Mesoporous metal organic framework material as well as preparation method and application thereof

Abstract

The invention relates to the technical field of metal organic framework materials, and discloses a mesoporous metal organic framework material as well as a preparation method and application thereof. The mesoporous metal organic framework material comprises a compound represented by a formula I [(Tmtp) k (Zn) x (ppc) y] formula I, Tmtp represents 2, 3, 5, 6-tetra (4-pyridyl phenyl) pyrazine, ppc represents a-bivalent deprotonated terephthalic acid series compound, Zn is + bivalent, y is + bivalent, y is + bivalent, y is + bivalent, y is + bivalent, y is + bivalent, y is + bivalent, y is + bivalent, y is + bivalent, y is + bivalent, y is + bivalent, and y is + bivalent. K is 1, x is 2, y is 2, and the structure of the 2, 3, 5, 6-tetra (4-pyridyl phenyl) pyrazine is shown as a formula II. The mesoporous metal organic framework material is large in surface area and adjustable in aperture, and has good adsorption performance on macromolecular alkane # imgabs0 #

Description

Technical Field

[0001] The present invention relates to the technical field of metal-organic framework materials, and particularly relates to a mesoporous metal-organic framework material, a preparation method thereof and an application thereof. Background Art

[0002] Metal-organic framework materials are a class of organic-inorganic hybrid materials with an infinitely expandable three-dimensional network structure formed by the self-assembly coordination of metal ions and organic ligands. Among more than 100,000 MOF crystals, only a very small number have mesoporous (2-50 nm) cages, but most of the MOFs reported so far are microporous (pore diameter less than 2 nm), and the proportion of mesoporous MOFs is less than 1%. Mesoporous metal-organic framework (MOF) materials have a high specific surface area, a relatively large pore diameter (2-50 nm) and structural tunability, and are widely used in the fields of catalyst loading, adsorption, separation, etc.

[0003] Although traditional adsorption materials such as activated carbon and silica gel have mesopores and macropore distributions, their pore structures are disordered and the pores are not connected, which affects the rapid mass transfer and desorption performance during the adsorption process. Metal-organic framework materials have an ordered network structure and are very advantageous in gas adsorption. At present, most microporous metal-organic framework materials are mainly used for the adsorption and storage of small molecules such as methane and carbon dioxide. The micropore diameter limits the adsorption of large molecule VOCs, especially alkanes with more than 4 carbon atoms.

[0004] The synthesis strategy of novel mesoporous metal-organic framework materials is a very urgent and challenging task. At present, the preparation methods of mesoporous metal-organic framework materials mainly include the extended ligand method, the mixed ligand method, the template method, the post-treatment method, etc. However, when the ligand length is extended excessively, the obtained mesoporous material framework is relatively empty and prone to collapse. The template method can prepare mesoporous metal-organic framework materials to a certain extent, but during the process of removing the template agent, the framework structure may be damaged, and the operation steps and difficulty are increased. The post-treatment method is difficult to form regular mesopores and is also difficult to design and control the mesopore size of the material. The mixed ligand method for synthesizing mesoporous metal-organic framework materials is simple to operate, does not require excessive post-treatment, and the material has good stability. However, the mesoporous metal-organic framework materials in the prior art have poor adsorption effect on alkanes. Summary of the Invention

[0005] The purpose of the present invention is to overcome the problems existing in the preparation methods of mesoporous materials such as the extended ligand method, the template method, and the post-treatment method, such as unstable structure and difficult pore size adjustment, and the problem that the mesoporous metal-organic framework materials prepared by the existing mixed ligand method have poor adsorption effect on alkanes, and to provide a mesoporous metal-organic framework material, a preparation method thereof and an application thereof. The mesoporous metal-organic framework material has a large surface area, adjustable pore diameter, and good adsorption performance for large molecule alkanes.

[0006] To achieve the above object, on the one hand, the present invention provides a mesoporous metal-organic framework material, which comprises a compound represented by Formula I,

[0007] [(Tmtp) k (Zn) x (ppc) y Formula I

[0008] Tmtp represents 2,3,5,6-tetrakis(4-pyridylphenyl)pyrazine, ppc represents a -2-valent deprotonated terephthalic acid-based compound, and Zn is +2-valent; k is 1, x is 2, y is 2,

[0009] The structure of the 2,3,5,6-tetrakis(4-pyridylphenyl)pyrazine is shown in Formula II:

[0010]

[0011] Preferably, the unit cell parameters of the mesoporous metal-organic framework material are: a = 21.62, b = 38.48, c = 17.66, α = 90°, β = 111°, γ = 90°, belonging to the monoclinic system, the space group is C2 / m, and there is a two-fold interpenetrating structure in the crystal.

[0012] Preferably, the specific surface area of the mesoporous metal-organic framework material is 400 - 800 m 2 / g, preferably 600 - 800 m 2 / g; the average pore diameter is 3 - 5 nm, preferably 4 - 5 nm.

[0013] Preferably, the terephthalic acid-based compound is selected from one or more of terephthalic acid, 2-hydroxyterephthalic acid, 2-aminoterephthalic acid, 2-methylterephthalic acid, 2-methoxyterephthalic acid, 2-chloroterephthalic acid, 2-bromoterephthalic acid, 2-nitroterephthalic acid, 2-sulfonatoterephthalic acid, 2,5-dihydroxyterephthalic acid, and 2,5-dibromoterephthalic acid.

