Amidoxime functionalized defect type metal organic framework material as well as preparation method and application thereof

Abstract

The invention discloses an amidoxime functionalized defective metal organic framework material as well as a preparation method and application thereof, and belongs to the technical field of preparation of functional MOFs (Metal Organic Frameworks) materials. The preparation method of the amidoxime functional defect type metal organic framework material comprises the following steps: taking metal salt, a regulator ligand and terephthalic acid as reactants, and performing solvothermal reaction to prepare a cyanation defect type MOFs material; and carrying out amidoxime functionalization on the cyanation defect type MOFs material, so as to obtain the amidoxime functionalized defect type MOFs material. The amidoxime functional defect type metal organic framework material provided by the invention has excellent adsorption and selection capabilities on hexavalent uranium, and is further compounded with graphene / cellulose aerogel, so that on the basis of solving the problem of MOFs particle aggregation, the excellent photo-thermal conversion performance of the graphene / cellulose aerogel is utilized, and the material can be used for preparing a metal organic framework material. The adsorption capacity of the composite material on hexavalent uranium is further improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of the preparation of functional MOFs materials, and specifically relates to an amidoxime-functionalized defective metal-organic framework material, a preparation method thereof, and an application thereof. Background Art

[0002] Nuclear energy, with its excellent high energy density and extremely low carbon emission characteristics, has emerged as a strong alternative to fossil fuels. Uranium is the main raw material for nuclear reactors, and its sufficient supply is crucial for the sustainable and healthy development of the nuclear energy industry and a sustainable future. However, uranium resources face huge challenges. It is estimated that there are only about 4.5 million tons of uranium ore on land globally and the ore grade is low, which is insufficient to meet global energy demand. Fortunately, uranium resources in seawater are very rich. It is estimated that about 4.5 billion tons of uranium can be utilized in the ocean. This potential uranium source is sufficient to support the booming development of the nuclear energy industry for thousands of years and provides strong support for alleviating the global energy crisis and exploring a green and sustainable energy future.

[0003] However, the ultra-low concentration of uranium (3.3 ppb) in seawater and the great complexity of the marine environment pose huge challenges for the effective extraction of uranium. Among various methods for extracting uranium from seawater, selective adsorption by functional materials is considered the most feasible way to recover marine uranium resources due to its wide source, simple operation, and environmental friendliness.

[0004] However, existing adsorbents still have problems such as slow adsorption rate, low adsorption efficiency, and poor recyclability. It is crucial to develop a uranium adsorbent with high adsorption efficiency, stable structure, and safety and environmental protection. Summary of the Invention

[0005] The purpose of the present invention is to provide an amidoxime-functionalized defective metal-organic framework material, a preparation method thereof, and an application thereof. The provided defective metal-organic framework material has excellent adsorption and selectivity for hexavalent uranium. Further compounding it with graphene / cellulose aerogel can solve the problem of MOFs particle aggregation and, on this basis, utilize the excellent photothermal conversion performance of graphene / cellulose aerogel to further improve the adsorption capacity of the composite material for hexavalent uranium.

[0006] To achieve the above purpose, the present invention provides the following technical solutions:

[0007] One of the technical solutions of the present invention: Provide a preparation method for an amidoxime-functionalized defective metal-organic framework material, comprising the following steps:

[0008] Using a metal salt, a regulator ligand, and terephthalic acid as reactants, through a solvothermal reaction, a cyanated defective MOFs material is prepared;

[0009] The cyanated defective MOFs material is subjected to amidoxime functionalization to obtain the amidoxime-functionalized defective MOFs material;

[0010] The regulator ligand is 3-cyanobenzoic acid, 4-cyanobenzoic acid or cyanoacetic acid.

[0011] The second technical solution of the present invention: provides a preparation method of an amidoxime-functionalized defective metal-organic framework @ graphene / cellulose aerogel composite material, comprising the following steps:

[0012] Using graphene / cellulose aerogel as a carrier, immersing it in a solution containing metal salt, and stirring to obtain metal ion-loaded graphene / cellulose aerogel;

[0013] Using the metal ion-loaded graphene / cellulose aerogel, a regulator ligand and terephthalic acid as reactants, and performing a solvothermal reaction to prepare a cyanated defective MOFs@graphene / cellulose aerogel composite material;

[0014] The cyanated defective MOFs@graphene / cellulose aerogel composite material is subjected to amidoxime functionalization to obtain the defective metal-organic framework @ graphene / cellulose aerogel composite material;

[0015] The regulator ligand is 3-cyanobenzoic acid, 4-cyanobenzoic acid or cyanoacetic acid.

