Cucurbituril-based supramolecular organic framework material as well as preparation method and application thereof

Abstract

The invention relates to the technical field of nuclear waste treatment, in particular to a cucurbituril-based supramolecular organic framework material as well as a preparation method and application thereof. A construction unit of the supramolecular organic framework material is constructed by taking cucurbit [8] uril (CB8) as a subject and terephthalyl viologen ligand 1, 1 ''-(1, 4-phenylene) bis ([4, 4 '-bipyridyl]-1-onium) salt (PBV. 2X) as an object through the bonding effect of the subject and the object; in the molecular structure of the supramolecular organic framework material, the construction units are staggered and stacked in parallel in the space, and NO3 <-> is located at the gap of the adjacent CB8. The supramolecular organic framework material disclosed by the invention has high structural stability and cationic framework characteristics, and a rigid framework and a pyridine conjugated system of CB8 endow the material with excellent chemical / irradiation stability, so that the material shows ultrahigh removal rate on ReO4 <-> / TcO4 <-> in extreme environments (strong acid, strong alkali and high irradiation).

Description

Technical Field

[0001] This invention relates to the field of nuclear waste treatment technology, and in particular to a supramolecular organic framework material based on cucurbituril, its preparation method and application. Background Technology

[0002] In the global transition to low-carbon energy, the increasing proportion of nuclear power as a clean energy source has made the safety management of nuclear fuel throughout its entire life cycle a focal point of the industry. Among these, technetium-99 (… 99 Tc (half-life 2.13 × 10⁻⁶) 5 Technetium peroxide (TcO4) is a key radionuclide comprising up to 6% of spent fuel fission products, typically present as pertechnetate (TcO4). - It exists in a hydrated form (hydration radius of only 3.6 Å, solubility of 11.3 mol / L at 20℃), has weak adsorption in geological media, and is extremely prone to long-distance migration in environmental water bodies, posing a long-term risk of radioactive pollution to nuclear waste disposal sites and surrounding ecosystems.

[0003] In the field of spent fuel reprocessing, the PUREX (Plutonium-Uranium Reduction Extraction) process is the mainstream technology, and its first cycle contains TcO4 - Simultaneous extraction with key nuclides such as uranium (U), plutonium (Pu), and zirconium (Zr) not only reduces the separation purity of the target nuclides but also significantly increases the complexity of subsequent processes, becoming a key bottleneck restricting the improvement of post-processing efficiency. Currently, for TcO4... - The separation technologies mainly include reduction fixation, precipitation, solvent extraction, and ion exchange, but all have significant limitations. While precipitation offers advantages such as being green and low-consumption, it suffers from poor stability in extreme wastewater systems such as high-acid / high-salt environments, and its effectiveness is limited by the selective TcO4 content. - The limitations of this method restrict its large-scale application in nuclear waste treatment. The reduction fixation method relies on high-valent reducing agents to reduce TcO4... - It is converted into Tc(IV) insoluble substances, but the reducing agent is prone to introducing secondary pollution and has a high risk of failure under strong radiation. Although solvent extraction has excellent separation efficiency, the toxicity and flammability of organic solvents and the subsequent wastewater treatment problems limit its industrial applicability. Traditional ion exchange materials lack specific recognition sites, and in environments containing NO3... - SO4 2- The selectivity is extremely low in complex systems with competing anions.

[0004] Nuclear waste disposal often involves conditions of strong acid (pH<1), strong base (pH>13), high ionic strength (>1M), and strong radiation (>100kGy). Existing materials are prone to structural collapse or degradation of functional groups, leading to the deterioration of TcO4. -The removal rate dropped sharply. For example, in simulated Hanford wastewater (containing 6M HNO3), commercial anion exchange resins showed a significant decrease in TcO4 removal rate. - Its adsorption capacity is less than 5 mg / g, and its performance degrades by more than 80% after irradiation. Summary of the Invention

[0005] This invention provides a supramolecular organic framework material based on cucurbituril, its preparation method, and its application, to address the challenges posed by existing TcO4 materials. - Separation technologies are prone to structural instability or degradation under extreme waste liquid conditions, and lack specific recognition sites.

[0006] According to a first aspect of the present invention, the present invention provides a supramolecular organic framework material based on cucurbituril, wherein the building unit is cucurbituril[8]CB8 as the host and terephthalovioletin ligand 1,1''-(1,4-phenylene)bis([4,4'-bipyridine]-1-onium) salt PBV·2X as the guest, and is constructed by host-guest bonding; wherein X is chloride ion or hexafluorophosphate ion; In the molecular structure of the supramolecular organic framework material, the building units are spatially misaligned and stacked in parallel, NO3 - Located at the gap between adjacent CB8; Taking X as a chloride ion as an example, the structure of the building unit is as follows: .

