A covalent organic framework material for xenon-nitrogen separation and a preparation method and application thereof

Abstract

The application discloses a kind of covalent organic framework material for xenon gas nitrogen separation and its preparation method and application, select the high affinity of metal ions to phenanthroline, and prepare two-dimensional and three-dimensional covalent organic framework with it as monomer respectively;Periodically arranged phenanthroline covalent organic framework structural unit can provide a large number of adsorption sites for metal ions, at the same time, using the strong adsorption of metal ions to Xe, introduce metal ions as accessible polar sites on the surface of covalent organic framework pore, enhance its ability to induce Xe polarization, improve its adsorption separation efficiency;The material prepared by the application has good xenon gas nitrogen separation performance, after adsorbing nickel ions, the xenon adsorption capacity of covalent organic framework is increased by 2.24 times, the xenon adsorption capacity can reach 8.7 cm 3 / g under the condition of 298 K, 1 bar, and IAST selectivity can reach 3.8.The organic covalent framework gas separation performance presented by the application is good, and it has important significance for high-performance xenon gas nitrogen separation.

Description

Technical Field

[0001] This invention belongs to the field of materials preparation and relates to a method for preparing a covalent organic framework material, specifically a covalent organic framework material for xenon-nitrogen separation, its preparation method, and its application. Background Technology

[0002] Xenon (Xe) is an important rare gas in the national economy, and its high price is used in industries such as lighting displays, electronic chips, satellite medical systems, and building doors and windows. Nuclear energy, as a clean energy source, plays an irreplaceable role in my country's efforts to achieve carbon neutrality and peak carbon emissions. However, the natural abundance of rare gases decreases with increasing atomic number, directly affecting their market price. For example, the price of one gram of xenon can be comparable to, or even higher than, the price of gold. A decrease in the market price of high-quality xenon will benefit the medical and commercial sectors and promote the development of new xenon applications.

[0003] The high cost of xenon stems from the current energy- and capital-intensive cryogenic distillation separation process for air, as well as the low concentration of xenon in the air. Traditional krypton-xenon separation typically relies on cryogenic distillation based on the boiling point difference between krypton and xenon molecules. This method is mature and has been industrialized on a large scale; however, it requires sophisticated equipment, consumes enormous amounts of energy, and does not meet the requirements for low-carbon and environmentally friendly practices.

[0004] The selective adsorption of xenon from exhaust gases using nanoporous adsorbents has become an important research direction in recent years. Porous materials with customizable pore sizes, functionalizable surfaces, and rich host-guest chemistry have been extensively studied. Adsorption-based separation methods mainly include carbon materials, zeolites, metal-organic frameworks (MOFs), and porous organic solids. Emerging crystalline MOFs exhibit excellent xenon adsorption performance due to their uniform pore size and tunable pore surface chemistry. However, because MOFs are primarily composed of coordination bonds, they suffer from extremely poor stability under high temperature, high humidity, and high radiation conditions, especially during spent fuel reprocessing when several radioactive gases and coexisting acidic gases (such as NO) are present. x In the case of HNO3, strong covalently bonded covalent organic frameworks (MOFs) exhibit excellent chemical and thermal stability, making them suitable for xenon separation under harsh conditions. However, the xenon adsorption and separation efficiency of MOFs is lower than that of representative MOFs because they have weaker polarization effects on inert gases, resulting in lower xenon adsorption capacity and selectivity. For xenon adsorbent systems, inductive interactions mainly arise from the electronic charge on the porous solid surface. Therefore, introducing metal ions as accessible polar sites on the porous surface of MOFs can enhance their ability to induce xenon polarization and improve their adsorption and separation efficiency. Summary of the Invention

[0005] The purpose of this invention is to provide a covalent organic framework material for xenon-nitrogen separation, its preparation method, and its application. The prepared material has good xenon adsorption and xenon-nitrogen separation performance.