[0016] In the present invention, the metal-organic framework material (MOFs) is a porous material formed by the coordination between metal centers (clusters or metal ions) and the organic framework, with an ordered porous scaffold, a high specific surface area, controllable functionality and structural diversity. MOFs materials have the characteristics of porous structure, precise construction, easy functionalization, etc., and can interact with uranyl ions in multiple dimensions, such as precise recognition, adsorption, etc., so that MOFs stand out in the field of uranium removal. By further controlling the internal defects of MOFs in the present invention, the pore channels can be enlarged and the adsorption active sites can be increased, so as to enhance the adsorption performance. The ingeniously embedded amidoxime groups greatly optimize the pore structure and specific surface area of MOFs, significantly increasing the selective active sites, thus greatly improving its adsorption performance and selectivity. It can effectively overcome the problems existing in traditional MOFs materials, such as limited pore size, scarce and low-utilization adsorption sites, and insufficient selectivity for hexavalent uranium.

[0017] In the present invention, the graphene / cellulose aerogel has advantages such as ultra-light weight, high mechanical strength, and excellent photothermal conversion performance, and is a very promising material in the field of adsorption. In the present invention, an in-situ growth technique is used to firmly anchor the amidoxime-functionalized defective metal-organic framework material on the graphene / cellulose aerogel matrix. While effectively avoiding the aggregation of MOF particles, the excellent photothermal conversion performance of the graphene-based aerogel is utilized to enable the composite material to have more excellent adsorption performance.

[0018] Preferably, the metal ions in the metal salt include Zr 4+ , Ce 3+ , Ni 2+ or Cu 2+ .

[0019] Preferably, the molar ratio of the regulating ligand to the terephthalic acid is 1 to 30:1.

[0020] Preferably, the solvent for the solvothermal reaction is N,N-dimethylformamide, the temperature is 100 to 120 °C, and the time is 12 to 48 h.

[0021] Preferably, the steps for amidoxime functionalization include: blending the raw material to be functionalized, hydroxylamine hydrochloride, and anhydrous potassium carbonate in a mixed solvent of ethanol and water, and reacting under an inert atmosphere to complete the amidoxime functionalization.

[0022] More preferably, the mass ratio of the raw material to be functionalized, the hydroxylamine hydrochloride, and the anhydrous potassium carbonate is 0.2 to 1:1:1; the volume ratio of ethanol to water in the mixed solvent is 9:1 to 3; the reaction temperature is 60 to 90 °C, and the time is 8 to 12 h.

[0023] Preferably, the mass ratio of the metal ions in the metal salt to the graphene / cellulose aerogel is 27.3:5 to 20.

[0024] Preferably, the preparation steps of the graphene / cellulose aerogel include: using graphene oxide and cellulose as reactants, using ethylenediamine as a crosslinking agent, and obtaining the graphene / cellulose aerogel through a hydrothermal reaction.

[0025] More preferably, the mass ratio of the graphene oxide to the cellulose is 1:0.1 to 2; the dosage ratio of the graphene oxide to the ethylenediamine is 0.05 to 0.2 g:20 μL; the temperature of the hydrothermal reaction is 100 to 120 °C, and the time is 6 to 10 h.

[0026] The third technical solution of the present invention: provides an amidoxime-functionalized defective metal-organic framework material prepared according to the above preparation method.

[0027] The fourth technical solution of the present invention: Provide an amidoxime-functionalized defective metal-organic framework@graphene / cellulose aerogel composite material prepared according to the above preparation method.

[0028] The fifth technical solution of the present invention: Provide an application of the above-mentioned amidoxime-functionalized defective metal-organic framework material in enriching hexavalent uranium.

[0029] The sixth technical solution of the present invention: Provide an application of the above-mentioned amidoxime-functionalized defective metal-organic framework@graphene / cellulose aerogel composite material in enriching hexavalent uranium.

