Preparation method of ordered mesoporous MOFs (Metal-Organic Frameworks) with hollow structure and uranium extraction application of ordered mesoporous MOFs

Abstract

The invention relates to a preparation method of ordered mesoporous MOFs with a hollow structure and uranium extraction application of the ordered mesoporous MOFs, the molar ratio of terephthalic acid to aminoterephthalic acid is controlled at 92: 8 by accurately regulating and controlling the variety and content of organic ligands in a reaction system, and the uranium extraction application of the ordered mesoporous MOFs with the hollow structure can be realized while amino functionalization is realized. The ordered mesoporous MOFs with the hollow structure are rapidly synthesized in one step, and the method is simple and high in operability. Experiments prove that the ordered mesoporous MOFs with the hollow structure have excellent anti-interference capability, show high-selectivity adsorption on uranium, and provide a new idea and choice for extraction of uranium from seawater.

Description

Technical Field

[0001] The present invention belongs to the field of nuclear engineering technology, and specifically relates to a novel material of ordered mesoporous MOFs with a hollow structure, a simple synthesis and preparation method thereof, and the application of the material in the adsorption and extraction of key radioactive nuclides uranium in seawater. Background Art

[0002] As global energy demand continues to rise and carbon emissions constraints become increasingly stringent, the advantages of nuclear energy as a new clean energy source are becoming increasingly prominent. However, uranium, an irreplaceable nuclear fuel, has extremely uneven distribution of land-based deposits and faces the dilemma of soaring mining costs. In contrast, the total amount of marine uranium resources (measured as [UO2(CO3)3] 4- Existing in the form of complexes, uranium could theoretically meet humanity's energy needs for millennia. This makes seawater uranium extraction a strategically important topic. Current materials used for uranium extraction, including carbon nitride and covalent organic frameworks, suffer from a variety of issues, including poor stability, weak adsorption capacity, and poor selectivity. The development of new adsorbents is urgently needed.

[0003] Metal-Organic Frameworks (MOFs), as a new generation of functional materials for uranium extraction from seawater, have shown significant advantages in the field of uranium adsorption in seawater due to their unique structural controllability, ultra-high specific surface area, and precisely adjustable pore chemical environment. Its periodic self-assembly characteristics allow for the molecular-level design of metal cluster nodes and organic ligands to achieve precise regulation of pore size distribution, surface functional group types (such as amino groups, thiol groups, etc.), and topological structures (such as ZIF-8, UiO-66 series), thereby establishing efficient ion recognition and selective capture mechanisms. However, traditional MOFs materials face multiple technical difficulties in actual marine environments: first, the micropore-dominated structure (pore diameter <2 nm) leads to obstructed mass transfer paths, limited diffusion of uranyl ions, and a delayed adsorption rate; second, the saturated coordination of metal nodes results in insufficient exposure of effective active sites, resulting in a significant gap between the adsorption capacity and the theoretical value; third, the competitive ion interference (such as V 5+ Limitations such as the presence of bacteria (e.g., bacteria) and biofouling (e.g., E. coli) have severely impaired the material's practical application. To address the low mass transfer efficiency associated with the microporous structure of MOFs, Huitao Fan et al. successfully prepared an ordered mesoporous OM-Ce-MOF using Planck F127 as a soft template, cerium ammonium nitrate as a metal source, and terephthalic acid as an organic ligand. However, in practical applications, the adsorption capacity and rate were only marginally improved.

[0004] In summary, it is necessary to invent new materials with better uranium adsorption effects. Summary of the Invention

[0005] The application aims to solve the technical problem that the existing metal organic framework material is not ideal for uranium adsorption effect, and provides a technical solution of optimizing MOFs structure and modifying functional groups, so that a new MOFs material is prepared through a simple step, and a more ideal seawater uranium extraction effect is achieved.