[0006] This invention is achieved through the following technical solution:

[0007] A method for preparing a covalent organic framework material for xenon-nitrogen separation includes the following steps:

[0008] First, the aldehyde monomer of o-phenanthroline was prepared;

[0009] Then, covalent organic frameworks were synthesized using aldehyde-modified monomers of o-phenanthroline;

[0010] Finally, based on the properties of o-phenanthroline, its pore surface was modified with metal ions, and metal ions were introduced into the covalent organic framework to adjust its surface electric field, thereby promoting the selective adsorption of xenon by the covalent organic framework and obtaining a covalent organic framework material for xenon-nitrogen separation.

[0011] Furthermore, the preparation method of the aldehyde-modified monomer of o-phenanthroline specifically involves adding 3,8-dibromo-1,10-phenanthroline, pinacol ester of 4-formylphenylboronic acid, and potassium carbonate in a molar ratio of (0.5-1):(1-3):(1-4) to a mixed solvent of tetrahydrofuran and deionized water; after purging with nitrogen for a period of time, adding 0.05-0.3 times the molar amount of tetra(triphenylphosphine)palladium to 3,8-dibromo-1,10-phenanthroline, and reacting at 60-80 °C for 24-72 h under a nitrogen atmosphere to obtain the aldehyde-modified o-phenanthroline monomer.

[0012] Furthermore, the covalent organic framework consists of two-dimensional sp... 2 Carbon-carbon linked o-phenanthroline covalent organic framework and three-dimensional imine linked o-phenanthroline covalent organic framework.

[0013] Furthermore, the two-dimensional sp 2 The preparation method of carbon-carbon linked o-phenanthroline covalent organic framework involves adding aldehyde-modified o-phenanthroline monomer, 2,4,6-trimethyl-1,3,5-triazine, benzoic acid, and benzoic anhydride in a molar ratio of (1-3):(1-2):(0.1-1):(1-6) into a Pyrex tube, rapidly freezing it with liquid nitrogen, sealing the glass tube with a flame, and reacting it at 120-180 °C for 48-72 h to obtain a two-dimensional covalent organic framework for xenon-nitrogen separation.

[0014] Furthermore, the preparation method of the three-dimensional imine-linked o-phenanthroline covalent organic framework specifically involves adding aldehyde-modified o-phenanthroline monomer and tetra(4-aminophenyl)methane in a ratio of (1-4):(0.5-2) to a Pyrex tube, followed by the addition of a mixed solution of trimesic acid and 1,4-dioxane. After ultrasonic homogenization, a 3-9 mol / L acetic acid solution is added, with the volume ratio of trimesic acid, 1,4-dioxane, and acetic acid solution being (5-9):(1-5):(0.4-1.2). After rapid freezing with liquid nitrogen, the glass tube is sealed with a flame and reacted at 120-180 °C for 48-72 h to obtain a three-dimensional covalent organic framework for xenon-nitrogen separation.

[0015] Furthermore, the specific method for modifying the pore surface of covalent organic frameworks with metal ions is as follows: prepare a 1-10 g / L metal salt solution, take 1-10 mg of organic covalent framework and immerse it in 10 mL of metal salt solution, stir for 8-24 h and sonicate for 10 min at the beginning and end respectively, filter and collect the solid product after the end, and obtain the metal ion modified covalent organic framework material, which is the covalent organic framework material used for xenon and nitrogen separation.

[0016] Furthermore, the metal salts used are nickel chloride, europium chloride hexahydrate, or cobalt chloride.

[0017] Application of covalent organic framework materials for xenon-nitrogen separation.

[0018] Features and advantages of the preparation method provided by this invention:

[0019] This invention is the first to use o-phenanthroline to construct a two-dimensional sp 2 A three-dimensional covalent organic framework (COB) was developed. A large number of metal binding sites were provided for the COB by constructing periodically arranged o-phenanthroline functional groups. Subsequently, the surface of the COB pores was modified by adsorbed metals, generating an induced electric field within the micropores, which could selectively capture and separate xenon. Utilizing the strong adsorption of Xe by metal ions, metal ions were introduced as accessible polar sites on the COB pore surface, enhancing its ability to induce Xe polarization and improving its adsorption and separation efficiency. It exhibited excellent xenon-nitrogen separation performance; the xenon adsorption capacity of the COB increased by 2.24 times after nickel ion adsorption, reaching 8.7 cm³ at 298 K and 1 bar. 3 / g, IAST selectivity can reach 3.8.