[0030] The beneficial technical effects of the present invention are as follows:

[0031] The amidoxime-functionalized defective metal-organic framework material or the amidoxime-functionalized defective metal-organic framework@graphene / cellulose aerogel composite material provided by the present invention not only has excellent adsorption performance and uranium selectivity, but also the raw material selection is environmentally friendly, non-toxic and harmless, and the cost is low. Description of the Drawings

[0032] Figure 1 SEM images of the samples prepared in Example 1, Example 4 and Example 5. Among them, a is the SEM image of UiO-66-3BA-AO prepared in Example 1, b is the SEM image of UiO-66-4BA-AO prepared in Example 4, and c is the SEM image of UiO-66-AA-AO prepared in Example 5.

[0033] Figure 2 SEM image of UiO-66-3BA-AO / GCA prepared in Example 3. Among them, a is the low-magnification image and b is the high-magnification image.

[0034] Figure 3 X-ray diffraction patterns of the samples prepared in Example 1, Example 4 and Example 5.

[0035] Figure 4 Infrared spectra of the samples prepared in Example 1, Example 4 and Example 5. Among them, a is the infrared spectrum of UiO-66-3BA-AO prepared in Example 1 and the intermediate product before amidoximation, b is the infrared spectrum of UiO-66-4BA-AO prepared in Example 4 and the intermediate product before amidoximation, and c is the infrared spectrum of UiO-66-AA-AO prepared in Example 5 and the intermediate product before amidoximation.

[0036] Figure 5Nitrogen adsorption - desorption isotherm diagrams and pore size distribution diagrams of the samples prepared in Example 1, Example 4, Example 5 and Comparative Example 2, where a is the nitrogen adsorption - desorption isotherm diagram and b is the pore size distribution diagram.

[0037] Figure 6 Adsorption performance diagrams of the samples prepared in Example 1, Example 3, Example 4, Example 5, Example 6, Example 7, Example 8, Example 9, Example 10, Example 11 and Comparative Example 2 for hexavalent uranium.

[0038] Figure 7 Diagram showing the relationship between the adsorption amount of the sample prepared in Example 1 for hexavalent uranium and time.

[0039] Figure 8 Diagram showing the relationship between the adsorption amount of the sample prepared in Example 3 for uranium and time under dark and light conditions.

[0040] Figure 9 Diagram showing the relationship between the adsorption amount of the sample prepared in Example 1 for hexavalent uranium and temperature.

[0041] Figure 10 Performance diagram of the sample prepared in Example 1 for cyclic adsorption of hexavalent uranium.

[0042] Figure 11 Performance diagram of the sample prepared in Example 1 for selective adsorption of hexavalent uranium. Detailed implementation manners

[0043] Now, various exemplary implementation manners of the present invention will 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, characteristics and implementation schemes of the present invention. It should be understood that the terms used in the present invention are only for describing specific implementation manners and are not used to limit the present invention.

[0044] It should be noted that the aspects not described in detail in the present invention are all conventional operation means in the art and are not the focus of the present invention.

[0045] In addition, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded from the range.

[0046] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Although this invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of this invention.

[0047] Regarding the use of "comprising", "including", "having", "containing", etc. herein, they are all open-ended terms, meaning including but not limited to.

[0048] Example 1

[0049] Preparation of amidoxime-functionalized defective metal-organic framework materials:

[0050] S1. Disperse 0.3 mmol of ZrCl4 in 10 mL of DMF, and obtain a homogeneous solution after ultrasonic treatment for 10 min, denoted as solution A.

[0051] S2. Disperse 0.3 mmol of terephthalic acid and 6 mmol of 3-cyanobenzoic acid into 10 mL of DMF, and perform ultrasonic treatment for 5 min, denoted as solution B.

[0052] S3. Mix solution A and solution B and perform ultrasonic treatment for 10 min, then transfer the mixed solution to a high-pressure reaction kettle lined with polytetrafluoroethylene, and react at 120 °C for 24 h. After natural cooling to room temperature, centrifuge to collect the solid product, wash it three times with N,N-dimethylformamide and ethanol respectively. Finally, dry the product under vacuum at 60 °C for 24 h to obtain cyanated defective MOFs materials.

[0053] S4. Disperse 0.2 g of cyanated defective MOFs materials, 0.4 g of hydroxylamine hydrochloride, and 0.4 g of potassium carbonate into 60 mL of 90 vol.% ethanol solution, and react at 80 °C for 8 h under nitrogen protection. After cooling, collect the sample, wash it three times with water and ethanol in sequence, and finally dry it under vacuum at 60 °C for 12 h to obtain amidoxime-functionalized defective metal-organic framework materials, denoted as UiO-66-3BA-AO.

