A MOFs derived metal monatomic and MXene composite electrocatalytic uranium extraction material, and a preparation method and application thereof

Abstract

This invention discloses a MOF-derived metal single-atom and MXene composite electrocatalytic uranium extraction material, its preparation method, and its application, relating to the fields of chemistry and environmental technology. The preparation method includes the following steps: using monolayer MXene, a metal ion source, and an organic ligand as reactants, a defective MOF-supported MXene composite material is prepared via a solvothermal reaction; using the defective MOF-supported MXene composite material and a cobalt source as reactants, a metal ion-modified defective MOF-supported MXene composite material is prepared via a solvothermal reaction, followed by calcination to obtain the MOF-derived metal single-atom and MXene composite electrocatalytic uranium extraction material. This invention effectively improves the dispersibility of the added metal by introducing defect sites in MOFs, which is beneficial for the stable construction of single-atom metal sites, endowing the material with superior catalytic performance for uranyl ions and improving the extraction performance and selectivity of the material for hexavalent uranium. Furthermore, this preparation method is simple and efficient, suitable for industrial production and widespread application.

Description

Technical Field

[0001] This invention relates to the fields of chemistry and environmental technology, and in particular to a composite electrocatalytic uranium extraction material of MOFs-derived metal single atoms and MXene, its preparation method and application. Background Technology

[0002] With the continuous rise in global energy demand, traditional fossil fuels, limited by finite reserves and environmental pollution, are no longer adequate to meet the core requirements of sustainable development. Nuclear energy, with its high energy density and low carbon emissions, has stood out among various energy sources and has become an indispensable key support in the global low-carbon energy transition. As the basic fuel for nuclear power production, uranium's strategic value is gradually increasing, attracting more and more widespread attention and importance. Terrestrial uranium mines are the world's primary source of uranium resources, but currently, the world's proven terrestrial uranium reserves are only about 7.7 million tons, and their geographical distribution is extremely uneven, with most countries having relatively scarce uranium resources. Marine uranium resources are extremely abundant, with a total content of up to 4.5 billion tons, far exceeding the proven terrestrial uranium reserves. If efficient recovery of uranium resources from seawater can be achieved, it will not only provide a long-term and stable source of raw materials for the nuclear industry but also significantly reduce dependence on terrestrial uranium mines, thereby reducing the ecological damage and other problems caused by terrestrial uranium mining.

[0003] However, seawater uranium extraction technology still faces numerous problems and challenges. The primary difficulty is the extremely low concentration of uranium in seawater, only around 3.3 ppb. Such a low concentration poses a significant challenge to the uranium enrichment and capture process. Electrochemical extraction technology, which converts uranyl ions into insoluble, electrically neutral products, is considered a promising route for selective uranium separation. Compared with traditional physicochemical adsorption, the electrochemical conversion process avoids the Coulomb repulsion effect, overcomes the limitations of thermodynamic adsorption, and improves the extraction performance of uranium.

[0004] Nevertheless, existing uranium electrocatalytic materials exhibit slow kinetics when driving the conversion of uranyl ions to insoluble, electrically neutral species. Coupled with poor cycling performance and limited extraction capacity, this poses a significant obstacle to the practical industrial application of uranium extraction from seawater. Summary of the Invention

[0005] The purpose of this invention is to provide a MOF-derived metal single-atom and MXene composite electrocatalytic uranium extraction material, its preparation method, and its application, to solve the problems existing in the prior art. The MOF-derived metal single-atom and MXene composite electrocatalytic uranium extraction material of this invention can effectively promote the conversion of uranyl ions into insoluble, electrically neutral products, thereby significantly improving uranium extraction performance.

[0006] To achieve the above objectives, the present invention provides the following solution: One of the technical solutions of the present invention: a method for preparing a MOFs-derived metal single atom and MXene composite electrocatalytic uranium extraction material, comprising the following steps: A defect MOF-supported MXene composite material was prepared by solvothermal reaction using monolayer MXene, a metal ion source, and organic ligands; the organic ligands included terephthalic acid and 3-cyanobenzoic acid. Using the aforementioned defective MOFs-supported MXene composite material and a cobalt source as reactants, a metal ion-modified defective MOFs-supported MXene composite material was prepared via a solvothermal reaction. The MXene composite material supported on defective MOFs modified with metal ions was calcined to obtain the MOFs-derived metal single atom and MXene composite electrocatalytic uranium extraction material.