[0020] Compared to metal-organic frameworks (MOFs) commonly used for xenon adsorption and separation, the covalent organic framework prepared in this invention exhibits superior chemical and thermal stability, making it suitable for separation applications under harsh conditions such as high temperature and high humidity. This ensures greater reliability and durability during long-term and cyclic use. Furthermore, by introducing metal ions as accessible polar sites onto the pore surface of the covalent organic framework, this invention allows for the alteration of its interaction with xenon molecules by adjusting the surface charge distribution, thereby achieving effective separation of xenon and nitrogen. Attached Figure Description

[0021] Figure 1 This is a schematic diagram illustrating the synthesis of the covalent organic framework material 2D PhenCOF from Example 1.

[0022] Figure 2 The infrared spectra of the covalent organic framework material 2D PhenCOF of Example 1 and the monomers aldehyde-modified o-phenanthroline and 2,4,6-trimethyl-1,3,5-triazine used in its synthesis process are shown.

[0023] Figure 3 The X-ray diffraction pattern of 2D PhenCOF, the covalent organic framework material of Example 1;

[0024] Figure 4 This is a schematic diagram illustrating the synthesis of the covalent organic framework material 3D PhenCOF in Example 2;

[0025] Figure 5 The infrared spectra of the covalent organic framework material 3D PhenCOF of Example 2 and the monomers aldehyde-modified o-phenanthroline and tetra(4-aminophenyl)methane used in its synthesis process;

[0026] Figure 6 The X-ray diffraction pattern of the covalent organic framework material 3D PhenCOF in Example 2 is shown below.

[0027] Figure 7 The nitrogen adsorption-desorption curves at 77 K for the covalent organic framework materials 3D PhenCOF and 3D PhenCOF-Ni in Example 2 are shown.

[0028] Figure 8 The xenon adsorption curves at 298 K room temperature for the covalent organic framework materials 3D PhenCOF and 3D PhenCOF-Ni in Example 2 are shown.

[0029] Figure 9 The xenon and nitrogen adsorption curves at 298 K room temperature are for the covalent organic framework material 3D PhenCOF-Ni in Example 2.

[0030] Figure 10 The IAST selectivity curves for xenon adsorption at 298 K and nitrogen adsorption at 298 K for the covalent organic framework material 3D PhenCOF-Ni in Example 2 are shown.

[0031] Figure 11 The diagram shows the structure of the 2D PhenCOF-Ni covalent organic framework material prepared in Example 1 that adsorbs xenon.

[0032] Figure 12 The diagram shows the structure of the 3D PhenCOF-Ni covalent organic framework material prepared in Example 2, which adsorbs xenon. Detailed Implementation

[0033] The present invention will be further described in detail below with reference to specific embodiments. These descriptions are for explanation purposes only and are not intended to limit the scope of the invention.

[0034] Unless otherwise specified, the experimental methods in the following specific embodiments are conventional methods; the reagents and consumables used are commercially available unless otherwise specified.

[0035] Example 1

[0036] sp 2 Synthesis of carbon-carbon linked o-phenanthroline (COF):

[0037] (1) Synthesis of aldehyde-modified o-phenanthroline monomer: 3,8-dibromo-1,10-phenanthroline (1 g, 2.96 mmol), pinacol ester of 4-formylphenylboronic acid (2.0599 g, 8.876 mmol), and potassium carbonate (1.6356 g, 11.834 mmol) were added to a three-necked flask, followed by 50 mL of tetrahydrofuran and 10 mL of deionized water. Nitrogen gas was introduced and the mixture was stirred at room temperature for 30 min. Then, tetra(triphenylphosphine)palladium (0.8128 g, 0.444 mmol) was added, and nitrogen gas was introduced and the mixture was stirred for another 30 min. The mixture was then heated under reflux at 80 °C for 72 h. After the reaction was completed, the solution was cooled, filtered, and the solid was collected and washed three times with deionized water and tetrahydrofuran, respectively. Finally, the solid was dried under vacuum at 70 °C for 24 h to obtain a pale yellow aldehyde-modified o-phenanthroline monomer product.

