Three-dimensional crown ether COFs (Covalent Organic Frameworks) material with specific recognition sites as well as preparation method and application of three-dimensional crown ether COFs material

Abstract

The invention provides a three-dimensional crown ether COFs (Covalent Organic Frameworks) material with specific recognition sites as well as a preparation method and application thereof, and relates to the technical field of thorium adsorption materials. The material disclosed by the invention is constructed by carrying out condensation reaction on a tetraaldehyde 18-crown-6 monomer with C4 symmetry and an amino monomer with C3 symmetry, and presents a double-interspersed three-dimensional network structure. The three-dimensional crown ether COFs material is used for adsorption and separation of radionuclide thorium ions for the first time, the core advantage of the three-dimensional crown ether COFs material is derived from the unique synergistic effect of a crown ether functional unit and a three-dimensional porous framework, specific recognition sites for thorium ions are provided for a cavity structure of crown ether, and high-selectivity complexing of thorium ions is achieved; due to the double interpenetrating structure of the three-dimensional COFs framework, the high specific surface area, ordered pore channels and excellent stability are provided, full utilization of adsorption sites is ensured, and the application prospect is wide.

Description

Technical Field

[0001] This invention relates to the field of thorium adsorption materials technology, and in particular to a three-dimensional crown ether COFs material with specific recognition sites, its preparation method and application. Background Technology

[0002] Nuclear energy is considered one of the most promising energy sources of the future due to its cleanliness and efficiency. Currently, nuclear energy primarily relies on uranium fission; however, given the limited availability of traditional uranium resources, there is an urgent need to find an alternative nuclear fuel. Thorium is one such convertible nuclear fuel. 232 Th can be converted into usable nuclear fuel after being bombarded by neutrons. 233 Thorium, being 3 to 4 times more abundant than uranium on Earth, is considered the most ideal substitute for uranium. However, the development and utilization of thorium resources generate large amounts of thorium-containing wastewater, which poses a threat to human health. Therefore, the selective separation and enrichment of thorium from thorium-containing wastewater is of great significance.

[0003] Among the many methods for enriching and separating thorium, adsorption is widely used in the treatment of industrial thorium-containing wastewater due to its low cost, simple operation, and high efficiency. However, the separation effect of adsorption is highly dependent on the performance of the adsorbent. Currently, commonly used adsorbents for treating thorium-containing wastewater include MOF, silica, zeolite, and modified clay. The literature *Journal of Materials Science*, 2018, 53(5): 3398-3416 reports a functional fiber-structured bimodal mesoporous silica (F-SiO2-DP) material and uses it for the adsorption and separation of U(VI) and Th(Ⅳ) ions. At pH 3.8, the maximum adsorption capacity for Th(Ⅳ) is only 277 mg g. -1 Most previously reported adsorbents suffer from drawbacks such as small adsorption capacity, poor selectivity, and poor stability.

[0004] COFs are porous organic framework materials linked by covalent bonds. These materials are composed of light elements such as C, H, O, N, and B, and have advantages such as low density, high porosity, large specific surface area, high stability, good crystallinity, well-defined structure, and tunable function. They have broad application prospects in adsorption, separation, catalysis, and energy storage.

[0005] Crown ethers are cyclic ether compounds. The negatively charged oxygen atoms in crown ethers, under the influence of dipole-charge, can complex with positively charged metal cations to form stable complexes. Due to their unique cavity structure and complexing effect on metal ions, crown ether molecules are widely used as adsorbents. However, there are no reports on the use of crown ether-based COFs for the selective adsorption and separation of radioactive thorium ions. Summary of the Invention

[0006] In view of this, the present invention provides a three-dimensional crown ether COFs material with specific recognition sites, its preparation method, and its applications to solve the above problems. The three-dimensional crown ether COFs material prepared by the present invention shows great application potential in the field of efficient separation and recovery of thorium ions in nuclear waste liquids.

[0007] The technical solution of this invention is implemented as follows: A three-dimensional crown ether COFs material with specific recognition sites, wherein the three-dimensional crown ether COFs material is constructed by a condensation reaction between a tetraaldehyde 18-crown-6 monomer with C4 symmetry and an amino monomer with C3 symmetry.

[0008] Furthermore, the C4-symmetric tetraaldehyde 18-crown-6 monomer is 4,4',4'',4'''-(6,7,9,10,17,18,20,21-octahydrodi[b,k][1,4,7,10,13,16]hexaoxane-octadecene-2,3,13,14-tetramethyl)tetrabenzaldehyde; the C3-symmetric amino monomer is one of tris(4-aminophenyl)amine or 1,3,5-tris(4-aminophenyl)benzene.

[0009] Furthermore, the molar ratio of the tetraaldehyde 18-crown-6 monomer with C4 symmetry to the amino monomer with C3 symmetry is 1:1~3.