[0007] This invention discloses a supramolecular organic framework material based on cucurbituril, using CB8 as the host and PBV·2X as the guest. A stable supramolecular complex is formed through host-guest bonding. The CB8 cavity forms multiple non-covalent interactions (CH···π, cation-dipole) with the pyridine units of PBV, endowing the material with high structural stability and cationic framework characteristics. This invention introduces a cationic supramolecular framework with precise anion recognition function into the material cavity, interacting with TcO4. - / ReO4 - Size / charge matched sites (such as the rigid hydrophobic cavity and extracavitary recognition sites of cucurbituril) enable precise molecular recognition of TcO4. - / ReO4 - Its efficient capture and selective separation provide a more efficient and environmentally friendly solution for spent fuel reprocessing technology.

[0008] Furthermore, each of the CB8 bodies encapsulates two of the PBV guest molecules; in terms of molecular configuration, the two PBV guests are arranged in a parallel J-shape; the CB8 body is nested outside the pyridine unit of the PBV guest; the two pyridine rings on the PBV guest molecule are connected by a benzene ring.

[0009] In the supramolecular organic framework material of this invention, each CB8 encapsulates two PBV molecules, forming a parallel J-shaped arrangement to maximize space utilization. The CB8 is nested outside the PBV pyridine ring, and the pyridine units bridged by the benzene ring form rigid hydrophobic channels, which are TcO4. - / ReO4 - Size-matched adsorption provides sites for NO3. - Filling the interstitial spaces of CB8, it can be converted to TcO4 via ion exchange. - / ReO4 - Displacement.

[0010] Furthermore, the molecular formula of the supramolecular organic framework material is C0 74 H 68 N 38 O 22 With a molecular weight of 1841.57, the crystals are orange-yellow and elongated. Due to the photoreactivity of viologen, it exhibits a photochromic phenomenon from yellow to green under ultraviolet light.

[0011] According to a second aspect of the present invention, the present invention also provides a method for preparing the above-described supramolecular organic framework material, comprising the following steps: Step (1): Cucurbita[8]urea and 1,1''-(1,4-phenylene)bis([4,4'-bipyridine]-1-onium) salt (PBV·2X) are used as reaction raw materials, and are mixed with water, aqueous nitric acid solution and aqueous copper nitrate hexahydrate solution to prepare a reaction mixture; wherein, X in PBV·2X is chloride ion or hexafluorophosphate ion; Step (2): The reaction mixture prepared in step (1) is subjected to a self-assembly reaction to obtain a supramolecular organic framework material.

[0012] This invention employs a self-assembly reaction to prepare the supramolecular organic framework material CB8-CSP. The crystalline material is synthesized in one step by reacting CB8 with PBV·2X in copper nitrate and nitric acid aqueous solution. Copper nitrate acts as a structure directing agent, promoting the directional alignment of CB8 and PBV to form a regular framework and then crystallize. The preparation method of this invention is simple, has a high yield, and is suitable for large-scale production.

[0013] Further, in step (1), the molar ratio of CB8 to PBV·2X is 1:(1-2). Within this molar ratio range, excess PBV enhances the mechanical strength of the framework through π-π stacking, improves the material's resistance to swelling in strong acids / bases, and ensures that the CB8 cavity is completely saturated with PBV, avoiding uncoordinated PBV residue.

[0014] Furthermore, in step (1), the molar ratio of CB8 to copper nitrate in the aqueous solution of copper nitrate hexahydrate is 1:(2-6). This molar ratio is more conducive to promoting the directional arrangement of CB8 and PBV, forming a regular framework and then crystallizing.

[0015] Furthermore, the volume ratio of the water to the aqueous solution of copper nitrate hexahydrate is (5-8):1. This volume ratio ensures that PBV is fully dissolved and avoids local supersaturation that could lead to amorphous precipitation.

[0016] Furthermore, in step (1), the pH value of the reaction mixture is <4. This pH condition can inhibit the excessive protonation of the pyridine ring of PBV and avoid electrostatic repulsion that could disrupt the host-guest interaction.