[0038] (2) sp 2Synthesis of carbon-carbon linked o-phenanthroline (COF): Aldehyde-modified o-phenanthroline monomer (116.5 mg, 0.3 mmol), 2,4,6-trimethyl-1,3,5-triazine (24.7 mg, 0.2 mmol), benzoic acid (7.3 mg, 0.06 mmol), and benzoic anhydride (135.7 mg, 0.6 mmol) were added to a Pyrex tube. The tube was flash-frozen in liquid nitrogen at 77 K, and then sealed with a flame. The reaction was carried out at 180 °C for 72 h. After the reaction, the solid was collected and ground into powder. The obtained solid was extracted with Soxhlet in an acetone / methanol (1:1) mixture and chloroform solution for 12 h each. The powder was then dried under vacuum at 60 °C for 24 h to obtain sp. 2 Carbon-carbon linked o-phenanthroline COF (2D PhenCOF). The reaction process is as follows: Figure 1 As shown.

[0039] Depend on Figure 2 As can be seen from the infrared spectrum of the material prepared in this embodiment, characteristic peaks of C=C and trans-C=C groups appear. Simultaneously, the C=O characteristic peak belonging to the o-phenanthroline monomer disappears, indicating that a condensation reaction occurred between the two monomers, successfully generating a COF structure with carbon-carbon double bonds.

[0040] Depend on Figure 3 It can be seen that the material prepared in this embodiment exhibits a distinct diffraction peak around 1.5°, which matches the simulation results well. The X-ray diffraction pattern confirms that this covalent organic framework material has good crystallinity.

[0041] (3) Adsorption of metal ions: Prepare a 4.59 g / L nickel chloride solution. Soak 10 mg of 2D PhenCOF in 10 mL of nickel chloride solution. Stir for 24 h and sonicate for 10 min at the beginning and end of the process. After the process, filter and collect the solid product, and vacuum dry at 80 ℃ for 24 h to obtain the sp(s) adsorbed nickel ions. 2 Carbon-carbon linked o-phenanthroline COF (2D PhenCOF-Ni).

[0042] Example 2

[0043] Synthesis of 3D imine-linked o-phenanthroline COF:

[0044] (1) Synthesis of aldehyde-modified o-phenanthroline monomer: 3,8-dibromo-1,10-phenanthroline (1 g, 2.96 mmol), pinacol ester of 4-formylphenylboronic acid (2.0599 g, 8.876 mmol), and potassium carbonate (1.6356 g, 11.834 mmol) were added to a three-necked flask, followed by 50 mL of tetrahydrofuran and 10 mL of deionized water. Nitrogen gas was introduced and the mixture was stirred at room temperature for 30 min. Then, tetra(triphenylphosphine)palladium (0.8128 g, 0.444 mmol) was added, and nitrogen gas was introduced and the mixture was stirred for another 30 min. The mixture was then heated under reflux at 80 °C for 72 h. After the reaction was completed, the solution was cooled, filtered, and the solid was collected and washed three times with deionized water and tetrahydrofuran, respectively. Finally, the solid was dried under vacuum at 70 °C for 24 h to obtain a pale yellow aldehyde-modified o-phenanthroline monomer product.

[0045] (2) Synthesis of 3D imine-linked o-phenanthroline COF: Aldehyde-modified o-phenanthroline monomer (116.5 mg, 0.3 mmol), tetrakis(4-aminophenyl)methane (57 mg, 0.15 mmol), 3.6 mL trimesic acid, 0.4 mL 1,4-dioxane, and 0.4 mL 9 M acetic acid solution were added to a Pyrex tube. The tube was rapidly frozen in liquid nitrogen at 77 K, and then sealed with a flame. The reaction was carried out at 120 °C for 72 h. After the reaction, the solid was collected, washed several times with hot chloroform, and then Soxhlet extracted in chloroform solution for 12 h. The solid was then vacuum dried at 60 °C for 24 h to obtain 3D imine-linked o-phenanthroline COF (3DPhenCOF). The reaction process is as follows: Figure 4 As shown.