[0010] A method for preparing three-dimensional crown ether COFs materials with specific recognition sites includes the following steps: adding a tetraaldehyde 18-crown-6 monomer with C4 symmetry and an amino monomer with C3 symmetry to a reaction tube, adding organic solvent A, and ultrasonically mixing to obtain a homogeneous mixture; then adding a catalyst to the mixture, freezing the reaction tube in liquid nitrogen, evacuating and purging it with nitrogen using a vacuum pump, sealing the tube with a flame, and then obtaining the target three-dimensional crown ether COFs material after heating and crystallization, washing with organic solvent B, and vacuum drying.

[0011] Furthermore, the organic solvent A is o-dichlorobenzene; the catalyst is an aqueous solution of acetic acid; and the concentration of the aqueous solution of acetic acid is 6-9 mol / L. -1 .

[0012] Furthermore, the total mass ratio of the tetraaldehyde 18-crown-6 monomer with C4 symmetry and the amino monomer with C3 symmetry to the volume ratio of organic solvent A is 45~85 mg: 1.0~2.0 mL.

[0013] Furthermore, the volume ratio of the catalyst to organic solvent A is 1~5:10.

[0014] Furthermore, the temperature for heating and crystallization is 100~120℃, and the reaction time is 3~5 days; the temperature for vacuum drying is 80℃~120℃, and the drying time is 12h~24h.

[0015] Furthermore, the organic solvent B is one or more of tetrahydrofuran, methanol, N,N-dimethylformamide, and N,N-dimethylacetamide.

[0016] The present invention relates to the application of three-dimensional crown ether COFs materials with specific recognition sites in the adsorption of YIC thorium ions.

[0017] Compared with the prior art, the beneficial effects of the present invention are: (1) This invention is the first to use three-dimensional crown ether COFs materials for the adsorption and separation of thorium ions. Its high performance is due to two core designs: on the one hand, the double-interlaced three-dimensional network structure provides abundant transport channels and adsorption sites; on the other hand, the cavity structure of the crown ether functional unit can specifically recognize thorium ions. The two work together to achieve rapid removal of thorium ions from aqueous solution.

[0018] (2) The three-dimensional crown ether COFs material prepared in this invention has a maximum saturation adsorption capacity of 1340 mgg for thorium ions. -1 Its thorium / uranium separation factor exceeds 100, which is higher than most currently reported adsorbents. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structural model of the three-dimensional crown ether COFs materials prepared in Examples 1 and 3 of the present invention; wherein, Figure 1 (a) is a schematic diagram of the structural model of CE-TAPA-COF prepared in Example 1. Figure 1 (b) is a schematic diagram of the structural model of CE-TAPB-COF prepared in Example 3.

[0020] Figure 2 The images show the powder X-ray diffraction (PXRD) spectra of the three-dimensional crown ether COFs materials prepared in Examples 1 and 3 of this invention; wherein, Figure 2 (a) is the PXRD spectrum of CE-TAPA-COF obtained in Example 1. Figure 2 (b) is the PXRD spectrum of CE-TAPB-COF prepared in Example 3.

[0021] Figure 3 The images show the Fourier transform infrared (FT-IR) spectra of the three-dimensional crown ether COFs materials prepared in Examples 1 and 3 of this invention; wherein, Figure 3 (a) is the FT-IR spectrum of CE-TAPA-COF prepared in Example 1. Figure 3 (b) is the FT-IR spectrum of CE-TAPB-COF prepared in Example 3. Figure 4 These are scanning electron microscope (SEM) images of the three-dimensional crown ether COFs materials prepared in Examples 1 and 3 of this invention; wherein, Figure 4 (a) is a SEM image of CE-TAPA-COF prepared in Example 1. Figure 4 (b) is a SEM image of CE-TAPB-COF prepared in Example 3. In the figure, 100 nm represents the magnification.

[0022] Figure 5 The graph shows the adsorption amount and removal rate of Th(Ⅳ) of the three-dimensional crown ether COFs materials prepared in Examples 1 and 3 of this invention under different pH conditions. In the graph, the cylinder represents the adsorption amount and the broken line represents the removal rate.

[0023] Figure 6 This diagram shows the selective adsorption performance of the three-dimensional crown ether COFs materials prepared in Examples 1 and 3 of this invention for different metal ions. The horizontal axis represents different metal ions, such as strontium (Sr), cesium (Cs), uranium (U), lanthanum (La), praseodymium (Pr), samarium (Sm), gadolinium (Gd), lutetium (Lu), and thorium (Th), and the vertical axis represents K. d This represents the allocation coefficient.

