A three-dimensional crown ether cofs material with specific recognition sites, and a preparation method and application thereof

Abstract

The application provides a three-dimensional crown ether COFs material with specific recognition sites and a preparation method and application thereof, and relates to the technical field of thorium adsorption materials.The material is constructed through condensation reaction of a four-aldehyde 18-crown-6 monomer with C4 symmetry and an amino monomer with C3 symmetry, and presents a double-interpenetrated 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, and the core advantage is derived from the synergistic effect of the unique crown ether functional unit and the three-dimensional porous framework, which provides specific recognition sites for the cavity structure of the crown ether to realize high-selectivity complexation of thorium ions, and the double-interpenetrated structure of the three-dimensional COFs skeleton provides a high specific surface area, ordered channels and excellent stability, so that the adsorption sites are fully utilized, and the application prospect is wide.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of thorium adsorption materials, and particularly relates to a three-dimensional crown ether COFs material with specific recognition sites and a preparation method and application thereof. BACKGROUND

[0002] Nuclear energy is considered as one of the most promising energy sources in the future due to its cleanliness and high efficiency. At present, nuclear energy use mainly relies on the fission of uranium, however, considering the limited amount of traditional uranium ore resources, it is urgent to find an alternative nuclear fuel. Thorium is a convertible nuclear fuel, 232 Th can be converted into a directly used nuclear fuel after neutron bombardment 233 U, and the content of thorium on earth is 3-4 times that of uranium, so it is considered as the most ideal substitute for uranium. However, a large amount of thorium-containing wastewater will be generated in the development and utilization of thorium resources, which is harmful to human health. Therefore, it is of great significance to selectively separate and enrich thorium from thorium-containing wastewater.

[0003] Among the many methods for enriching and separating thorium, the adsorption method is widely used in the treatment of industrial thorium-containing wastewater due to its low cost, simple operation and high efficiency. The separation effect of the adsorption method is highly dependent on the performance of the adsorbent. The adsorbents commonly used for treating thorium-containing wastewater at present mainly include MOF, silicon dioxide, zeolite, modified clay and the like. The literature Journal of Materials Science, 2018, 53(5): 3398-3416 reports a functional fiber layered bimodal mesoporous silicon dioxide (F-SiO2-DP) material, and uses the material for the adsorption and separation of U(Ⅵ) and Th(Ⅳ) ions. The maximum adsorption capacity of Th(Ⅳ) is only 277 mg g -1 Most of the adsorbents reported in the past have the disadvantages of small adsorption capacity, poor selectivity and poor stability.

[0004] The COFs material is a kind of porous organic framework material connected by covalent bonds. This material is composed of light elements such as C, H, O, N and B, and has the advantages of low density, high porosity, large specific surface area, high stability, good crystallinity, clear structure and adjustable function, and has wide application prospects in the fields of adsorption, separation, catalysis and energy storage.

[0005] Crown ether is a kind of cyclic ether compound. The negatively charged oxygen atoms in the crown ether can complex with positively charged metal cations under the action of dipole-charge to generate stable complexes. With its unique cavity structure and complexation with metal ions, crown ether molecules are widely used in adsorbents. However, there is no report on the use of crown ether-based COFs materials for selective adsorption and separation of radionuclide thorium ions. SUMMARY

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

[0007] The technical scheme of the present application is as follows:

[0008] A three-dimensional crown ether COFs material with specific recognition sites, the three-dimensional crown ether COFs material is constructed by condensation reaction of a tetraaldehyde 18-crown-6 monomer with C4 symmetry and an amino monomer with C3 symmetry.

[0009] Further, the tetraaldehyde 18-crown-6 monomer with C4 symmetry is 4,4',4'',4'''-(6,7,9,10,17,18,20,21-octahydrodi[b,k][1,4,7,10,13,16]hexaoxacyclooctadecine-2,3,13,14-tetrayl) tetrabenzaldehyde; the amino monomer with C3 symmetry is one of tris(4-aminophenyl)amine or 1,3,5-tris(4-aminophenyl)benzene.

[0010] Further, the molar ratio of the tetraaldehyde 18-crown-6 monomer with C4 symmetry to the amino monomer with C3 symmetry is 1:1-3.

[0011] The preparation method of the three-dimensional crown ether COFs material with specific recognition sites comprises the following steps: adding a tetraaldehyde 18-crown-6 monomer with C4 symmetry, an amino monomer with C3 symmetry into a reaction tube, ultrasonic mixing to obtain a mixture after adding an organic solvent A; then adding a catalyst into the mixture, freezing the reaction tube in liquid nitrogen, vacuumizing and filling nitrogen gas through a vacuum pump, flame sealing the tube after heating, crystallization, organic solvent B washing and vacuum drying, and then the target three-dimensional crown ether COFs material can be obtained.