[0007] This invention introduces monolayer MXene into the synthesis of MOFs, directly constructing a MOF structure rich in defect sites on the surface of the monolayer MXene. Utilizing the highly dispersed nature of the defect sites in MOFs, highly dispersed metal ions are further loaded onto the defects. After high-temperature calcination, a MOF-derived metal single-atom and MXene composite electrocatalytic uranium extraction material was successfully prepared (this material uses MXene and zirconium oxide as supports, and Co single atoms as the active component). This invention effectively improves the dispersion of the added metal by introducing defect sites into MOFs, which is beneficial to the stable construction of single-atom metal sites, endowing the material with superior catalytic performance for uranyl ions and improving the extraction performance and selectivity of the material for hexavalent uranium.

[0008] Furthermore, the preparation steps of the monolayer MXene include: dispersing multiple layers of MXene in water and ultrasonically exfoliating them in an ice-water bath to obtain the monolayer MXene.

[0009] Monolayer MXene obtained by ultrasonic exfoliation can expose more catalytic sites, thereby improving the utilization rate of catalytic sites and catalytic activity.

[0010] Furthermore, the ratio of the multilayer MXene to water is 10~30 mg:3 mL.

[0011] Furthermore, the ultrasonic ablation is performed under a protective atmosphere.

[0012] Furthermore, the ultrasonic ablation time is 2 hours.

[0013] Furthermore, after the ultrasonic ablation is completed, the process also includes centrifugation to collect the supernatant and drying it; the drying method is freeze drying.

[0014] Furthermore, the metal ion source includes Zr. 4+ Source, Fe3+ Source or Ce 3+ source.

[0015] Furthermore, the ratio of the metal ion source to the monolayer MXene is 0.3 mmol: 5~30 mg.

[0016] Furthermore, the molar ratio of the metal ion source to the terephthalic acid and the 3-cyanobenzoic acid is 0.3:0.3:6.

[0017] Furthermore, the solvothermal reaction temperature for preparing defect MOFs-supported MXene composites was 120 °C, and the time was 12–48 h.

[0018] Furthermore, the solvent used in the solvothermal reaction is N,N-dimethylformamide (DMF).

[0019] Furthermore, the preparation steps of the defect MOFs-loaded MXene composite material include: mixing a metal ion source, a monolayer MXene, and a solvent to obtain solution A; mixing terephthalic acid, 3-cyanobenzoic acid, and a solvent to obtain solution B; mixing solution A and solution B and performing a solvothermal reaction to obtain the defect MOFs-loaded MXene composite material.

[0020] Furthermore, the ratio of the metal ion source to the solvent is 0.3 mmol: 5-15 mL.

[0021] Furthermore, the ratio of terephthalic acid to solvent is 0.3 mmol: 5-15 mL.

[0022] Furthermore, the cobalt (Co) source includes cobalt chloride (CoCl2).

[0023] Furthermore, the mass ratio of the defect MOFs-loaded MXene composite material to the cobalt source is 1~8:100.

[0024] Furthermore, the solvothermal reaction of the MOFs-derived metal single atoms with the MXene composite electrocatalytic uranium extraction material was carried out at a temperature of 85 °C for 8–24 h.

[0025] Furthermore, the step of preparing metal ion-modified defective MOFs-supported MXene composite material by solvothermal reaction using the defective MOFs-supported MXene composite material and cobalt source as reactants includes: mixing the defective MOFs-supported MXene composite material, cobalt source and solvent, and carrying out solvothermal reaction.

[0026] Furthermore, the ratio of the cobalt source to the solvent is 0.5 g: 10-20 mL.

[0027] Furthermore, the calcination treatment is carried out at a temperature of 400~800 ℃ for a time of 2~6 h.

[0028] Furthermore, the calcination treatment is carried out under a protective atmosphere.

[0029] Optionally, the protective atmosphere is either nitrogen or argon.

[0030] Furthermore, the heating rate of the calcination treatment is 2 °C / min.

[0031] The second technical solution of the present invention: a MOFs-derived metal single atom and MXene composite electrocatalytic uranium extraction material prepared by the preparation method of the above-mentioned MOFs-derived metal single atom and MXene composite electrocatalytic uranium extraction material.

[0032] The third technical solution of the present invention: the application of the above-mentioned MOFs-derived metal single atom and MXene composite electrocatalytic uranium extraction material in uranium extraction and recovery in water.

[0033] Furthermore, the steps for uranium extraction and recovery from water include: loading the MOFs-derived single-atom modified and MXene-supported composite material onto a conductive substrate, using it as a working electrode for electrocatalytic extraction of uranium-containing water.

[0034] Furthermore, the voltage for the electrocatalytic extraction is 0.5~1.5 V.