[0024] Figure 7 The figures show the adsorption isotherms of the three-dimensional crown ether COFs materials prepared in Examples 1 and 3 of this invention; wherein, Figure 7 (a) is the adsorption isotherm of CE-TAPA-COF prepared in Example 1; Figure 7 (b) shows the adsorption isotherm of CE-TAPB-COF prepared in Example 3. Langmuir represents the Irwin-Langmuir adsorption isotherm model, and Freundlich represents the Freundlich adsorption isotherm model. The Irwin-Langmuir model is based on the assumptions that the adsorbent surface is homogeneous, adsorption is a monolayer, and there are no interactions between adsorbed molecules. The Freundlich model, on the other hand, is an empirical formula, more suitable for describing adsorption on heterogeneous surfaces. Detailed Implementation

[0025] To better understand the technical content of this invention, specific embodiments are provided below to further illustrate the invention.

[0026] Unless otherwise specified, the experimental methods used in the embodiments of this invention are all conventional methods.

[0027] Unless otherwise specified, all materials and reagents used in the embodiments of this invention are commercially available.

[0028] In this invention, 4,4',4'',4'''-(6,7,9,10,17,18,20,21-octahydrobis[b,k][1,4,7,10,13,16]hexaoxane-octadecene-2,3,13,14-tetramethyl)tetrabenzaldehyde is abbreviated as CE; tris(4-aminophenyl)amine is abbreviated as TAPA; and 1,3,5-tris(4-aminophenyl)benzene is abbreviated as TAPB.

[0029] The above substances are described using corresponding abbreviations in the specific embodiments.

[0030] Pyrex tubes are also known as Pyrex tubes.

[0031] Example 1: Preparation of CE-TAPA-COF material CE (50 mg, 64 μmol) and TAPA (24.92 mg, 86 μmol) were added to a Pyrex tube, followed by the addition of 2 mL of o-dichlorobenzene. The mixture was then ultrasonically mixed to obtain a homogeneous solution. 0.2 mL of a 6 M acetic acid aqueous solution was added to the mixture. The Pyrex tube was then frozen in liquid nitrogen, evacuated under vacuum and purged with nitrogen three times, flame-sealed, and cooled to room temperature before being placed in a 120 °C oven for 3 days. After the reaction, the tube was washed sequentially with N,N-dimethylacetamide and tetrahydrofuran, and then vacuum-dried at 100 °C for 12 h to obtain a yellow powder product, named CE-TAPA-COF. A schematic diagram of the CE-TAPA-COF material structure model is shown below. Figure 1 As shown in (a).

[0032] Example 2: Preparation of CE-TAPA-COF(Ⅰ) material CE (25 mg, 32 μmol) and TAPA (24.92 mg, 86 μmol) were added to a Pyrex tube, followed by the addition of 1 mL of o-dichlorobenzene and ultrasonic mixing to obtain a homogeneous mixture. Then, 0.1 mL of acetic acid aqueous solution with a catalyst concentration of 9 M was added to the mixture. The Pyrex tube was placed in liquid nitrogen for freezing, and the tube was evacuated and purged with nitrogen three times using a vacuum pump. The tube was then flame-sealed, cooled to room temperature, and placed in a 100 °C oven for 5 days. After the reaction was completed, the tube was washed with N,N-dimethylformamide and methanol, and then dried under vacuum at 80 °C for 18 h to obtain a yellow powder product, which was named CE-TAPA-COF(Ⅰ).

[0033] Example 3: Preparation of CE-TAPB-COF material CE (50 mg, 64 μmol) and TAPB (30.16 mg, 86 μmol) were added to a Pyrex tube, followed by the addition of 2 mL of o-dichlorobenzene. The mixture was then ultrasonically mixed to obtain a homogeneous solution. 0.2 mL of a 6 M acetic acid aqueous solution was added to the mixture. The Pyrex tube was then frozen in liquid nitrogen, evacuated under vacuum and purged with nitrogen three times, flame-sealed, and cooled to room temperature before being placed in a 120 °C oven for 3 days. After the reaction, the tube was washed with N,N-dimethylacetamide and tetrahydrofuran, and then vacuum-dried at 100 °C for 12 h to obtain a white powder product, named CE-TAPB-COF. A schematic diagram of the structural model of this CE-TAPB-COF material is shown below. Figure 1 As shown in (b).

[0034] Example 4: Preparation of CE-TAPB-COF(Ⅰ) material CE (25 mg, 32 μmol) and TAPB (30.16 mg, 86 μmol) were added to a Pyrex tube, followed by the addition of 1 mL of o-dichlorobenzene and ultrasonic mixing to obtain a homogeneous mixture. Then, 0.1 mL of an aqueous acetic acid solution with a catalyst concentration of 9 M was added to the mixture. The Pyrex tube was placed in liquid nitrogen for freezing, and the tube was evacuated and purged with nitrogen three times using a vacuum pump. The tube was then flame-sealed, cooled to room temperature, and placed in a 100°C oven for 5 days. After the reaction was completed, the tube was washed with N,N-dimethylformamide and methanol, and then dried under vacuum at 120°C for 24 hours to obtain a white powder product, which was named CE-TAPB-COF(Ⅰ).