[0012] Further, the organic solvent A is o-dichlorobenzene; the catalyst is an acetic acid aqueous solution; the concentration of the acetic acid aqueous solution is 6-9 mol / L. -1 .

[0013] Further, the total mass of the tetraaldehyde 18-crown-6 monomer with C4 symmetry and the amino monomer with C3 symmetry to the volume of the organic solvent A is 45-85 mg:1.0-2.0 mL.

[0014] Further, the volume ratio of the catalyst to the organic solvent A is 1-5:10.

[0015] Further, the temperature of the heating crystallization is 100-120 DEG C, and the reaction time is 3-5 days; the temperature of the vacuum drying is 80 DEG C-120 DEG C, and the drying time is 12 h-24 h.

[0016] Further, the organic solvent B is one or more of tetrahydrofuran, methanol, N,N-dimethylformamide and N,N-dimethylacetamide.

[0017] The application of the three-dimensional crown ether COFs material with specific recognition sites to adsorption of YIC and thorium ions.

[0018] Compared with the prior art, the application has the following beneficial effects:

[0019] (1) The three-dimensional crown ether COFs material is used for adsorption and separation of thorium ions for the first time, and its high performance is due to two core designs: on the one hand, the double-interpenetrated three-dimensional network structure provides rich transmission channels and adsorption sites; on the other hand, the cavity structure of the crown ether functional unit can specifically recognize thorium ions, and the two can work together to quickly remove thorium ions in an aqueous solution.

[0020] (2) The three-dimensional crown ether COFs material prepared by the application has a maximum saturated adsorption capacity of thorium ions of 1340 mg / g -1 , and a thorium / uranium separation factor of more than 100, which are higher than most of the reported adsorbents. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 Fig. 1 is a structural model schematic diagram of the three-dimensional crown ether COFs material prepared in Example 1 and Example 3 of the application; wherein, Figure 1 (a) is a structural model schematic diagram of the CE-TAPA-COF prepared in Example 1, Figure 1 (b) is a structural model schematic diagram of the CE-TAPB-COF prepared in Example 3.

[0022] Figure 2 Fig. 2 is a powder X-ray diffraction (PXRD) spectrum of the three-dimensional crown ether COFs material prepared in Example 1 and Example 3 of the application; wherein, Figure 2 (a) is a PXRD spectrum of the CE-TAPA-COF prepared in Example 1, Figure 2 (b) is a PXRD spectrum of the CE-TAPB-COF prepared in Example 3.

[0023] Figure 3 Fig. 3 is a Fourier transform infrared (FT-IR) spectrum of the three-dimensional crown ether COFs material prepared in Example 1 and Example 3 of the application; wherein, Figure 3(a) FT-IR spectrum of CE-TAPA-COF prepared in Example 1, Figure 3 (b) FT-IR spectrum of CE-TAPB-COF prepared in Example 3.

[0024] Figure 4 Scanning electron microscope (SEM) images of three-dimensional crown ether COFs materials prepared in Example 1 and Example 3 of the present application; wherein, Figure 4 (a) SEM image of CE-TAPA-COF prepared in Example 1, Figure 4 (b) SEM image of CE-TAPB-COF prepared in Example 3. 100 nm in the figure represents the magnification.

[0025] Figure 5 Adsorption capacity and removal rate of Th(IV) of three-dimensional crown ether COFs materials prepared in Example 1 and Example 3 of the present application under different pH conditions, wherein the column represents the adsorption capacity and the broken line represents the removal rate.

[0026] Figure 6 Selective adsorption performance of three-dimensional crown ether COFs materials prepared in Example 1 and Example 3 of the present application to different metal ions. The abscissa 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 ordinate K d represents the distribution coefficient.

[0027] Figure 7 Adsorption isotherm of three-dimensional crown ether COFs materials prepared in Example 1 and Example 3 of the present application; wherein, Figure 7 (a) Adsorption isotherm of CE-TAPA-COF prepared in Example 1; Figure 7 (b) Adsorption isotherm of CE-TAPB-COF prepared in Example 3. Wherein, Langmuir represents the Langmuir adsorption isotherm model, and Freundlich represents the Freundlich adsorption isotherm model. The Langmuir model is based on the assumption that the adsorbent surface is uniform, the adsorption is a monolayer and there is no interaction between the adsorbed molecules. The Freundlich model is an empirical formula, which is more suitable for describing the adsorption of heterogeneous surfaces. DETAILED DESCRIPTION

[0028] In order to better understand the technical content of the present application, the following specific examples are provided to further illustrate the present application.