[0054] Example 2

[0055] Preparation of graphene / cellulose aerogel:

[0056] S1. Take 0.05 g of graphene oxide and add it to 5 mL of ultrapure water, and perform ultrasonic treatment for 2 h to obtain a graphene oxide dispersion solution.

[0057] S2. Take 0.005 g of cellulose and add it to 5 mL of ultrapure water, and stir for 1 h to obtain a cellulose dispersion.

[0058] S3. Mix the graphene oxide dispersion and the cellulose dispersion, then add 10 μL of ethylenediamine and stir for 15 min. Pour the mixed solution into a high-pressure reactor lined with polytetrafluoroethylene and react at 120 °C for 8 h. After cooling to room temperature, soak it in a 15 vol.% ethanol solution for 24 h, then put it in the refrigerator and freeze for 24 h. Finally, dry it in a freeze-dryer for 72 h to obtain graphene / cellulose aerogel (GCA).

[0059] Example 3

[0060] Preparation of amidoxime-functionalized defective metal-organic framework@graphene / cellulose aerogel composite material:

[0061] S1. Weigh 0.3 mmol of ZrCl4, disperse it in 10 mL of DMF, and obtain a homogeneous solution after ultrasonic treatment for 10 min. Then add 10 mg of the GCA prepared in Example 2 and stir at 25 °C for 24 h.

[0062] S2. Weigh 0.3 mmol of terephthalic acid and 6 mmol of 3-cyanobenzoic acid and disperse them in 10 mL of DMF, and obtain a homogeneous solution after ultrasonic treatment for 5 min.

[0063] S3. Mix the solutions obtained in S1 and S2 and stir for 10 min, then transfer them to a high-pressure reactor lined with polytetrafluoroethylene and react at 120 °C for 24 h. After cooling, collect the solid product and wash it three times with N,N-dimethylformamide and ethanol respectively. Finally, dry the product under vacuum at 60 °C for 24 h to obtain a cyanated defective MOFs@graphene / cellulose aerogel composite material, denoted as UiO-66-3BA-CN / GCA.

[0064] S4. Disperse 0.2 g of UiO-66-3BA-CN / GCA, 0.4 g of hydroxylamine hydrochloride, and 0.4 g of potassium carbonate in 60 mL of a 90 vol.% ethanol solution, and react at 80 °C for 8 h under nitrogen protection. After cooling, collect the sample and wash it three times with water and ethanol in sequence. Finally, dry it under vacuum at 60 °C for 12 h to obtain an amidoxime-functionalized defective metal-organic framework@graphene / cellulose aerogel composite material, denoted as UiO-66-3BA-AO / GCA.

[0065] Example 4

[0066] Compared with Example 1, the difference is only that 3-cyanobenzoic acid is replaced with an equimolar amount of 4-cyanobenzoic acid, and the obtained sample is denoted as UiO-66-4BA-AO.

[0067] Example 5

[0068] Compared with Example 1, the difference is only that 3-cyanobenzoic acid is replaced with an equimolar amount of cyanoacetic acid, and the obtained sample is denoted as UiO-66-AA-AO.

[0069] Example 6

[0070] Compared with Example 1, the difference is only that the amount of 3-cyanobenzoic acid is adjusted to 3 mmol.

[0071] Example 7

[0072] Compared with Example 1, the difference is only that the amount of 3-cyanobenzoic acid is adjusted to 4.5 mmol.

[0073] Example 8

[0074] Compared with Example 1, the difference is only that the amount of 3-cyanobenzoic acid is adjusted to 7.5 mmol.

[0075] Example 9

[0076] Compared with Example 1, the difference is only that the amount of 3-cyanobenzoic acid is adjusted to 9 mmol.

[0077] Example 10

[0078] Compared with Example 3, the difference is only that the amount of GCA is adjusted to 5 mg.

[0079] Example 11

[0080] Compared with Example 3, the difference is only that the amount of GCA is adjusted to 15 mg.

[0081] Comparative Example 1

[0082] Preparation of cyanated defective MOFs material:

[0083] S1. Disperse 0.3 mmol of ZrCl4 in 10 mL of DMF, and obtain a homogeneous solution after ultrasonic treatment for 10 min, denoted as solution A.