[0014] On the second aspect, the present invention provides a method for preparing a mesoporous metal-organic framework material, the method comprising: performing a solvothermal reaction on a zinc salt, a terephthalic acid-based compound, 2,3,5,6-tetrakis(4-pyridylphenyl), and an organic solvent, and then activating the reaction product;

[0015] The structure of the 2,3,5,6-tetrakis(4-pyridylphenyl)pyrazine is shown in Formula II:

[0016]

[0017] Preferably, the zinc salt is selected from one or more of zinc nitrate hydrate, zinc acetate hydrate, zinc chloride, and zinc sulfate hydrate.

[0018] Preferably, the terephthalic acid-based compound is selected from one or more of terephthalic acid, 2-hydroxyterephthalic acid, 2-aminoterephthalic acid, 2-methylterephthalic acid, 2-methoxyterephthalic acid, 2-chloroterephthalic acid, 2-bromoterephthalic acid, 2-nitroterephthalic acid, 2-sulfoterephthalic acid, 2,5-dihydroxyterephthalic acid, and 2,5-dibromoterephthalic acid.

[0019] Preferably, the molar ratio of the zinc salt, the terephthalic acid-based compound, and 2,3,5,6-tetrakis(4-pyridylphenyl)pyrazine is 1.5 - 2.5:2:1, preferably 1.8 - 2.2:2:1, with the zinc salt calculated as zinc ions.

[0020] Preferably, the conditions of the solvothermal reaction include: temperature of 90 - 180 °C, preferably 130 - 180 °C; time of 12 - 96 hours, preferably 20 - 60 hours.

[0021] Preferably, the organic solvent is selected from one or more of N,N-dimethylformamide, N,N-dimethylacetamide, N,N-diethylformamide, and dimethyl sulfoxide.

[0022] Preferably, the activation conditions include: temperature of 60 - 100 °C, time of 10 - 20 hours, and pressure of 0 to -0.1 MPa.

[0023] Preferably, the method specifically includes: subjecting the zinc salt, the terephthalic acid-based compound, 2,3,5,6-tetrakis(4-pyridylphenyl), and the organic solvent to a solvothermal reaction, and separating, washing, and activating the crude reaction product.

[0024] The third aspect of the present invention provides a mesoporous metal-organic framework material prepared by the method described above.

[0025] The fourth aspect of the present invention provides an adsorbent, which contains the mesoporous metal-organic framework material described above or the mesoporous metal-organic framework material described above.

[0026] The fifth aspect of the present invention provides a method for adsorbing alkanes, which includes adsorbing alkanes using the mesoporous metal-organic framework material described above or the mesoporous metal-organic framework material described above or the adsorbent described above.

[0027] Preferably, the alkane is an alkane with 4 or more carbon atoms.

[0028] Preferably, the alkane is selected from one or more of n-butane, isobutane, n-pentane, and isopentane.

[0029] Compared with the prior art, the present invention has at least the following advantages:

[0030] The mesoporous metal-organic framework material provided by the present invention belongs to the monoclinic system, with a space group of C2 / m. There is a structure of two-fold interpenetrating and conjugated benzene ring structures in the crystal, the pore size can be controlled to be 4-5 nm, and the surface area is relatively large.

[0031] The present invention prepares the mesoporous metal-organic framework material by the mixed ligand method. It only needs to carry out a solvothermal reaction on a specific metal source and a specific ligand, with simple operation and stable synthesized materials.

[0032] The mesoporous metal-organic framework material provided by the present invention has good adsorption performance for macromolecular alkanes, especially macromolecular VOCs such as n-butane, isobutane, n-pentane, and isopentane. Description of the Drawings

[0033] Figure 1 is the single crystal X-ray diffraction pattern of the material prepared in Example 2;

[0034] Figure 2 is the crystal structure diagram analyzed from the single crystal X-ray diffraction results of the material prepared in Example 2;

[0035] Figures 3 - 6 are the adsorption curves of n-butane, isobutane, n-pentane, and isopentane of the mesoporous metal-organic framework material prepared in Example 2 at different temperatures (25 °C, 35 °C, and 50 °C), respectively. Detailed Embodiments

[0036] The following further describes in detail the specific embodiments of the present invention with reference to the drawings. It should be understood that the specific embodiments described herein are only for the purpose of illustrating and explaining the present invention, and are not intended to limit the present invention.

[0037] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0038] The first aspect of the present invention provides a mesoporous metal-organic framework material, which includes a compound represented by Formula I,

[0039] [(Tmtp) k (Zn)x (ppc) y Formula I

[0040] Tmtp represents 2,3,5,6-tetrakis(4-pyridylphenyl)pyrazine, ppc represents a divalent deprotonated terephthalic acid-based compound, and Zn is +2 valence; k is 1, x is 2, y is 2,

[0041] The structure of the 2,3,5,6-tetrakis(4-pyridylphenyl)pyrazine is shown in Formula II:

[0042]

[0043] In the mesoporous metal-organic framework material of the present invention, the Zn is a metal ion, and 2,3,5,6-tetrakis(4-pyridylphenyl)pyrazine and the deprotonated terephthalic acid-based compound are ligands. Formula I represents the repeating unit of the mesoporous metal-organic framework material.

