A hydrogen-bonding organic framework material based on electron-rich alkyne functionalization and a preparation method and application thereof

Abstract

The application discloses a kind of hydrogen bond organic framework (HOFs) material based on electron-rich alkyne functionalization and preparation method and application thereof.The material is porous crystalline material formed by hydrogen chain connection self-assembly from tetracarboxylic acid organic ligand, structure is typical sql topology, with one-dimensional rhombic channel with window size of, and the abundant electron-rich alkyne and carboxylic acid oxygen site are distributed on pore surface.Preparation method is as follows: using higher purity tetracarboxylic acid organic ligand ethynyl biphenyl-3,3',5,5'-tetracarboxylic acid (H4EBDC);H4EBDC is dissolved in organic reagent, after gas phase diffusion, solvent exchange, activation, HOF material for efficient separation of ethane / ethylene can be obtained.The HOF material has the characteristics of strong predictability, regular ordered channel, electron-rich alkyne functionalization in structure, shows excellent ethane / ethylene separation performance, good cycle performance and easy to repair and renewable characteristics in function, has application prospect in important industrial field of light hydrocarbon separation.

Description

Technical Field

[0001] This invention relates to the technical field of hydrogen-bonded organic nanomaterials and the purification of important olefin gases, specifically to a hydrogen-bonded organic framework (HOF) material based on electron-rich alkyne functionalization, its preparation method and application, which can be used for the efficient and selective separation of ethane / ethylene. Background Technology

[0002] Ethylene (C2H4) is a basic chemical raw material for synthetic fibers, rubber, plastics (polyethylene and polyvinyl chloride), and ethanol (alcohol), and is one of the world's largest-produced chemical products. The ethylene industry plays a vital role in the national economy, and ethylene production is considered a key indicator of a country's petrochemical development level. Currently, ethylene is mainly produced industrially from naphtha or ethane (C2H6) through steam cracking. This process inevitably produces a certain amount of ethane impurities (approximately 5-9%). However, ethylene and ethane have very similar molecular sizes and volatility, making their efficient separation extremely challenging. At present, industrial separation mainly relies on heat-driven methods such as cryogenic distillation. This method requires repeated distillation-compression cycles in large distillation columns with high tray numbers (>100) under low temperature (183-258K) and high pressure (7-28 bar) conditions. This process is not only cumbersome and inefficient but also results in significant energy and cost consumption. In contrast, adsorption separation technology based on porous materials has attracted widespread attention due to its great potential in reducing energy consumption and costs.

[0003] The development of highly efficient separation adsorbents is crucial for the advancement of this separation technology. Generally, porous materials used for ethylene / ethane separation can be divided into two main categories: ethylene-selective materials and ethane-selective materials. Ethane-selective adsorbents are preferred because they allow for the direct production of high-purity ethylene at the outlet, significantly reducing energy consumption and complexity. In recent years, metal-organic frameworks (MOFs) and metal-containing zeolites have been used for ethylene / ethane separation. However, because the metal ions / clusters in these materials typically form highly polar pore surface environments, they interact more strongly with ethylene molecules, which have higher quadrupole moments. This results in most MOF materials and metal-containing zeolites preferentially adsorbing ethylene, hindering the simplification of separation steps and the reduction of energy consumption. In recent years, a new class of hydrogen-bonded organic frameworks (HOFs) materials have been considered as very promising ethane-selective materials because they are self-assembled by organic ligands linked by hydrogen bonds, have high specific surface area, strong solvent processability, easy regeneration and self-repair, and their naturally metal-free nonpolar / inert porous surface is conducive to the preferential adsorption of ethane molecules.

