Three-dimensional flexible metal organic framework material as well as preparation method and application thereof

Abstract

The invention relates to the technical field of chemical separation, in particular to a three-dimensional flexible metal organic framework material and a preparation method and application thereof. The structural general formula of the metal organic framework material is A (TIB) 2, A is a transition metal cation, and TIB is 1, 3, 5-tri (1H-imidazole-1-yl) benzene. Transition metal cations and TIB are self-assembled in an octahedral hexa-coordination mode to form a two-dimensional layered frame, and the two-dimensional layered frame is further stacked to form a three-dimensional flexible structure. The material has a two-dimensional layered skeleton with high stability and a pore surface with a partial electrostatic potential, not only shows a strong capture capability on carbon dioxide, but also provides a suitable storage space for acetylene, can selectively adsorb and separate an acetylene / carbon dioxide / ethylene mixed system, and realizes one-step purification of ethylene from a ternary mixture. In addition, due to excellent cyclic regeneration performance, solvent stability and thermal stability, the adsorbent is expected to be an efficient adsorbent applied to industrial adsorption separation.

Description

Technical Field

[0001] This invention relates to the field of chemical separation technology, specifically to a three-dimensional flexible metal-organic framework material, its preparation method, and its application. Background Technology

[0002] Ethylene (C2H4), one of the world's largest-produced chemical products, is a crucial raw material for the petrochemical industry. Currently, the main industrial technologies for producing C2H4 are steam cracking and methane oxidative coupling. Although these processes have high production efficiency, they inevitably produce small amounts of acetylene (C2H2) and carbon dioxide (CO2) as byproducts. These impurities can poison polyethylene synthesis catalysts during downstream polymerization, severely affecting reaction efficiency and product quality. Therefore, selectively removing C2H2 and CO2 impurities from the CO2 / C2H2 / C2H4 ternary mixture to obtain polymer-grade C2H4 has become a crucial and highly challenging step. Because CO2, C2H2, and C2H4 molecules have similar kinetic molecular sizes (3.3 Å, 3.3 Å, 4.2 Å) and similar physical properties (boiling points: CO2, 194.7 K; C2H2, 189.3 K; C2H4, 169.4 K), their separation process is widely recognized as one of the most complex and difficult separation processes in the field of chemical separation. Currently, industrial purification strategies mainly rely on multi-step heterogeneous processes such as noble metal catalytic hydrogenation and organic amine solvent absorption to remove the aforementioned impurities. However, these processes suffer from problems such as complex operation, high energy consumption, and severe environmental pollution. Therefore, developing a stable, efficient, and alternative separation method to selectively remove CO2 and C2H2 from ternary gas mixtures and prepare high-purity C2H4 in one step has become an urgent research need.

[0003] Compared to traditional porous adsorbents (such as zeolite molecular sieves and activated carbon), metal-organic frameworks (MOFs) or porous coordination polymers (PCPs), as emerging crystalline porous materials, have shown significant advantages in the separation of light hydrocarbon mixtures. Traditional materials are often limited by low adsorption capacity and selectivity, making it difficult to meet the demands of industrial applications. An ideal CO2 / C2H2 / C2H4 separation adsorbent should possess good adsorption capacity, high selectivity, and moderate heat of adsorption; furthermore, industrial applications must consider important parameters such as stability and scalability. However, in the reported MOFs used for the separation of this ternary mixture, there is often a trade-off between adsorption capacity and separation selectivity. On the one hand, pursuing high selectivity usually requires precise control of the pore size and surface chemistry of MOFs to enable them to interact strongly and specifically with target gas molecules. However, this often leads to narrow pores or limited effective adsorption space, thus sacrificing overall adsorption capacity. On the other hand, MOFs with high adsorption capacity typically have large specific surface areas and pore volumes, but this may allow a large number of different gas molecules to be adsorbed, thereby weakening the separation selectivity for specific gases (Changlong Wang, Mingxing Zhang, Weidong Fan, Jingjing Zhang, Xianhui Bu, Quan-Guo Zhai et al. Efficient C2H2 / CO2 separation by transition state crystals (J). Angewandte Chemie International Edition, 2023, e202311838.). This problem is widespread and has not yet been effectively solved. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a three-dimensional flexible metal-organic framework (MOF) material, its preparation method, and its applications. The MOF material uses 1,3,5-tris(1H-imidazol-1-yl)benzene as the organic ligand and transition metals as metal nodes, forming a highly stable two-dimensional layered framework structure through self-assembly. Its surface exhibits a biased positive electrostatic potential distribution. The MOF adsorbent demonstrates strong adsorption capacity for carbon dioxide molecules and good adsorption effect for acetylene, enabling efficient separation of CO2 / C2H2 / C2H4 mixed systems and achieving one-step purification of ethylene from ternary gases. Furthermore, the MOF material prepared by this invention exhibits excellent solvent stability, thermal stability, and recyclability, demonstrating its application potential as a practical material for industrial adsorption and separation.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: The first objective of this invention is to provide a three-dimensional flexible metal-organic framework material with the general structural formula A(TIB)2, wherein A is a transition metal cation and TIB is 1,3,5-tris(1H-imidazol-1-yl)benzene; in the three-dimensional flexible metal-organic framework material, in the 1,3,5-tris(1H-imidazol-1-yl)benzene ligand, all nitrogen atoms on the imidazole that are not connected to the benzene ring are coordinated with the transition metal cation to form a two-dimensional layered network structure, and each transition metal cation in the two-dimensional layered network structure forms an octahedral coordination configuration with six nitrogen atoms; and each two-dimensional layered network structure is stacked and assembled through non-covalent interactions to form a three-dimensional framework structure, thereby obtaining a three-dimensional flexible metal-organic framework material.