[0044] The mesoporous metal-organic framework material provided by the present invention is a novel mesoporous metal-organic framework material. Specifically, the unit cell parameters of the mesoporous metal-organic framework material are: a = 21.62, b = 38.48, c = 17.66, α = 90°, β = 111°, γ = 90°, belonging to the monoclinic system, the space group is C2 / m, and there is a two-fold interpenetrating structure in the crystal.

[0045] The mesoporous metal-organic framework material of the present invention has a large specific surface area. In a specific embodiment, the specific surface area of the mesoporous metal-organic framework material can be 400 - 800 m 2 / g, preferably 600 - 800 m 2 / g.

[0046] The average pore diameter of the mesoporous metal-organic framework material of the present invention has a small range. In a preferred embodiment, the average pore diameter of the mesoporous metal-organic framework material is 3 - 5 nm, preferably 4 - 5 nm.

[0047] In the mesoporous metal-organic framework material of the present invention, the terephthalic acid-based compound can be a conventional choice in the art.

[0048] In a specific embodiment, the terephthalic acid-based compound can be selected from one or more of terephthalic acid, 2-hydroxyterephthalic acid, 2-aminoterephthalic acid, 2-methylterephthalic acid, 2-methoxyterephthalic acid, 2-chloroterephthalic acid, 2-bromoterephthalic acid, 2-nitroterephthalic acid, 2-sulfonatoterephthalic acid, 2,5-dihydroxyterephthalic acid, and 2,5-dibromoterephthalic acid. In a preferred embodiment, the terephthalic acid-based compound is terephthalic acid.

[0049] In a second aspect of the present invention, a method for preparing a mesoporous metal-organic framework material is provided. The method includes: carrying out a solvothermal reaction on a zinc salt, a terephthalic acid-based compound, 2,3,5,6-tetrakis(4-pyridylphenyl)pyrazine and an organic solvent, and then activating the reaction product;

[0050] The structure of the 2,3,5,6-tetrakis(4-pyridylphenyl)pyrazine is shown in Formula II:

[0051]

[0052] The present invention adopts a mixed ligand method. Only by carrying out a solvothermal reaction on a zinc salt, a terephthalic acid-based compound ligand and a 2,3,5,6-tetrakis(4-pyridylphenyl) ligand can a novel mesoporous metal-organic framework material with unit cell parameters of: a = 21.62, b = 38.48, c = 17.66, α = 90°, β = 111°, γ = 90°, monoclinic system, space group C2 / m, and a two-fold interpenetrating structure in the crystal be obtained.

[0053] In the method of the present invention, the zinc salt is not particularly limited as long as it can be dissolved in the organic solvent for the solvothermal reaction.

[0054] In a specific embodiment, the zinc salt can be selected from one or more of zinc nitrate hydrate, zinc acetate hydrate, zinc chloride and zinc sulfate hydrate.

[0055] In the method of the present invention, the terephthalic acid-based compound can be a conventional choice in the art.

[0056] In a specific embodiment, the terephthalic acid-based compound can be selected from one or more of terephthalic acid, 2-hydroxyterephthalic acid, 2-aminoterephthalic acid, 2-methylterephthalic acid, 2-methoxyterephthalic acid, 2-chloroterephthalic acid, 2-bromoterephthalic acid, 2-nitroterephthalic acid, 2-sulfonatoterephthalic acid, 2,5-dihydroxyterephthalic acid and 2,5-dibromoterephthalic acid. In a preferred embodiment, the terephthalic acid-based compound is terephthalic acid.

[0057] In the present invention, the molar ratio of the metal ion Zn 2+ , the terephthalic acid-based compound ligand and the 2,3,5,6-tetrakis(4-pyridylphenyl)pyrazine ligand needs to be limited within a suitable range to obtain a mesoporous metal-organic framework material with the aforementioned characteristics.

[0058] In a specific embodiment, the molar ratio of the zinc salt, the terephthalic acid-based compound, and the 2,3,5,6-tetrakis(4-pyridylphenyl)pyrazine is 1.5 to 2.5:2:1. The zinc salt is calculated based on zinc ions, that is, the molar ratio of the divalent zinc ions in the zinc salt, the terephthalic acid-based compound, and the 2,3,5,6-tetrakis(4-pyridylphenyl)pyrazine is 1.5 to 2.5:2:1.

[0059] In a preferred embodiment, the molar ratio of the zinc salt, the terephthalic acid-based compound, and the 2,3,5,6-tetrakis(4-pyridylphenyl)pyrazine is 1.8 to 2.2:2:1, with the zinc salt calculated based on zinc ions. Limiting the ratio of metal ions to ligands within this range can yield a mesoporous metal-organic framework material with a moderate pore size and a relatively large specific surface area.

[0060] In the present invention, the reaction needs to be carried out under specific conditions to obtain the mesoporous metal-organic framework material of the present invention. In a specific embodiment, the temperature of the solvothermal reaction is 90 to 180 °C, and the time of the solvothermal reaction is 12 to 96 hours.

[0061] In a preferred embodiment, in order to fully react and obtain a mesoporous metal-organic framework material with a larger pore size and specific surface area, the temperature of the solvothermal reaction is 130 to 180 °C.