[0006] The strategy of the application team to optimize MOFs is to construct an ordered mesoporous structure and modify functional groups. Considering that amino groups can specifically bind to uranyl ions to improve material selectivity, it is initially conceived to perform amino functionalization on the basis of an ordered mesoporous structure. Direct synthesis method is tried, that is, other components (acetic acid, sodium perchlorate monohydrate, Pluronic F127, cerium nitrate ammonia) in the reaction system remain unchanged, and part of terephthalic acid is replaced with amino terephthalic acid to directly synthesize amino functionalized OM-Ce-MOF. During the test, when the material synthesized in one of the tests was characterized by transmission electron microscopy, we were shocked to find that the material surprisingly formed a hollow structure while having an ordered mesoporous structure and amino functionalization, so it was named H-OM-Ce-MOF-NH2. After the material is used for uranium extraction experiments, it is found that its adsorption performance and adsorption rate are greatly improved compared with microporous Ce-MOF and OM-Ce-MOF, which is because the coexistence of hollow structure and ordered mesoporous structure greatly improves the utilization rate of active sites of the material, and amino functionalization further improves the number of active sites. Through further systematic investigation and arrangement, the complete technical solution of the application is formed, as follows: The first aspect of the application is to provide a rapid preparation method of hollow ordered mesoporous MOFs, which is unique in that the structure of the material is controlled by adjusting the type and content of organic ligand, and the whole reaction process has only one step: After acetic acid, sodium perchlorate monohydrate, Pluronic F127, cerium nitrate ammonia, terephthalic acid and amino terephthalic acid are added to deionized water and uniformly mixed, they are reacted at 55-65 DEG C for 24-28 min, centrifuged, washed and dried to obtain the product; The molar ratio of terephthalic acid to amino terephthalic acid is 92:8.

[0007] Further, the reaction time is 25 min.

[0008] Further, the molar ratio of sodium perchlorate monohydrate, Pluronic F127, cerium nitrate ammonia, terephthalic acid and amino terephthalic acid is 300-400:0.7-0.9:90-110:92:8.

[0009] Furthermore, the molar ratio of the sodium perchlorate monohydrate, Planck F127, cerium ammonium nitrate, terephthalic acid and aminoterephthalic acid is 356:0.79:100:92:8.

[0010] Furthermore, the volume ratio of the deionized water to the acetic acid is 18-25:1; preferably, the volume ratio of the deionized water to the acetic acid is 20:1.

[0011] Furthermore, the mass volume ratio of the Planck F127 to the deionized water is 100 mg:5-10 mL; preferably, the mass volume ratio of the Planck F127 to the deionized water is 100 mg:6 mL.

[0012] Furthermore, the washing is performed sequentially with distilled water and DMF.

[0013] Furthermore, after the centrifugal washing, the obtained solid material is immersed in ethanol at 55-65° C. for 1-3 days to remove the Planck F127 template, and the ethanol needs to be replaced at least 4 times a day during this period.

[0014] Furthermore, the drying is carried out in a vacuum drying oven at 60-80°C for 12-24 hours.

[0015] The second aspect of the present invention provides ordered mesoporous MOFs with a hollow structure obtained by the above method.

[0016] The third aspect of the present invention provides the application of the obtained hollow structure ordered mesoporous MOFs in extracting radioactive nuclide uranium from seawater.

[0017] Further, the following steps are included: (1) taking a solution containing radioactive nuclide uranium, adding the hollow structure ordered mesoporous MOFs as an adsorbent, adjusting the pH, and performing adsorption; (2) The product obtained in step (1) is shaken in a constant temperature oscillator and then centrifuged. Furthermore, the pH in step (1) is 8.25-8.35, the adsorption temperature is 25°C; the initial concentration of the radionuclide solution is 10-80 mg / L, and the mass concentration of the adsorbent is 0.1 g / L.

[0018] Furthermore, the shaking time in step (2) is 12 h.

[0019] The beneficial effects of adopting the above technical solution are: (1) The reaction process of the present invention can prepare MOFs that integrate ordered mesoporous structure, hollow structure and amino functionalization in just one step. The operation is simple, no harmful substances are generated, the stability is strong, and the storage is easy. It is feasible for commercial production.