[0035] Figure 1 These are schematic diagrams of the structural models of CE-TAPA-COF prepared in Example 1 and CE-TAPB-COF prepared in Example 3. Figure 1 As can be seen, both materials exhibit a dual-interlaced three-dimensional network structure.

[0036] Powder X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy experiments were performed on the CE-TAPA-COF material prepared in Example 1 and the CE-TAPB-COF material prepared in Example 3.

[0037] (1) Powder X-ray diffraction experiment Powder X-ray diffraction experiments of the materials in Examples 1 and 3 were performed on an XRD-SmartLab using a Cu-Kα radiation source (λ=1.542 Å). Powder samples of the COFs materials prepared in Examples 1 and 3 were ground in an agate mortar. 10 mg of the ground powder sample was filled into the glass sample groove of the sample stage using a spatula, and then evenly pressed down with a glass slide to ensure the surface was flush with the sample stage to prevent peak shift. The chamber door was unlocked, the sample stage was inserted into the bracket slot, and after ensuring a secure fixation, the chamber door was closed and locked (confirming the safety indicator light was on). In the software interface, the scanning range was entered as 2°-40°, the scanning speed as 10° / min, the save location and file name were set, and "Run" was clicked to start the scan, with real-time monitoring of the spectra. After acquisition, the raw data was automatically saved in .rasx format, and then converted to .txt format using Rasx Converser. Data processing was performed using Origin software. The Origin software data processing procedure is as follows: 1. Launch OriginPro, create a new blank project, and a blank worksheet will be automatically generated. 2. Click Date → Import From File → Multiple ASCII in the menu bar, and select the verified .txt file; 3. In the import dialog box, confirm that the Column Definition is: Col (A)=2θ, Col (B)=Intensity, click OK, remove the header and unit rows, and keep only the two columns of data. Set the columns to XY. 4. Select the two columns of data, Col(A) and Col(B), in the worksheet; 5. Click Plot → Basic 2D → Line in the toolbar to automatically generate a basic PXRD line plot.

[0038] Obtain the corresponding PXRD pattern, such as Figure 2 As shown.

[0039] Figure 2 Powder X-ray diffraction patterns of CE-TAPA-COF and CE-TAPB-COF. (The text appears to be incomplete and contains errors. A more accurate translation would require the full context.) Figure 2 Both materials exhibit distinct characteristic diffraction peaks, indicating the successful synthesis of three-dimensional crown ether COFs materials.

[0040] (2) Fourier transform infrared spectroscopy experiment Fourier transform infrared spectroscopy (FT-IR) experiments were performed on an FT / IR-6800 instrument. The regulated power supply, optical stage, and computer were turned on sequentially, the operating software was started, and the light source was allowed to warm up for 30 minutes to stabilize. The parameters were set to a scanning range of 4000–400 cm⁻¹. -1 Resolution 4 cm -1 The scan was performed 16 times; the spectrum was saved by clicking "Acquire Background". Using the ATR method, powder samples of the CE-TAPA-COF material prepared in Example 1 and the CE-TAPB-COF material prepared in Example 3 were placed on the surface of a diamond crystal and compacted. The scan was started by selecting "Acquire Sample"; the spectrum was monitored in real time. After acquisition, the raw data was saved as a .txt file, and data processing was performed using Origin software. The Origin software data processing procedure is as follows: 1. Launch OriginPro, create a new blank project, and a blank worksheet will be automatically generated. 2. Click Date → Import From File → Multiple ASCII, and select the exported FT-IR .txt file; 3. Import settings: Confirm Col (A) = Wavenumber (cm) - ¹), Col (B) = Absorbance (Abs), remove the header and unit rows, keep only two columns of data, and set the columns to XY; 4. Select Col (A) (wavenumber) and Col (B) (absorbance); 5. Click Plot → Basic 2D → Line in the toolbar to generate the FT-IR spectrum and obtain the corresponding FT-IR spectrum, such as... Figure 3 As shown.

[0041] Figure 3 The images show the FT-IR spectra of CE-TAPA-COF and CE-TAPB-COF. From... Figure 3 The disappearance of amino and aldehyde peaks and the obvious C=N bond stretching vibration peaks can be observed, which proves the successful synthesis of the two three-dimensional crown ether COFs materials.

[0042] (3) Scanning electron microscope experiment Scanning electron microscopy (SEM) tests were performed on a FEI Talos F200X microscope. The sample was fixed to the stage with conductive tape and sputter-coated with gold. Morphological observation was conducted at an accelerating voltage of 5 kV. The test procedure was as follows: The regulated power supply, SEM unit, and computer were turned on sequentially, and the operating software was started. A vacuum was evacuated to the working vacuum level. The sample stage with the fixed sample was placed into the sample chamber. After the vacuum was restored, the voltage was increased to 5 kV, and an appropriate working distance and probe current were selected. The sample area was located under low magnification, and the focus and astigmatism were adjusted. The magnification was gradually increased to the target magnification, and the brightness and contrast were adjusted. A typical field of view was selected for image acquisition, and the images were saved as .tif or .jpg original files. Image processing software was used for subsequent analysis and annotation.