[0035] The present invention discloses the following technical effects: The metal-organic frameworks (MOFs) of this invention are a class of porous network structures built through self-assembly, using metal ions or metal clusters as core units and organic ligands as connecting bridges. They possess well-defined nanochannels, highly customizable functional structures, and large specific surface areas, allowing for various functionalizations through further structural design. MXene, in this invention, is a class of two-dimensional (2D) layered transition metal carbides or nitrides with excellent hydrophilicity, high conductivity, efficient ion insertion / extraction capabilities, and abundant surface functional groups. This invention employs an in-situ growth strategy, introducing a monocarboxylic acid ligand (3-cyanobenzoic acid) and utilizing its competitive coordination with terephthalic acid and metals to directly construct a MOF structure rich in defect sites on a monolayer MXene surface. Taking advantage of the highly dispersed nature of the MOF defect sites, highly dispersed metal ions are further loaded at the defects. After high-temperature calcination, a MOF-derived metal single-atom and MXene composite electrocatalytic uranium extraction material was successfully prepared, achieving stable anchoring and uniform distribution of single-atom active centers on the MXene matrix.

[0036] The MOF-derived metal single-atom and MXene composite electrocatalytic uranium extraction material prepared in this invention can be used as an electrocatalyst for the electrocatalytic extraction of uranium. It can absorb highly water-soluble uranyl ions (UO2). 2+ The uranium is converted into (UO2)O2·2H2O, which has lower solubility, thus achieving efficient separation and enrichment of uranium. The introduction of single-atom sites in the metal significantly enhances the intrinsic catalytic activity of the material, effectively reducing the overpotential of the catalytic process and improving electron transfer efficiency and the stability of active intermediates, thereby endowing the composite material with rapid capture and deep extraction capabilities for uranium. Furthermore, the excellent conductivity of the monolayer MXene further improves the electron transport performance of the material, thereby enhancing its catalytic activity. Therefore, this composite material exhibits excellent removal performance and selectivity for uranium, while also possessing good recyclability, making it a functional material for uranium extraction with significant practical application value.

[0037] The preparation method of this invention is simple and efficient, and is suitable for industrial production and widespread application. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 The image shows the SEM and EDS mappings of Co-UiO / MXene prepared in Example 1.

[0040] Figure 2 The images shown are high-resolution transmission (HRTEM) images of Co-UMX prepared in Example 2, where (a) is a low-magnification image and (b) is a high-magnification image.

[0041] Figure 3 The image shows a high-angle annular dark-field scanning transmission electron microscope (HAADF-STEM) image of the Co-UMX prepared in Example 2.

[0042] Figure 4 X-ray diffraction patterns of Co-UiO / MXene prepared in Example 1, Cu-UiO / MXene prepared in Comparative Example 3, Ni-UiO / MXene prepared in Comparative Example 4, UiO / MXene prepared in Comparative Example 1, and monolayer MXene.

[0043] Figure 5X-ray diffraction patterns of Co-UMX prepared in Example 2, Cu-UMX prepared in Comparative Example 5, Ni-UMX prepared in Comparative Example 6, and UMX prepared in Comparative Example 2.

[0044] Figure 6 Linear scan voltammetry of Co-UMX prepared in Example 2, Cu-UMX prepared in Comparative Example 5, and Ni-UMX prepared in Comparative Example 6.

[0045] Figure 7 The effect of pH value on the uranium extraction yield of Co-UMX prepared in Example 2, Cu-UMX prepared in Comparative Example 5, and Ni-UMX prepared in Comparative Example 6.

[0046] Figure 8 The effect of extraction time on the uranium extraction yield of Co-UMX prepared in Example 2, Cu-UMX prepared in Comparative Example 5, and Ni-UMX prepared in Comparative Example 6.

[0047] Figure 9 The uranium extraction performance of the samples prepared for Examples 2-7, Comparative Examples 2, and Comparative Examples 5-7.

[0048] Figure 10 The effect of initial uranium concentration on the uranium extraction yield of Co-UMX prepared in Example 2.

[0049] Figure 11 The results of the cyclic regeneration performance test of Co-UMX prepared in Example 2 are shown.

[0050] Figure 12 The results show the uranium selectivity performance of Co-UMX prepared in Example 2. Detailed Implementation

[0051] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0052] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0053] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0054] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0055] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0056] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0057] Unless otherwise specified, the room temperature mentioned in the following embodiments and test examples of this invention refers to 20~30℃.

[0058] All raw materials used in the following embodiments and test examples of this invention are common commercially available products, among which multilayer MXene is multilayer clay Ti3C2 with a purity ≥98%.