[0020] (2) As a new type of adsorbent, the multifunctional MOFs obtained in the present invention have been experimentally verified to have a high adsorption capacity, a fast adsorption rate and excellent selectivity in the field of uranium removal from seawater. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The structural diagram and transmission electron microscope images of the MOFs described in Experimental Investigation Example 1 of the present invention at different reaction times are shown; Figure 2 The structural diagram, transmission electron microscope image and corresponding adsorption kinetics of the materials synthesized by MOFs at different aminoterephthalic acid ratios described in Experimental Investigation Example 2 of the present invention are shown; Wherein: a is a schematic structural diagram of different molar ratios of aminoterephthalic acid; b1 is a transmission electron microscope image of aminoterephthalic acid at a molar ratio of 1%; b2 is an adsorption curve of aminoterephthalic acid at a molar ratio of 1%; c1 is a transmission electron microscope image of aminoterephthalic acid at a molar ratio of 3%; c2 is an adsorption curve of aminoterephthalic acid at a molar ratio of 3%; d1 is a transmission electron microscope image of aminoterephthalic acid at a molar ratio of 5%; d2 is an adsorption curve of aminoterephthalic acid at a molar ratio of 5%; e1 is a transmission electron microscope image of aminoterephthalic acid at a molar ratio of 8%; e2 is an adsorption curve of aminoterephthalic acid at a molar ratio of 8%; f1 is a transmission electron microscope image of aminoterephthalic acid at a molar ratio of 10%; f2 is an adsorption curve of aminoterephthalic acid at a molar ratio of 10%; Figure 3 N2 adsorption-desorption curves of H-OM-Ce-MOF-NH2, OM-Ce-MOF, and microporous Ce-MOF described in structural characterization test example 1 of the present invention; Figure 4 The infrared spectra of H-OM-Ce-MOF-NH2, OM-Ce-MOF and microporous Ce-MOF described in the structural characterization test example 1 of the present invention are shown; Figure 5 The adsorption isotherms of H-OM-Ce-MOF-NH2, OM-Ce-MOF and microporous Ce-MOF described in Example 2 are used to investigate the effect of the present invention. DETAILED DESCRIPTION

[0022] In order to make the objectives, technical solutions and advantages of the present invention more clear, the invention is described clearly and completely below with reference to specific embodiments and accompanying drawings.

[0023] The experimental methods in the following examples and comparative examples, unless otherwise specified, are conventional methods; the experimental materials used, unless otherwise specified, are purchased from conventional biochemical reagent manufacturers.

[0024] Example 1 Preparation of hollow structured ordered mesoporous MOFs (H-OM-Ce-MOF-NH2): 0.36 mL of acetic acid, 600 mg of sodium perchlorate monohydrate, 120 mg of Planck F127, 658 mg of cerium ammonium nitrate, 183.27 mg of terephthalic acid, and 17.38 mg of aminoterephthalic acid (molar ratio of 92:8) were added to 9 mL of deionized water, mixed thoroughly, and reacted at 60°C for 25 min. The resulting material was collected by centrifugation and washed three times with 36 mL of distilled water and three times with DMF. After centrifugation, the resulting material was soaked in 60 mL of anhydrous ethanol at 60°C for two days to remove the F127 template, with the ethanol replaced every six hours. After soaking in anhydrous ethanol, the resulting material was placed in a vacuum drying oven at 65°C for 12 hours to obtain H-OM-Ce-MOF-NH2.

[0025] Example 2 Preparation of hollow structured ordered mesoporous MOFs (H-OM-Ce-MOF-NH2): 0.40 mL of acetic acid, 674.16 mg of sodium perchlorate monohydrate, 136.71 mg of Planck F127, 723.80 mg of cerium ammonium nitrate, 183.27 mg of terephthalic acid, and 17.38 mg of aminoterephthalic acid (molar ratio of 92:8) were added to 9 mL of deionized water, mixed thoroughly, and reacted at 60°C for 25 min. The resulting material was collected by centrifugation and washed three times with 36 mL of distilled water and three times with DMF. After centrifugation, the resulting material was soaked in 60 mL of anhydrous ethanol at 60°C for two days to remove the F127 template, with the ethanol replaced every six hours. After soaking in anhydrous ethanol, the resulting material was placed in a vacuum drying oven at 65°C for 12 hours to obtain H-OM-Ce-MOF-NH2.