[0004] Currently, research on HOF materials for ethane / ethylene separation is relatively limited, and due to the lack of suitable functional sites, they generally suffer from low ethane adsorption capacity and poor selectivity. However, due to the unique properties of hydrogen bonds (weak bond energy and poor directionality), the functionalization of HOF materials is extremely challenging. Common functional sites, such as Lewis N sites, –NH2, and –OH, participate in hydrogen bond formation, often failing to achieve the desired structure and function. This invention utilizes an alkynyl-functionalized organic ligand of tetracarboxylic acid, ethynylbiphenyl-3,3',5,5'-tetracarboxylic acid (H4EBDC), to successfully synthesize a novel hydrogen-bonded organic framework material with an SQL topology. This material exhibits strong structural predictability, possessing regular and ordered one-dimensional rhombic channels with abundant electronegative alkynyl sites and carboxylic acid oxygen sites, enabling preferential adsorption of ethane molecules, resulting in high ethane adsorption capacity and ethane / ethylene selectivity, thus achieving efficient separation of ethane / ethylene. Summary of the Invention

[0005] This invention addresses the shortcomings of existing technologies by providing an electron-rich alkyne-functionalized hydrogen-bonded organic framework (HOF) material, its preparation method, and its applications. This HOF material possesses regularly ordered one-dimensional rhombic channels, enabling preferential adsorption of ethane molecules in an ethane / ethylene mixture, resulting in high-purity ethylene in a single step and achieving highly efficient ethane / ethylene separation. The HOF material exhibits high ethane adsorption capacity and good ethane / ethylene separation selectivity, demonstrating promising application prospects in the fields of ethane / ethylene separation and ethylene purification.

[0006] The present invention adopts the following technical solution:

[0007] A HOF material based on electron-rich alkyne functionalization, wherein the material is a framework material with a two-dimensional network structure formed by the self-assembly of the organic ligand ethynylbiphenyl-3,3',5,5'-tetracarboxylic acid through hydrogen bonding; the HOF material has The rhombic one-dimensional channels contain abundant electronegative alkynyl sites and carboxylic acid oxygen sites, which can provide a favorable adsorption environment for ethane gas and achieve excellent ethane / ethylene separation performance.

[0008] The preparation method of the HOF material includes the following steps:

[0009] (1) Obtain the tetracarboxylic acid organic ligand ethynylbiphenyl-3,3',5,5'-tetracarboxylic acid (abbreviated as H4EBDC);

[0010] (2) H4EBDC was dissolved in a good organic solvent and then placed in a poor solvent vapor atmosphere to obtain the HOF material ZJU-HOF-60 with good crystallinity by gas phase diffusion method.

[0011] (3) After solvent exchange of HOF material with low boiling point reagent, solvent molecules in its pores are removed by supercritical carbon dioxide activation method and vacuum activation method to obtain HOF material ZJU-HOF-60a for efficient separation of ethane / ethylene.

[0012] In the above technical solution, furthermore, in step (1), tetracarboxylic acid organic ligands H4EBDC of different purities can be obtained by different methods, the methods of which include the following:

[0013] 1) Synthesis of high-purity H4EBDC via reaction: A substitution reaction is employed, with palladium(II) di(triphenylphosphine) dichloride, copper iodide (I), and diethyl 5-iodo-1,3-benzenediacarboxylic acid added to a mixed solution of tetrahydrofuran and diisopropylamine. Subsequently, a tetrahydrofuran solution containing diethyl 5-ethynyl-1,3-benzenediacarboxylic acid is added dropwise, and the reaction is stirred at 25°C for 24 h. After rotary evaporation, drying, and column chromatography purification, 5,5'-(1,2-ethynyl)bis(1,3-benzenediacarboxylic acid) diethyl ester is obtained. A hydrolysis reaction is then employed, with the above product solution poured into a mixed solution of methanol and potassium hydroxide, and the reaction is stirred and heated in a pressure tube for 12 h. After cooling, rotary evaporation, acidification, washing, filtration, recrystallization, and drying, the target product H4EBDC with high purity (typically >99%) is finally obtained.

[0014] 2) Purchase commercially available unpurified H4EBDC (typically with a purity ≤98%);

[0015] The different purities of H4EBDC have a significant impact on the phase composition of the HOF materials subsequently prepared. Using unpurified commercially available H4EBDC usually results in a mixed-phase HOF powder, which cannot be obtained as a single crystal and will affect the performance of the material.