[0059] Example 1 A method for preparing a metal ion-modified defect MOF-supported MXene composite material, the preparation steps are as follows: S1. 150 mg of multilayer MXene was dispersed in 30 mL of deionized water and ultrasonically exfoliated in an ice-water bath (0 °C) under argon protection for 2 h. Subsequently, the mixture was centrifuged at 3500 rpm for 45 min, the supernatant was collected, and the monolayer MXene solid was obtained by freeze-drying.

[0060] S2. Add 0.3 mmol ZrCl4 to 10 mL DMF, sonicate for 10 min, then add 20 mg of monolayer MXene and stir at room temperature for 2 h. This is denoted as solution A. Add 0.3 mmol terephthalic acid and 6 mmol 3-cyanobenzoic acid to another 10 mL DMF, sonicate to dissolve, and this is denoted as solution B. Mix solutions A and B, stir for 10 min, then transfer to a reaction vessel and react at 120 °C for 24 h. After cooling to room temperature, wash three times each with DMF and ethanol, and dry under vacuum at 60 °C for 12 h. The product is denoted as UiO / MXene.

[0061] S3. Add 20 mg UiO / MXene to DMF (15 mL) containing 0.5 g CoCl2. Solvothermal reaction at 85 °C for 24 h. After the reaction is complete, wash three times with DMF and ethanol respectively, and dry under vacuum at 60 °C for 12 h to obtain the metal ion modified defect MOFs supported MXene composite material, denoted as Co-UiO / MXene.

[0062] Example 2 A method for preparing a MOF-derived metal single-atom and MXene composite electrocatalytic uranium extraction material, the preparation steps are as follows: S1. 150 mg of multilayer MXene was dispersed in 30 mL of deionized water and ultrasonically exfoliated in an ice-water bath (0 °C) under argon protection for 2 h. Subsequently, the mixture was centrifuged at 3500 rpm for 45 min, and the supernatant was collected and freeze-dried to obtain a monolayer MXene solid.

[0063] S2. Add 0.3 mmol ZrCl4 to 10 mL DMF, sonicate for 10 min, then add 20 mg of monolayer MXene and stir at room temperature for 2 h. This is denoted as solution A. Add 0.3 mmol terephthalic acid and 6 mmol 3-cyanobenzoic acid to another 10 mL DMF, sonicate to dissolve, and this is denoted as solution B. Mix solutions A and B, stir for 10 min, then transfer to a reaction vessel and react at 120 °C for 24 h. After cooling to room temperature, wash three times each with DMF and ethanol, and dry under vacuum at 60 °C for 12 h. The product is denoted as UiO / MXene.

[0064] S3. Add 20 mg UiO / MXene to 15 mL of DMF containing 0.5 g CoCl2. Solvothermal reaction at 85 °C for 24 h. After the reaction is complete, wash three times with DMF and ethanol respectively, and dry under vacuum at 60 °C for 12 h. The product is denoted as Co-UiO / MXene.

[0065] S4. Co-UiO / MXene was heated to 600℃ under a nitrogen atmosphere at a heating rate of 2℃ / min and calcined for 3 h to obtain a MOF-derived metal single atom and MXene composite electrocatalytic uranium extraction material, denoted as Co-UMX.

[0066] Example 3 Same as Example 2, except that the amount of monolayer MXene used in step S2 is adjusted to 5 mg.

[0067] Example 4 Same as Example 2, except that the amount of monolayer MXene used in step S2 is adjusted to 10 mg.

[0068] Example 5 Same as Example 2, except that the amount of monolayer MXene used in step S2 is adjusted to 15 mg.

[0069] Example 6 Same as Example 2, except that the calcination temperature is adjusted to 400 °C.

[0070] Example 7 Same as Example 2, except that the calcination temperature is adjusted to 800 °C.

[0071] Comparative Example 1 A method for preparing defect MOFs-supported MXene composite materials, comprising the following steps: S1. 150 mg of multilayer MXene was dispersed in 30 mL of deionized water and ultrasonically exfoliated in an ice-water bath (0 °C) under argon protection for 2 h. Subsequently, the mixture was centrifuged at 3500 rpm for 45 min, and the supernatant was collected and freeze-dried to obtain a monolayer MXene solid.

[0072] S2. Add 0.3 mmol ZrCl4 to 10 mL DMF, sonicate for 10 min, then add 20 mg of monolayer MXene and stir at room temperature for 2 h, denoted as solution A. Add 0.3 mmol terephthalic acid and 6 mmol 3-cyanobenzoic acid to another 10 mL DMF, sonicate to dissolve, denoted as solution B. Mix solutions A and B, stir for 10 min, then transfer to a reaction vessel and react at 120 ℃ for 24 h. After cooling to room temperature, wash three times with DMF and ethanol respectively, and vacuum dry at 60 ℃ for 12 h to obtain the defect MOFs-supported MXene composite material, denoted as UiO / MXene.