[0006] In a preferred embodiment of the present invention, the transition metal cation is cadmium ion, cobalt ion, nickel ion, zinc ion, copper ion or manganese ion.

[0007] In a preferred embodiment of the present invention, the three-dimensional flexible metal-organic framework material has a cavity structure with dimensions of 0.6 nm × 0.65 nm × 0.8 nm, and adjacent cavities are interconnected through channels with dimensions of 0.3 nm × 0.2 nm; the pore volume is 0.04 cm³. 3 / g~0.08cm 3 / g, specific surface area is 181m² 2 / g~182m 2 / g.

[0008] The second objective of this invention is to provide a method for preparing the above-mentioned three-dimensional flexible metal-organic framework material, comprising the following steps: using 1,3,5-tris(1H-imidazol-1-yl)benzene as an organic ligand and a transition metal salt as a metal salt, performing a coordination reaction at room temperature to obtain the three-dimensional flexible metal-organic framework material.

[0009] In a preferred embodiment of the present invention, the molar ratio of the metal salt to 1,3,5-tris(1H-imidazol-1-yl)benzene is 1:0.5~10, and the metal salt is cadmium nitrate, cobalt nitrate, nickel nitrate, zinc nitrate, copper nitrate, or manganese nitrate.

[0010] A third objective of this invention is to provide an application of the above-mentioned three-dimensional flexible metal-organic framework material in the selective adsorption of carbon dioxide and acetylene.

[0011] In a preferred embodiment of the present invention, when the adsorption temperature is -50℃ to 100℃ and the adsorption pressure is 0 bar to 10 bar, the mixed gas is brought into contact with the three-dimensional flexible metal-organic framework material in the adsorption column to adsorb carbon dioxide and acetylene in the mixed gas.

[0012] In a preferred embodiment of the present invention, the mixed gas is composed of carbon dioxide, acetylene and ethylene, wherein the volume ratio of carbon dioxide, acetylene and ethylene is 0.01~0.99:0.01~0.99:0.01~0.99.

[0013] In a preferred embodiment of the present invention, the contact mode between the mixed gas and the three-dimensional flexible metal-organic framework material is fixed bed adsorption, fluidized bed adsorption, or moving bed adsorption.

[0014] In a preferred embodiment of the present invention, the contact adsorption process is at least one of a single-tower or multi-tower pressure swing adsorption process, a temperature swing adsorption process, or a vacuum desorption adsorption process.

[0015] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention provides a three-dimensional flexible metal-organic framework (MOF) material, using 1,3,5-tris(1H-imidazol-1-yl)benzene as the organic ligand and transition metal ions as metal nodes, forming a highly stable two-dimensional layered framework structure through self-assembly, with a surface exhibiting a biased electrostatic potential distribution. Specifically, the nitrogen atoms in each imidazole layer of the 1,3,5-tris(1H-imidazol-1-yl)benzene ligand that are not connected to the benzene ring coordinate with transition metal cations to form a two-dimensional layered network structure. Each transition metal cation in the two-dimensional layer forms an octahedral coordination configuration with six nitrogen atoms. Furthermore, each two-dimensional layer is further assembled into a three-dimensional framework structure through π-π interactions, CH···π interactions, and van der Waals force stacking. The MOF adsorbent exhibits strong adsorption capacity for carbon dioxide molecules and good adsorption effect for acetylene, enabling efficient separation of CO2 / C2H2 / C2H4 mixed systems, achieving one-step purification of ethylene from ternary gases. Furthermore, the metal-organic framework material prepared by this invention exhibits excellent solvent stability, thermal stability, and recyclability, demonstrating its application potential as a practical material for industrial adsorption and separation.

[0016] 2. The three-dimensional flexible metal-organic framework material provided by the present invention has the following characteristics: efficient and selective capture of carbon dioxide and acetylene from carbon dioxide / acetylene / ethylene mixture, excellent dynamic penetration performance, material recyclability and solvent stability, and good thermal stability.

[0017] 3. The three-dimensional flexible metal-organic framework material prepared by this invention can be used to obtain a stable product by adjusting the synthesis method and stirring at room temperature. It can capture carbon dioxide and acetylene in a mixture of carbon dioxide / acetylene / ethylene gas and produce high-purity ethylene products. Attached Figure Description

[0018] Figure 1 This is a physical image of the Cd(TIB)2 material prepared in Example 1 of the present invention.

[0019] Figure 2 This is a powder image of the Cd(TIB)2 material prepared in Example 1 of the present invention.

[0020] Figure 3 The process route and structural diagram of the Cd(TIB)2 material prepared in Example 1 of this invention are shown.

[0021] Figure 4 The X-ray diffraction pattern shows the purity of the synthesized phase of the Cd(TIB)2 material in Example 1 of this invention and its stability after immersion in an organic solution. Figure 4 Figure (a) shows the X-ray diffraction pattern of the synthesized phase purity of Cd(TIB)2 material, and Figure (b) shows the X-ray diffraction pattern of the stability test of Cd(TIB)2 material after immersion in organic solution.