[0043] Obtain the corresponding SEM image, such as Figure 4 As shown.

[0044] Figure 4 SEM images of CE-TAPA-COF and CE-TAPB-COF. From Figure 4 (a) It can be seen that CE-TAPA-COF is composed of irregularly stacked, horn-shaped nanostructures, and from... Figure 4 (b) It can be seen that CE-TAPB-COF is composed of irregularly shaped spherical nanostructures stacked together.

[0045] Example 5: Thorium adsorption performance experiment under different pH conditions The three-dimensional crown ether COFs materials prepared in Examples 1 and 3 were subjected to thorium adsorption performance experiments at different pH values ​​under room temperature conditions.

[0046] A 2w / v% pure nitric acid aqueous solution was used as a blank solution for instrument baseline calibration.

[0047] A thorium standard stock solution with an initial concentration of 1000 ppm was prepared using thorium nitrate and 1 M nitric acid solution at room temperature.

[0048] Take 5 mL of thorium standard stock solution, dilute with water, and then add 0.1 mol·L⁻¹ dropwise. - ¹Nitric acid solution or 0.1 mol·L - ¹Sodium hydroxide solution was used to adjust the pH of the solution to 1, 2, 3, and 4, and then the volume was brought to 50 mL to prepare 100 ppm adsorption solutions under four different pH conditions. Then, 2 mg of the three-dimensional crown ether COFs material prepared in Examples 1 and 3 was added to 6 mL of each pH adsorption solution for adsorption experiments, with an adsorption time of 24 h. After adsorption, the adsorption solution was filtered through a 0.22 μm filter membrane. 1.0 mL of the filtered adsorption solution was diluted 10 times with 9.0 mL of 2% HNO3 aqueous solution to prepare the final test sample solution.

[0049] Using a 2w / v% HNO3 aqueous solution as the matrix, a series of standard solutions with concentrations of 0.5, 1.0, 2.5, 5.0 and 10.0 ppm were prepared from the thorium standard stock solution to establish calibration curves.

[0050] All solutions are prepared with a consistent matrix acidity to effectively eliminate matrix interference and ensure the accuracy and reliability of the analytical process.

[0051] The mass concentration of thorium in the adsorption solution and the sample solution before and after adsorption in Examples 1 and 3 was measured using an inductively coupled plasma optical emission spectrometer (ICP-OES model Plasma 3000, NAK). The adsorption amount and removal rate of thorium were calculated according to the formula. The experimental results are as follows: Figure 5 As shown.

[0052] The ICP-OES measurement process is as follows: First, turn on the regulated power supply, circulating water system (water temperature 22-25 ℃), exhaust equipment, and argon main valve (partial pressure 0.6-0.8 MPa) sequentially. Then, start the main power supply and operating software, preheat for 30 minutes, install the peristaltic pump tubing, and check the gas path sealing and liquid inlet / outlet operation. Confirm that the instrument's optical chamber temperature is stable at 38 ℃ and the detector temperature is stable at -35 ℃. Click "Ignition" in the software and observe that the flame is a stable white cone shape. Preheat for 20 minutes. Optimize the parameters: RF generator power 1200 W, carrier gas flow rate 0.65 L / min. -1 0.5 L / min of auxiliary gas -1 The exposure time was 8 s, the injection time was 51 s, and the observation mode was radial. An analytical method was established, elemental spectral lines were selected, and standard concentrations were set (6 points, covering the concentration range of the sample solution to be tested). The test sequence was blank solution, series of standard solutions, and sample solution to be tested; all samples were tested three times.

[0053] During instrument operation, the software monitors and acquires signals in real time. The instrument automatically measures the blank solution and a series of standard solutions to generate a calibration curve. Subsequently, all sample solutions are measured sequentially to directly obtain quantitative data of the target components in each sample. After all data acquisition is complete, the raw data file is saved. Further processing, analysis, and plotting of the raw data are then performed. Among these steps: Adsorption capacity: , Removal rate: , Wherein, q e Adsorption capacity, in mg / g -1 ; C is the removal rate; C0 is the initial concentration of thorium ions, in ppm; C eV represents the equilibrium concentration of thorium ions after adsorption, in ppm; V is the volume of the thorium solution, in mL; m is the mass of the three-dimensional crown ether COFs materials of Examples 1 and 3, in mg.