[0046] Depend on Figure 5 It can be seen from the infrared spectrum of the material prepared in this embodiment at 3400 cm⁻¹ -1 The NH peak belonging to tetra(4-aminophenyl)methane disappears and the 1600 cm⁻¹ peak is reached. -1 The formation of 3D PhenCOF belonging to C=N indicates that the material preparation was successful.

[0047] Depend on Figure 6 As can be seen, the material prepared in this embodiment exhibits strong diffraction peaks. The X-ray diffraction pattern confirms that this covalent organic framework material has good crystallinity.

[0048] (3) Adsorption of metal ions: Prepare a 4.59 g / L nickel chloride solution. Take 10 mg of 3D PhenCOF and soak it in 10 mL of nickel chloride solution. Stir for 24 h and sonicate for 10 min at the beginning and end. After the process, filter and collect the solid product, and dry it under vacuum at 80 ℃ for 24 h to obtain 3D imine-linked o-phenanthroline COF (3D PhenCOF-Ni) that adsorbs nickel ions.

[0049] Depend on Figure 7 It can be seen that the specific surface area and low-temperature nitrogen adsorption capacity of the material prepared in this embodiment slightly increased after nickel adsorption. The specific surface area of ​​the material before nickel adsorption was 16.0672 m². 2 / g increased to 23.0906m after adsorption. 2 / g. Simultaneously, after nickel adsorption, the material's low-temperature nitrogen adsorption capacity increased from 62.91 cm⁻¹. 3 / g increased to 64.73 cm 3 / g.

[0050] Depend on Figure 8 It can be seen that the xenon adsorption capacity of the material prepared in this embodiment increased by 2.24 times after adsorbing nickel. The increase in xenon adsorption capacity is due to the polarization effect between the large number of metal ions adsorbed on the o-phenanthroline monomer in the covalent organic framework material and xenon.

[0051] Depend on Figure 9 It can be seen that the material prepared in this embodiment has good xenon-nitrogen selectivity, and the xenon adsorption capacity can reach 8.7 cm⁻¹ under the conditions of 298 K and 1 bar. 3 / g, far exceeding the nitrogen adsorption capacity of 1.7 cm. 3 / g.

[0052] Depend on Figure 10 It can be seen that the material prepared in this embodiment has good xenon-nitrogen selectivity. According to the ideal adsorption solution theory (IAST), the xenon-nitrogen selectivity can reach 7-3.8 under 0-1 bar conditions.

[0053] like Figure 11 and Figure 12 The diagram shows the structure of the materials prepared in Examples 1 and 2 after xenon adsorption.

[0054] Example 3

[0055] sp 2 Synthesis of carbon-carbon linked o-phenanthroline (COF):

[0056] (1) Synthesis of aldehyde-modified o-phenanthroline monomer: 1.5 mmol of 3,8-dibromo-1,10-phenanthroline, 3.0 mmol of pinacol 4-formylphenylboronic acid, and 1.5 mmol of potassium carbonate were added to a three-necked flask, followed by 50 mL of tetrahydrofuran and 10 mL of deionized water. Nitrogen gas was introduced and the mixture was stirred at room temperature for 30 min. Then, 0.8128 g (0.444 mmol) of tetra(triphenylphosphine)palladium was added, and nitrogen gas was introduced and the mixture was stirred for another 30 min. The mixture was then heated under reflux at 60 °C for 70 h. After the reaction was completed, the solution was cooled, filtered, and the solid was collected and washed three times with deionized water and tetrahydrofuran, respectively. Finally, the solid was dried under vacuum at 70 °C for 24 h to obtain a pale yellow aldehyde-modified o-phenanthroline monomer product.

