COFs material for adsorbing radioactive element uranium and preparation method thereof
By reducing the imine bonds in COFs materials to secondary amine bonds and adjusting their functional groups, the problems of low efficiency and poor selectivity in adsorbing radioactive element uranium are solved, and an efficient and highly selective uranium adsorption effect is achieved.
Patent Information
- Application Number
- CN202510315589.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-17
- Publication Date
- 2025-05-13
AI Technical Summary
Existing materials have low efficiency and poor selectivity when adsorbing radioactive element uranium, and lack the selective adsorption ability to specific target molecules.
By reducing the imine bonds in COFs materials to secondary amine bonds, the functionalized groups of COFs materials are adjusted and their adsorption ability to the radioactive element uranium is improved.
It significantly improves the adsorption ability of COFs materials to radioactive element uranium, has strong uranium-benefitability, can effectively remove uranium pollution in water bodies, and has good adsorption performance, chemical stability and reusability.
Smart Images
Figure CN119978277A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the field of chemistry and environmental technology, and particularly relates to a COFs material for adsorbing radioactive element uranium and a preparation method thereof. Background Art
[0002] With the widespread application of nuclear energy technology, the pollution problem of radioactive uranium has gradually attracted global attention. As a heavy metal radioactive element, uranium is widely present in water and soil, seriously affecting the environment and human health. At present, the removal method for uranium is mainly based on adsorption, but existing materials such as activated carbon and zeolite still have certain deficiencies in uranium adsorption efficiency and selectivity, and it is urgent to develop new and efficient adsorption materials.
[0003] Covalent organic frameworks (COFs) materials have shown excellent performance in the field of adsorption due to their highly ordered porous structure, high specific surface area and adjustable functional sites. In recent years, the application of imine bonds (-C=N-) in COFs materials has gradually attracted attention, but due to the high stability of imine bonds, they lack the selective adsorption ability for specific target molecules. Therefore, how to adjust the functional groups of COFs materials to improve their adsorption capacity for radioactive uranium has become a problem that needs to be solved urgently.
[0004] The present invention prepares a COFs material for adsorbing the radioactive element uranium. By regulating the structure of the COFs material, the shortcomings of the existing materials in adsorbing the radioactive element uranium, such as low efficiency and poor selectivity, are overcome, and the COFs material has high application value and broad market prospects. Summary of the invention
[0005] The purpose of the present invention is to provide a COFs material for adsorbing radioactive element uranium and a preparation method thereof, and the adsorption capacity of the COFs material for the radioactive element uranium is improved by reducing the imine bond in the COFs to a secondary amine bond.
[0006] The method for preparing the COFs material for adsorbing the radioactive element uranium comprises the following steps: S1. Preliminary synthesis of COFs materials: add amino monomer and aldehyde monomer into a sealed tube, add solvent and sonicate for 1-3 minutes, then add catalyst, place at 115-125°C for reaction for 3-7 days, cool to room temperature, filter the solid and wash with a polar solution gradient, place at 115-125°C for drying, and obtain the preliminarily synthesized COFs material; S2. Reduction reaction of imine bond: Add the reducing agent and the preliminarily synthesized COFs material into a flask at 23-25°C and react for 45-50 hours to obtain the product.
[0007] Preferably, the amino monomer is 4,4'-(buta-1,3-diyne-1,4-diyl)diphenylamine.
[0008] Preferably, the aldehyde monomer is 1,3,5-tri(4-formylphenyl)benzene.
[0009] By selecting specific amino monomers and aldehyde monomers to prepare COFs materials, the adsorption rate of COFs materials for uranium ions can be enhanced. This may be because 4,4'-(butane-1,3-diyne-1,4-diyl)diphenylamine provides -NH2 as a nucleophile to participate in the imine condensation reaction, while 1,3,5-tri(4-formylphenyl)benzene provides -CHO as an electrophile, forming a two-dimensional ordered network through a three-node symmetrical structure, thereby enhancing the crystallinity of COFs. In addition, 4,4'-(butane-1,3-diyne-1,4-diyl)diphenylamine introduces a diacetylene (C≡CC≡C) structure into the COFs material. The conjugation of diacetylene can not only improve the conductivity and adsorption site density of the material, but also provide a more uniform electronic environment for subsequent reduction, enhance the coordination ability of uranyl ions, thereby improving its selective adsorption ability for uranium ions, and thus improving the adsorption rate of uranium ions. Its rigid skeleton can also inhibit the interlayer slip of COFs, forming a more stable pore structure, improving the thermal stability and chemical stability of the material, and thus improving the adsorption stability.