[0022] Figure 5 This is a thermal stability diagram of the Cd(TIB)2 material in Example 1 of the present invention. Figure 5 Figure (a) shows the variable-temperature X-ray diffraction pattern, and Figure (b) shows the thermogravimetric curve.

[0023] Figure 6 This is the CO2 adsorption isotherm at 195 K for the Cd(TIB)2 material in Example 1 of the present invention.

[0024] Figure 7 This is an adsorption isotherm diagram of the Cd(TIB)2 material of Example 1 of the present invention for carbon dioxide, acetylene and ethylene at 298K.

[0025] Figure 8 This is a kinetic adsorption curve of the Cd(TIB)2 material of Example 1 of the present invention, showing the change of acetylene and carbon dioxide adsorption capacity over time at 298K.

[0026] Figure 9 The image shows the dynamic breakthrough curves of the Cd(TIB)2 material of Example 1 of the present invention at 298K for different flow rates of carbon dioxide / acetylene / ethylene mixed gas components (volume ratio 25:25:50).

[0027] Figure 10 The diagram shows the cyclic dynamic breakthrough curve of the Cd(TIB)2 material of Example 1 of the present invention at 298 K with a mixed gas composition of carbon dioxide / acetylene / ethylene (volume ratio 25:25:50, flow rate 4.0 mL / min).

[0028] Figure 11 The image shows the dynamic breakthrough curve of the Cd(TIB)2 material of Example 1 of the present invention at 298 K and a flow rate of 4 mL / min for a mixed gas composition of carbon dioxide / acetylene / ethylene (volume ratio 9:1:90).

[0029] Figure 12 This is a powder image of the Co(TIB)2 material prepared in Example 2 of the present invention.

[0030] Figure 13 This is an X-ray diffraction pattern of the Co(TIB)2 material in Example 2 of the present invention.

[0031] Figure 14 This is an adsorption isotherm diagram of the Co(TIB)2 material of Example 2 of the present invention for carbon dioxide, acetylene and ethylene at 298K.

[0032] Figure 15 This is an X-ray diffraction pattern of the Ni(TIB)2 material in Example 3 of the present invention.

[0033] Figure 16 This is an adsorption isotherm diagram of the Ni(TIB)2 material of Example 3 of the present invention for carbon dioxide, acetylene and ethylene at 298K.

[0034] Figure 17 This is an X-ray diffraction pattern of the Zn(TIB)2 material in Example 4 of the present invention.

[0035] Figure 18 This is an X-ray diffraction pattern of Cu(TIB)2 material in Example 5 of the present invention.

[0036] Figure 19 This is an X-ray diffraction pattern of the Mn(TIB)2 material in Example 6 of the present invention.

[0037] Figure 20 This is the X-ray diffraction pattern of the Ca(TIB)2 material of Comparative Example 1 of the present invention.

[0038] Figure 21 This is an adsorption isotherm diagram of the Ca(TIB)2 material of Comparative Example 1 of the present invention for carbon dioxide, acetylene and ethylene at 298 K. Detailed Implementation

[0039] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] It should be noted that the technical terms used in this invention are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of this invention. Unless otherwise specified, all raw materials, reagents, instruments and equipment used in the following embodiments of this invention can be purchased from the market or prepared by existing methods.

[0041] Compared to traditional porous adsorbents such as zeolite molecular sieves and activated carbon, metal-organic frameworks (MOFs) or porous coordination polymers (PCPs), as emerging crystalline porous materials, have shown significant advantages in the separation of light hydrocarbon mixtures. Traditional materials are often limited by low adsorption capacity and selectivity, making it difficult to meet the demands of industrial applications. An ideal CO2 / C2H2 / C2H4 separation adsorbent should possess good adsorption capacity, high selectivity, and moderate heat of adsorption; furthermore, industrial applications must consider important parameters such as stability and scalability. However, in currently reported MOFs used for the separation of this ternary mixture, a trade-off often exists between adsorption capacity and separation selectivity, a problem that is widespread and has not yet been effectively resolved. Therefore, developing novel adsorbents that combine high adsorption performance with practical application potential remains a significant challenge in this field.

[0042] Based on this, firstly, the present invention provides a three-dimensional flexible metal-organic framework material, the general structural formula of which is A(TIB)2, wherein A is a transition metal cation and TIB is 1,3,5-tris(1H-imidazol-1-yl)benzene; in the three-dimensional flexible metal-organic framework material, the nitrogen atom in each imidazole on the 1,3,5-tris(1H-imidazol-1-yl)benzene ligand that is not connected to the benzene ring coordinates with the transition metal cation to form a two-dimensional layered network structure, and each transition metal cation in the two-dimensional layer forms an octahedral coordination configuration with six nitrogen atoms; and each two-dimensional layer is further assembled into a three-dimensional framework structure through π-π interaction, CH···π interaction and van der Waals force stacking to obtain the three-dimensional flexible metal-organic framework material.

[0043] It should be noted that in the aforementioned A(TIB)2 three-dimensional flexible MOF, the layers are stacked and assembled through a series of non-covalent interactions (mainly π-π stacking, supplemented by CH···π interactions and van der Waals forces), rather than through strong chemical bonds (coordination bonds). It is these relatively weak interactions that give the material its "flexible" characteristic—when external stimuli (such as gas adsorption, temperature, and pressure changes) occur, the distance and relative position between the layers can be reversibly adjusted to a certain extent, thus exhibiting excellent selective adsorption and separation performance for specific gases.