[0029] The experimental methods used in the examples of the present application are conventional methods unless otherwise specified.

[0030] The materials, reagents and the like used in the embodiments of the present application can be obtained from commercial channels unless otherwise specified.

[0031] The 4,4',4'',4'''-(6,7,9,10,17,18,20,21-octahydrodi[b,k][1,4,7,10,13,16]hexaoxacyclooctadecine-2,3,13,14-tetrayl) tetrakisbenzaldehyde in the present application is abbreviated as CE; tri(4-aminophenyl)amine is abbreviated as TAPA; 1,3,5-tris(4-aminophenyl)benzene is abbreviated as TAPB.

[0032] The above substances are described by using corresponding abbreviations in specific embodiments.

[0033] Pyrex tube is a Pyrex tube.

[0034] Preparation of CE-TAPA-COF material in Example 1

[0035] CE (50 mg, 64 umol) and TAPA (24.92 mg, 86 umol) were added to a Pyrex tube, 2 mL of o-dichlorobenzene was added and then ultrasonically mixed to obtain a mixture, 0.2 mL of 6M acetic acid aqueous solution was added to the mixture as a catalyst, the Pyrex tube was frozen in liquid nitrogen, and the vacuum pump was used to extract the vacuum and fill the nitrogen gas for three cycles, the tube was flame-sealed, and after cooling to room temperature, it was placed in a 120℃ oven for reaction for 3 days, after the reaction was completed, N,N-dimethylacetamide and tetrahydrofuran were used for washing, followed by vacuum drying at 100℃ for 12h, and finally a yellow powder product was obtained, which was named as CE-TAPA-COF. The structural model diagram of the CE-TAPA-COF material is shown in Figure 1 (a).

[0036] Preparation of CE-TAPA-COF(I) material in Example 2

[0037] CE (25 mg, 32 umol) and TAPA (24.92 mg, 86 umol) were added to a Pyrex tube, 1 mL of o-dichlorobenzene was added and then ultrasonically mixed to obtain a mixture, 0.1 mL of 9M acetic acid aqueous solution was added to the mixture as a catalyst, the Pyrex tube was frozen in liquid nitrogen, and the vacuum pump was used to extract the vacuum and fill the nitrogen gas for three cycles, the tube was flame-sealed, and after cooling to room temperature, it was placed in a 100℃ oven for reaction for 5 days, after the reaction was completed, N,N-dimethylformamide and methanol were used for washing, followed by vacuum drying at 80℃ for 18h, and finally a yellow powder product was obtained, which was named as CE-TAPA-COF(I).

[0038] Preparation of CE-TAPB-COF material in Example 3

[0039] The CE (50 mg, 64 umol) and TAPB (30.16 mg, 86 umol) were added into a Pyrex tube, mixed homogeneously by ultrasonic after adding 2 mL of o-dichlorobenzene to obtain a mixture, then 0.2 mL of catalyst concentration of 6 M acetic acid aqueous solution was added to the mixture, the Pyrex tube was frozen in liquid nitrogen, and the vacuum pump was used to vacuum and fill nitrogen for three times, then the tube was flame-sealed, and after cooling to room temperature, it was placed in a 120°C oven for reaction for 3 days. After the reaction was completed, it was washed with N,N-dimethylacetamide, tetrahydrofuran, and then dried at 100°C under vacuum for 12 h, and finally the white powder product was obtained, named as CE-TAPB-COF. The structural model diagram of the CE-TAPB-COF material is shown in Figure 1 (b) shown.

[0040] Example 4 Preparation of CE-TAPB-COF (I) material

[0041] The CE (25 mg, 32 umol) and TAPB (30.16 mg, 86 umol) were added into a Pyrex tube, mixed homogeneously by ultrasonic after adding 1 mL of o-dichlorobenzene to obtain a mixture, then 0.1 mL of catalyst concentration of 9 M acetic acid aqueous solution was added to the mixture, the Pyrex tube was frozen in liquid nitrogen, and the vacuum pump was used to vacuum and fill nitrogen for three times, then the tube was flame-sealed, and after cooling to room temperature, it was placed in a 100°C oven for reaction for 5 days. After the reaction was completed, it was washed with N,N-dimethylformamide, methanol, and then dried at 120°C under vacuum for 24 h, and finally the white powder product was obtained, named as CE-TAPB-COF (I).