[0062] In a preferred embodiment, the time of the solvothermal reaction is 20 - 60 hours. In the present invention, appropriately extending the reaction time can also obtain a mesoporous metal-organic framework material with a high specific surface area.

[0063] In the present invention, the organic solvent can be a conventional choice in the art. In a specific embodiment, the organic solvent is selected from one or more of N,N-dimethylformamide (DMF), N,N-dimethylacetamide, N,N-diethylformamide, and dimethyl sulfoxide.

[0064] In a preferred embodiment, the method of the present invention specifically includes: performing a solvothermal reaction on a zinc salt, a terephthalic acid-based compound, 2,3,5,6-tetrakis(4-pyridylphenyl), and an organic solvent, and separating, washing, and activating the crude reaction product.

[0065] In a specific embodiment, the step of separating the crude reaction product includes: soaking the crude reaction product in an organic solvent for 10 - 20 hours, then performing ultrasonic oscillation (frequency: 30 - 60 Hz), and separating.

[0066] In a specific embodiment, the step of washing includes: washing the separated solid product with absolute ethanol, preferably washing multiple times.

[0067] In a specific embodiment, the activation step includes: treating the washed product under vacuum conditions.

[0068] In the present invention, the processes of separation and washing can prevent the pores of the prepared mesoporous metal-organic framework material from being blocked, resulting in a decrease in pore size and a reduction in specific surface area.

[0069] In a more specific embodiment, the activation conditions include: a temperature of 60-100 °C, a time of 10-20 hours, and a pressure of 0 to -0.1 MPa. Herein, the pressure is the absolute pressure.

[0070] The third aspect of the present invention provides a mesoporous metal-organic framework material prepared by the method described above.

[0071] Preferably, the mesoporous metal-organic framework material includes a compound represented by Formula I,

[0072] [(Tmtp)k(Zn)x(ppc)y] Formula I

[0073] Tmtp represents 2,3,5,6-tetrakis(4-pyridylphenyl)pyrazine, ppc represents a -2-valent deprotonated terephthalic acid-based compound, Zn is +2-valent; k is 1, x is 2, and y is 2.

[0074] The structure of the 2,3,5,6-tetrakis(4-pyridylphenyl)pyrazine is shown in Formula II:

[0075]

[0076] In a preferred embodiment, the unit cell parameters of the mesoporous metal-organic framework material are: a = 21.62, b = 38.48, c = 17.66, α = 90°, β = 111°, γ = 90°, belonging to the monoclinic system, with a space group of C2 / m, and there is a two-fold interpenetrating structure in the crystal.

[0077] In a preferred embodiment, the specific surface area of the mesoporous metal-organic framework material is 400-800 m 2 / g, and the average pore diameter is 4-5 nm.

[0078] In a preferred embodiment, the terephthalic acid-based compound is selected from one or more of terephthalic acid, 2-hydroxyterephthalic acid, 2-aminoterephthalic acid, 2-methylterephthalic acid, 2-methoxyterephthalic acid, 2-chloroterephthalic acid, 2-bromoterephthalic acid, 2-nitroterephthalic acid, 2-sulfonatoterephthalic acid, 2,5-dihydroxyterephthalic acid, and 2,5-dibromoterephthalic acid.

[0079] The fourth aspect of the present invention provides an adsorbent, which contains the mesoporous metal-organic framework material described above or the mesoporous metal-organic framework material described above.

[0080] Using the mesoporous metal-organic framework material prepared by the present invention as an adsorbent, gases including but not limited to alkanes and metal ions can be adsorbed.

[0081] The fifth aspect of the present invention provides a method for adsorbing alkanes, which includes adsorbing alkanes using the mesoporous metal-organic framework material described above or the mesoporous metal-organic framework material described above or the adsorbent described above.

[0082] In a specific embodiment, the alkane is an alkane with 4 or more carbon atoms.

[0083] In a preferred embodiment, the alkane is selected from one or more of n-butane, isobutane, n-pentane, and isopentane.

[0084] The present invention will be described in detail below through examples, but the protection scope of the present invention is not limited thereto. In the following examples, unless otherwise specified, the raw materials used are commercially available products.

[0085] In the following examples, the structure of 2,3,5,6-tetrakis(4-pyridylphenyl)pyrazine is:

[0086]

[0087] Example 1

[0088] (1) Zinc nitrate hexahydrate (0.160 g), terephthalic acid (0.125 g), and 2,3,5,6-tetrakis(4-pyridylphenyl)pyrazine (0.256 g) were successively added to 30 ml of DMF, and stirred evenly with a magnetic stirrer. The molar ratio of zinc ion, terephthalic acid, and 2,3,5,6-tetrakis(4-pyridylphenyl)pyrazine was 1.5:2:1. The mixed solution was transferred to the inner lining of a polytetrafluoroethylene high-temperature reaction kettle, put into the stainless steel reaction kettle sleeve with the lid closed, the kettle lid was tightened, and placed in an oven at 150 °C for 24 hours to obtain a crude reaction product;

[0089] (2) The crude reaction product was soaked in DMF for 12 hours, then ultrasonically oscillated (frequency 40 Hz), centrifuged, and then washed 3 times with absolute ethanol to obtain a washed reaction product;

[0090] (3) The washed crude reaction product was placed in a vacuum drying oven and evacuated (pressure -0.1 MPa) at 80 °C for 12 hours to obtain the mesoporous metal-organic framework material.