[0010] Preferably, the molar ratio of the amino monomer to the aldehyde monomer is (1-1.6):1.
[0011] Preferably, the solvent comprises dioxane.
[0012] The medium polar solvent dioxane is selected as the solvent, which can not only dissolve aromatic monomers containing amino groups and aldehyde groups at the same time and promote uniform mixing, but its weak Lewis alkalinity can stabilize the imine condensation intermediates and avoid the occurrence of side reactions such as aldehyde oxidation, thereby ensuring the formation of the ordered structure of COFs materials. At the same time, considering that imine condensation is a reversible reaction, sufficient time is required to correct errors and form long-range ordered structures. Therefore, the reaction time is preferably 3-7 days. Too short a time may result in the failure to form an ordered structure, while too long a time will waste energy.
[0013] Preferably, the solid-liquid ratio of the total mass of the aldehyde monomer and the amino monomer to the solvent is (0.6-0.8) g:1 mL.
[0014] Preferably, the catalyst comprises aqueous acetic acid.
[0015] Preferably, the molar concentration of the acetic acid aqueous solution is 3-6 mol / L.
[0016] Preferably, the solid-liquid ratio of the total mass of the aldehyde monomer and the amino monomer to the catalyst is (12-16) g:1 mL.
[0017] Preferably, the polar solvent includes one or both of tetrahydrofuran and dichloromethane.
[0018] The use of specific polar solvents for gradient washing of the reaction products can avoid the residual monomers and small molecule byproducts while reducing the damage of non-polar solvents to the COFs pores, thereby ensuring the adsorption rate of uranium ions. This may be because tetrahydrofuran and dichloromethane have moderate polarity, which can not only effectively dissolve residual monomers (such as unreacted aldehyde compounds) and small molecule byproducts (such as water and acetic acid), but also their lower surface tension can reduce the damage of capillary forces to the COFs pores during washing, avoid pore collapse, and protect the pore structure. On this basis, according to the polarity difference between tetrahydrofuran and dichloromethane (tetrahydrofuran is a medium-grade solvent and dichloromethane is a weakly polar solvent), impurities of different polarities are gradually removed through sequential gradient washing of tetrahydrofuran and dichloromethane to maximize the protection of the structural integrity of COFs.
[0019] Preferably, the reducing agent comprises sodium borohydride.
[0020] Preferably, the molar ratio of the reducing agent to the preliminarily synthesized COFs material is 1:(0.9-1.1); further preferably, it is 1:1.
[0021] The second aspect of the present invention provides a COFs material prepared by the method for preparing the COFs material for adsorbing the radioactive element uranium.
[0022] Compared with the prior art, the advantages and beneficial effects of the present invention are: 1. The present invention prepares a new covalent organic framework (COFs) material with a secondary amine bond structure through imine bond reduction technology. Compared with traditional imine bond-connected COFs, this material achieves directional regulation of the skeleton electron cloud density and coordination ability through chemical bond reduction, breaking through the limitation of the single functional group of traditional COFs and providing a new molecular construction strategy for the design of multifunctional adsorption materials.
[0023] 2. The present invention significantly improves the adsorption capacity of the radioactive element uranium by reducing the imine bond in COFs to a secondary amine bond. At the same time, combined with the synthesis method and modification treatment described in the present invention, the obtained COFs material shows excellent performance in the adsorption of radioactive element uranium, has a strong affinity for uranium, and can effectively remove uranium pollution in water bodies. Compared with the unreduced original COFs material, its adsorption capacity is significantly improved. It not only has good adsorption performance, but also has good chemical stability and reusability, and can provide more effective solutions in the field of uranium removal and environmental remediation.
[0024] 3. This invention applies the reduced COFs material to the field of efficient adsorption of radioactive uranium for the first time, breaking the technical gap of traditional COFs materials in nuclear waste treatment. The reduced COFs material has a 100% removal rate for uranium ions, which can effectively reduce the uranium concentration in radioactive wastewater and block the risk of uranium entering the food chain through water and soil from the source, providing an efficient and environmentally friendly solution for scenarios such as nuclear power plant wastewater and uranium mine contaminated groundwater.