[0054] The raw concentration data obtained from ICP-OES is multiplied by 10 to obtain the true adsorption data. This data is then converted using the adsorption capacity calculation formula and the removal rate formula to obtain the corresponding adsorption performance data (such as adsorption capacity, removal rate, etc.). Data processing is performed using Origin software. The specific process for data processing using Origin software is as follows: 1. Launch OriginPro, create a new blank project, and a blank worksheet will be automatically generated.

[0055] 2. Input the calculated adsorption data in order of pH.

[0056] 3. Confirm that Col (A) is the pH (1, 2, 3, 4 respectively), Col (B) is the adsorption capacity of CE-TAPA-COF, Col (C) is the adsorption capacity of CE-TAPB-COF, Col (D) is the removal rate of CE-TAPA-COF, and Col (E) is the removal rate of CE-TAPB-COF.

[0057] 4. In the worksheet, select both Col (A) (pH) and the adsorption data columns Col (B) and Col (C). Click Plot → Column / Bars → Grouped Columns. This will generate a grouped bar chart with pH as the X-axis and adsorption amount as the left Y-axis.

[0058] 5. With the generated graphics window active, click Insert→New Layer (Axes)→Right-Y in the top menu bar to add a new layer with an independent right Y-axis.

[0059] 6. When Layer 2 is activated, click Graph → Add Plot to Layer → Line in the menu bar. Select X as the pH data for Col (A), and select Y as the removal rate data columns Col (D) and Col (E). Click OK. The removal rate line plot will be added to the right Y-axis, resulting in a graph showing the adsorption amount and removal rate of Th(Ⅳ) by the three-dimensional COFs material under different pH conditions.

[0060] like Figure 5As shown, the three-dimensional crown ether COFs materials CE-TAPA-COF and CE-TAPB-COF hardly adsorb or have low adsorption capacity under pH conditions of 1.0 to 3.0, while they both reach the maximum adsorption capacity at pH 4.0, with a removal rate of 100%.

[0061] Example 6: Multi-component adsorption experiment As shown in the thorium adsorption performance experiment of Example 5, the three-dimensional crown ether COFs materials CE-TAPA-COF and CE-TAPB-COF have a high affinity for thorium ions at pH = 4.0. Therefore, a multi-component adsorption selectivity experiment was conducted at pH = 4.0. Different competing ions Sr(II), Cs(I), U(VI), La(III), Pr(III), Sm(III), Gd(III), Lu(III), and Th(IV) were coexisting in a mixed solution. The concentrations of both competing ions and thorium ions were 50 ppm. Then, 2 mg of the three-dimensional crown ether COFs materials prepared in Examples 1 and 3 were added to 6 mL of the mixed solution for adsorption experiments. The adsorption time was 24 h. The concentrations of each ion before and after adsorption were measured using a Plasma 3000 ICP-OES (Inductively Coupled Plasma Emission Spectrometer) according to the test method of Example 5. The partition coefficient and separation factor were calculated according to the following formula. The results are as follows. Figure 6 As shown, the thorium / uranium separation factor results for Examples 1 and 3 are summarized in Table 1.

[0062] Table 1. Thorium / uranium separation factor (SF) of three-dimensional crown ether COFs materials in Examples 1 and 3 under multi-component conditions. Th / U

[0063] like Figure 6 As shown, under the conditions of pH=4.0 and ion concentration of 50ppm, the three-dimensional crown ether COFs materials of Examples 1 and 3 showed almost no adsorption or extremely low adsorption of competing ions such as Sr(II), Cs(I), U(VI), La(III), Pr(III), Sm(III), Gd(III), and Lu(III). Table 1 shows that the thorium / uranium separation factor SF of the three-dimensional crown ether COFs material of Example 1 was [missing information]. Th / U The thorium / uranium separation factor (SF) of the three-dimensional crown ether COFs material in Example 3 is 104.80. Th / U The value of 138.76 indicates that the three-dimensional crown ether COFs material of the present invention exhibits excellent adsorption selectivity for thorium under the condition of multiple competing ions, and can achieve adsorption and separation of thorium.

[0064] Allocation coefficient: , Separation factor: , Where: C0 is the initial concentration of ions before adsorption, in ppm; C e The equilibrium concentration of ions after adsorption is expressed in ppm; m is the mass of the COFs materials used in Examples 1 and 3, expressed in mg; V is the volume of the mixed solution used in the experiment, expressed in mL. The partition coefficient for thorium ions is expressed in mL / g. -1 ; The partition coefficient for competing metal ions, expressed in mL / g. -1 .

[0065] Example 7: Adsorption isotherm experiment of thorium on three-dimensional crown ether COFs materials As shown in the thorium adsorption performance experiment of Exercise 5, when pH=4.0, the three-dimensional crown ether COFs materials CE-TAPA-COF and CE-TAPB-COF have a high affinity for thorium ions. Therefore, an adsorption isotherm experiment was carried out at pH=4.0.