[0042] Figure 1 The structural model diagrams of the CE-TAPA-COF prepared in Example 1 and the CE-TAPB-COF prepared in Example 3 can be seen from Figure 1 , which show that both materials exhibit a double-interpenetrated three-dimensional network structure.

[0043] The CE-TAPA-COF material prepared in Example 1 and the CE-TAPB-COF material prepared in Example 3 were subjected to powder X-ray diffraction experiment, Fourier transform infrared spectroscopy experiment and scanning electron microscope experiment.

[0044] (1) Powder X-ray diffraction experiment

[0045] The powder X-ray diffraction experiment of the materials of Example 1 and Example 3 was carried out on XRD-SmartLab, using Cu-Ka radiation source (λ = 1.542 Å). The powder samples of the COFs materials prepared by Example 1 and Example 3 were respectively placed in a maroon mortar for grinding, 10 mg of the ground powder sample was taken with a medicine spoon and filled into the glass sample groove of the sample stage, and a glass slide was used to flatten it evenly, so as to ensure that the surface was flush with the sample stage to prevent peak deviation. Unlock the hatch, insert the sample stage into the bracket card slot, make sure it is fixed firmly, then close the hatch and lock it (confirm that the safety indicator light is on), input the scan range as 2°-40° in the software interface, the scan speed is 10° / min, set the save location and file name, click "Run" to start scanning, and monitor the spectrum in real time. After the collection is completed, the original data is automatically saved in.rasx format, and the original data is converted into.txt format through Rasx Converster. Origin software is used for data processing. The data processing process of Origin software is as follows:

[0046] 1. Start OriginPro, create a new blank project (Project), and automatically generate a blank worksheet (Worksheet);

[0047] 2. Click the menu bar Date→ Import From File→ Multiple ASCII, and select the verified.txt file;

[0048] 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 row, and only keep the two column data, and set the column as X Y;

[0049] 4. Select the two column data of Col (A) and Col (B) in the worksheet;

[0050] 5. Click the toolbar Plot→ Basic 2D→ Line to automatically generate a basic PXRD line graph.

[0051] The corresponding PXRD spectrum is shown in Figure 2 .

[0052] Figure 2 The powder X-ray diffraction patterns of CE-TAPA-COF and CE-TAPB-COF. It can be observed from Figure 2 that both materials have obvious characteristic diffraction peaks, indicating the successful synthesis of three-dimensional crown ether COFs materials.

[0053] (2) Fourier transform infrared spectroscopy experiment

[0054] Fourier transform infrared spectroscopy experiment (FT-IR) was carried out on FT / IR-6800 instrument. Turn on the voltage stabilizer, optical bench host and computer in turn, start the operation software, and preheat for 30 minutes to stabilize the light source. Set the parameters as follows: scanning range 4000~400 cm -1 -1, resolution 4 cm -1 -1, scanning times 16 times; click "Collect background" to save the spectrum. Using ATR method, the powder samples of CE-TAPA-COF material prepared in Example 1 and CE-TAPB-COF material prepared in Example 3 were placed on the surface of diamond crystal and compacted. Select "Collect sample" to start scanning; real-time monitoring of the spectrum, save the raw data as.txt format after collection, and use Origin software for data processing. The data processing process of Origin software is as follows:

[0055] 1. Start OriginPro, create a new blank project (Project), and automatically generate a blank worksheet (Worksheet);

[0056] 2. Click Date → Import From File → Multiple ASCII, and select the exported FT-IR.txt file;

[0057] 3. Import settings: confirm Col (A)= wave number (cm - -1), Col (B)= absorbance (Abs), remove header and unit row, and only keep two columns of data, and set column as X Y;

[0058] 4. Select Col (A) (wave number) and Col (B) (absorbance);

[0059] 5. Click toolbar Plot → Basic 2D → Line to generate FT-IR spectrum to obtain the corresponding FT-IR spectrum, as shown in Figure 3 .

[0060] Figure 3 FT-IR spectra of CE-TAPA-COF and CE-TAPB-COF. From Figure 3 , it can be seen that the amino peak and aldehyde group peak disappear and there is a obvious C=N bond stretching vibration peak, which can prove the successful synthesis of the two three-dimensional crown ether COF materials.