[0025] 4. The reduced COFs material prepared by the present invention only requires two steps of reaction (imine bond COFs synthesis + liquid phase reduction), does not require high pressure / high temperature equipment, has mild reaction conditions (normal temperature and pressure), and has high yield. Compared with the complex process of traditional functional adsorption materials (such as MOFs) that require multiple steps of modification, the production cost is reduced by about 50%, and it has the potential for industrial mass production.
[0026] 5. The present invention can enhance the adsorption rate of uranium ions by the COFs material by selecting specific amino monomers and aldehyde monomers to prepare the COFs material.
[0027] 6. The present invention uses a specific polar solvent to perform gradient washing on the reaction product, which can avoid the residual monomers and small molecular by-products while reducing the damage of non-polar solvents to the COFs pores, thereby ensuring the adsorption rate of uranium ions. BRIEF DESCRIPTION OF THE DRAWINGS
[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art.
[0029] Figure 1 The UV-visible absorption spectra of the COFs material without adding COFs material, the unreduced COFs material prepared in Comparative Example 1, and the reduced COFs material prepared in Example 1 to uranium ions. DETAILED DESCRIPTION
[0030] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0031] Example 1 This embodiment provides a COFs material for adsorbing the radioactive element uranium, and a preparation method thereof, the steps are: S1. Preliminary synthesis of COFs materials: 697 mg (0.003 mmol) of amino monomer and 780.86 mg (0.002 mol) of aldehyde monomer were added to a sealed tube, 2 mL of solvent was added and ultrasonicated for 2 min, then 0.1 mL of 6 mol / L acetic acid aqueous solution was added, and the mixture was reacted at 120 °C for 5 days, cooled to room temperature, the solid was filtered and washed with a polar solution gradient, and dried at 120 °C to obtain the preliminarily synthesized COFs material; S2. Reduction reaction of imine bond: At 25°C, add sodium borohydride and the preliminarily synthesized COFs material into a flask and react for 48 hours to obtain.
[0032] The amino monomer is 4,4'-(buta-1,3-diyne-1,4-diyl)diphenylamine.
[0033] The aldehyde monomer is 1,3,5-tri(4-formylphenyl)benzene.
[0034] The solvent is dioxane.
[0035] The polar solvent is tetrahydrofuran or dichloromethane.
[0036] The molar ratio of the sodium borohydride to the preliminarily synthesized COFs material is 1:1.
[0037] Example 2 The difference between this embodiment and embodiment 1 is: S1. Preliminary synthesis of COFs material: 464.56 mg (0.002 mol) of amino monomer and 780.86 mg (0.002 mol) of aldehyde monomer were added to a sealed tube, 2 mL of solvent was added and ultrasonicated for 2 min, then 0.1 mL of 6 mol / L acetic acid aqueous solution was added, and the mixture was reacted at 120° C. for 5 days, cooled to room temperature, the solid was filtered and washed with a polar solution gradient, and dried at 120° C. to obtain the preliminarily synthesized COFs material.
[0038] Comparative Example 1 The difference between this comparative example and Example 1 is that the COFs material for adsorbing the radioactive element uranium, the preparation method thereof, the steps are: adding 697 mg (0.003 mmol) of amino monomer and 780.86 mg (0.002 mol) of aldehyde monomer into a sealed tube, adding 2 mL of solvent and ultrasonicating for 2 minutes, adding 0.1 mL of 6 mol / L acetic acid aqueous solution, placing at 120 ° C to react for 5 days, cooling to room temperature, filtering the solid and washing it with a polar solution gradient, placing at 120 ° C to dry, and obtaining.
[0039] Comparative Example 2 The difference between this comparative example and Example 1 is that the amino monomer is p-phenylenediamine.
[0040] Comparative Example 3 The difference between this comparative example and Example 1 is that the solvent is N,N-dimethylformamide.
[0041] Comparative Example 4 The difference between this comparative example and Example 2 is: S1. Preliminary synthesis of COFs material: 464.56 mg (0.002 mol) of amino monomer and 780.86 mg (0.002 mol) of aldehyde monomer were added to a sealed tube, 2 mL of solvent was added and ultrasonicated for 2 min, then 0.1 mL of 6 mol / L acetic acid aqueous solution was added, and the mixture was reacted at 120 ° C for 5 days, cooled to room temperature, the solid was filtered and washed with a non-polar solution, and dried at 120 ° C to obtain the preliminarily synthesized COFs material.