[0084] S2. Disperse 0.3 mmol of terephthalic acid and 6 mmol of 3-cyanobenzoic acid in 10 mL of DMF, and perform ultrasonic treatment for 5 min, denoted as solution B.

[0085] S3. Mix solution A and solution B, and perform ultrasonic treatment for 10 min. Then transfer the mixed solution to a high-pressure reaction kettle lined with polytetrafluoroethylene, and react at 120 °C for 24 h. After natural cooling to room temperature, centrifuge to collect the solid product, wash it three times with N,N-dimethylformamide and ethanol respectively. Finally, dry the product under vacuum at 60 °C for 24 h to obtain the cyanated defective MOFs material, denoted as UiO-66-3BA-CN.

[0086] Comparative Example 2

[0087] Preparation of defect-free MOF materials:

[0088] S1. Disperse 0.3 mmol of ZrCl4 in 10 mL of DMF, and after ultrasonic treatment for 10 min, a homogeneous solution is obtained, denoted as solution A.

[0089] S2. Disperse 0.3 mmol of terephthalic acid in 10 mL of DMF, and ultrasonic treatment for 5 min, denoted as solution B.

[0090] S3. Mix solution A and solution B and ultrasonic treatment for 10 min, then transfer the mixture to a high-pressure reactor with a polytetrafluoroethylene liner, and react at 120 °C for 24 h. After natural cooling to room temperature, the solid product is collected by centrifugation, washed three times with N,N-dimethylformamide and ethanol respectively. Finally, the product is vacuum dried at 60 °C for 24 h to obtain defect-free MOF materials, denoted as UiO-66.

[0091] Figure 1 The SEM images of the samples prepared in Example 1, Example 4 and Example 5 are shown in Figure 1 , where a is the SEM image of UiO-66-3BA-AO prepared in Example 1, b is the SEM image of UiO-66-4BA-AO prepared in Example 4, and c is the SEM image of UiO-66-AA-AO prepared in Example 5.

[0092] Figure 1 It shows that all three samples present uniform regular octahedrons, indirectly proving the successful preparation of the samples.

[0093] The SEM image of UiO-66-3BA-AO / GCA prepared in Example 3 is shown in Figure 2 , where a is the low-magnification image and b is the high-magnification image.

[0094] Figure 2 It shows that UiO-66-3BA-AO / GCA is a polyhedral structure, the in-situ growth of UiO-66-3BA-AO is successful, and it is uniformly dispersed on the surface of GCA.

[0095] The X-ray diffraction patterns of the samples prepared in Example 1, Example 4 and Example 5 are shown in Figure 3 .

[0096] Figure 3 It shows that the peak positions of the three samples are basically the same as those of the simulated samples, indicating that the three samples are all successfully prepared.

[0097] The infrared spectra of the samples prepared in Example 1, Example 4 and Example 5 are shown inFigure 3 Among them, a is the infrared spectrum of UiO-66-3BA-AO and the intermediate product before amidoximation prepared in Example 1, b is the infrared spectrum of UiO-66-4BA-AO and the intermediate product before amidoximation prepared in Example 4, and c is the infrared spectrum of UiO-66-AA-AO and the intermediate product before amidoximation prepared in Example 5.

[0098] Figure 4 It shows that the presence of cyano groups proves the successful introduction of the regulator ligand. After the amidoximation reaction, the disappearance of cyano groups and the appearance of C=N, C-N, and N-O indicate the success of amidoximation and the successful preparation of the material.

[0099] The nitrogen adsorption-desorption isotherm diagrams and pore size distribution diagrams of the samples prepared in Example 1, Example 4, Example 5, and Comparative Example 2 are shown in Figure 5 where a is the nitrogen adsorption-desorption isotherm diagram and b is the pore size distribution diagram.

[0100] Figure 5 It shows that the prepared samples all have a large specific surface area and are of microporous structure, which is beneficial for uranium adsorption.

[0101] To test the adsorption performance of different samples, the experimental procedure is as follows: 2 mg of different samples are respectively added to a solution containing hexavalent uranium, where the uranium concentration is 100 mg / L, the adsorption time is 180 min, the adsorption pH is 6, and the adsorption temperature is 25 °C. The adsorption performance diagrams of the samples prepared in Example 1, Example 3, Example 4, Example 5, Example 6, Example 7, Example 8, Example 9, Example 10, Example 11, and Comparative Example 2 for hexavalent uranium are shown in Figure 6 .