[0044] The transition metal cations mentioned are cadmium ions, cobalt ions, nickel ions, zinc ions, copper ions, or manganese ions.

[0045] The aforementioned three-dimensional flexible metal-organic framework material has a size of (0.6 × 0.65 × 0.8) nm. 3 The cavity structure is interconnected by channels with dimensions of 0.3 nm × 0.2 nm; the pore volume is 0.04 cm³.3 / g~0.08cm 3 / g, specific surface area is 181m² 2 / g~182m 2 / g.

[0046] Secondly, this invention provides a method for preparing the above-mentioned three-dimensional flexible metal-organic framework material, comprising the following steps: Using 1,3,5-tris(1H-imidazol-1-yl)benzene as the organic ligand and a transition metal salt as the metal salt, a stirring or diffusion reaction was carried out in a solvent reaction system at room temperature. After filtration, washing, and subsequent vacuum activation, a three-dimensional flexible metal-organic framework material was obtained.

[0047] Preparation process such as Figure 3 As shown, in the metal-organic framework material, the nitrogen atom in each imidazole of each 1,3,5-tris(1H-imidazol-1-yl)benzene ligand that is not connected to the benzene ring is coordinated with the metal cation to form a regular two-dimensional layered network structure; each metal cation in the two-dimensional layer forms an octahedral coordination configuration with six nitrogen atoms, and each two-dimensional layer is further assembled into a stable three-dimensional framework structure through orderly stacking.

[0048] The molar ratio of the metal salt to 1,3,5-tris(1H-imidazol-1-yl)benzene is 1:0.5~10, and the metal salt is cadmium nitrate, cobalt nitrate, nickel nitrate, zinc nitrate, copper nitrate, or manganese nitrate. In a preferred embodiment of the present invention, the molar ratio of the metal salt to 1,3,5-tris(1H-imidazol-1-yl)benzene is 1:2.

[0049] The vacuum activation temperature is 60℃~120℃, and the time is 1h~24h.

[0050] When the three-dimensional flexible metal-organic framework material is in powder form, a stirred reaction is employed for 36 hours using methanol as the solvent, with a molar volume ratio of metal salt to solvent of 0.2 mmol:20 mL. The specific steps of the stirred reaction are as follows: the metal salt and 1,3,5-tris(1H-imidazol-1-yl)benzene are dissolved in methanol and transferred to a round-bottom flask containing a stir bar. The mixture is stirred with a magnetic stirrer at room temperature to obtain a powder. The powder is then washed three times with a methanol solution under vacuum and dried overnight to obtain the activated powder sample.

[0051] When the three-dimensional flexible metal-organic framework material is crystalline, a diffusion reaction is employed with ethanol and ethylene glycol as solvents. The specific steps are as follows: the metal salt and 1,3,5-tris(1H-imidazol-1-yl)benzene are dissolved in ethanol and ethylene glycol, respectively. After complete dissolution, the ethylene glycol solution containing 1,3,5-tris(1H-imidazol-1-yl)benzene is first transferred to a round-bottom glass tube. Then, an equal volume of ethanol and ethylene glycol mixed solution is slowly added to this layer to allow for separation. Subsequently, an ethanol solution containing the metal salt is slowly added, causing further separation. Finally, through slow diffusion, a crystalline sample is obtained after two weeks. The obtained crystals are collected by vacuum filtration, washed three times with methanol solution, and dried overnight under vacuum at 60°C to obtain the activated crystalline sample. In one specific embodiment, the volume of ethanol is 5 mL, the volume of ethylene glycol is 5 mL, and the volume of the equal volume ethanol and ethylene glycol mixed solution is 5 mL.

[0052] Finally, this invention provides an application of the above-mentioned three-dimensional flexible metal-organic framework material in the selective adsorption of carbon dioxide and acetylene.

[0053] The application process involves contacting the mixed gas with the three-dimensional flexible metal-organic framework material in the adsorption column at an adsorption temperature of -50℃ to 100℃ and an adsorption pressure of 0 bar to 10 bar, thereby adsorbing carbon dioxide and acetylene from the mixed gas.

[0054] The mixed gas is composed of carbon dioxide, acetylene and ethylene, wherein the volume ratio of carbon dioxide, acetylene and ethylene is 0.01~0.99:0.01~0.99:0.01~0.99.

[0055] The contact mode between the mixed gas and the three-dimensional flexible metal-organic framework material is any one of fixed bed adsorption, fluidized bed adsorption, and moving bed adsorption; the contact adsorption process is one or more combinations of single-tower or multi-tower pressure swing adsorption process, temperature swing adsorption process, and vacuum desorption adsorption process.

[0056] In one specific embodiment, a metal-organic framework material is packed into a fixed-bed adsorption column with an inner diameter of 4.6 mm and a length of 20 cm. At 298 K and 1 bar, a carbon dioxide / acetylene / ethylene mixture flows through the Cd(TIB)₂-packed fixed-bed adsorption column at a fixed flow rate of 2.0 mL / min, 4.0 mL / min, or 8.0 mL / min. The ethylene component preferentially penetrates the bed, resulting in high-purity ethylene gas (>99.95%) at the tail end of the adsorption column. Adsorption is stopped once the column has completely penetrated. The adsorption column is regenerated by purging it with helium at 120 °C; alternatively, it is regenerated by desorption using a vacuum pump at 120 °C and a vacuum level of 0.05 bar.