[0016] Furthermore, the H4EBDC benign organic solvent mentioned in step (2) is one or more of N,N-dimethylformamide, N,N-diethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, tetrahydrofuran, ethanol, and methanol; preferably tetrahydrofuran;

[0017] Furthermore, the unsuitable solvent for H4EBDC mentioned in step (2) is one or more of diethyl ether, n-hexane, acetone, dichloromethane, chloroform, ethyl acetate, petroleum ether, and cyclohexane; preferably ethyl acetate.

[0018] Furthermore, the concentration of the organic ligand H4EBDC in step (2) is 2-30 mg / mL. –1 ;

[0019] Furthermore, the temperature of the gas phase diffusion in step (2) is 0-50℃; the gas phase diffusion time is 7-21 days; the preferred temperature is 25℃ and the preferred time is 14 days.

[0020] Furthermore, the low-boiling-point solvent mentioned in step (3) is one of anhydrous diethyl ether, anhydrous n-hexane, high-purity acetone, and high-purity dichloromethane (high purity refers to a concentration ≥99.8%); preferably high-purity acetone.

[0021] Furthermore, the solvent exchange in step (3) is performed no less than 8 times, with an interval of no less than 3 hours between each exchange. Then, supercritical carbon dioxide activation and vacuum activation at room temperature for 12 hours are performed sequentially to obtain HOF material with solvent molecules removed.

[0022] Unless otherwise stated, all raw materials and reagents used are commercially available analytical grade products and have not undergone further purification before use.

[0023] The above preparation method can yield HOF materials with good crystallinity. The HOF material ZJU-HOF-60 in this invention crystallizes in a triclinic crystal system. The space group is I2 / m, and the cell parameters are a = 6.824(2), b = 14.235(4), c = 14.278(3), α = 70.00(3)°, β = 88.62(2)°, γ = 76.31(2)°. ZJU-HOF-60a crystallizes in the monoclinic system, space group I2 / m, and the cell parameters are a = 3.647(3), b = 16.438(14), c = 20.954(2), α = γ = 90°, β = 91.58(6)°.

[0024] In this invention, by introducing electron-rich alkynyl groups, the surface of the HOF material is covered with abundant electronegative alkynyl sites and carboxylic acid oxygen sites, which enables high ethane adsorption capacity and high ethane / ethylene separation selectivity, thereby achieving efficient ethane / ethylene separation performance. It also has good self-healing and regenerability, making the HOF material show good application prospects in the important industrial field of light hydrocarbon separation.

[0025] The inventive principle of this invention is as follows:

[0026] This invention addresses the significant challenges in industrial ethane / ethylene separation, including insufficient adsorption capacity and low selectivity, as well as the difficulty in functionalizing HOF materials. It designs and synthesizes a novel HOF material functionalized with electron-rich alkyne groups, achieving highly efficient separation of ethane / ethylene mixtures. First, a high-purity tetracarboxylic acid organic ligand, H4EBDC, is synthesized via a chemical reaction. Then, a novel alkyne-functionalized HOF material is prepared via gas-phase diffusion. This HOF material possesses regularly ordered one-dimensional rhombic channels with a pore size of [missing information]. Compared with common ethane-selective HOF materials that utilize nonpolar / inert pore surfaces, this HOF material has abundant electronegative alkyne and carboxylic acid oxygen sites on its pore surface, which can provide a favorable adsorption environment for ethane gas, thereby achieving efficient separation of ethane / ethylene and showing good application prospects in the important industrial field of light hydrocarbon separation.

[0027] The beneficial effects of this invention are as follows:

[0028] This invention provides a hydrogen-bonded organic framework (HOF) material based on electron-rich alkyne functionalization, which can be used as a physical adsorbent for the efficient separation of ethane and ethylene, showing promising application prospects in the important industrial field of light hydrocarbon separation. Compared with existing technologies, its main advantages are as follows:

[0029] (1) The organic molecular units involved in this invention have the advantages of being environmentally friendly and biocompatible.

[0030] (2) A novel electron-rich alkyne-functionalized HOF material was designed and synthesized. The material is a novel HOF material formed by self-assembly through hydrogen bonding using a tetracarboxylic acid organic ligand as a linker. It has good crystallinity, which is beneficial for determining the material structure by single-crystal analysis and for studying the relationship between the material structure and properties.