[0066] The experimental procedure was as follows: Th(Ⅳ) solutions with pH=4 and initial concentrations of 25, 50, 100, 150, 200, 300, 400, 500, and 600 ppm were prepared at room temperature. Then, 2 mg of the three-dimensional crown ether COFs material prepared in Examples 1 and 3 were added to 6 mL of Th(Ⅳ) solutions of different concentrations for adsorption isotherm experiments. The adsorption time was 24 h. Following the test method in Example 5, the thorium ion concentration before and after adsorption was measured using a Plasma 3000 ICP-OES (Inductively Coupled Plasma Emission Spectrometer). The adsorption amount at different equilibrium concentrations was calculated. The experimental results are as follows: Figure 7 As shown.

[0067] The adsorption isotherm plot was drawn using Origin software. The specific data processing steps in Origin software are as follows: 1. Launch OriginPro, create a new blank project, and a blank worksheet will be automatically generated. 2. Name the data column. Set Col(A) to C. e (mg L -1 Col(B) is q e (mg g -1 ); 3. Calculate C e With q e The data were entered into Col(A) and Col(B) sequentially. Click the top menu Plot → Basic 2D → Scatter to generate a scatter plot of the experimental data; 4. Select the data in the figure and perform nonlinear curve fitting (Langmuir and Freundlich models) to obtain adsorption isotherm plots.

[0068] like Figure 7 As shown, at pH=4.0, the maximum adsorption capacity of thorium by the material in Example 1 (CE-TAPA-COF) was 1292 mg g. -1 The maximum adsorption capacity of the material in Example 3 (CE-TAPB-COF) for thorium was 1340 mg g. -1 .

[0069] Comparative Example 1 25 mg (50 μmol) of 1,3,5,7-tetra(4-phenylmethylamino)adamantane (TAM) and 30.9 mg (50 μmol) of 1,3,6,8-tetra(p-aldehydephenyl)pyrene (TFPPy) were added to a Pyrex tube. 1.0 mL of o-dichlorobenzene was added to the tube, followed by sonication to fully dissolve and mix the monomers. Then, 0.1 mL of a 6 M aqueous acetic acid solution was added to the mixture. The Pyrex tube was placed in liquid nitrogen and frozen. The tube was then evacuated and purged with nitrogen three times using a vacuum pump. The tube was flame-sealed, cooled to room temperature, and then placed in an oven at 160 °C for 5 days. After the reaction, the resulting solid product was washed several times with tetrahydrofuran and N,N-dimethylformamide solvents. The product was then vacuum-dried at 120 °C for 3 hours to obtain a yellow powdery three-dimensional COF material, named TAM-TFPPy-COF. The TAM-TFPPy-COF material prepared in the comparative example was subjected to adsorption isotherm experiments according to the test method in Example 7, and its saturated adsorption capacity for thorium was found to be 437 mg g. -1 .

[0070] Comparative Example 2 12.5 mg (25 μmol) of 1,3,5,7-tetra(4-phenylmethylamino)adamantane (TAM) and 59.5 mg (445 μmol) of terephthalaldehyde (TPA) were added to a Pyrex tube. 1.0 mL of o-dichlorobenzene was added to the tube, followed by sonication to fully dissolve and mix the monomers. Then, 0.2 mL of a 6 M aqueous acetic acid solution was added to the mixture. The Pyrex tube was frozen in liquid nitrogen, evacuated by a vacuum pump, and purged with nitrogen three times. The tube was then flame-sealed, cooled to room temperature, and placed in an oven at 120 °C for 3 days. After the reaction, the resulting solid product was washed several times with tetrahydrofuran and N,N-dimethylacetamide solvents. The product was then vacuum-dried at 120 °C for 3 hours to obtain a yellow powdery three-dimensional COF material, named TAM-TPA-COF. The TAM-TPA-COF material prepared in the comparative example was subjected to adsorption isotherm experiments according to the test method in Example 7, and its saturated adsorption capacity for thorium was found to be 501 mg g. -1 .

[0071] Comparative Example 3 Add (25 mg, 32 μmol) of 4,4',4'',4'''-(6,7,9,10,17,18,20,21-octahydrodibenzo[B,K][1,4,7,10,13,16]hexaoxane-octadecene-2,3,13,14-tetramethyl)tetrabenzaldehyde (CE) and (7 mg, 64 μmol) of 2,5-dimethylpyrazine (TT) to a Pyrex tube. Then add 1 mL of a 1:1 mixture of mesitylene / methanol and sodium hydroxide (9.1 mL / v). After ultrasonic treatment to fully dissolve and mix the monomer (mg), the Pyrex tube was placed in liquid nitrogen for freezing, evacuated and purged with nitrogen three times using a vacuum pump, flame-sealed, cooled to room temperature, and then placed in an oven at 180°C for 4 days. After the reaction, the obtained solid product was washed several times with N,N-dimethylformamide, tetrahydrofuran, and ethanol, and then vacuum-dried at 100°C for 6 hours to obtain a pale yellow powdery COF material, named COF-DB18C6. The COF-DB18C6 material prepared in this comparative example was subjected to adsorption isotherm experiments according to the test method in Example 7, and its saturated adsorption capacity for thorium was found to be 252 mg g. -1 .