[0073] Comparative Example 2 A method for preparing a zirconia-supported MXene composite material, comprising the following steps: S1. 150 mg of multilayer MXene was dispersed in 30 mL of deionized water and ultrasonically exfoliated in an ice-water bath (0 °C) under argon protection for 2 h. Subsequently, the mixture was centrifuged at 3500 rpm for 45 min, and the supernatant was collected and freeze-dried to obtain a monolayer MXene solid.

[0074] S2. Add 0.3 mmol ZrCl4 to 10 mL DMF, sonicate for 10 min, then add 20 mg of monolayer MXene and stir at room temperature for 2 h. This is denoted as solution A. Add 0.3 mmol terephthalic acid and 6 mmol 3-cyanobenzoic acid to another 10 mL DMF, sonicate to dissolve, and this is denoted as solution B. Mix solutions A and B, stir for 10 min, then transfer to a reaction vessel and react at 120 °C for 24 h. After cooling to room temperature, wash three times each with DMF and ethanol, and dry under vacuum at 60 °C for 12 h. The product is denoted as UiO / MXene.

[0075] S3. UiO / MXene was heated to 600℃ at a heating rate of 2℃ / min under a nitrogen atmosphere and calcined for 3h to obtain zirconia-supported MXene composite material, denoted as UMX.

[0076] Comparative Example 3 Same as Example 1, except that CoCl2 was replaced with CuCl2 by mass, and the resulting sample was denoted as Cu-UiO / MXene.

[0077] Comparative Example 4 Same as Example 1, except that CoCl2 was replaced with NiCl2 by mass, and the resulting sample was denoted as Ni-UiO / MXene.

[0078] Comparative Example 5 Same as Example 2, except that CoCl2 was replaced with CuCl2 by mass, and the resulting sample was denoted as Cu-UMX.

[0079] Comparative Example 6 Same as Example 2, except that CoCl2 was replaced with NiCl2 by mass, and the resulting sample was denoted as Ni-UMX.

[0080] Comparative Example 7 A method for preparing MOF-derived metal single-atom electrocatalytic uranium extraction materials, comprising the following steps: S1. Add 0.3 mmol ZrCl4 to 10 mL DMF and sonicate for 10 min, denoted as solution A. Add 0.3 mmol terephthalic acid and 6 mmol 3-cyanobenzoic acid to another 10 mL DMF and sonicate to dissolve, denoted as solution B. Mix solutions A and B, stir for 10 min, then transfer to a reaction vessel and react at 120 °C for 24 h. After cooling to room temperature, wash three times each with DMF and ethanol, and dry under vacuum at 60 °C for 12 h. The product is denoted as UiO.

[0081] S2. Add 20 mg UiO to 15 mL of DMF containing 0.5 g CoCl2. Solvothermal reaction at 85 °C for 24 h. After the reaction is complete, wash three times with DMF and ethanol respectively, and dry under vacuum at 60 °C for 12 h. The product is denoted as Co-UiO.

[0082] S3. Co-UiO was heated to 600℃ under a nitrogen atmosphere at a heating rate of 2℃ / min and calcined for 3 h to obtain MOFs-derived metal single-atom electrocatalytic uranium extraction material, denoted as CoU.

[0083] Test Example 1 Characterization data: Figure 1 The SEM and EDS mapping images of Co-UiO / MXene prepared in Example 1 show that the regular octahedral particles are evenly distributed, indicating that the defect UiO-66 has been successfully grown in situ in Co-UiO / MXene; at the same time, the introduced Co element is evenly distributed, confirming that Co has been successfully loaded.

[0084] Figure 2 The images shown are high-resolution transmission electron microscopy (HRTEM) images of Co-UMX prepared in Example 2, where (a) is a low-magnification image and (b) is a high-magnification image. It can be seen that only diffraction fringes of MXene and zirconium oxide (ZrO2) are observed in Co-UMX; no diffraction fringes of metallic cobalt or cobalt oxide are detected, indicating that cobalt exists in an atomically dispersed form.

[0085] Figure 3 The image shown is a high-angle annular dark-field scanning transmission electron microscope (HAADF-STEM) image of Co-UMX prepared in Example 2, where the yellow circles represent zirconium oxide and the red circles represent cobalt single atoms. It can be seen that the metallic cobalt single atoms are well dispersed, proving the successful preparation of atomically dispersed cobalt.