[0026] Example 3 Preparation of hollow structured ordered mesoporous MOFs (H-OM-Ce-MOF-NH2): 0.35 mL of acetic acid, 507.6 mg of sodium perchlorate monohydrate, 106 mg of Planck F127, 591.9 mg of cerium ammonium nitrate, 183.27 mg of terephthalic acid, and 17.38 mg of aminoterephthalic acid (molar ratio of 92:8) were added to 9 mL of deionized water, mixed thoroughly, and reacted at 60°C for 25 min. The resulting material was collected by centrifugation and washed three times with 36 mL of distilled water and three times with DMF. After centrifugation, the resulting material was soaked in 60 mL of anhydrous ethanol at 60°C for two days to remove the F127 template, with the ethanol replaced every six hours. After soaking in anhydrous ethanol, the resulting material was placed in a vacuum drying oven at 65°C for 12 hours to obtain H-OM-Ce-MOF-NH2.

[0027] Test investigation example 1 This experiment investigates the structure of MOFs materials prepared at different reaction times: 0.36 mL of acetic acid, 600 mg of sodium perchlorate monohydrate, 120 mg of Planck F127, 658 mg of cerium ammonium nitrate, 183.27 mg of terephthalic acid, and 17.38 mg of aminoterephthalic acid (molar ratio of 92:8) were added to 9 mL of deionized water, mixed evenly, and reacted at 60°C for 15, 20, 35, and 50 min, respectively. The synthesized material was collected by centrifugation and washed three times with 36 mL of distilled water and DMF, respectively. After centrifugation, the obtained material was soaked in 60 mL of anhydrous ethanol at 60°C for two days to remove the F127 template, and the anhydrous ethanol was replaced every 6 hours. After the anhydrous ethanol soaking was completed, the obtained material was placed in a vacuum drying oven at 65°C for 12 hours. The MOFs obtained at different reaction times were analyzed by transmission electron microscopy. The structural diagram and transmission electron microscopy images are shown in Figure 2. Figure 1 As shown. By controlling the time of the material synthesis reaction (15-50 min), the formation and decomposition mechanism of the H-OM-Ce-MOF-NH2 hollow structure was revealed. The material undergoes five stages of morphological evolution: the initial stage (15 min) forms dense solid nanospheres ( Figure 1 a, b); During the core-shell structure formation period (20 min), an obvious core-shell interface appeared ( Figure 1 c, d); hollowing stage (25 min) by self-template sacrificial etching to form dispersed hollow spheres ( Figure 1 e,f); During the structural instability period (35 min), the surface of the sphere was observed to collapse inward ( Figure 1 g, h); in the final stage (50 min), the material structure completely collapsed ( Figure 1 i,j). This process is guided by the Kirkendall effect and Oswald ripening. Under the initial supersaturated condition, Ce 4+Rapid coordination with ligands to form solid nanospheres. As the reaction proceeds, the core region (high surface energy Ce 4+ Asymmetric diffusion occurs between the core (the organic ligand-enriched region) and the shell (the organic ligand-stabilized region), leading to interfacial vacancy enrichment (Kirkendall effect). Acetic acid, acting as an etchant, selectively dissolves the core, while the shell forms a stable layer through enhanced Ce-OC coordination bonds and π-π stacking. Oswald ripening promotes the directional migration of small grains toward larger ones, accelerating the formation of hollow structures. However, when the reaction time exceeds a certain value (35 min), excessive ligand hydrolysis leads to a decrease in shell crosslinking, while complete removal of the F127 template destabilizes the mesoporous structure. This leads to stress imbalance within the shell, causing the surface to collapse inward. After a reaction time of 50 min, the complete decomposition of the coordination framework leads to complete collapse of the material.