[0091] Example 2

[0092] (1) Zinc nitrate hexahydrate (0.22 g), terephthalic acid (0.125 g), and 2,3,5,6-tetrakis(4-pyridylphenyl)pyrazine (0.256 g) were successively added to 30 ml of DMF and stirred evenly with a magnetic stirrer. The molar ratio of zinc ions, terephthalic acid, and 2,3,5,6-tetrakis(4-pyridylphenyl)pyrazine was 2:2:1. The mixed solution was transferred to the inner lining of a polytetrafluoroethylene high-temperature reaction kettle, covered and placed in a stainless steel reaction kettle sleeve, the kettle lid was tightened, and it was placed in an oven at 150 °C for 24 hours to obtain a crude reaction product.

[0093] (2) The crude reaction product was soaked in DMF for 12 hours, then ultrasonically oscillated (frequency 40 Hz), centrifuged, and then washed 3 times with absolute ethanol to obtain the washed reaction product;

[0094] (3) The washed crude reaction product was placed in a vacuum drying oven and evacuated (pressure -0.1 MPa) at 80 °C for 12 hours to obtain the mesoporous metal-organic framework material.

[0095] Example 3

[0096] (1) Zinc nitrate hexahydrate (0.27 g), terephthalic acid (0.125 g), and 2,3,5,6-tetrakis(4-pyridylphenyl)pyrazine (0.256 g) were successively added to 30 ml of DMF and stirred evenly with a magnetic stirrer. The molar ratio of zinc ions, terephthalic acid, and 2,3,5,6-tetrakis(4-pyridylphenyl)pyrazine was 2.5:2:1. The mixed solution was transferred to the inner lining of a polytetrafluoroethylene high-temperature reaction kettle, covered and placed in a stainless steel reaction kettle sleeve, the kettle lid was tightened, and it was placed in an oven at 150 °C for 24 hours to obtain a crude reaction product;

[0097] (2) The crude reaction product was soaked in DMF for 12 hours, then ultrasonically oscillated (frequency 40 Hz), centrifuged, and then washed 3 times with absolute ethanol to obtain the washed reaction product;

[0098] (3) The washed crude reaction product was placed in a vacuum drying oven and evacuated (pressure -0.1 MPa) at 80 °C for 12 hours to obtain the mesoporous metal-organic framework material.

[0099] Example 4

[0100] (1) Zinc nitrate hexahydrate (0.22 g), terephthalic acid (0.125 g), and 2,3,5,6-tetrakis(4-pyridylphenyl)pyrazine (0.256 g) were successively added to 30 ml of DMF and stirred evenly with a magnetic stirrer. The molar ratio of zinc ions, terephthalic acid, and 2,3,5,6-tetrakis(4-pyridylphenyl)pyrazine was 2:2:1. The mixed solution was transferred to the inner lining of a polytetrafluoroethylene high-temperature reaction kettle, covered and placed in a stainless steel reaction kettle sleeve, the kettle lid was tightened, and it was placed in an oven at 120 °C for reaction for 24 hours to obtain a crude reaction product;

[0101] (2) The crude reaction product was soaked in DMF for 12 hours, then ultrasonically oscillated (frequency 40 Hz), centrifuged, and then washed 3 times with absolute ethanol to obtain the washed reaction product;

[0102] (3) The washed crude reaction product was placed in a vacuum drying oven and evacuated (pressure -0.1 MPa) at 80 °C for 12 hours to obtain the mesoporous metal-organic framework material.

[0103] Example 5

[0104] (1) Zinc nitrate hexahydrate (0.22 g), terephthalic acid (0.125 g), and 2,3,5,6-tetrakis(4-pyridylphenyl)pyrazine (0.256 g) were successively added to 30 ml of DMF and stirred evenly with a magnetic stirrer. The molar ratio of zinc ions, terephthalic acid, and 2,3,5,6-tetrakis(4-pyridylphenyl)pyrazine was 2:2:1. The mixed solution was transferred to the inner lining of a polytetrafluoroethylene high-temperature reaction kettle, covered and placed in a stainless steel reaction kettle sleeve, the kettle lid was tightened, and it was placed in an oven at 180 °C for reaction for 24 hours to obtain a crude reaction product;

[0105] (2) The crude reaction product was soaked in DMF for 12 hours, then ultrasonically oscillated (frequency 40 Hz), centrifuged, and then washed 3 times with absolute ethanol to obtain the washed reaction product;

[0106] (3) The washed crude reaction product was placed in a vacuum drying oven and evacuated (pressure -0.1 MPa) at 80 °C for 12 hours to obtain the mesoporous metal-organic framework material.