[0057] The aforementioned three-dimensional flexible metal-organic framework material can selectively adsorb carbon dioxide and acetylene, directly yielding ethylene gas at the tail end. The material possesses a highly stable two-dimensional layered framework and a porous surface with a positive electrostatic potential, exhibiting not only a strong ability to capture carbon dioxide molecules but also providing suitable storage space for acetylene. It can selectively adsorb and separate acetylene / carbon dioxide / ethylene mixtures, thereby achieving one-step purification of ethylene from ternary mixtures. Furthermore, its excellent recyclability, solvent stability, and thermal stability make it a promising high-efficiency adsorbent for industrial adsorption and separation applications.

[0058] The following specific examples will provide further explanation.

[0059] Example 1 A method for preparing a three-dimensional flexible metal-organic framework material crystal includes the following steps: S1. Dissolve 0.1 mmol of cadmium nitrate tetrahydrate and 0.2 mmol of 1,3,5-tris(1H-imidazol-1-yl)benzene in 5 mL of ethanol and 5 mL of ethylene glycol, respectively. After complete dissolution, first transfer the 5 mL ethylene glycol solution containing 1,3,5-tris(1H-imidazol-1-yl)benzene to a round-bottom glass tube. Then, slowly add 5 mL of an equal volume mixture of ethanol and ethylene glycol to this layer to allow for separation. Subsequently, slowly add 5 mL of an ethanol solution containing cadmium nitrate tetrahydrate to allow for further separation. Finally, through slow diffusion, a flaky white crystalline sample can be obtained after 14 days.

[0060] S2. The obtained flaky white crystals were collected by vacuum filtration, and the sample was washed three times with methanol solution. The sample was then dried under vacuum at 60°C for 12 hours to obtain the activated crystal sample. (See image below.) Figure 1 As shown.

[0061] A method for preparing a three-dimensional flexible metal-organic framework material powder includes the following steps: S1. Dissolve 0.2 mmol of cadmium nitrate tetrahydrate and 0.4 mmol of 1,3,5-tris(1H-imidazol-1-yl)benzene in 20 mL of methanol, and transfer the solution to a round-bottom flask containing a stir bar. Stir with a magnetic stirrer at room temperature for 36 h to obtain a white powder.

[0062] S2. The white powder was washed three times with methanol solution by filtration, and dried under vacuum at 60°C for 12 hours to obtain the activated powder sample. (See image below.) Figure 2 As shown.

[0063] Example 2 A method for preparing a three-dimensional flexible metal-organic framework material crystal includes the following steps: S1. Dissolve 0.1 mmol of cobalt nitrate hexahydrate and 0.2 mmol of 1,3,5-tris(1H-imidazol-1-yl)benzene in 5 mL of ethanol and 5 mL of ethylene glycol, respectively. After complete dissolution, first transfer the 5 mL ethylene glycol solution containing 1,3,5-tris(1H-imidazol-1-yl)benzene to a round-bottom glass tube. Then, slowly add 5 mL of an equal volume mixture of ethanol and ethylene glycol to this layer to allow for separation. Subsequently, slowly add 5 mL of an ethanol solution containing cobalt nitrate hexahydrate to allow for further separation. Finally, through slow diffusion, a flaky, light pink crystalline sample can be obtained after 14 days.

[0064] A method for preparing a three-dimensional flexible metal-organic framework material powder includes the following steps: S1. Dissolve 0.2 mmol of cobalt nitrate hexahydrate and 0.4 mmol of 1,3,5-tris(1H-imidazol-1-yl)benzene in 20 mL of methanol, and transfer the solution to a round-bottom flask containing a stir bar. Stir with a magnetic stirrer at room temperature for 36 h to obtain a pink powder.

[0065] S2. The pink powder was filtered and washed three times with methanol solution, and then dried under vacuum at 60°C for 12 hours to obtain the activated powder sample. (See image below.) Figure 12 As shown.

[0066] Example 3 A method for preparing a three-dimensional flexible metal-organic framework material crystal includes the following steps: S1. Dissolve 0.1 mmol of nickel nitrate hexahydrate and 0.2 mmol of 1,3,5-tris(1H-imidazol-1-yl)benzene in 5 mL of ethanol and 5 mL of ethylene glycol, respectively. After complete dissolution, first transfer the 5 mL ethylene glycol solution containing 1,3,5-tris(1H-imidazol-1-yl)benzene to a round-bottom glass tube. Then, slowly add 5 mL of an equal volume mixture of ethanol and ethylene glycol to this layer to allow for separation. Subsequently, slowly add 5 mL of the ethanol solution containing nickel nitrate hexahydrate to allow for further separation. Finally, through slow diffusion, a plate-like light green crystalline sample can be obtained after 14 days.

[0067] A method for preparing a three-dimensional flexible metal-organic framework material powder includes the following steps: Dissolve 0.2 mmol of nickel nitrate hexahydrate and 0.4 mmol of 1,3,5-tris(1H-imidazol-1-yl)benzene in 20 mL of methanol, and transfer the solution to a round-bottom flask containing a stir bar. Stir with a magnetic stirrer at room temperature for 36 h to obtain a light green powder.

[0068] Example 4 A method for preparing a three-dimensional flexible metal-organic framework material powder includes the following steps: Dissolve 0.2 mmol of zinc nitrate hexahydrate and 0.4 mmol of 1,3,5-tris(1H-imidazol-1-yl)benzene in 20 mL of methanol, and transfer the solution to a round-bottom flask containing a stir bar. Stir with a magnetic stirrer at room temperature for 36 h to obtain a white powder.