[0031] (3) The HOF material involved in this invention has good structural designability. Its structure is a typical two-dimensional network structure, which realizes the functional construction of the HOF structure without introducing additional hydrogen bonds; it has regular and ordered one-dimensional rhombic channels with a pore size of [missing information]. The surface of the pores is covered with a rich array of electronegative alkynyl and carboxylic acid oxygen atoms, which can provide multiple binding sites for ethane molecules.

[0032] (4) The HOF material involved in this invention successfully achieves high ethane adsorption capacity and high ethane / ethylene selectivity. Currently reported ethane-selective HOF materials often fail to achieve both high adsorption capacity and selectivity simultaneously due to a lack of functional sites. The HOF material described above exhibits an ethane adsorption capacity as high as 3.79 mmol g under ambient temperature and pressure (296 K and 1 bar) conditions. –1 Under these conditions, the ethane / ethylene adsorption ratio reaches 1.58, and the separation selectivity is calculated to be 1.80. Its overall performance ranks among the top in commercially available porous materials and similar materials reported to date.

[0033] (5) The HOF material involved in this invention has the characteristics of good cycle stability, simple preparation process, mild synthesis conditions, easy regeneration and self-repair, which is conducive to its large-scale industrial production and application. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of a specific process for the synthesis of organic ligands in this invention.

[0035] Figure 2 This invention relates to the nuclear magnetic resonance (NMR) of organic ligands. 1 H and 13 C) Atlas.

[0036] Figure 3 This is a schematic diagram of the microcrystalline structure of the material in Example 1.

[0037] Figure 4 The image shows the PXRD pattern of the material in Example 1.

[0038] Figure 5 The image shows the 77K nitrogen isotherm full adsorption curve of the material in Example 1.

[0039] Figure 6 The images show the PXRD patterns of the material before and after the adsorption test in Example 1.

[0040] Figure 7 The image shows the single-component isothermal adsorption curves (296 K) of ethane and ethylene in Example 1.

[0041] Figure 8 The IAST separation selectivity (296K) of the material in Example 1 for ethane / ethylene (50 / 50, v / v) and ethane / ethylene (10 / 90, v / v) mixtures.

[0042] Figure 9 The material-packed column in Example 1 was subjected to a pressure of 298 K, 1 bar total pressure, and 1.25 mL min. –1 Dynamic breakthrough test curves of 50 / 50 ethane / ethylene under total flow rate. Detailed Implementation

[0043] The following examples will further illustrate the content of the present invention. However, these examples do not limit the scope of protection of the present invention. Based on the technical solution of the present invention, various modifications or variations that can be made by those skilled in the art without creative effort are still within the scope of protection of the present invention.

[0044] Example 1

[0045] Organic ligand synthesis process:

[0046] Synthesis of compound 5,5'-(1,2-ethynyl)bis(1,3-phthalic acid)diethyl ester (3):

[0047] First, 20 mL of tetrahydrofuran and 10 mL of diisopropylamine were added to a 50 mL reaction flask, and the solvent was bubbled with nitrogen to remove gas. 35.5 mg of bis(triphenylphosphine)palladium dichloride (II), 28.7 mg of copper iodide (I), and 315 mg of diethyl 5-iodo-1,3-benzenediacarboxylate (1) were added to the reaction flask, and the mixture was stirred at 25 °C for 30 min. Then, 200 mg of diethyl 5-ethynyl-1,3-benzenediacarboxylate (2) was dissolved in 5 mL of tetrahydrofuran, and the solvent was added dropwise to the reaction flask. The mixture was then reacted at 25 °C for 24 h. After the reaction was complete, the organic solvent was dried by rotary evaporation, and the crude product was purified by column chromatography to obtain a high-purity pale yellow compound 3. Yield: 310 g, 82%. 1 H NMR (400MHz, CDCl3, ppm): δ = 8.68 (t, J = 1.6Hz, 2H), 8.40 (d, J = 1.6Hz 2H), 4.45 (q, J = 7.2Hz, 8H), 1.45 (t, J = 7.2Hz, 12H); 13 CNMR (100MHz, CDCl3) δ = 165.46, 136.87, 131.83, 130.94, 123.88, 89.50, 62.06, 14.72.