[0028] Test investigation example 2: This experiment investigates the preparation of MOFs materials with different molar ratios of terephthalic acid and 2-aminoterephthalic acid: 0.36 mL of acetic acid, 600 mg of sodium perchlorate monohydrate, 120 mg of Planck F127, and 658 mg of cerium ammonium nitrate were added to 9 mL of deionized water, mixed well, and reacted at 60°C for 25 min. The synthesized material was collected by centrifugation and washed three times with 36 mL of distilled water and three times with DMF. After centrifugation, the resulting material was soaked in 50 mL of ethanol at 60°C for two days to remove the F127 template, with the ethanol replaced every six hours. After soaking in ethanol, the resulting material was placed in a vacuum drying oven at 65°C for 12 hours.

[0029] The MOFs synthesized with different ratios of terephthalic acid and aminoterephthalic acid were analyzed by transmission electron microscopy. The structural diagram and transmission electron microscopy images are shown in Figure 2. Figure 2As shown. When the proportion of BDC-NH2 is low (1-3%), the material presents a solid spherical structure with a diameter of 550 to 450 nm, which is attributed to the homogeneous nucleation and isotropic growth under equilibrium coordination, that is, the symmetrical coordination mode dominated by BDC promotes the uniform aggregation of metal clusters. As the proportion of BDC-NH2 increases to 5-10%, the morphology of the material changes significantly, forming a hollow spherical structure with a diameter of 400 to 200 nm, and the particle size decreases with the increase of amino content. This structural change is caused by the combined action of three aspects. First, the carboxylic acid-amino bifunctional group of BDC-NH2 and Ce 4+ It can form a strong coordination network and build a stable rigid shell, while the reduction of BDC ratio weakens the coordination cross-linking density of the core region, resulting in stronger thermodynamic instability of the core region; secondly, Ce 4+ The outward diffusion rate of ions is significantly higher than the inward migration rate of ligands, resulting in a concentration difference at the core-shell interface and inducing vacancy aggregation; finally, the increase in BDC-NH2 content increases the nucleation density, resulting in a decrease in the size of primary grains. Small-sized grains migrate to the surface of large particles through the dissolution and re-deposition process, ultimately forming a hollow structure with a dense shell and uniform size.

[0030] This experiment demonstrates that precise transitions from solid to hollow structures can be achieved by simply adjusting the ratio of the two ligands, providing new insights into the morphology engineering of MOFs. Experimental results indicate that adsorption performance reaches its peak at an 8% BDC-NH₂ ratio (BDC / BDC-NH₂ = 92:8), declining at a higher amino group density (10%). The optimal performance of this material stems from a balanced pore-ligand synergy, where the mesopores enable rapid diffusion of uranyl ions, while the moderate -NH₂ density provides ample active sites with minimal steric hindrance. The hollow structure maximizes accessible surface area while maintaining structural integrity. Furthermore, partial ligand substitution introduces coordinatively unsaturated Ce sites, enhancing uranyl ion binding. However, an excessive amino group content (10%) results in overcrowding of -NH₂ groups that block the pores, reducing the utilization of active sites and, consequently, lowering adsorption efficiency.

[0031] This study confirmed that a BDC / BDC-NH2 ratio of 92:8 can achieve the optimal balance between mass transfer efficiency and coordination strength, providing a new strategy for designing highly selective radionuclide adsorbents.

[0032] Comparative Example 1 Preparation of MOFs materials with ordered mesoporous structures without hollow structures (OM-Ce-MOF): 0.36 mL of acetic acid, 600 mg of sodium perchlorate monohydrate, 120 mg of Planck F127, 658 mg of cerium ammonium nitrate, and 199.2 mg of terephthalic acid were added to 9 mL of deionized water, mixed thoroughly, and reacted at 60°C for 25 minutes. The resulting material was collected by centrifugation and washed three times with 36 mL of distilled water and three times with DMF. After centrifugation, the resulting material was soaked in 60 mL of ethanol at 60°C for two days to remove the F127 template, with the ethanol replaced every six hours. After soaking in ethanol, the resulting material was placed in a vacuum drying oven at 65°C for 12 hours.

[0033] Comparative Example 2 Preparation of Ce-MOF with only microporous structure: Dissolve 35.4 mg of terephthalic acid in a mixture of 1.2 mL of DMF and 400 μL of 0.5333 M cerium ammonium nitrate solution. Add 1 mL of formic acid as a modifier. Transfer the mixture to a 10 mL glass vial, seal it, and stir at 100°C for 15 minutes. After the reaction, collect the pale yellow precipitate by centrifugation and wash it three times with DMF and then acetone to remove any unreacted products. Finally, place the resulting material in a vacuum drying oven at 60°C for 12 hours.