[0017] Further, in step (2), the self-assembly reaction is carried out under hydrothermal conditions at a temperature of 100-180 °C for 6-48 h. The self-assembly reaction is carried out under hydrothermal conditions of 100-180 °C for 6-48 h, which can drive cucurbita[8]urea and terephthalocyanine ligand to rapidly and directionally form a highly crystalline supramolecular organic framework CB8-CSP within a mild and controllable temperature-time window. This process has both high yield and low energy consumption, ensuring fewer crystal defects and more active sites, thereby directly improving the adsorption capacity, selectivity and structural stability of the material for pertechnetate / perrhenate, laying a solid foundation for the efficient capture of radioactive anions under extreme environments.

[0018] According to a third aspect of the present invention, the present invention also provides the application of the above-described supramolecular organic framework material or the supramolecular organic framework material prepared by the above-described preparation method in nuclear waste treatment.

[0019] The beneficial effects of this invention are: The present invention provides a supramolecular organic framework material based on cucurbita[8] urea (CB8) as the host and terephthaloviolet ligand (PBV) as the guest, which is formed by host-guest bonding. The material has high structural stability and cationic framework characteristics. The rigid skeleton of CB8 and the pyridine conjugated system endow the material with excellent chemical / irradiation stability, making it resistant to ReO4 under extreme environments (1M HNO3 strong acid, 3M NaOH strong base and 800 kGy high irradiation). - / TcO4 - It exhibits an extremely high removal rate. The removal rate remains 100% within the pH range of 3-12, and it also shows a high removal rate for SO4. 2- / NO3 - It maintains high selectivity even in the presence of competing ions, and its adsorption capacity does not decrease after 800 kGy γ-irradiation. CB8-CSP can quantitatively remove over 99% of [the ions] within 3 min. 99TcO4 - ReO4 under extreme conditions - / TcO4 - It provides a groundbreaking solution for pollution control. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0021] Figure 1 This is a crystal structure diagram of CB8-CSP provided in Embodiment 1 of the present invention; wherein, (A) is a crystal packing diagram; (B) is NO3 in the tetrahedral cavity formed by CB8-CSP. - (C) represents the J-shaped arrangement of 1D polymer molecular chains.

[0022] Figure 2 The CB8-CSP provided in Example 1 of this invention affects ReO4 under different pH conditions. - The removal efficiency graph.

[0023] Figure 3 The CB8-CSP provided in Example 1 of this invention, in the presence of competing ions, affects ReO4. - Adsorption selectivity diagram.

[0024] Figure 4 The CB8-CSP provided in Example 1 of this invention, under different gamma-ray irradiation doses, affects ReO4. - The removal efficiency graph.

[0025] Figure 5 The CB8-CSP provided in Embodiment 1 of this invention is used to treat ReO4 under 1M HNO3 conditions. - Adsorption kinetics diagram.

[0026] Figure 6 The CB8-CSP provided in Example 1 of this invention is used to treat ReO4 under 3M NaOH conditions. - The removal efficiency graph.

[0027] Figure 7 The CB8-CSP provided in Embodiment 1 of this invention is for TcO4 - Adsorption kinetics diagram. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0029] Example 1 This embodiment provides a supramolecular organic framework material CB8-CSP based on cucurbituril.

[0030] Figure 1 This is a crystal structure diagram of CB8-CSP. The crystal structure of CB8-CSP was measured using X-ray single-crystal diffraction. Figure 1 (C) As can be seen, each CB8 macrocycle simultaneously encapsulates two PBV guest molecules through host-guest interactions, forming a 1:2 supramolecular complex. In terms of molecular configuration, the two viologen guests adopt a parallel J-shaped arrangement. The CB8 host macrocycle is nested outside the guest pyridine unit, stabilized through multiple CH···π interactions and cation-dipole interactions. The two pyridine rings on the guest molecule are connected by a benzene ring, and the quasi-rotaxane CB8-CSP molecules are spatially misaligned and parallelly stacked, NO3 - Located within a tetrahedral cavity formed by four adjacent CB8 macrorings, it provides a connection with ReO4. - The location of ion exchange ( Figure 1 (B)).

[0031] This embodiment also provides a method for preparing the supramolecular organic framework material CB8-CSP, including the following steps: 17 mg of PBV·2Cl (0.025 mmol) and 16.6 mg of CB8 (0.0125 mmol) were placed in a polytetrafluoroethylene reactor, followed by 2 mL of ultrapure water and 320 μL of 0.2 M copper nitrate hexahydrate aqueous solution. Then, 60 μL of 1 M HNO3 aqueous solution was added to protonate the guest. The pH of the resulting reaction mixture was 3.0. The mixture was sealed and placed in an oven at 150 °C for 48 h. After cooling to room temperature with the oven, the reaction solution was obtained. The solution was filtered and the crystals were washed several times with ultrapure water. The crystals were then dried at 60 °C to obtain the supramolecular organic framework material CB8-CSP.