[0086] Figure 4The X-ray diffraction patterns of Co-UiO / MXene prepared in Example 1, Cu-UiO / MXene prepared in Comparative Example 3, Ni-UiO / MXene prepared in Comparative Example 4, UiO / MXene prepared in Comparative Example 1, and monolayer MXene are shown. The results indicate that the diffraction peaks of UiO / MXene, Co-UiO / MXene, Cu-UiO / MXene, and Ni-UiO / MXene are basically consistent with those of simulated UiO-66, indicating that the materials were successfully prepared.

[0087] Figure 5 The X-ray diffraction patterns of Co-UMX prepared in Example 2, Cu-UMX prepared in Comparative Example 5, Ni-UMX prepared in Comparative Example 6, and UMX prepared in Comparative Example 2 are shown. The results show that only diffraction peaks belonging to MXene and zirconium oxide were observed in the X-ray diffraction patterns of Co-UMX, Cu-UMX, and Ni-UMX. No characteristic peaks corresponding to the crystalline or metal oxide phases of the introduced metal were observed. This confirms that the metal exists in an atomically dispersed state in Co-UMX, Cu-UMX, and Ni-UMX.

[0088] Test Example 2 Catalytic performance test: (1) Linear sweep voltammetry Test method: Using the sample to be tested (a sample prepared in a certain embodiment or comparative example) as the electrode material, it is mixed with a mixed solution of ethanol and naphthol (prepared by mixing 75% ethanol solution and naphthol at a volume ratio of 40:1) at a volume ratio of 1g:25mL. After stirring evenly, the solution is applied at 2 mg / cm³. 2 The working electrode was prepared by coating a sample with a loading amount (based on the sample content) onto conductive carbon paper. A platinum sheet was used as the counter electrode, and Ag / AgCl was used as the reference electrode, forming a three-electrode system. The system operated within a voltage range of 0 to -1.5 V on sodium nitrate and uranium (specifically UO2). 2+ A mixed solution of sodium nitrate (20 g / L, UO2) 2+ The linear scan voltammogram was determined in a solution with a concentration of 100 mg / L.

[0089] Figure 6 Linear scanning voltammetry (DSV) plots of Co-UMX prepared in Example 2, Cu-UMX prepared in Comparative Example 5, and Ni-UMX prepared in Comparative Example 6 were obtained. The results show that Co-UMX, Cu-UMX, and Ni-UMX exhibit redox peaks at -0.48 V, -0.81 V, and -0.85 V, respectively, confirming that all three materials possess electrocatalytic activity. Among them, Co-UMX has the smallest absolute peak potential, indicating that it has superior catalytic ability.

[0090] (2) Test on the effect of pH value on uranium extraction yield Test method: A three-electrode system was used. The construction of the three-electrode system (i.e., the preparation method of the working electrode, and the selection of the counter and reference electrodes) was performed in the same linear scan voltammetry test. Uranium (UO2) was used as the electrode. 2+ Solutions with an initial concentration of 100 mg / L and a sodium nitrate concentration of 20 g / L, and with different pH values ​​(pH 3–9), were used as electrolytes (i.e., the solutions to be extracted). Extraction was performed at a constant voltage of 1.2 V for 3 h to investigate the uranium extraction behavior within the pH range of 3–9. After extraction, the extracted solution was filtered through a filter membrane, and the absorbance of the solutions before and after extraction was measured at 652 nm using a UV spectrophotometer. The uranium extraction yield of the material was calculated (UO2 extracted per unit mass of electrocatalytic uranium extraction material). 2+ (The same applies below).

[0091] Figure 7 The effect of pH on the uranium extraction yield of Co-UMX prepared in Example 2, Cu-UMX prepared in Comparative Example 5, and Ni-UMX prepared in Comparative Example 6 was investigated. The results showed that within the test range of pH 3–9, the uranium extraction yield of Co-UMX was consistently higher than that of the other samples, exhibiting the best extraction performance. In particular, within the pH range of 4–8, the uranium extraction yield of Co-UMX showed no significant decrease, demonstrating excellent pH tolerance, further confirming its superior extraction performance.

[0092] (3) Effect of extraction time on uranium extraction performance Test method: A three-electrode system was used. The construction of the three-electrode system (i.e., the preparation method of the working electrode, and the selection of the counter and reference electrodes) was performed in the same manner as linear scan voltammetry. Uranium (UO2) was used as the electrode material. 2+ An initial solution with a concentration of 100 mg / L, a sodium nitrate concentration of 20 g / L, and a pH of 5 was used as the electrolyte (i.e. the solution to be extracted). Extraction was carried out at a constant voltage of 1.2 V to investigate the effect of contact time on the uranium extraction performance of the material.