[0107] Example 6

[0108] (1) Zinc nitrate hexahydrate (0.22 g), terephthalic acid (0.125 g), and 2,3,5,6-tetrakis(4-pyridylphenyl)pyrazine (0.256 g) were successively added to 30 ml of DMF and stirred evenly with a magnetic stirrer. The molar ratio of zinc ions, terephthalic acid, and 2,3,5,6-tetrakis(4-pyridylphenyl)pyrazine was 2:2:1. The mixed solution was transferred to the inner lining of a polytetrafluoroethylene high-temperature reaction kettle, covered and placed into the stainless-steel reaction kettle sleeve, the kettle lid was tightened, and it was placed in an oven at 120 °C for 48 hours to obtain the crude reaction product;

[0109] (2) The crude reaction product was soaked in DMF for 12 hours, then ultrasonically oscillated (frequency 40 Hz), centrifuged, and then washed 3 times with absolute ethanol to obtain the washed reaction product;

[0110] (3) The washed crude reaction product was placed in a vacuum drying oven and evacuated (pressure -0.1 MPa) at 80 °C for 12 hours to obtain the mesoporous metal-organic framework material.

[0111] Example 7

[0112] (1) Zinc nitrate hexahydrate (0.22 g), terephthalic acid (0.125 g), and 2,3,5,6-tetrakis(4-pyridylphenyl)pyrazine (0.256 g) were successively added to 30 ml of DMF and stirred evenly with a magnetic stirrer. The molar ratio of zinc ions, terephthalic acid, and 2,3,5,6-tetrakis(4-pyridylphenyl)pyrazine was 2:2:1. The mixed solution was transferred to the inner lining of a polytetrafluoroethylene high-temperature reaction kettle, covered and placed into the stainless-steel reaction kettle sleeve, the kettle lid was tightened, and it was placed in an oven at 150 °C for 24 hours to obtain the crude reaction product;

[0113] (2) The crude reaction product was washed 3 times with absolute ethanol to obtain the washed reaction product;

[0114] (3) The washed crude reaction product was placed in a vacuum drying oven and evacuated (pressure -0.1 MPa) at 80 °C for 12 hours to obtain the mesoporous metal-organic framework material.

[0115] Example 8

[0116] (1) Zinc nitrate hexahydrate (0.22 g), terephthalic acid (0.125 g), and 2,3,5,6-tetrakis(4-pyridylphenyl)pyrazine (0.256 g) were successively added to 30 ml of DMF and stirred evenly with a magnetic stirrer. The molar ratio of zinc ions, terephthalic acid, and 2,3,5,6-tetrakis(4-pyridylphenyl)pyrazine was 2:2:1. The mixed solution was transferred to the inner lining of a polytetrafluoroethylene high-temperature reaction kettle, covered and placed into the stainless-steel reaction kettle sleeve, the kettle lid was tightened, and it was placed in an oven at 150 °C for 24 hours to obtain the crude reaction product;

[0117] (2) Immerse the crude reaction product in DMF for 12 hours, then perform ultrasonic oscillation (frequency 40 Hz), centrifuge and separate, and then wash once with absolute ethanol to obtain the washed reaction product;

[0118] (3) Place the washed crude reaction product in a vacuum drying oven, evacuate (pressure is -0.1 MPa) at 80 °C for 12 hours to obtain the mesoporous metal-organic framework material.

[0119] Comparative Example 1

[0120] Carry out according to the method of Example 2, except that the terephthalic acid-based compound is not added.

[0121] The specific operation is as follows:

[0122] (1) Add zinc nitrate hexahydrate (0.22 g) and 2,3,5,6-tetrakis(4-pyridylphenyl)pyrazine (0.256 g) to 30 ml of DMF in sequence, stir evenly with a magnetic stirrer, and the molar ratio of zinc ions to 2,3,5,6-tetrakis(4-pyridylphenyl)pyrazine is 2:1. Transfer the mixed solution to the inner lining of a polytetrafluoroethylene high-temperature reaction kettle, install it in the stainless steel reaction kettle sleeve with the lid, tighten the kettle lid, and place it in an oven at 150 °C for reaction for 24 hours to obtain the crude reaction product;

[0123] (2) Immerse the crude reaction product in DMF for 12 hours, then perform ultrasonic oscillation (frequency 40 Hz), centrifuge and separate, and then wash 3 times with absolute ethanol to obtain the washed reaction product;

[0124] (3) Place the washed crude reaction product in a vacuum drying oven, evacuate (pressure is -0.1 MPa) at 80 °C for 12 hours.

[0125] In this comparative example, zinc nitrate hexahydrate and 2,3,5,6-tetrakis(4-pyridylphenyl)pyrazine cannot react and no product can be obtained.

[0126] Comparative Example 2

[0127] Carry out according to the method of Example 2, except that 2,3,5,6-tetrakis(4-pyridylphenyl) is not added.

[0128] The specific operation is as follows:

[0129] (1) Zinc nitrate hexahydrate (0.22 g) and terephthalic acid (0.125 g) were successively added to 30 ml of DMF and stirred evenly with a magnetic stirrer. The molar ratio of zinc ions to terephthalic acid was 2:2. The mixed solution was transferred to the inner lining of a polytetrafluoroethylene high-temperature reaction kettle, covered and placed in the stainless steel reaction kettle sleeve, the kettle lid was tightened, and it was placed in an oven at 150 °C for reaction for 24 hours to obtain the crude reaction product;

[0130] (2) The crude reaction product was soaked in DMF for 12 hours, then ultrasonically oscillated (frequency 40 Hz), centrifuged, and then washed 3 times with absolute ethanol to obtain the washed reaction product;

[0131] (3) The washed crude reaction product was placed in a vacuum drying oven and evacuated (pressure -0.1 MPa) at 80 °C for 12 hours.