[0072] The saturated adsorption capacity of thorium by each COFs material in Example 7 and Comparative Examples 1, 2, and 3 was compared, as shown in Table 2.

[0073] Table 2. Saturated adsorption capacity of thorium for different COFs materials

[0074] As shown in Table 2, the three-dimensional crown ether COFs materials of Examples 1 and 3 of this invention have significantly better adsorption capacity for Th(Ⅳ) than the three-dimensional COFs materials without crown ethers (TAM-TFPPy-COF and TAM-TPA-COF) and carbon. A two-dimensional crown ether COF material (COF-DB18C6) with carbon double bonds is presented. The key to this material's performance breakthrough lies in the synergistic effect of three major advantages: first, the doubly interwoven three-dimensional network provides a stable framework and abundant channels for thorium adsorption; second, the crown ether units achieve highly selective chelation of Th(Ⅳ); and third, the strong chemisynergistic effect of imine bonds with Th(Ⅳ) in the COF material. Benefiting from the synergistic effect of these three advantages, this material exhibits outstanding advantages in thorium adsorption selectivity and adsorption capacity, demonstrating enormous application potential.

[0075] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A three-dimensional crown ether COFs material with specific recognition sites, characterized in that, The three-dimensional crown ether COFs material is constructed by a condensation reaction between a tetraaldehyde 18-crown-6 monomer with C4 symmetry and an amino monomer with C3 symmetry.

2. The three-dimensional crown ether COFs material with specific recognition sites according to claim 1, characterized in that, The C4-symmetric tetraaldehyde 18-crown-6 monomer is 4,4',4'',4'''-(6,7,9,10,17,18,20,21-octahydrodi[b,k][1,4,7,10,13,16]hexaoxane-octadecene-2,3,13,14-tetramethyl)tetrabenzaldehyde; the C3-symmetric amino monomer is one of tris(4-aminophenyl)amine or 1,3,5-tris(4-aminophenyl)benzene.

3. The three-dimensional crown ether COFs material with specific recognition sites according to claim 1, characterized in that, The molar ratio of the tetraaldehyde 18-crown-6 monomer with C4 symmetry to the amino monomer with C3 symmetry is 1:1~3.

4. The method for preparing the three-dimensional crown ether COFs material with specific recognition sites according to any one of claims 1-3, characterized in that, Includes the following steps: A tetraaldehyde 18-crown-6 monomer with C4 symmetry and an amino monomer with C3 symmetry are added to a reaction tube. After adding organic solvent A, the mixture is ultrasonically mixed to obtain a homogeneous mixture. Then, a catalyst is added to the mixture, and the reaction tube is placed in liquid nitrogen for freezing. After vacuuming and purging with nitrogen using a vacuum pump, the tube is flame-sealed. After heating and crystallization, washing with organic solvent B, and vacuum drying, the target three-dimensional crown ether COFs material can be obtained.

5. The method for preparing three-dimensional crown ether COFs materials with specific recognition sites according to claim 4, characterized in that, The organic solvent A is o-dichlorobenzene; the catalyst is an aqueous acetic acid solution; the concentration of the aqueous acetic acid solution is 6-9 mol / L. -1 .

6. The method for preparing three-dimensional crown ether COFs materials with specific recognition sites according to claim 4, characterized in that, The total mass ratio of the tetraaldehyde 18-crown-6 monomer with C4 symmetry and the amino monomer with C3 symmetry to the volume of organic solvent A is 45~85 mg: 1.0~2.0 mL.

7. The method for preparing three-dimensional crown ether COFs materials with specific recognition sites according to claim 4, characterized in that, The volume ratio of the catalyst to organic solvent A is 1~5:

10.

8. The method for preparing three-dimensional crown ether COFs materials with specific recognition sites according to claim 4, characterized in that, The temperature for heating and crystallization is 100~120℃, and the reaction time is 3~5 days; the temperature for vacuum drying is 80℃~120℃, and the drying time is 12 h~24 h.

9. The method for preparing three-dimensional crown ether COFs materials with specific recognition sites according to claim 4, characterized in that, The organic solvent B is one or more of tetrahydrofuran, methanol, N,N-dimethylformamide, and N,N-dimethylacetamide.

10. The application of the three-dimensional crown ether COFs material according to any one of claims 1-3 or the three-dimensional crown ether COFs material with specific recognition sites prepared by the preparation method according to any one of claims 4-9 in the adsorption of thorium ions.

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