[0069] Example 5 A method for preparing a three-dimensional flexible metal-organic framework material powder includes the following steps: Dissolve 0.2 mmol of copper nitrate trihydrate and 0.4 mmol of 1,3,5-tris(1H-imidazol-1-yl)benzene in 20 mL of methanol, and transfer the solution to a round-bottom flask containing a stir bar. Stir with a magnetic stirrer at room temperature for 36 h to obtain a light blue powder.

[0070] Example 6 A method for preparing a three-dimensional flexible metal-organic framework material powder includes the following steps: Dissolve 0.2 mmol of manganese chloride and 0.4 mmol of 1,3,5-tris(1H-imidazol-1-yl)benzene in 20 mL of methanol and transfer the solution to a round-bottom flask containing a stir bar. Stir with a magnetic stirrer at room temperature for 36 h to obtain a light brown powder.

[0071] Comparative Example 1 A method for preparing Ca(TIB)2 powder, a metal-organic framework material, includes the following steps: S1. Dissolve 0.2 mmol of calcium chloride and 0.4 mmol of 1,3,5-tris(1H-imidazol-1-yl)benzene in 20 mL of methanol, and transfer the solution to a round-bottom flask containing a stir bar. Stir the solution with a magnetic stirrer at room temperature for 36 h to obtain the powder.

[0072] S2. The powder was washed three times by filtration with methanol solution and dried under vacuum at 60°C for 12 hours to obtain the activated powder sample.

[0073] The structure and properties of the metal-organic framework material powders of Examples 1 to 6 and Comparative Example 1 were characterized.

[0074] Figure 4 The X-ray diffraction pattern shows the purity of the synthesized phase of the Cd(TIB)2 material in Example 1 of this invention and its stability after immersion in an organic solution. Figure 4 Figure (a) shows the X-ray diffraction pattern of the synthesized phase purity of Cd(TIB)₂ material, and Figure (b) shows the X-ray diffraction pattern of the stability test of Cd(TIB)₂ material after immersion in an organic solution. Figure 4It can be seen that the Cd(TIB)2 material synthesized in Example 1 exhibits high diffraction peak intensity, indicating that it has excellent crystallinity and phase purity. After being soaked in organic solution and aqueous solution for 7 days, the position and intensity of its X-ray diffraction peaks did not change significantly, further confirming that the Cd(TIB)2 material has good chemical and water stability.

[0075] Figure 5 This is a thermal stability diagram of the Cd(TIB)2 material in Example 1 of the present invention. Figure 5 Figure (a) shows a variable-temperature X-ray diffraction pattern, and figure (b) shows a thermogravimetric curve. Figure 5 As shown, the Cd(TIB)2 material synthesized in Example 1 exhibits significant weight loss at 350°C, indicating the collapse of the framework structure and demonstrating the material's high thermal stability up to 350°C.

[0076] Figure 6 This is the CO2 adsorption isotherm at 195 K for the Cd(TIB)2 material in Example 1 of the present invention. Figure 6 The smaller figures show the CO2 adsorption isotherm and pore distribution curve at 195 K. (See figures for details.) Figure 6 As shown, the Cd(TIB)₂ material synthesized in Example 1 has a specific surface area of ​​181.61 m² after CO₂ adsorption calculations at 195 K. 2 / g, pore volume is 0.04cm³ 3 / g~0.08cm 3 / g.

[0077] Figure 7 This is an adsorption isotherm diagram of carbon dioxide, acetylene, and ethylene at 298 K for the Cd(TIB)2 material of Example 1 of the present invention. Figure 7 As shown, under 298K conditions, the Cd(TIB)2 material synthesized in Example 1 adsorbed carbon dioxide, acetylene, and ethylene at adsorption capacities of 1.44 mmol / g, 1.25 mmol / g, and 0.16 mmol / g, respectively.

[0078] Figure 8 This is a kinetic adsorption curve of the Cd(TIB)2 material of Example 1 of the present invention, showing the change of acetylene and carbon dioxide adsorption capacity over time at 298K. Figure 8 The smaller graphs are linear fit plots of the kinetic adsorption curves. For example... Figure 8 As shown, when the equilibrium pressure is 1000 mbar, carbon dioxide reaches adsorption equilibrium in a very short time, acetylene reaches equilibrium in about 70 minutes, while ethylene is basically not adsorbed.

[0079] Application Example 1 The metal-organic framework material Cd(TIB)2 obtained in Example 1 was packed into a fixed-bed adsorption column with an inner diameter of 4.6 mm and a length of 20 cm. At 298 K and 1 bar, a carbon dioxide / acetylene / ethylene mixture with a volume ratio of 25:25:50 was flowed through the fixed-bed adsorption column packed with Cd(TIB)2 at a fixed flow rate of 2.0 mL / min. The ethylene component preferentially penetrated the bed, and high-purity ethylene gas (>99.95%) was obtained at the tail end of the adsorption column. Adsorption was stopped when the adsorption column had completely penetrated. The adsorption column was regenerated by purging with helium at 120 °C; or by desorption regeneration using a vacuum pump at 120 °C and a vacuum degree of 0.05 bar.