[0093] Figure 8 To investigate the effect of extraction time on the uranium extraction yield of Co-UMX prepared in Example 2, Cu-UMX prepared in Comparative Example 5, and Ni-UMX prepared in Comparative Example 6, the results showed that Co-UMX, Cu-UMX, and Ni-UMX reached extraction equilibrium within 120 min, 180 min, and 180 min, respectively, with corresponding equilibrium extraction yields of 2405.9 mg / g, 1658.6 mg / g, and 1321.5 mg / g. This demonstrates that Co-UMX not only had the shortest equilibrium time but also the highest extraction yield, exhibiting extremely rapid reaction kinetics and excellent uranium extraction performance.

[0094] (4) Uranium extraction performance test of different samples Test method: A three-electrode system was used. The construction of the three-electrode system (i.e., the preparation method of the working electrode, and the selection of the counter and reference electrodes) was performed in the same manner as linear scan voltammetry. Uranium (UO2) was used as the electrode material. 2+ A solution with an initial concentration of 100 mg / L, a sodium nitrate concentration of 20 g / L, and a pH of 5 was used as the electrolyte (i.e. the solution to be extracted). Extraction was carried out at a constant voltage of 1.2 V for 3 h to evaluate the uranium extraction capability of different materials.

[0095] Figure 9 The extraction performance of uranium by the samples prepared for Examples 2-7, Comparative Examples 2, and Comparative Examples 5-7 was investigated. The results showed that the composite material with the introduction of single atoms had superior uranium extraction performance compared with the material without metal single-atom support (Comparative Example 2). This also verified that the introduction of metal single atoms effectively promoted the material's ability to extract uranium. Compared with the material without MXene support (Comparative Example 7), the material with MXene support showed better catalytic effect, confirming that monolayer MXene has a significant promoting effect on the material's uranium extraction.

[0096] (5) Effect of initial uranium concentration on uranium extraction performance Test method: A three-electrode system was used. The construction of the three-electrode system (i.e., the preparation method of the working electrode, and the selection of the counter and reference electrodes) was performed in the same manner as linear scan voltammetry. Uranium (UO2) was used as the electrode material. 2+ Solutions with initial concentrations of 5–400 mg / L, sodium nitrate concentrations of 20 g / L, and pH values ​​of 5 were used as electrolytes (i.e., the solutions to be extracted). Extraction was carried out at a constant voltage of 1.2 V for 3 h to investigate the effect of initial concentrations on the uranium extraction performance of the materials.

[0097] Figure 10 The effect of initial uranium concentration on the uranium extraction yield of Co-UMX prepared in Example 2 was investigated. The results showed that when the initial uranium concentration was 400 mg / L, the uranium extraction yield of Co-UMX reached 9960.9 mg / g, with a removal rate of 97.75%, which fully demonstrates that Co-UMX is an extremely high-performance uranium extraction material.

[0098] (6) Cyclic regeneration performance test Test method: A three-electrode system was used. The construction of the three-electrode system (i.e., the preparation method of the working electrode, and the selection of the counter and reference electrodes) was performed in the same manner as linear scan voltammetry. Uranium (UO2) was used as the electrode material. 2+An initial solution with a concentration of 100 mg / L, a sodium nitrate concentration of 20 g / L, and a pH of 5 was used as the electrolyte (i.e., the solution to be extracted). Extraction was carried out at a constant voltage of 1.2 V for 3 h. After extraction, the working electrode was rinsed with ultrapure water (the (UO2)O2·2H2O generated after catalytic extraction will be directly deposited at the bottom of the container, and there is no residue on the catalyst surface, so only the residual solution on the catalyst surface needs to be rinsed). The electrode was then placed in a vacuum oven to dry. After drying, the next extraction experiment was carried out (extraction conditions were the same as the first extraction), and the cycle was repeated twenty times.

[0099] Figure 11 The results of the recycling performance test of Co-UMX prepared in Example 2 show that after twenty recycling cycles, the extraction efficiency of uranium by Co-UMX is still as high as 99.6%, with almost no decay compared to the initial efficiency, indicating that the material has good structural stability and excellent recycling performance.