[0034] Structural characterization test example 1 (1) N2 adsorption and desorption tests were performed on H-OM-Ce-MOF-NH2 prepared in Example 1, OM-Ce-MOF prepared in Comparative Example 1, and microporous Ce-MOF prepared in Comparative Example 2, and N2 adsorption and desorption curves were plotted as shown in the figure. Figure 3 As shown in Figure 2, H-OM-Ce-MOF-NH2 and OM-Ce-MOF exhibit type IV isotherms, while Ce-MOF exhibits type I isotherms. Figure 2 ) It can also be seen that H-OM-Ce-MOF-NH2 and OM-Ce-MOF both have mesoporous structures, while Ce-MOF only has a microporous structure, confirming the successful construction of the mesoporous structure.

[0035] (2) Infrared spectroscopy The H-OM-Ce-MOF-NH2 prepared in Example 1, the OM-Ce-MOF prepared in Comparative Example 1, and the microporous Ce-MOF prepared in Comparative Example 2 were measured by infrared spectroscopy. The results are as follows: Figure 4 As shown, except for 1654cm -1 Ce 4+ -Carboxylic acid coordination characteristic peaks and 1550 / 1390 cm -1 Asymmetric / symmetric COO at -In addition to the stretching vibration peak, H-OM-Ce-MOF-NH2 is significantly higher than OM-Ce-MOF and microporous Ce-MOF at 3200 cm⁻. 1 A new peak appeared at , corresponding to the vibration of the amino group, confirming the successful introduction of the amino group.

[0036] Effect Investigation Example 1 The H-OM-Ce-MOF-NH2 prepared in Example 1, the OM-Ce-MOF prepared in Comparative Example 1, and the microporous Ce-MOF prepared in Comparative Example 2 were used to adsorb uranyl carbonate solution at 25°C in a dark environment. The specific steps are as follows: (1) Take 0.1 g / L of adsorbent and add it to 10 mg / L uranyl carbonate solution with a pH of 8.3, and place it at 25°C for reaction.

[0037] (2) The supernatant was collected using a sampler at 3, 5, 10, 15, 20, 30, 40, and 55 min, filtered, and its absorbance was measured. The residual uranium concentration was calculated using a standard curve.

[0038] (3) Calculate the equilibrium concentration and the amount of uranyl carbonate adsorbed by the material based on the initial concentration and the measured residual concentration.

[0039] (4) Draw a graph of adsorption time and adsorption amount, and infer the adsorption process of the adsorbent through pseudo-first-order kinetics and pseudo-second-order kinetics.

[0040] Results indicate that H-OM-Ce-MOF-NH2 reaches equilibrium within 30 minutes, with an adsorption capacity of 76.4 mg / g, and exhibits a faster adsorption rate than OM-Ce-MOF and Ce-MOF. Comparison of the correlation coefficients between pseudo-first-order and pseudo-second-order kinetics indicates that the adsorption process on H-OM-Ce-MOF-NH2 is more consistent with second-order kinetics, confirming that the adsorption of H-OM-Ce-MOF-NH2 is a physicochemical adsorption process.

[0041] The pseudo-first-order kinetics and pseudo-second-order kinetics models are used to fit the kinetic curve of the material to describe the removal behavior of the material. The specific formulas are shown in Equation 1 and Equation 2: ln( q e - q t ) = ln q e - K 1 t (1) (2) In the formula K 1 —— Pseudo-first-order adsorption constant (min−1 ); K 2 —— Pseudo-secondary adsorption constant (g·(mg·min −1 )); q t —— Reaction time is t Adsorption capacity (mg·g −1 ); q e —— Adsorption amount at reaction equilibrium (mg·g −1 ).