[0102] Figure 6 It shows that compared with the defect-free MOFs material (Comparative Example 2), the defective MOFs and their composites exhibit more excellent adsorption performance, which confirms that the introduction of structural defects effectively promotes the uranium adsorption capacity of the material.

[0103] To investigate the relationship between the adsorption performance and time of the sample prepared in Example 1, the experimental procedure is as follows: 2 mg of the sample is added to a solution containing hexavalent uranium, where the uranium concentration is 100 mg / L, the adsorption pH is 6, and the adsorption temperature is 25 °C. The relationship diagram between the adsorption amount of the sample prepared in Example 1 for hexavalent uranium and time is shown in Figure 7 .

[0104] Figure 7It shows that UiO-66-3BA-AO can reach the adsorption equilibrium in 90 min, and the adsorption capacity for uranium is as high as 666.7 mg / g, indicating that UiO-66-3BA-AO has extremely fast adsorption kinetics and excellent adsorption performance.

[0105] The adsorption performance of the sample prepared in Example 3 under light and dark conditions was investigated. The experimental procedure was as follows: 2 mg of the sample was added to a solution containing hexavalent uranium with a uranium concentration of 100 mg / L, and the adsorption was carried out under dark and light conditions for 150 min at an adsorption pH of 6. The relationship between the adsorption amount of uranium and time for the sample prepared in Example 3 under dark and light conditions is shown in Figure 8 .

[0106] Figure 8 It shows that under dark conditions, the equilibrium adsorption amount of UiO-66-3BA-AO / GCA for uranium is 415.6 mg / L, and the adsorption equilibrium can be reached in 45 min. The abundant adsorption sites and more dispersed MOFs endow the adsorbent with excellent adsorption performance; under light conditions, the adsorption amount of UiO-66-3BA-AO / GCA for uranium increases to 545.5 mg / g, indicating that UiO-66-3BA-AO / GCA has excellent photothermal conversion performance.

[0107] The relationship between the adsorption performance of the sample prepared in Example 1 and temperature was investigated. The experimental procedure was as follows: 2 mg of the sample was respectively added to a solution containing hexavalent uranium with a uranium concentration of 100 mg / L, the adsorption time was 3 h, and the adsorption pH was 6. The relationship between the adsorption amount of hexavalent uranium and temperature for the sample prepared in Example 1 is shown in Figure 9 .

[0108] Figure 9 It shows that the adsorption amount of the UiO-66-3BA-AO sample for uranium gradually increases with the increase of temperature, and the adsorption amount is as high as 796.1 mg / g when the temperature is 313 K, indicating that this adsorption process is an endothermic process.

[0109] The cyclic adsorption performance of the sample prepared in Example 1 was investigated. The experimental procedure was as follows: 2 mg of the sample was added to a solution containing hexavalent uranium with a uranium concentration of 100 mg / L, the adsorption time was 3 h, the adsorption pH was 6, and the adsorption temperature was 25 °C. After adsorption, desorption was carried out with 0.1 M hydrochloric acid solution for 3 h. After desorption, it was washed with ultrapure water and then placed in a vacuum oven for drying. After drying, the next adsorption experiment was carried out. The cycle was repeated ten times. The performance diagram of the sample prepared in Example 1 for cyclic adsorption of hexavalent uranium is shown in Figure 10 .

[0110] Figure 10It is shown that after ten cycles of regeneration, the regeneration performance of the sample is still as high as 87.2% (87.2% of the initial adsorption capacity), proving that the UiO-66-3BA-AO structure is stable and has excellent cyclic regeneration performance.

[0111] The selective adsorption performance of the sample prepared in Example 1 for hexavalent uranium was investigated. The experimental procedure was as follows: 2 mg of the adsorbent was added to the simulated seawater containing hexavalent uranium, and the adsorption time was 24 h. After adsorption, the concentration changes of various ions in the simulated seawater before and after adsorption were measured by ICP-MS. The initial concentrations of Na, Mg, V, Mn, Co, Cu, Zn, Ba, Ca, and U before adsorption were 1149.1, 455.5, 180.7, 244.4, 238.4, 239.4, 259.1, 232.8, 510.7, and 295.8 μg / L, respectively. The concentrations of Na, Mg, V, Mn, Co, Cu, Zn, Ba, Ca, and U after adsorption were 907.9, 425.5, 72.4, 244.3, 236.8, 234.1, 251.8, 183.2, 421.9, and 49.7 μg / L, respectively. The adsorption amounts of the adsorbent for various ions were calculated. The selectivity of the sample prepared in Example 1 for hexavalent uranium is shown in Figure 11 .