[0061] (3) Scanning electron microscope experiment

[0062] Scanning electron microscope (SEM) test was carried out on FEI Talos F200X, and the sample was fixed on the sample stage with conductive tape, gold spraying treatment was carried out, and the morphology observation was carried out at an accelerating voltage of 5 kV. The test steps are as follows: turn on the voltage stabilizer, electron microscope host and computer in turn, start the operation software, and carry out vacuum pumping to the working vacuum degree. The sample stage with the fixed sample is loaded into the sample chamber, and after the vacuum is restored, the high voltage is added to 5 kV, and the appropriate working distance and probe current are selected. The sample area is found under the low power lens, the focus and astigmatism are adjusted, and the target magnification is gradually enlarged, and the brightness and contrast are adjusted. Select a typical field of view for image acquisition, save as.tif or.jpg format original file, and use image processing software for subsequent analysis and labeling.

[0063] The corresponding SEM images are shown in Figure 4 .

[0064] Figure 4 The SEM images of CE-TAPA-COF and CE-TAPB-COF are shown in Figure 4 (a), it can be seen that CE-TAPA-COF is stacked by irregular horn-shaped nanostructures, and from Figure 4 (b), it can be seen that CE-TAPB-COF is stacked by irregular spherical nanostructures.

[0065] Example 5 Thorium adsorption performance experiment under different pH conditions

[0066] The three-dimensional crown ether COF materials prepared in examples 1 and 3 were subjected to thorium adsorption performance experiments under different pH conditions at room temperature.

[0067] 2w / v% pure nitric acid aqueous solution was used as a blank solution for instrument baseline calibration.

[0068] Thorium nitrate and 1 M nitric acid solution were used to prepare a thorium-containing solution with an initial concentration of 1000 ppm as a thorium standard stock solution at room temperature.

[0069] 5 mL of the thorium standard stock solution was taken, diluted with water, and 0.1 mol·L - ¹ nitric acid solution or 0.1 mol·L - ¹ sodium hydroxide solution was added dropwise, the pH of the solution was adjusted to 1, 2, 3 and 4, and finally diluted to 50 mL to prepare 100 ppm adsorption solutions under four different pH conditions. Then 2 mg of the three-dimensional crown ether COF materials prepared in examples 1 and 3 were added to 6 mL of the adsorption solution with different pH values for adsorption test, and the adsorption time was 24 h. After adsorption, the adsorption solution was filtered with a 0.22 μm filter membrane, 1.0 mL of the filtered adsorption solution was taken, and 9.0 mL of 2% HNO3 aqueous solution was added to dilute it 10 times to prepare the final sample solution to be tested.

[0070] Th standard stock solution was prepared into series standard solutions with concentrations of 0.5, 1.0, 2.5, 5.0 and 10.0 ppm using 2 w / v% HNO3 aqueous solution as the matrix for establishing the calibration curve.

[0071] The matrix of all solutions was kept consistent in acidity to effectively eliminate matrix interference and ensure the accuracy and reliability of the analysis process.

[0072] The mass concentrations of thorium in the adsorption solutions before and after adsorption of Example 1 and Example 3 and the sample solutions to be tested were tested using an inductively coupled plasma emission spectrometer (Plasma 3000 ICP-OES), and the adsorption capacity and removal rate of thorium were calculated according to the formula, and the experimental results are shown in Table 1. Figure 5

[0073] The ICP-OES determination process is as follows: turn on the stabilized power supply, the circulating water system (water temperature 22-25 ℃), the exhaust equipment and the argon total valve (partial pressure 0.6-0.8 MPa) in sequence; start the main machine power supply and the operation software, preheat for 30 minutes, install the peristaltic pump tube, check the airway tightness and whether the liquid inlet and outlet are normal. Confirm that the instrument light room temperature is stable at 38 ℃, the detector temperature is stable at -35 ℃, click "ignition" in the software, observe that the flame is a stable white cone, preheat for 20 minutes; optimize the parameters: radio frequency driver power 1200 W, carrier gas flow 0.65 L min -1 , auxiliary gas 0.5 L min -1 , exposure time 8 s, sample time 51 s, observation mode radial. Establish the analysis method, select the element spectrum, set the standard sample concentration (6 points, covering the concentration range of the sample solution to be tested), test the order blank, series standard solution, sample solution to be tested, all samples are tested three times.

[0074] During the instrument running stage, the software monitors and collects signals in real time. The instrument automatically measures the blank and the series standard solution, and generates a calibration curve accordingly. Subsequently, all sample solutions to be tested are measured in sequence, and the quantitative data of the target components in each sample are directly obtained. After all data collection is completed, the original data file is saved. The original data is further sorted, analyzed and plotted subsequently. Among them:

[0075] Adsorption capacity: ,

[0076] Removal rate: ,

[0077] Wherein, q e is the adsorption capacity, unit mg g -1 ; ​is the removal rate; C0is the initial concentration of thorium ions, in ppm; C e is 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 COF material of Example 1 and Example 3, in mg.