[0042] Effect Investigation Example 2 The H-OM-Ce-MOF-NH2 prepared in Example 1, the OM-Ce-MOF prepared in Comparative Example 1, and the microporous Ce-MOF prepared in Comparative Example 2 were used to adsorb uranyl carbonate solutions of different concentrations at 25° C. The specific steps are as follows: (1) Take 0.1 g / L of the above materials and add them to 10, 20, 30, 40, 50, 60, 70, and 80 mg / L uranyl carbonate solution (pH 8.3) in sequence, and shake them in a shaker overnight.

[0043] (2) After the reaction is complete, centrifuge and collect the supernatant, measure its absorbance, and calculate its remaining uranium concentration using the standard curve.

[0044] (3) Calculate the equilibrium concentration and the amount of uranyl carbonate adsorbed by the material based on the initial concentration and the measured residual concentration.

[0045] (4) Draw a curve graph of equilibrium concentration and adsorption amount, and determine the adsorption type by fitting the Langmuir and Freundlich isotherm adsorption models and comparing the fit.

[0046] Adsorption isotherms such as Figure 5 As shown in Figure 2, the maximum extraction yield of H-OM-Ce-MOF-NH2 calculated using the Langmuir model is 95.5 mg / g, significantly higher than that of OM-Ce-MOF (64.4 mg / g) and microporous Ce-MOF (46.9 mg / g). Comparing the correlation coefficients between the two models (0.985 < 0.907) indicates that the adsorption process is more consistent with the Langmuir model, i.e., monolayer adsorption.

[0047] The Langmuir and Freundlich models were used to simulate the adsorption isotherms of the materials. The specific formulas are shown in Equations 3 and 4: (3) ln q e = ln K F +ln C e (4) In the formula q e —— Pollutant adsorption capacity at reaction equilibrium (mg·g −1 ); q max —— Maximum theoretical adsorption capacity for U(VI) (mg·g −1 ); C e —— Pollutant concentration at reaction equilibrium (mg·L −1 ); K L —— Langmuir model coefficient parameter (L·mg −1 ); K F —— Freundlich model coefficient parameter (mg 1−n ·L n ·g −1 ).

[0048] Effect Investigation Example 3 The effect of H-OM-Ce-MOF-NH2 prepared in Example 1 on adsorption of uranyl carbonate solution under different background ion conditions at 25°C was tested. The specific steps are as follows: (1) Take 0.1 g / L of multifunctional uranium extraction material and add it to 10 mg / L uranyl carbonate solution with pH = 8.3, then add 0.01M background ion solution (i.e. KNO3, Ca(NO3)2, Co(NO3)2, Cu(NO3)2, Mg(NO3)2, Sr(NO3)2, Zn(NO3)2, NaVO3, Na2SO4) in sequence, and place it in a shaker and shake overnight.

[0049] (2) After the reaction is complete, centrifuge and collect the supernatant, measure its absorbance, and calculate its remaining uranium concentration using the standard curve.

[0050] (3) Calculate the equilibrium concentration and the amount of uranyl carbonate adsorbed by the material based on the initial concentration and the measured residual concentration.

[0051] (4) Compare the adsorption capacity without adding background ions and with adding different background ions, and summarize the effects of different ions on the adsorption capacity of the material.

[0052] The results show that divalent cations exhibit stronger interference, which is due to the enhanced Coulomb force at the active site as the ion valence increases. - Despite these interferences, H-OM-Ce-MOF-NH2 maintains excellent selectivity, showing a significant inhibitory effect due to its preferential coordination with -NH2 groups.

[0053] Effect Investigation Example 4 The adsorption effect of H-OM-Ce-MOF-NH2 prepared in Example 1 on uranyl carbonate solution at 25°C with different NaCl concentrations was tested. The specific steps are as follows: (1) Prepare a homogeneous solution of NaCl (0.1 / 0.2 / 0.3 / 0.4 / 0.5 / 0.6 / 0.7 / 0.8 mol / L) and uranyl carbonate at different concentrations and stir to ensure that the solution is free of precipitates.

[0054] (2) Add 0.1 g / L H-OM-Ce-MOF-NH2 to the above solution at 10 mg / L and pH = 8.3, and shake overnight in a shaker.