[0080] Application Example 2 The metal-organic framework material Cd(TIB)2 obtained in Example 1 was packed into a fixed-bed adsorption column with an inner diameter of 4.6 mm and a length of 20 cm. At 298 K and 1 bar, a carbon dioxide / acetylene / ethylene mixture with a volume ratio of 25:25:50 was flowed through the fixed-bed adsorption column packed with Cd(TIB)2 at a fixed flow rate of 4.0 mL / min. The ethylene component preferentially penetrated the bed, and high-purity ethylene gas (>99.95%) was obtained at the tail end of the adsorption column. Adsorption was stopped when the adsorption column had completely penetrated. The adsorption column was regenerated by purging with helium at 120 °C; or by desorption regeneration using a vacuum pump at 120 °C and a vacuum degree of 0.05 bar.

[0081] Application Example 3 The metal-organic framework material Cd(TIB)2 obtained in Example 1 was packed into a fixed-bed adsorption column with an inner diameter of 4.6 mm and a length of 20 cm. At 298 K and 1 bar, a carbon dioxide / acetylene / ethylene mixture with a volume ratio of 25:25:50 was flowed through the fixed-bed adsorption column packed with Cd(TIB)2 at a fixed flow rate of 8.0 mL / min. The ethylene component preferentially penetrated the bed, and high-purity ethylene gas (>99.95%) was obtained at the tail end of the adsorption column. Adsorption was stopped after the column had completely penetrated. The adsorption column was regenerated by purging it with helium at 120 °C; or by desorption regeneration using a vacuum pump at 120 °C and a vacuum degree of 0.05 bar.

[0082] Application Example 4 The metal-organic framework material Cd(TIB)2 obtained in Example 1 was packed into a fixed-bed adsorption column with an inner diameter of 4.6 mm and a length of 20 cm. At 298 K and 1 bar, a carbon dioxide / acetylene / ethylene mixture with a volume ratio of 9:1:90 was flowed through the fixed-bed adsorption column packed with Cd(TIB)2 at a fixed flow rate of 4 mL / min. The ethylene component preferentially penetrated the bed, and high-purity ethylene gas (>99.95%) was obtained at the tail end of the adsorption column. Adsorption was stopped after the column had completely penetrated. The adsorption column was regenerated by purging it with helium at 120 °C; alternatively, it was regenerated by desorption using a vacuum pump at 120 °C and a vacuum degree of 0.05 bar.

[0083] Figure 9 This is a dynamic breakthrough curve of the Cd(TIB)2 material of Example 1 of the present invention at 298 K for different flow rates of a carbon dioxide / acetylene / ethylene mixed gas component (volume ratio 25:25:50). Figure 9 As shown, carbon dioxide, acetylene, and ethylene have distinct separation operating ranges, and all exhibit excellent separation performance at three flow rates (2.0 mL / min, 4.0 mL / min, and 8.0 mL / min).

[0084] Figure 10 This is a dynamic breakthrough curve of the Cd(TIB)2 material of Example 1 of the present invention at 298 K for a carbon dioxide / acetylene / ethylene mixed gas composition (volume ratio 25:25:50, flow rate 4.0 mL / min). Figure 10 As shown, the breakthrough time intervals for carbon dioxide, acetylene, and ethylene did not decrease significantly in the five cycles, maintaining good cycle stability.

[0085] Figure 11 This is a dynamic breakthrough curve of the Cd(TIB)2 material of Example 1 of the present invention at 298 K and a flow rate of 4 mL / min for a mixed gas composition of carbon dioxide / acetylene / ethylene (volume ratio 9:1:90). Figure 11 As shown, carbon dioxide, acetylene, and ethylene have distinct separation operating ranges, demonstrating excellent separation performance.

[0086] Figure 13 This is the X-ray diffraction pattern of the Co(TIB)2 material in Example 2 of the present invention. Figure 13 It can be seen that the Co(TIB)2 material synthesized in Example 2 exhibits high diffraction peak intensity, indicating that it has excellent crystallinity and phase purity.

[0087] Figure 14 This is an adsorption isotherm diagram of the Co(TIB)2 material of Example 2 of the present invention for carbon dioxide, acetylene, and ethylene at 298 K. Figure 14As shown, under 298K conditions, the Co(TIB)2 material synthesized in Example 2 adsorbed carbon dioxide, acetylene, and ethylene at adsorption capacities of 1.57 mmol / g, 1.12 mmol / g, and 0.31 mmol / g, respectively.

[0088] Figure 15 This is the X-ray diffraction pattern of the Ni(TIB)₂ material in Example 3 of the present invention. Figure 15 It can be seen that the Ni(TIB)2 material synthesized in Example 3 exhibits high diffraction peak intensity, indicating that it has excellent crystallinity and phase purity.

[0089] Figure 16 This is the adsorption isotherm diagram of the Ni(TIB)2 material of Example 3 of the present invention for carbon dioxide, acetylene, and ethylene at 298 K. Figure 16 As shown, under 298K conditions, the Ni(TIB)2 material synthesized in Example 3 adsorbed carbon dioxide, acetylene, and ethylene at adsorption capacities of 1.67 mmol / g, 1.23 mmol / g, and 0.22 mmol / g, respectively.

[0090] Figure 17 This is the X-ray diffraction pattern of the Zn(TIB)₂ material in Example 4 of the present invention. Figure 17 It can be seen that the Zn(TIB)2 material synthesized in Example 4 exhibits high diffraction peak intensity, indicating that it has excellent crystallinity and phase purity.