[0078] The original concentration data measured by ICP-OES is multiplied by 10 to obtain the true adsorption data, which is converted according to the adsorption capacity calculation formula and the removal rate formula, so as to obtain the corresponding adsorption performance data (such as adsorption capacity, removal rate, etc.). The Origin software is used for data processing, and the specific process of data processing by the Origin software is as follows:

[0079] 1. Start OriginPro, create a blank project (Project), and automatically generate a blank worksheet (Worksheet).

[0080] 2. Input the calculated adsorption data according to pH in sequence.

[0081] 3. Confirm that Col (A) is 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.

[0082] 4. In the worksheet, select Col (A) (pH) and the adsorption capacity data columns Col (B), Col (C) at the same time. Click Plot → Column / Bars → Grouped Columns. At this time, a grouped column chart with pH as the X-axis and adsorption capacity as the left Y-axis will be generated.

[0083] 5. In the activated state of the generated graph window, click Insert→New Layer (Axes)→Right-Y in the top menu bar to add a new layer with an independent right Y-axis.

[0084] 6. When Layer 2 is activated, click Graph→Add Plot to Layer→Line in the menu bar. Select X as the pH data of Col (A), and select Y as the removal rate data columns Col (D), Col (E). Click OK, and the removal rate line chart will be added to the right Y-axis, obtaining the adsorption capacity and removal rate chart of the three-dimensional COFs material for Th(Ⅳ) under different pH conditions.

[0085] For example, Figure 5As shown, the three-dimensional crown ether COFs materials CE-TAPA-COF and CE-TAPB-COF have almost no adsorption or low adsorption capacity at pH 1.0-3.0, and reach the maximum adsorption capacity at pH 4.0, and the removal rate reaches 100%.

[0086] Example 6 Multi-component adsorption experiment

[0087] From the thorium adsorption performance experiment of Example 5, it can be seen that the three-dimensional crown ether COFs materials CE-TAPA-COF and CE-TAPB-COF have high affinity for thorium ions at pH 4.0, so under the condition of pH 4.0, a multi-component adsorption selectivity experiment was carried out, different competitive ions Sr(II), Cs(I), U(Ⅵ), La(Ⅲ), Pr(Ⅲ), Sm(Ⅲ), Gd(Ⅲ), Lu(Ⅲ) and Th(Ⅳ) coexist in a mixed solution, and the concentration of the competitive ions and thorium ions is 50 ppm, then 2 mg of the three-dimensional crown ether COFs materials prepared in Examples 1 and 3 are respectively taken and added into 6 mL of the mixed solution for adsorption experiment, the adsorption time is 24 h, the concentration of each ion before and after adsorption is determined according to the test method of Example 5 using a steel nanogram Plasma 3000 type ICP-OES (full spectrum inductively coupled plasma emission spectrometer), and the distribution coefficient and separation factor are calculated according to the following formula. The results are shown in Figure 6 Table 1, wherein the thorium / uranium separation factor results of Examples 1 and 3 are summarized in Table 1.

[0088] Table 1 Thorium / uranium separation factor SF of the three-dimensional crown ether COFs materials of Examples 1 and 3 under multi-component conditions Th / U

[0089]

[0090] As shown in Figure 6 , under the condition of pH 4.0 and the concentration of each ion being 50 ppm, the three-dimensional crown ether COFs materials of Examples 1 and 3 have almost no adsorption or very low adsorption capacity for competitive ions such as Sr(II), Cs(I), U(Ⅵ), La(Ⅲ), Pr(Ⅲ), Sm(Ⅲ), Gd(Ⅲ), Lu(Ⅲ); and from Table 1, the thorium / uranium separation factor SF of the three-dimensional crown ether COFs material of Example 1 is 104.80, and the thorium / uranium separation factor SF of the three-dimensional crown ether COFs material of Example 3 is 138.76, which indicates that the three-dimensional crown ether COFs material of the present application exhibits excellent adsorption selectivity for thorium under the condition of the presence of various competitive ions, and can realize the adsorption and separation of thorium. Th / U Th / U

[0091] Distribution coefficient: ,

[0092] ​​Separation factor: ,

[0093] Wherein: Co is the initial concentration of ions before adsorption, unit ppm; C e is the equilibrium concentration of ions after adsorption, unit ppm; m is the mass of COFs material used in Example 1 and Example 3, unit mg; V is the volume of mixed solution used for experiment, unit mL; is the distribution coefficient of thorium ions, unit mL g -1 ; is the distribution coefficient of competitive metal ions, unit mL g -1 .