[0057] (2) sp 2 Synthesis of carbon-carbon linked o-phenanthroline (COF): Aldehyde-modified o-phenanthroline monomer (0.3 mmol), 2,4,6-trimethyl-1,3,5-triazine (0.3 mmol), benzoic acid (0.03 mmol), and benzoic anhydride (0.3 mmol) were added to a Pyrex tube. The tube was flash-frozen in liquid nitrogen at 77 K, and then sealed with a flame. The reaction was carried out at 120 °C for 70 h. After the reaction, the solid was collected and ground into powder. The obtained solid was extracted by Soxhlet extraction in an acetone / methanol (1:1) mixture and chloroform solution for 12 h, respectively. The powder was then dried under vacuum at 60 °C for 24 h to obtain sp. 2 Carbon-carbon linked o-phenanthroline COF (2D PhenCOF).

[0058] (3) Adsorption of metal ions: Prepare a 10 g / L europium chloride hexahydrate solution. Soak 5 mg of 2D PhenCOF in 10 mL of nickel chloride solution. Stir for 10 h and sonicate for 10 min at the beginning and end of the process. After completion, filter and collect the solid product, and vacuum dry at 80 ℃ for 24 h to obtain the sp(s) of adsorbed nickel ions. 2 Carbon-carbon linked o-phenanthroline COF (2D PhenCOF-Ni).

[0059] Example 4

[0060] Synthesis of 3D imine-linked o-phenanthroline COF:

[0061] (1) Synthesis of aldehyde-modified o-phenanthroline monomer: 2.1 mmol of 3,8-dibromo-1,10-phenanthroline, 6.0 mmol of pinacol 4-formylphenylboronic acid, and 7.5 mmol of potassium carbonate were added to a three-necked flask, followed by 50 mL of tetrahydrofuran and 10 mL of deionized water. Nitrogen gas was introduced and the mixture was stirred at room temperature for 30 min. Then, 0.8128 g (0.444 mmol) of tetra(triphenylphosphine)palladium was added, and stirring was continued for another 30 min under nitrogen gas. The mixture was then heated under reflux at 70 °C for 24 h. After the reaction was complete, the solution was cooled, filtered, and the solid was collected and washed three times with deionized water and tetrahydrofuran, respectively. Finally, the solid was dried under vacuum at 70 °C for 24 h to obtain a pale yellow aldehyde-modified o-phenanthroline monomer.

[0062] (2) Synthesis of 3D imine-linked o-phenanthroline COF: Aldehyde-modified o-phenanthroline monomer (0.1 mmol), tetrakis(4-aminophenyl)methane (0.05 mmol), 2.0 mL trimesic acid, 2.0 mL 1,4-dioxane, and 0.16 mL 3 M acetic acid solution were added to a Pyrex tube. The tube was rapidly frozen in liquid nitrogen at 77 K, and then sealed with a flame. The reaction was carried out at 180 °C for 48 h. After the reaction, the solid was collected, washed several times with hot chloroform, and then Soxhlet extracted in chloroform solution for 12 h. The solid was then dried under vacuum at 60 °C for 24 h to obtain 3D imine-linked o-phenanthroline COF (3D PhenCOF).

[0063] (3) Adsorption of metal ions: Prepare a 1 g / L cobalt chloride solution. Take 10 mg of 3D PhenCOF and soak it in 10 mL of nickel chloride solution. Stir for 8 h and sonicate for 10 min at the beginning and end. After the process, filter and collect the solid product, and dry it under vacuum at 80 ℃ for 24 h to obtain 3D imine-linked o-phenanthroline COF (3D PhenCOF-Ni) that adsorbs nickel ions.

[0064] Example 5

[0065] sp 2 Synthesis of carbon-carbon linked o-phenanthroline (COF):

[0066] (1) Synthesis of aldehyde-modified o-phenanthroline monomer: 2.4 mmol of 3,8-dibromo-1,10-phenanthroline, 7.5 mmol of pinacol 4-formylphenylboronic acid, and 9.0 mmol of potassium carbonate were added to a three-necked flask, followed by 50 mL of tetrahydrofuran and 10 mL of deionized water. Nitrogen gas was introduced and the mixture was stirred at room temperature for 30 min. Then, 0.8128 g (0.444 mmol) of tetra(triphenylphosphine)palladium was added, and stirring was continued for another 30 min under nitrogen gas. The mixture was then heated under reflux at 60 °C for 70 h. After the reaction was complete, the solution was cooled, filtered, and the solid was collected and washed three times with deionized water and tetrahydrofuran, respectively. Finally, the solid was dried under vacuum at 65 °C for 50 h to obtain a pale yellow aldehyde-modified o-phenanthroline monomer solid product.