[0042] The non-polar solvent is n-hexane.
[0043] Performance Testing Test of uranium ion removal rate: Dissolve 10 mg of uranyl sulfate in 1 L of water to prepare a 10 mg / L uranyl ion solution. Add 0.1 mol / L hydrochloric acid, 0.1% color developer arsenic dichloride, and 10 mg / L uranyl ion solution to 5 mL of pure water to test the ultraviolet absorption peak of uranyl ions. The results are shown in Figure 1 .from Figure 1 It can be seen that at the displacement of 650nm, the absorption peak of uranyl ions can be seen. 2mg of the prepared COFs material was added to the above test solution, and its ultraviolet absorption peak was tested, and the uranium ion removal rate was calculated according to the absorbance. The results are shown in Table 1.
[0044] Adsorption stability test: The prepared COFs material was subjected to the above adsorption rate experiment 10 times, and the removal rate of uranium ions after the 10th time was recorded. The results are shown in Table 1.
[0045] Table 1 Measurement results
[0046] As can be seen from Table 1, the COFs material for adsorbing the radioactive element uranium prepared by Examples 1 to 2 of the present invention has a high removal rate for uranium ions, reaching 100% removal. Comparative Example 1 did not perform a reduction treatment on the COFs material. Comparative Example 2 did not contain a diacetylene structure in the amino monomer, resulting in the absence of a diacetylene structure in the prepared COFs material. Comparative Example 3 did not use the medium-polar solvent dioxane, and N,N-dimethylformamide is a strong polar solvent, which will cause excessive solvation of the monomer, inhibit the reversibility of dynamic covalent bonds, and hinder the formation of an ordered structure. Comparative Example 4 did not use a polar solvent for washing, and n-hexane was a non-polar solvent. The removal rate of the prepared COFs material for uranium ions was low, indicating that its adsorption performance for uranium ions was poor, and the removal rate after 10 times was also low, indicating that its adsorption stability was poor. The UV-visible absorption spectra of uranium ions of the unreduced COFs material prepared by Comparative Example 1 and the reduced COFs material prepared by Example 1 were tested, as shown in FIG. Figure 1 .from Figure 1 It can also be seen that the reduced COFs material has a high removal rate for uranium ions.
[0047] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.
Claims
1. A method for preparing a COFs material for adsorbing radioactive element uranium, characterized in that: The following steps are involved: S1. Preliminary synthesis of COFs materials: add amino monomer and aldehyde monomer into a sealed tube, add solvent and sonicate for 1-3 minutes, then add catalyst, place at 115-125°C for reaction for 3-7 days, cool to room temperature, filter the solid and wash with a polar solution gradient, place at 115-125°C for drying, and obtain the preliminarily synthesized COFs material; S2. Reduction reaction of imine bond: Add the reducing agent and the preliminarily synthesized COFs material into a flask at 23-25°C and react for 45-50 hours to obtain the product.
2. The method for preparing a COFs material for adsorbing radioactive element uranium according to claim 1, characterized in that: The amino monomer is 4,4'-(buta-1,3-diyne-1,4-diyl)diphenylamine.
3. The method for preparing a COFs material for adsorbing radioactive element uranium according to claim 2, characterized in that: The aldehyde monomer is 1,3,5-tri(4-formylphenyl)benzene.
4. The method for preparing a COFs material for adsorbing radioactive element uranium according to claim 3, characterized in that: The molar ratio of the amino monomer to the aldehyde monomer is (1.4-1.6):
1.
5. The method for preparing a COFs material for adsorbing radioactive element uranium according to claim 4, characterized in that: The solvent includes dioxane.
6. The method for preparing a COFs material for adsorbing radioactive element uranium according to claim 1, characterized in that: The catalyst includes an aqueous solution of acetic acid.
7. The method for preparing a COFs material for adsorbing radioactive element uranium according to claim 1, characterized in that: The polar solvent includes one or both of tetrahydrofuran and dichloromethane.
8. The method for preparing a COFs material for adsorbing radioactive element uranium according to claim 1, characterized in that: The reducing agent includes sodium borohydride.
9. The method for preparing a COFs material for adsorbing radioactive element uranium according to claim 8, characterized in that: The molar ratio of the reducing agent to the preliminarily synthesized COFs material is 1:(0.9-1.1).
10. A COFs material prepared according to the method for preparing a COFs material for adsorbing radioactive element uranium according to any one of claims 1 to 9.