absorption correction using the SADABS 2016 / 2 program. The crystal structure was resolved using the direct method with the SHELXT-2014 program, and then refined using the full matrix least squares method based on F² with the SHELXL-2014 program. All of the above processes were completed in the Olex2 software package.

[0086] Experimental results: Single-crystal structure data with a resolution of up to 1.03 Å were obtained through precise analysis.

[0087] .

[0088] 77K nitrogen adsorption isotherm:

[0089] Experimental apparatus: 2-station micropore and specific surface area analyzer (Konta, Autosorb IQ2).

[0090] Experimental conditions: The temperature was controlled at 77 K using a liquid nitrogen bath; ultra-high purity (>99.999%) N2 and He gas were stored in a steel cylinder; approximately 30-100 mg of the activated sample was transferred to a glass sample tube for testing in an Ar atmosphere glove box.

[0091] Experimental Results: Multiple nitrogen adsorption isotherms were tested at 77 K, confirming the permanent porosity of the MOF materials in Examples 1-4. The adsorption capacity of the materials in Examples 1-4 was 2860-2960 cm⁻¹ at P / P₀ = 0.99. 3 / g. The MOF materials of Examples 1-4 exhibit Type IV(b) adsorption isotherms characteristic of narrow mesoporous materials. This stepwise adsorption behavior was verified by N2 (77K) adsorption isotherms simulated using the giant canonical Monte Carlo (GCMC) method. Secondary adsorption growth was observed in the MOF materials of Examples 1-4 at P / P0 = 0.23-0.25, which is consistent with experimental results.

[0092] 200 bar high-pressure methane adsorption isotherm:

[0093] Experimental apparatus: High-pressure adsorption isotherm (maximum pressure 200 bar) was measured on Quantachrome's iSorb™ HP1 instrument.

[0094] Experimental conditions: Approximately 0.5-1 g of the activated sample was transferred to a 4.2 mL stainless steel sample tube in an Ar atmosphere glove box for testing.

[0095] Experimental results: The MOF materials in Examples 1-4 achieved a thickness of 1364 cm⁻¹ under conditions of 298 K and 200 bar. 3 STP The total adsorption capacity was 0.975 g / g, with an adsorption heat of 7.3 kJ / mol. The MOF materials in Examples 1-4 reached a molecular weight of 1292 cm⁻¹ under conditions of 298 K and 200-5.8 bar. 3 STP / g of working capacity.

[0096] Thermogravimetric analysis

[0097] Experimental apparatus: TGA instrument (PerkinElmer, TGA 4000).

[0098] Experimental conditions: The temperature was increased from room temperature to 800℃ in an N2 gas flow at a rate of 5℃ / min; equilibrium gas: N2 40.0 mL / min; purge gas: N2 60.0 mL / min.

[0099] Experimental results: The mass decreased to 90% of its original mass at around 400℃ and to 75% of its original mass at around 800℃.

[0100] Specific surface area:

[0101] Based on the BET consistency criterion proposed by Rouquerol et al., the Brunauer-Emmett-Teller specific surface area was calculated from the N2 adsorption isotherm. The reliability of the BET specific surface area was also verified using the "BETSI" software, which calculated it to be 10918 m². 2 / g.

[0102] Pore ​​size distribution analysis: Pore volume was estimated based on the N2 adsorption plateau; pore size distribution was obtained by density functional theory fitting of the N2 adsorption isotherm measured at 77 K. The pore size distribution shows that the structure contains two types of pores with diameters of 20.0 Å and 34.3 Å, respectively.

[0103] While specific embodiments of the present invention have been described above, those skilled in the art should understand that these are merely illustrative examples, and the scope of protection of the present invention is defined by the appended claims. Those skilled in the art can make various changes or modifications to these embodiments without departing from the principles and essence of the present invention, but all such changes and modifications fall within the scope of protection of the present invention.