[0112] Figure 11 It is shown that in the simulated seawater environment, the UiO-66-3BA-AO material prepared in Example 1 exhibits excellent selective adsorption performance for hexavalent uranium, and its maximum adsorption capacity can reach 125.4 mg / L. This remarkable adsorption effect indicates that the material has important practical application value in the fields of uranium-containing wastewater treatment and uranium extraction from seawater.

[0113] The above-described embodiments are only descriptions of the preferred modes of the present invention and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A preparation method of an amidoxime-functionalized defective metal-organic framework material, characterized in that, It includes the following steps: Using a metal salt, a regulating ligand, and terephthalic acid as reactants, through a solvothermal reaction, a cyanide-deficient MOFs material is prepared; Performing amidoxime functionalization on the cyanide-deficient MOFs material to obtain the amidoxime-functionalized cyanide-deficient MOFs material; The regulating ligand is 3-cyanobenzoic acid, 4-cyanobenzoic acid, or cyanoacetic acid.

2. A preparation method of an amidoxime-functionalized defective metal-organic framework @ graphene / cellulose aerogel composite, characterized in that It includes the following steps: Using graphene / cellulose aerogel as a carrier, immersing it in a solution containing a metal salt, and stirring to obtain metal ion-loaded graphene / cellulose aerogel; Using the metal ion-loaded graphene / cellulose aerogel, a regulating ligand, and terephthalic acid as reactants, through a solvothermal reaction, a cyanide-deficient MOFs@graphene / cellulose aerogel composite material is prepared; Performing amidoxime functionalization on the cyanide-deficient MOFs@graphene / cellulose aerogel composite material to obtain the defective metal-organic framework@graphene / cellulose aerogel composite material; The regulating ligand is 3-cyanobenzoic acid, 4-cyanobenzoic acid, or cyanoacetic acid.

3. The preparation method according to claim 1 or 2, characterized in that, The metal ions in the metal salt include Zr 4 + , Ce 3+ , Ni 2+ or Cu 2+ ; and / or, the molar ratio of the regulating ligand to the terephthalic acid is 1 to 30:1; and / or, the solvent for the solvothermal reaction is N,N-dimethylformamide, the temperature is 100 to 120 °C, and the time is 12 to 48 h.

4. The preparation method according to claim 1 or 2, characterized in that, The step of amidoxime functionalization includes: mixing the raw material to be functionalized, hydroxylamine hydrochloride, and anhydrous potassium carbonate in a mixed solvent of ethanol and water, and reacting under an inert atmosphere to complete the amidoxime functionalization.

5. The preparation method according to claim 4, characterized in that, The mass ratio of the raw material to be functionalized, the hydroxylamine hydrochloride, and the anhydrous potassium carbonate is 0.2 - 1:1:1; the volume ratio of ethanol to water in the mixed solvent is 9:1 - 3; the temperature of the reaction is 60 - 90 °C, and the time is 8 - 12 h.

6. The preparation method according to claim 2, characterized in that, The mass ratio of the metal ion in the metal salt to the graphene / cellulose aerogel is 27.3:5 - 20.

7. The preparation method according to claim 2, characterized in that, The preparation step of the graphene / cellulose aerogel includes: using graphene oxide and cellulose as reactants, and ethylenediamine as a crosslinking agent, through a hydrothermal reaction, the graphene / cellulose aerogel is prepared.

8. An amidoxime-functionalized defective metal-organic framework material prepared by the preparation method according to any one of claims 1, 3 - 5.

9. An amidoxime-functionalized defective metal-organic framework@graphene / cellulose aerogel composite material prepared by the preparation method according to any one of claims 2, 3 - 7.

10. The application of the amidoxime-functionalized defective metal-organic framework material according to claim 8 or the amidoxime-functionalized defective metal-organic framework@graphene / cellulose aerogel composite material according to claim 9 in enriching hexavalent uranium.

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