[0048] Synthesis of the organic compound ethynylbiphenyl-3,3',5,5'-tetracarboxylic acid (4):

[0049] 200 mg of compound 3 (0.429 mmol), 240 mg of potassium hydroxide, and 2 mL of methanol were added to a 250 mL pressure tube. The mixture was heated to 80 °C and reacted for 12 h. After cooling, the organic layer was removed by spin-dip evaporation, and then a certain amount of water was added, followed by 2 mol L... –1The pH of the solution was adjusted to approximately 2 with HCl, resulting in a white precipitate. The white precipitate was filtered, washed, and dried to obtain a high-purity (>99%) white organic molecular unit 4. Yield: 140 mg, 70%. See [link to product description]. Figure 2 , 1 H NMR (400MHz, DMSO-d6, ppm): δ = 8.45 (s, 2H), 8.32 (s, 4H), 13.53 (bs, 4H); 13 CNMR (100MHz, DMSO-d6): δ=166.16, 136.24, 132.44, 130.51, 123.22, 89.31.

[0050] HOF material synthesis:

[0051] Add 10 mg of the organic molecular unit H4EBDC and 5 mL of tetrahydrofuran to a 20 mL vial. After sonicating to dissolve, seal the vial with plastic wrap, then poke a hole with a needle. Place the vial into a 100 mL sealed bottle containing 30 mL of ethyl acetate and seal it. After two weeks of gas-phase diffusion at 25 °C, colorless, transparent needle-like crystals can be obtained at the bottom of the vial, named ZJU-HOF-60.

[0052] The obtained homogeneous crystalline material was subjected to multiple solvent exchange processes in high-purity acetone, with each exchange occurring at least 3 hours apart. Subsequently, liquid carbon dioxide was used for exchange for 3 hours, during which time the liquid carbon dioxide was discharged under positive pressure for 5 minutes per hour, with the discharge rate consistently kept below the loading rate. After 3 hours of venting and soaking with liquid carbon dioxide, the drying chamber was sealed, and the temperature was raised to 40°C. This caused the chamber pressure to exceed the critical point of carbon dioxide (1300 psi), and the chamber was maintained above the critical point for 1 hour, during which time the chamber was slowly vented over 2 hours. Then, the dried sample was subjected to vacuum degassing at room temperature for 12 hours, ultimately yielding the HOF material ZJU-HOF-60a with solvent molecules removed.

[0053] The obtained HOF material was subjected to single-crystal X-ray diffraction tests, and its microstructure schematic diagram is shown in [Figure number missing]. Figure 3 PXRD characterization data can be found in Figure 4 The material is a frame material with a SQL topology network structure and one-dimensional rhombic channels, and its pore size is [missing information]. The pores contain abundant electronegative alkynyl sites and carboxylic acid oxygen sites, which can provide a favorable adsorption environment for ethane gas, enabling efficient separation of ethane / ethylene.

[0054] To test the specific surface area of ​​the activated ZJU-HOF-60a structure, a nitrogen isotherm adsorption test was performed at 77 K. The results are shown below. Figure 5The specific surface area of ​​BET is 1056.8 m². 2 g –1 .

[0055] To characterize the adsorption and performance of ZJU-HOF-60a for ethane and ethylene, its isothermal adsorption curves for ethane and ethylene at 296 K and 1 bar were tested. Figure 7 It can be seen that ZJU-HOF-60a exhibits excellent ethane / ethylene separation performance. (From...) Figure 8 It can be seen that this material has excellent separation performance for both 50 / 50 and 10 / 90 ethane / ethylene mixtures.

[0056] To simulate the actual industrial separation process, a dynamic breakthrough experiment was used to evaluate the practical separation effect of ZJU-HOF-60a on an ethane / ethylene mixture. 0.758 g of activated sample was packed into a packed column as the fixed bed of the adsorption tower, followed by a flow rate of 1.25 mL / min. –1 A breakthrough experiment was conducted by introducing a 50 / 50 ethane / ethylene mixture at a flow rate of [missing information]. Figure 9 As can be seen from the figure, ZJU-HOF-60a can achieve efficient separation of a 50 / 50 ethane / ethylene mixture.