Claims

1. A metal-organic framework material, characterized in that, The metal-organic framework material is formed by coordination bonds between the secondary building unit Zn4O and a six-linked organic ligand with the structure shown in Equation 1 below. The metal-organic framework material has a Nia-type crystallographic topology. 。 2. The metal-organic framework material as described in claim 1, characterized in that, It satisfies at least one of the following conditions: (1) The secondary building unit Zn4O has a regular octahedral geometry, in which four Zn(II) ions are located on the equatorial plane of the octahedron and are connected by μ4-O atoms to form a six-coordinate node; (2) The six-linked organic ligand is triangular prism-shaped and has six-directional linking sites. Each linking site is coordinated with a Zn4O secondary building unit through a carboxylate group. (3) The secondary building unit Zn4O and the organic ligand are periodically arranged in three-dimensional space to form a nia-type crystallographic topology; (4) The metal-organic framework material has a three-dimensional hierarchical pore structure, preferably including a rhomboid main channel (3.3) extending along the c-axis. 2 ×3.8 nm 3 ) and cubic octahedral secondary perforated cages distributed on plane ab (2.9 2 ×1.8 nm 3 ); (5) The specific surface area of ​​the metal-organic framework material is 9000-11000 m². 2 / g, for example 10917 m 2 / g; (6) The pore volume of the metal-organic framework material is 4.5-5.0 cm³. 3 / g, for example 4.57 cm 3 / g; (7) The porosity of the metal-organic framework material is 82.0-92.0%, for example 91.8%.

3. A method for preparing a metal-organic framework material, characterized in that, It includes the following steps: The metal-organic framework material is obtained by heating the compound with the structure shown in Formula 1 and the zinc salt in a polar solvent.

4. The preparation method according to claim 3, characterized in that, It satisfies at least one of the following conditions: (1) The zinc salt is zinc nitrate hydrate, such as zinc nitrate tetrahydrate or zinc nitrate hexahydrate; (2) The polar solvent is an amide solvent, preferably DMF or DEF, such as DMF; (3) The molar ratio of the compound with the structure shown in Formula 1 to the zinc salt is 1:(14-18), for example 1:16; (4) The molar volume ratio of the zinc salt to the polar solvent is 1:(20-26), for example 1:23; (5) The reaction temperature is 80-90℃, for example 85℃; The reaction time described in (6) is 1-3 days, for example 2 days.

5. The method for preparing the metal-organic framework material as described in claim 3, characterized in that, It also includes the following post-processing steps: washing, drying, and activation.

6. The method for preparing the metal-organic framework material as described in claim 5, characterized in that, It satisfies at least one of the following conditions: (1) The washing process is a gradient washing process; (2) The drying process is performed using supercritical carbon dioxide. (3) The activation is gas removal, for example, gas removal under a vacuum pressure of 15 mTorr; (4) The activation pressure is 12-15 mTorr, for example 15 mTorr; The activation temperature described in (5) is 100-120°C, for example 100°C.

7. The method for preparing the metal-organic framework material as described in claim 6, characterized in that, It satisfies at least one of the following conditions: (1) The gradient washing is the washing of different solvents in descending order of polarity, for example, washing with DMF and acetone in sequence, or washing with DMF, ethyl acetate, acetone, dichloromethane and n-hexane in sequence; (2) The amount of each solvent used in the gradient washing is 10-20 mL, for example 15 mL; (3) The gradient washing time is 3-12 days, for example, 10 days; The gradient washing described in (4) is performed 3-7 times per day, for example, 3 times.

8. A metal-organic framework material, characterized in that, It is prepared by the method for preparing metal-organic framework materials according to claim 6 or 7; preferably, it is prepared according to claim 1 or 2.

9. An application of a metal-organic framework material in gas adsorption and gas storage; wherein the metal-organic framework material is as described in claim 1, 2 or 8.

10. The application as described in claim 9, characterized in that, Application of the metal-organic framework material in the adsorption and storage of methane, hydrogen, nitrogen and argon.

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