[0132] The product obtained in the comparative example was the known material MOF-5, which is a microporous material.

[0133] Test Example 1

[0134] The specific surface area and pore size of the materials prepared in the examples and comparative examples were tested using a physical adsorption instrument, and the results are shown in Table 1.

[0135] The test method was as follows: The N2 adsorption-desorption curves of the samples prepared in Examples 1-8 and Comparative Example 2 were tested on a Micromeritics ASAP2020 specific surface area analyzer; the specific test process included: evacuating and degassing at 150 °C for 12 h, weighing and then transferring each sample to the analysis station, and measuring the N2 adsorption-desorption isotherm at 77 K; calculating the specific surface area of the sample by the Brunauer-Emmett-Teller (BET) method; calculating the pore size distribution of the sample by the Barrett-Joyner-Halenda (BJH) method.

[0136] Table 1

[0137]

[0138]

[0139] As can be seen from Table 1, the specific surface area of the mesoporous metal-organic framework material prepared in the examples of the present invention is 400-800 m 2 / g, and the average pore size is 4-5 nm.

[0140] As can be seen from Examples 1 - 3, whether the proportion of zinc ions used in synthesizing the mesoporous metal-organic framework material is too high or too low, it will affect the pore structure of the material. If the amount of zinc ions is too small, there will be too many unreacted organic ligands remaining in the pores, resulting in partial blockage of the material pores, reduction of pore diameter, and decrease of specific surface area. If the proportion of zinc ions is too high, there will be unsaturated coordination sites that are not coordinated with zinc ions, and the structure has defects, resulting in a relatively large pore diameter of the formed material.

[0141] As can be seen from Examples 2, 4 - 5, too low reaction temperature will lead to incomplete reaction, and the synthesized material pore structure contains unreacted raw materials, resulting in small pore diameter and low specific surface area of the material. As can be seen from Example 6, at low temperature, by appropriately prolonging the reaction time, mesoporous materials with high specific surface area can also be obtained.

[0142] As can be seen from Examples 7 - 8, solvent washing after the reaction is very important. Without DMF washing, the unreacted ligands cannot be washed clean enough and remain in the material pores, blocking the pores, reducing the pore diameter of the material, and decreasing the specific surface area. If the number of ethanol washes is insufficient and the high-boiling-point solvent DMF in the pores cannot be repeatedly displaced, it will also cause partial blockage of the material pores.

[0143] As can be seen from Comparative Examples 1 and 2, no reaction will occur without terephthalic acid ligand. Without 2,3,5,6 - tetra(4 - pyridylphenyl)pyrazine ligand, the known MOF - 5 material will be formed, which is a microporous material with high specific surface area and an average pore diameter of 0.78 nm.

[0144] Test Example 2

[0145] Single crystal X-ray diffraction was performed on the material prepared in Example 2, and the single crystal X-ray diffraction pattern (XRD curve) is as Figure 1 shown; and it was analyzed using shelxtl software, and the crystal structure diagram analyzed from the single crystal X-ray diffraction results is as Figure 2 shown.

[0146] The analysis results are as follows: The unit cell parameters are: a = 21.62, b = 38.48, c = 17.66, α = 90°, β = 111°, γ = 90°, belonging to the monoclinic system, and the space group is C2 / m.

[0147] The structure of the repeating unit of the mesoporous metal-organic framework material is as shown in Formula I:

[0148] [(Tmtp) k (Zn) x (ppc) y Formula I

[0149] Tmtp represents 2,3,5,6 - tetra(4 - pyridylphenyl)pyrazine, ppc represents a -2 valent deprotonated terephthalic acid-based compound, Zn is +2 valent; k is 1, x is 2, y is 2,

[0150] The structure of the 2,3,5,6-tetrakis(4-pyridylphenyl)pyrazine is shown in Formula II:

[0151]

[0152] The characterization results of other examples are the same as those of Example 2 and will not be elaborated here.

[0153] Test Example 3

[0154] The adsorption performance of the n-butane, isobutane, n-pentane, and isopentane adsorption curves of the materials prepared in the test examples and comparative examples was tested. The test results are shown in Table 2.

[0155] The test method is as follows: The alkane adsorption-desorption curve of the sample to be tested was tested on a Micromeritics ASAP 2020 specific surface area analyzer, and vacuum degassing was carried out at 150 °C for 12 h; the specific test process includes: after weighing the sample, it was transferred to the analysis station, and the adsorption-desorption curves of butane, isobutane in the pressure range of 0-1100 mbar, and pentane, isopentane in the pressure range of 0-300 mbar were measured at 298 K (25 °C). The maximum adsorption amount of the sample in this pressure range can be obtained from the curve.

[0156] Table 2

[0157]

[0158]

[0159] As can be seen from Table 2, the adsorption amounts of the mesoporous metal-organic framework materials prepared in the examples of the present invention for n-butane, isobutane, n-pentane, and isopentane are significantly increased. Compared with the microporous MOF-5 material prepared in Comparative Example 2, the adsorption amounts of macromolecules such as n-hexane of the mesoporous metal-organic framework materials prepared in the present invention are higher, because the mesoporous channels are beneficial to the adsorption and diffusion of macromolecules. Compared with the traditional activated carbon adsorption material, the adsorption amounts of macromolecules such as n-hexane of the mesoporous metal-organic framework materials prepared in the present invention are also higher, because activated carbon mainly consists of micropores. Therefore, the prepared mesoporous metal-organic framework materials have very excellent adsorption performance for n-butane, isobutane, n-pentane, and isopentane.