[0057] The above are only some preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art should understand that any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A hydrogen-bonded organic framework material based on electron-rich alkynyl functionalization, said material being formed by hydrogen bonding of organic ligands ethynylbiphenyl-3,3',5,5'-tetracarboxylic acid. SQL A two-dimensional framework material with a topological size of 8.1 × 8.9 Å. 2 The material has one-dimensional rhombic channels containing abundant electronegative alkynyl and carboxylic acid oxygen sites; the material is named ZJU-HOF-60a, and its structure crystallizes in a monoclinic crystal system. I The space group is 2 / m, and the cell parameters are a = 3.647(3), b = 16.438(14), c = 20.954(2), α = γ = 90°, β = 91.58(6)°.

2. The method for preparing hydrogen-bonded organic framework materials based on electron-rich alkyne functionalization according to claim 1, characterized in that, It is prepared by a method including the following steps: (1) Obtain the tetracarboxylic acid organic ligand ethynylbiphenyl-3,3',5,5'-tetracarboxylic acid; (2) Ethynylbiphenyl-3,3',5,5'-tetracarboxylic acid was dissolved in a good organic solvent to obtain an ethynylbiphenyl-3,3',5,5'-tetracarboxylic acid H4EBDC solution, which was then placed in a poor solvent vapor atmosphere and the HOF material with good crystallinity was obtained by gas phase diffusion method. (3) After solvent exchange of HOF material with low boiling point solvent, solvent molecules in its pores are removed by supercritical carbon dioxide activation method and vacuum activation method, and hydrogen bond organic framework material based on electron-rich alkyne functionalization can be obtained.

3. The method for preparing hydrogen-bonded organic framework materials based on electron-rich alkyne functionalization according to claim 2, characterized in that, The benign organic solvent is one or more of N,N-dimethylformamide, N,N-diethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, tetrahydrofuran, ethanol, and methanol.

4. The method for preparing hydrogen-bonded organic framework materials based on electron-rich alkyne functionalization according to claim 2, characterized in that, The benign organic solvent mentioned is tetrahydrofuran.

5. The method for preparing hydrogen-bonded organic framework materials based on electron-rich alkyne functionalization according to claim 2, characterized in that, The concentration of the H4EBDC solution is 2-30 mg / mL. –1 .

6. The method for preparing hydrogen-bonded organic framework materials based on electron-rich alkyne functionalization according to claim 2, characterized in that, The unsuitable solvent is one or more of the following: diethyl ether, n-hexane, acetone, dichloromethane, chloroform, ethyl acetate, petroleum ether, and cyclohexane.

7. The method for preparing hydrogen-bonded organic framework materials based on electron-rich alkyne functionalization according to claim 2, characterized in that, The unsuitable solvent is ethyl acetate.

8. The method for preparing hydrogen-bonded organic framework materials based on electron-rich alkyne functionalization according to claim 2, characterized in that, The temperature for gas phase diffusion is 0-60 ℃; the time for gas phase diffusion is 7-21 days.

9. The method for preparing hydrogen-bonded organic framework materials based on electron-rich alkyne functionalization according to claim 2, characterized in that, The gas phase diffusion temperature is 25 °C, and the time is 14 days.

10. The method for preparing hydrogen-bonded organic framework materials based on electron-rich alkyne functionalization according to claim 2, characterized in that, The low-boiling-point solvent is one of anhydrous diethyl ether, anhydrous n-hexane, high-purity acetone, and high-purity dichloromethane; the solvent exchange is performed no less than 8 times, with an interval of no less than 3 hours between each exchange.

11. An ethane adsorbent, characterized in that, The material contains the material as described in claim 1 or the hydrogen-bonded organic framework material obtained by the preparation method according to any one of claims 2-10.

12. The application of the material as described in claim 1 or the hydrogen-bonded organic framework material obtained by the preparation method according to any one of claims 2-10 in the separation of ethane / ethylene gas.

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