[0067] (2) sp 2 Synthesis of carbon-carbon linked o-phenanthroline (COF): Aldehyde-modified o-phenanthroline monomer (0.2 mmol), 2,4,6-trimethyl-1,3,5-triazine (0.15 mmol), benzoic acid (0.2 mmol), and benzoic anhydride (0.75 mmol) were added to a Pyrex tube. The tube was rapidly frozen in liquid nitrogen at 77 K, and then sealed with a flame. The reaction was carried out at 150 °C for 48 h. After the reaction, the solid was collected and ground into powder. The obtained solid was extracted with Soxhlet in an acetone / methanol (1:1) mixture and chloroform solution for 12 h each. The powder was dried under vacuum at 60 °C for 24 h to obtain sp. 2 Carbon-carbon linked o-phenanthroline COF (2DPhenCOF).

[0068] (3) Adsorption of metal ions: Prepare a 10 g / L europium chloride hexahydrate solution. Soak 5 mg of 2D PhenCOF in 10 mL of nickel chloride solution. Stir for 10 h and sonicate for 10 min at the beginning and end of the process. After completion, filter and collect the solid product, and vacuum dry at 80 ℃ for 24 h to obtain the sp(s) of adsorbed nickel ions. 2 Carbon-carbon linked o-phenanthroline COF (2D PhenCOF-Ni).

[0069] Example 6

[0070] Synthesis of 3D imine-linked o-phenanthroline COF:

[0071] (1) Synthesis of aldehyde-modified o-phenanthroline monomer: 2.1 mmol of 3,8-dibromo-1,10-phenanthroline, 6.0 mmol of pinacol 4-formylphenylboronic acid, and 7.5 mmol of potassium carbonate were added to a three-necked flask, followed by 50 mL of tetrahydrofuran and 10 mL of deionized water. Nitrogen gas was introduced and the mixture was stirred at room temperature for 30 min. Then, 0.8128 g (0.444 mmol) of tetra(triphenylphosphine)palladium was added, and stirring was continued for another 30 min under nitrogen gas. The mixture was then heated under reflux at 70 °C for 24 h. After the reaction was complete, the solution was cooled, filtered, and the solid was collected and washed three times with deionized water and tetrahydrofuran, respectively. Finally, the solid was dried under vacuum at 70 °C for 24 h to obtain a pale yellow aldehyde-modified o-phenanthroline monomer.

[0072] (2) Synthesis of 3D imine-linked o-phenanthroline COF: Aldehyde-modified o-phenanthroline monomer (0.4 mmol), tetrakis(4-aminophenyl)methane (0.2 mmol), 2.6 mL trimesic acid, 1.3 mL 1,4-dioxane, and 0.36 mL 6 M acetic acid solution were added to a Pyrex tube. The tube was rapidly frozen in liquid nitrogen at 77 K, and then sealed with a flame. The reaction was carried out at 150 °C for 60 h. After the reaction, the solid was collected, washed several times with hot chloroform, and then Soxhlet extracted in chloroform solution for 12 h. The solid was then vacuum dried at 60 °C for 24 h to obtain 3D imine-linked o-phenanthroline COF (3D PhenCOF).

[0073] (3) Adsorption of metal ions: Prepare a 1 g / L cobalt chloride solution. Take 10 mg of 3D PhenCOF and soak it in 10 mL of nickel chloride solution. Stir for 8 h and sonicate for 10 min at the beginning and end. After the process, filter and collect the solid product, and dry it under vacuum at 80 ℃ for 24 h to obtain 3D imine-linked o-phenanthroline COF (3D PhenCOF-Ni) that adsorbs nickel ions.