[0094] Example 7 Adsorption isotherm experiment of three-dimensional crown ether COFs material on thorium

[0095] From the thorium adsorption performance experiment of Example 5, it can be seen that the three-dimensional crown ether COFs materials CE-TAPA-COF and CE-TAPB-COF have high affinity for thorium ions when pH = 4.0, so the adsorption isotherm experiment is carried out at pH = 4.0.

[0096] The experimental process is: under room temperature condition, Th(Ⅳ) solution with initial concentration of 25, 50, 100, 150, 200, 300, 400, 500, 600 ppm and pH = 4 is configured, then 2 mg of three-dimensional crown ether COFs material prepared in Example 1, 3 is taken and added into 6 mL of Th(Ⅳ) solution with different concentrations to carry out adsorption isotherm experiment, the adsorption time is 24 h, the thorium ion concentration before and after adsorption is determined according to the test method of Example 5 using steel nanogram Plasma 3000 type ICP-OES (full spectrum inductively coupled plasma emission spectrometer), and the adsorption amount under different equilibrium concentrations is obtained by calculation, and the experimental results are shown in Figure 7 .

[0097] The adsorption isotherm graph is drawn using Origin software, and the specific process of data processing by Origin software is as follows:

[0098] 1. Start OriginPro, create a blank project (Project), and automatically generate a blank worksheet (Worksheet);

[0099] 2. Name the data column. Set Col(A) as C e (mg L -1 ), and Col(B) as q e (mg g -1 );

[0100] 3. Calculate the C e and q eThe 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;

[0101] 4. Select the data in the figure and perform nonlinear curve fitting (Langmuir and Freundlich models) to obtain adsorption isotherm plots.

[0102] 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 .

[0103] Comparative Example 1

[0104] 25 mg (50 μmol) of 1,3,5,7-tetrakis(4-phenylmethylamino)adamantane (TAM) and 30.9 mg (50 μmol) of 1,3,6,8-tetrakis(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 for freezing, 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 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 .

[0105] Comparative Example 2

[0106] Into a Pyrex tube, (12.5 mg, 25 umol) of 1,3,5,7-tetra(4-phenylamino)adamantane (TAM) and (59.5 mg, 445 umol) of p-xylylene aldehyde (TPA) were added, 1.0 mL of o-dichlorobenzene was added into the tube, and the mixture was sonicated to fully dissolve and mix the monomers; then 0.2 mL of 6 M aqueous acetic acid was added into the mixture, the Pyrex tube was frozen in liquid nitrogen, and the tube was evacuated and backfilled with nitrogen three times using a vacuum pump, the tube was flame-sealed, and the tube was cooled to room temperature and placed in an oven at 120 °C for 3 days; after the reaction was completed, the obtained solid product was repeatedly washed with tetrahydrofuran and N,N-dimethylacetamide solvents several times, and the product was vacuum dried at 120 °C for 3 hours to obtain a yellow powdery three-dimensional COFs material, which was named TAM-TPA-COF. The TAM-TPA-COF material prepared in this comparative example was subjected to the adsorption isotherm experiment according to the test method of Example 7, and the saturated adsorption amount of thorium was 501 mg g -1 .

[0107] Comparative Example 3

[0108] Into a Pyrex tube, (25 mg, 32 umol) of 4,4',4'',4'''-(6,7,9,10,17,18,20,21- octahydrodibenzo[B,K][1,4,7,10,13,16]hexaoxacyclooctadecine-2,3,13,14- tetrayl) tetrakisbenzaldehyde (CE) and (7 mg, 64 umol) of 2,5-dimethylpyrazine (TT) were added, 1 mL of a mixture of mesitylene / methanol (1:1 by volume) and sodium hydroxide (9.1 mg) was added into the tube, and the mixture was sonicated to fully dissolve and mix the monomers, the Pyrex tube was frozen in liquid nitrogen, and the tube was evacuated and backfilled with nitrogen three times using a vacuum pump, the tube was flame-sealed, and the tube was cooled to room temperature and placed in an oven at 180 °C for 4 days; after the reaction was completed, the obtained solid product was repeatedly washed with N,N-dimethylformamide, tetrahydrofuran and ethanol several times, and the product was vacuum dried at 100 °C for 6 hours to obtain a light yellow powdery COFs material, which was named COF-DB18C6. The COF-DB18C6 material prepared in this comparative example was subjected to the adsorption isotherm experiment according to the test method of Example 7, and the saturated adsorption amount of thorium was 252 mg g -1 .