[0100] (7) Selective testing Test Method: A three-electrode system was used. The construction of the three-electrode system (i.e., the preparation method of the working electrode, and the selection of the counter and reference electrodes) was the same as that for linear scan voltammetry. Simulated seawater was used as the electrolyte (i.e., the solution to be extracted). Extraction was performed at a constant voltage of 1.2 V for 24 h. After extraction, the concentration changes of each ion in the simulated seawater before and after adsorption were determined by ICP-MS. The concentration of Na (Na+) in the simulated seawater before extraction was... + ), Mg (Mg 2+ ), Ca (Ca 2+ ), Cu (Cu 2+ ), Ba (Ba 2+ ), V (V 2+ Mn (Mn) 2+ ), Ni (Ni 2+ ), Zn (Zn 2+ ), K (K + ), U (UO2) 2+ The initial concentrations of Na, Mg, Ca, Cu, Ba, V, Mn, Ni, Zn, K, and U after extraction were 577.5, 257.3, 298.1, 271.6, 262.0, 252.1, 231.5, 253.6, 236.2, 290.1, and 4.65 µg / L, respectively. The concentrations of these metals after extraction were 536.8, 251.6, 288.5, 264.5, 261.2, 244.9, 229.6, 239.0, 227.3, 282.0, and 0.077 µg / L, respectively. The removal rates of different metals by the material were calculated based on these data.

[0101] Figure 12The results of the uranium selectivity test of Co-UMX prepared in Example 2 show that Co-UMX has a uranium removal rate of up to 98.31%, which is much higher than the removal effect on other metals. This indicates that the material has excellent uranium selectivity and has excellent practical application in the field of seawater uranium extraction.

[0102] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing a MOF-derived metal single-atom and MXene composite electrocatalytic uranium extraction material, characterized in that, Includes the following steps: A defect MOF-supported MXene composite material was prepared by solvothermal reaction using monolayer MXene, a metal ion source, and organic ligands; the organic ligands included terephthalic acid and 3-cyanobenzoic acid. Using the aforementioned defective MOFs-supported MXene composite material and a cobalt source as reactants, a metal ion-modified defective MOFs-supported MXene composite material was prepared via a solvothermal reaction. The MXene composite material supported on defective MOFs modified with metal ions was calcined to obtain the MOFs-derived metal single atom and MXene composite electrocatalytic uranium extraction material.

2. The preparation method of the MOFs-derived metal single atom and MXene composite electrocatalytic uranium extraction material as described in claim 1, characterized in that, The preparation steps of the monolayer MXene include: dispersing multiple layers of MXene in water and ultrasonically exfoliating them in an ice-water bath to obtain the monolayer MXene.

3. The preparation method of the MOFs-derived metal single atom and MXene composite electrocatalytic uranium extraction material as described in claim 1, characterized in that, The metal ion source includes Zr. 4+ Source, Fe 3+ Source or Ce 3+ source; And / or, the ratio of the metal ion source to the monolayer Mxene is 0.3 mmol: 5~30 mg; And / or, the molar ratio of the metal ion source to the terephthalic acid and the 3-cyanobenzoic acid is 0.3:0.3:6; And / or, the solvothermal reaction temperature for preparing defective MOFs-supported MXene composites is 120 °C, and the time is 12~48 h.

4. The preparation method of the MOFs-derived metal single atom and MXene composite electrocatalytic uranium extraction material as described in claim 1, characterized in that, The cobalt source includes cobalt chloride; And / or, the mass ratio of the defect MOFs-loaded MXene composite material to the cobalt source is 1~8:100; And / or, the solvothermal reaction temperature for preparing MOFs-derived metal single atoms and MXene composite electrocatalytic uranium extraction materials is 85 °C, and the time is 8–24 h.

5. The preparation method of the MOFs-derived metal single atom and MXene composite electrocatalytic uranium extraction material as described in claim 1, characterized in that, The calcination treatment is carried out at a temperature of 400~800 ℃ for 2~6 h.

6. The preparation method of the MOFs-derived metal single atom and MXene composite electrocatalytic uranium extraction material as described in claim 1, characterized in that, The calcination process is carried out under a protective atmosphere.

7. A MOFs-derived metal single atom and MXene composite electrocatalytic uranium extraction material prepared by the preparation method of any one of claims 1-6.

8. The application of the MOFs-derived metal single atom and MXene composite electrocatalytic uranium extraction material as described in claim 7 in uranium extraction and recovery in water.

9. The application as described in claim 8, characterized in that, The steps for uranium extraction and recovery from water include: loading the MOFs-derived metal single atom and MXene composite electrocatalytic uranium extraction material onto a conductive substrate, and using it as a working electrode to perform electrocatalytic extraction of uranium-containing water.

10. The application as described in claim 9, characterized in that, The voltage for the electrocatalytic extraction is 0.5~1.5 V.

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