[0055] (3) After the reaction is complete, centrifuge and collect the supernatant, measure its absorbance, and calculate its remaining uranium concentration using the standard curve.

[0056] (4) Draw a bar graph of NaCl concentration and adsorption amount, and judge the effect of NaCl on material extraction efficiency by comparing the adsorption amount.

[0057] The results showed that with the increase of NaCl concentration, the extraction efficiency of the material tended to decrease gradually, but it could still maintain a high extraction efficiency.

[0058] Application Examples Determination of adsorption capacity by spiked actual seawater: (1) Actual seawater samples were taken from the southeastern sea area of ​​Xingcheng City, Huludao City, Liaoning Province, and used to dissolve uranyl nitrate ions and prepare the stock solution.

[0059] (2) Take 0.1 g / L of the material and add it to the prepared solutions of 10, 20, 30, 40, 50, 60, 70, and 80 mg / L in sequence, and place it on a shaker to shake for 2 days.

[0060] (3) After the reaction is complete, centrifuge and collect the supernatant, measure its absorbance, and calculate its remaining uranium concentration using the standard curve.

[0061] (4) Calculate the equilibrium concentration and the amount of adsorption of spiked seawater by the material based on the initial concentration and the measured residual concentration.

[0062] The calculated adsorption capacity is 13.92 mg·g−1 The ordered mesoporous MOFs with hollow structure obtained by the application can be applied to the field of uranium extraction from seawater.

[0063] Although the application is described in detail with reference to the foregoing embodiments, those skilled in the art can modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacements to some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the application.

Claims

1. A method for rapidly preparing ordered mesoporous MOFs with a hollow structure, characterized in that: The preparation method comprises: Add acetic acid, sodium perchlorate monohydrate, Planck F127, cerium ammonium nitrate, terephthalic acid and aminoterephthalic acid into deionized water, mix well, react at 55-65°C for 24-28 minutes, centrifuge, wash, and dry to obtain the product. The molar ratio of terephthalic acid to aminoterephthalic acid is 92:

8.

2. The rapid preparation method of ordered mesoporous MOFs with hollow structures according to claim 1, characterized in that: The molar ratio of the sodium perchlorate monohydrate, Planck F127, cerium ammonium nitrate, terephthalic acid and aminoterephthalic acid is 300-400:0.7-0.9:90-110:92:8; preferably 356:0.79:100:92:

8.

3. The rapid preparation method of ordered mesoporous MOFs with hollow structures according to claim 1, characterized in that: The volume ratio of the deionized water to the acetic acid is 18-25:1; the mass volume ratio of the Planck F127 to the deionized water is 100 mg:5-10 mL.

4. The method for rapidly preparing ordered mesoporous MOFs with hollow structures according to claim 1, characterized in that: The washing step is washing with distilled water and DMF in sequence.

5. The rapid preparation method of ordered mesoporous MOFs with hollow structures according to claim 1, characterized in that: After the centrifugal washing, the obtained solid material is immersed in ethanol at 55-65° C. for 1-3 days to remove the Planck F127 template, during which the ethanol needs to be replaced at least 4 times a day.

6. The method for rapidly preparing ordered mesoporous MOFs with a hollow structure according to claim 1, characterized in that: The drying step is to place the mixture in a vacuum drying oven at 60-80° C. for 12-24 hours.

7. Ordered mesoporous MOFs with a hollow structure obtained by the preparation method according to any one of claims 1 to 6.

8. Use of the ordered mesoporous MOFs with a hollow structure as claimed in claim 7 in extracting radioactive uranium from seawater.

9. The use according to claim 8, characterized in that The steps include: (1) taking a solution containing radioactive nuclide uranium, adding the ordered mesoporous MOFs with a hollow structure as an adsorbent, adjusting the pH, and performing adsorption; (2) The product obtained in step (1) was shaken in a constant temperature shaker and then centrifuged.

10. The use according to claim 9, characterized in that The pH in step (1) is 8.25-8.35, and the adsorption temperature is 25°C; the initial concentration of the radionuclide solution is 10-80 mg / L, and the mass concentration of the adsorbent is 0.1 g / L; and the oscillation time in step (2) is 12 h.

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