[0109] The saturated adsorption amounts of thorium of the COFs materials of Example 7 and Comparative Examples 1, 2 and 3 were compared, and the results are shown in Table 2.

[0110] Table 2 Saturated adsorption amounts of thorium of different COFs materials

[0111]

[0112] As can be seen from Table 2, the three-dimensional crown ether COFs materials of the embodiments 1 and 3 of the present application have significantly better adsorption capacity for Th(Ⅳ) than the three-dimensional COFs materials (TAM-TFPPy-COF and TAM-TPA-COF) without crown ether and carbon The two-dimensional crown ether COFs material (COF-DB18C6) connected by carbon double bond. The key to the performance breakthrough of the material lies in the synergistic effect of three advantages: first, the three-dimensional network of double interpenetration provides a stable skeleton and rich channels for thorium adsorption; second, the crown ether unit realizes high selective chelation of Th(Ⅳ); third, the strong chemical coordination of the imine bond in the COFs material with Th(Ⅳ). Thanks to the synergistic effect of the three advantages, the material has outstanding advantages in the adsorption selectivity and adsorption capacity of thorium, and shows great application potential.

[0113] The above merely describes preferred embodiments of the present application but should not be used to restrict the present application, and any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A three-dimensional crown ether COFs material with specific recognition sites, characterized in that, The three-dimensional crown ether COFs material is a three-dimensional crown ether COFs material constructed by condensation reaction of a tetraaldehyde-based 18-crown-6 monomer with C4 symmetry and an amino monomer with C3 symmetry; the tetraaldehyde-based 18-crown-6 monomer with C4 symmetry is 4,4',4'',4'''-(6,7,9,10,17,18,20,21-octahydrodi[b,k][1,4,7,10,13,16]hexaoxacyclooctadecine-2,3,13,14-tetrayl) tetrabenzaldehyde; and the amino monomer with C3 symmetry is 1,3,5-tris(4-aminophenyl) benzene.

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

3. The method of producing a three-dimensional crown ether COFs material with specific recognition sites according to any one of claims 1-2, characterized in that, The method comprises the following steps: The tetraaldehyde-based 18-crown-6 monomer with C4 symmetry, the amino monomer with C3 symmetry, and the organic solvent A are added into a reaction tube, and then ultrasonic mixing is performed to obtain a mixture; then a catalyst is added into the mixture, the reaction tube is frozen in liquid nitrogen, and after vacuumizing by a vacuum pump and filling with nitrogen, the reaction tube is flame-sealed; after heating crystallization, organic solvent B washing, and vacuum drying, the target three-dimensional crown ether COFs material is obtained.

4. The method for preparing three-dimensional crown ether COFs materials with specific recognition sites according to claim 3, characterized in that, The organic solvent A is o-dichlorobenzene; the catalyst is acetic acid aqueous solution; the concentration of the acetic acid aqueous solution is 6-9 mol / L -1 .

5. The method of claim 3, wherein the three-dimensional crown ether COFs material having specific recognition sites is prepared by the following steps: (1) preparing a compound having a crown ether structure; (2) preparing a compound having a specific recognition site; and (3) mixing the compound having a crown ether structure and the compound having a specific recognition site. The total mass of the tetraaldehyde-based 18-crown-6 monomer with C4 symmetry and the amino monomer with C3 symmetry and the volume of the organic solvent A are in a ratio of 45-85 mg:1.0-2.0 mL.

6. The method of claim 3, wherein the three-dimensional crown ether COFs material having specific recognition sites is prepared by the following steps: (1) preparing a compound having a crown ether structure; (2) preparing a compound having a specific recognition site; and (3) mixing the compound having a crown ether structure and the compound having a specific recognition site. The volume ratio of the catalyst to the organic solvent A is 1-5:

10.

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

8. The method of claim 3, wherein the three-dimensional crown ether COFs material having specific recognition sites is prepared by the following steps: (1) preparing a compound having a crown ether structure; (2) preparing a compound having a specific recognition site; and (3) mixing the compound having a crown ether structure and the compound having a specific recognition site. The organic solvent B is one or more of tetrahydrofuran, methanol, N,N-dimethylformamide, and N,N-dimethylacetamide.

9. Use of the three-dimensional crown ether COFs material of any one of claims 1-2 or the three-dimensional crown ether COFs material with specific recognition sites prepared by the preparation method of any one of claims 3-8 in selective adsorption of thorium ions.

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