Claims

1. A method for preparing a covalent organic framework material for xenon-nitrogen separation, characterized in that... Includes the following steps: First, the aldehyde monomer of o-phenanthroline was prepared; Then, covalent organic frameworks were synthesized using aldehyde-modified monomers of o-phenanthroline; Covalent organic frameworks are two-dimensional sp 2 Carbon-carbon linked o-phenanthroline covalent organic framework and three-dimensional imine linked o-phenanthroline covalent organic framework; Finally, based on the properties of o-phenanthroline, its pore surface was modified with metal ions, and metal ions were introduced into the covalent organic framework to adjust its surface electric field, thereby promoting the selective adsorption of xenon by the covalent organic framework and obtaining a covalent organic framework material for xenon-nitrogen separation.

2. The method for preparing the covalent organic framework material for xenon-nitrogen separation as described in claim 1, characterized in that: The preparation method of the aldehyde-modified monomer of o-phenanthroline is as follows: 3,8-dibromo-1,10-phenanthroline, pinacol ester of 4-formylphenylboronic acid, and potassium carbonate are added to a mixed solvent of tetrahydrofuran and deionized water in a molar ratio of (0.5-1):(1-3):(1-4); after purging with nitrogen for a period of time, 0.05-0.3 times the molar amount of tetra(triphenylphosphine)palladium is added, and the reaction is carried out at 60-80 °C for 24-72 h under a nitrogen atmosphere to obtain the aldehyde-modified o-phenanthroline monomer.

3. The method for preparing the covalent organic framework material for xenon-nitrogen separation as described in claim 1, characterized in that: The two-dimensional sp 2 The preparation method of carbon-carbon linked o-phenanthroline covalent organic framework involves adding aldehyde-modified o-phenanthroline monomer, 2,4,6-trimethyl-1,3,5-triazine, benzoic acid, and benzoic anhydride in a molar ratio of (1-3):(1-2):(0.1-1):(1-6) into a Pyrex tube, rapidly freezing it with liquid nitrogen, sealing the glass tube with a flame, and reacting it at 120-180 °C for 48-72 h to obtain a two-dimensional covalent organic framework for xenon-nitrogen separation.

4. The method for preparing the covalent organic framework material for xenon-nitrogen separation as described in claim 1, characterized in that: The preparation method of the three-dimensional imine-linked o-phenanthroline covalent organic framework specifically involves adding aldehyde-modified o-phenanthroline monomer and tetra(4-aminophenyl)methane in a ratio of (1-4):(0.5-2) to a Pyrex tube, followed by the addition of a mixed solution of trimesic acid and 1,4-dioxane. After ultrasonic homogenization, a 3-9 mol / L acetic acid solution is added, with the volume ratio of trimesic acid, 1,4-dioxane, and acetic acid solution being (5-9):(1-5):(0.4-1.2). After rapid freezing with liquid nitrogen, the glass tube is sealed with a flame and reacted at 120-180 °C for 48-72 h to obtain a three-dimensional covalent organic framework for xenon-nitrogen separation.

5. The method for preparing the covalent organic framework material for xenon-nitrogen separation as described in claim 1, characterized in that: The specific method for modifying the pore surface of covalent organic frameworks with metal ions is as follows: prepare a 1-10 g / L metal salt solution, take 1-10 mg of organic covalent framework and immerse it in 10 mL of metal salt solution, stir for 8-24 h, and sonicate for 10 min at the beginning and end respectively. After the end, filter and collect the solid product to obtain the metal ion modified covalent organic framework material, which is the covalent organic framework material used for xenon and nitrogen separation.

6. The method for preparing the covalent organic framework material for xenon-nitrogen separation as described in claim 5, characterized in that: The metal salts used are nickel chloride, europium chloride hexahydrate, or cobalt chloride.

7. A covalent organic framework material for xenon-nitrogen separation prepared by the preparation method according to any one of claims 1-6.

8. The application of the covalent organic framework material for xenon-nitrogen separation as described in claim 7 in xenon separation.

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