[0091] Figure 18 This is the X-ray diffraction pattern of the Cu(TIB)₂ material in Example 5 of the present invention. Figure 18 It can be seen that the Cu(TIB)2 material synthesized in Example 5 exhibits high diffraction peak intensity, indicating that it has excellent crystallinity and phase purity.

[0092] Figure 19 This is the X-ray diffraction pattern of the Mn(TIB)₂ material in Example 6 of the present invention. Figure 19 It can be seen that the Mn(TIB)2 material synthesized in Example 6 exhibits high diffraction peak intensity, indicating that it has excellent crystallinity and phase purity.

[0093] Figure 20 This is the X-ray diffraction pattern of the Ca(TIB)₂ material in Comparative Example 1 of this invention. Figure 20 It can be seen that its diffraction peaks have decreased significantly, and the baseline is too high overall, with uneven fluctuations.

[0094] Figure 21 This is an adsorption isotherm diagram of the Ca(TIB)₂ material of Comparative Example 1 of the present invention for carbon dioxide, acetylene, and ethylene at 298 K. Figure 21As shown, under 298K conditions, the Ca(TIB)2 material has almost no adsorption capacity for carbon dioxide and acetylene molecules.

[0095] It should be noted that when numerical ranges are involved in this invention, it should be understood that both endpoints of each numerical range, as well as any value between the two endpoints, can be selected. Since the steps and methods used are the same as in the embodiments, preferred embodiments are described here to avoid redundancy. Although preferred embodiments of this invention have been described, those skilled in the art, once they understand the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended scope of protection is intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of this invention.

[0096] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of protection of this invention and its equivalents, this invention also intends to include these modifications and variations.

Claims

1. A three-dimensional flexible metal-organic framework material, characterized in that, The general structural formula of the three-dimensional flexible metal-organic framework material is A(TIB)2, where A is a transition metal cation and TIB is 1,3,5-tris(1H-imidazol-1-yl)benzene. In the three-dimensional flexible metal-organic framework material, in the 1,3,5-tris(1H-imidazol-1-yl)benzene ligand, all nitrogen atoms on the imidazole that are not connected to the benzene ring are coordinated with the transition metal cation to form a two-dimensional layered network structure. Each transition metal cation in the two-dimensional layered network structure forms an octahedral coordination configuration with six nitrogen atoms. Furthermore, the two-dimensional layered network structures are stacked and assembled through non-covalent interactions to form a three-dimensional framework structure, thus obtaining the three-dimensional flexible metal-organic framework material.

2. The three-dimensional flexible metal-organic framework material according to claim 1, characterized in that, The transition metal cations are cadmium ions, cobalt ions, nickel ions, zinc ions, copper ions, or manganese ions.

3. The three-dimensional flexible metal-organic framework material according to claim 1, characterized in that, The three-dimensional flexible metal-organic framework material has a cavity structure with dimensions of 0.6 nm × 0.65 nm × 0.8 nm, and adjacent cavities are interconnected through channels with dimensions of 0.3 nm × 0.2 nm; the pore volume is 0.04 cm³. 3 / g~0.08cm 3 / g, specific surface area is 181m² 2 / g~182m 2 / g.

4. A method for preparing a three-dimensional flexible metal-organic framework material according to any one of claims 1 to 3, characterized in that, Includes the following steps: A three-dimensional flexible metal-organic framework material was obtained by using 1,3,5-tris(1H-imidazol-1-yl)benzene as an organic ligand and a transition metal salt as a metal salt for coordination reaction at room temperature.

5. The method for preparing the three-dimensional flexible metal-organic framework material according to claim 3, characterized in that, The molar ratio of the metal salt to 1,3,5-tris(1H-imidazol-1-yl)benzene is 1:0.5~10, and the metal salt is cadmium nitrate, cobalt nitrate, nickel nitrate, zinc nitrate, copper nitrate, or manganese nitrate.

6. The application of a three-dimensional flexible metal-organic framework material according to any one of claims 1 to 3 in the selective adsorption of carbon dioxide and acetylene.

7. The application of the three-dimensional flexible metal-organic framework material according to claim 6 in the selective adsorption of carbon dioxide and acetylene, characterized in that, When the adsorption temperature is -50℃ to 100℃ and the adsorption pressure is 0 bar to 10 bar, the mixed gas is brought into contact with the three-dimensional flexible metal-organic framework material in the adsorption column to adsorb carbon dioxide and acetylene in the mixed gas.

8. The application of the three-dimensional flexible metal-organic framework material according to claim 6 in the selective adsorption of carbon dioxide and acetylene, characterized in that, The mixed gas consists of carbon dioxide, acetylene, and ethylene, wherein the volume ratio of carbon dioxide, acetylene, and ethylene is 0.01~0.99:0.01~0.99:0.01~0.

99.

9. The application of the three-dimensional flexible metal-organic framework material according to claim 6 in the selective adsorption of carbon dioxide and acetylene, characterized in that, The contact modes between the mixed gas and the three-dimensional flexible metal-organic framework material are fixed-bed adsorption, fluidized-bed adsorption, or moving-bed adsorption.

10. The application of the three-dimensional flexible metal-organic framework material according to claim 6 in the selective adsorption of carbon dioxide and acetylene, characterized in that, The contact adsorption process is at least one of the following: single-tower or multi-tower pressure swing adsorption process, temperature swing adsorption process, and vacuum desorption adsorption process.

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