[0160] Figures 3 - 6 They are the adsorption curves of n-butane, isobutane, n-pentane, and isopentane of the mesoporous metal-organic framework material prepared in Example 2 at different temperatures (25 °C, 35 °C, and 50 °C), respectively.

[0161] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A mesoporous metal-organic framework material, characterized in that, The mesoporous metal-organic framework material comprises a compound represented by Formula I. [(Tmtp) k (Zn) x (ppc) y Formula I Tmtp represents 2,3,5,6-tetrakis(4-pyridylphenyl)pyrazine, ppc represents a -2-valent deprotonated terephthalic acid-based compound, and Zn is +2-valent; k is 1, x is 2, and y is 2. The structure of the 2,3,5,6-tetrakis(4-pyridylphenyl)pyrazine is as shown in Formula II:

2. The mesoporous metal-organic framework material according to claim 1, characterized in that The unit cell parameters of the mesoporous metal-organic framework material are: a = 21.62, b = 38.48, c = 17.66, α = 90°, β = 111°, γ = 90°, belonging to the monoclinic system, with the space group C2 / m, and there is a two-fold interpenetrating structure in the crystal.

3. The mesoporous metal-organic framework material according to claim 1 or 2, characterized in that, The specific surface area of the mesoporous metal-organic framework material is 400-800 m 2 / g, preferably 600-800 m 2 / g; the average pore diameter is 3-5 nm, preferably 4-5 nm.

4. The mesoporous metal-organic framework material according to any one of claims 1-3, characterized in that, The terephthalic acid-based compound is selected from one or more of terephthalic acid, 2-hydroxyterephthalic acid, 2-aminoterephthalic acid, 2-methylterephthalic acid, 2-methoxyterephthalic acid, 2-chloroterephthalic acid, 2-bromoterephthalic acid, 2-nitroterephthalic acid, 2-sulfonatoterephthalic acid, 2,5-dihydroxyterephthalic acid, and 2,5-dibromoterephthalic acid.

5. A method for preparing a mesoporous metal-organic framework material, characterized in that, The method includes: carrying out a solvothermal reaction on a zinc salt, a terephthalic acid-based compound, 2,3,5,6-tetrakis(4-pyridylphenyl), and an organic solvent, and then activating the reaction product. The structure of the 2,3,5,6-tetrakis(4-pyridylphenyl)pyrazine is as shown in Formula II:

6. The method according to claim 5, wherein The zinc salt is selected from one or more of zinc nitrate hydrate, zinc acetate hydrate, zinc chloride, and zinc sulfate hydrate.

7. The method according to claim 5 or 6, characterized in that, The terephthalic acid-based compound is selected from one or more of terephthalic acid, 2-hydroxyterephthalic acid, 2-aminoterephthalic acid, 2-methylterephthalic acid, 2-methoxyterephthalic acid, 2-chloroterephthalic acid, 2-bromoterephthalic acid, 2-nitroterephthalic acid, 2-sulfonatoterephthalic acid, 2,5-dihydroxyterephthalic acid, and 2,5-dibromoterephthalic acid.

8. The method according to any one of claims 5-7, characterized in that, The molar ratio of the zinc salt, the terephthalic acid-based compound, and the 2,3,5,6-tetrakis(4-pyridylphenyl)pyrazine is 1.5 - 2.5:2:1, preferably 1.8 - 2.2:2:1, with the zinc salt calculated as zinc ions.

9. The method according to any one of claims 5 - 8, characterized in that The conditions of the solvothermal reaction include: the temperature is 90 - 180 °C, preferably 130 - 180 °C; the time is 12 - 96 hours, preferably 20 - 60 hours.

10. The method according to any one of claims 5-9, characterized in that, The organic solvent is selected from one or more of N,N-dimethylformamide, N,N-dimethylacetamide, N,N-diethylformamide, and dimethyl sulfoxide.

11. The method according to any one of claims 5-10, characterized in that The conditions of the activation include: the temperature is 60 - 100 °C, the time is 10 - 20 hours, and the pressure is 0 to -0.1 MPa.

12. The method according to any one of claims 5-11, characterized in that, The method specifically includes: carrying out a solvothermal reaction on a zinc salt, a terephthalic acid-based compound, 2,3,5,6-tetrakis(4-pyridylphenyl), and an organic solvent, and separating, washing, and activating the crude reaction product.

13. A mesoporous metal-organic framework material prepared by the method according to any one of claims 5 - 13.

14. An adsorbent, characterized in that, The adsorbent contains the mesoporous metal-organic framework material described in any one of claims 1-4 or the mesoporous metal-organic framework material described in claim 13.

15. A method for adsorbing alkanes, characterized in that, The method includes adsorbing alkanes using the mesoporous metal-organic framework material described in any one of claims 1-4 or the mesoporous metal-organic framework material described in claim 13 or the adsorbent described in claim 14.

16. The method according to claim 15, characterized in that, The alkanes are alkanes with 4 or more carbon atoms; Preferably, the alkanes are selected from one or more of n-butane, isobutane, n-pentane, and isopentane.

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