[0032] The molecular formula of the supramolecular organic framework material CB8-CSP is C 74 H 68 N 38 O 22It has a molecular weight of 1841.57, and the crystals are orange-yellow and elongated, exhibiting a photochromic phenomenon from yellow to green under ultraviolet light.

[0033] Example 2: CB8-CSP of Example 1 for ReO4 - adsorption (1) Effects of different pH values ​​on ReO4 - Effect of adsorption removal rate ReO4 - ReO4 typically exists in water as negatively charged ions, and changes in pH can affect its concentration. - The charge state of ReO4 and its interaction with the adsorbent surface lead to different adsorption mechanisms. ReO4 solutions with pH values ​​of 2-13 were prepared using HNO3 and NaOH. - Aqueous solution, ReO4 in the solution - At a concentration of 67 ppm and 298 K, 4 mg of crystals were placed in 8 ml of ReO4 at different pH values. - The solution was vigorously shaken for 24 h, filtered through a 0.22 μm nylon membrane filter, and the residual ReO4 in the filtrate was determined by inductively coupled plasma mass spectrometry (ICP-OES). - Concentration and its effect on ReO4 - Removal rate. Based on Figure 2 The results showed that CB8-CSP, when fully adsorbed within a pH range of 3–12, reduced ReO4 content after 24 hours. - The removal rate reached 100%; even in strongly acidic environments (pH=2) and strongly alkaline environments (pH=13), the removal rate still reached 98.82% and 98.34%, respectively.

[0034] (2) CB8-CSP on ReO4 - Adsorption selectivity Anion exchange selectivity mainly explores the selective and preferential adsorption of target anion ReO4 by adsorbents in mixed ion systems. - The ability to adsorb depends on factors such as the charge density of the ions, the radius of the hydrated ions, and the functional groups and pore structure of the adsorbent material. This was demonstrated by using 0.2 mM ReO4 at pH 4. - Equivalent amounts of NaNO3, Na2SO4, Na2CO3, NaH2PO4, NaClO4, and NaCl were added to the solution to study the effect of CB8-CSP on ReO4. - Adsorption selectivity. The solid-liquid ratio was 0.5, and after shaking on a shaker for 8 hours, separation was performed using a 0.22 μm nylon microporous membrane. ReO4 in the aqueous solution was determined by ICP-OES. - The concentration. For example... Figure 3The results showed that, in other oxygen-containing competing anions (including NO3-), - SO4 2- CO3 2- H2PO4 - ClO4 - and Cl - Even in the presence of multiple competing ions, CB8-CSP can still remove ReO4 from the solution. - Complete removal indicates that CB8-CSP has a high reactivity towards ReO4. - High selectivity.

[0035] Therefore, CB8-CSP for ReO4 - It exhibits good adsorption selectivity. This is due to the Hofmeister effect; anions with lower hydration energies face a smaller desolvation energy barrier during ion exchange due to their weaker hydration shell characteristics, making them more easily selectively captured by hydrophobic solid materials. Furthermore, the -CH recognition site outside the CB8 cavity, along with ReO4... - It can form a CH…O hydrogen bond network, further enhancing the affinity of CB8-CSP for ReO4. - Specific recognition capability.

[0036] (3) Effects of different doses of irradiation on ReO4 - Effect of adsorption removal rate The structural stability and adsorption performance of the material under extreme radiation environments were systematically evaluated through gamma-ray irradiation experiments. Irradiation conditions of 50 kGy, 100 kGy, 200 kGy, 400 kGy, and 800 kGy were selected for gradient dose irradiation treatment of the material. Under pH 4 and a solid-liquid ratio of 0.5, 2 mg of the material was placed in 4 ml of 72 ppm ReO4 solution. - The solution was vigorously shaken on a shaker for 24 hours, then filtered for ICP-OES analysis. Figure 4 As shown, all irradiated samples achieved ReO4 in solution at adsorption equilibrium after 48 hours. - Complete removal of ReO4 was not significantly different from the unirradiated control group. Irradiation did not affect the effect of CB8-CSP on ReO4. - Adsorption performance.

[0037] (4) CB8-CSP on ReO4 under high acid conditions - Adsorption kinetics The sample was irradiated with 200 kGy and then subjected to CB8-CSP treatment of ReO4. - Removal kinetics experiments were conducted under 1M HNO3 conditions. The solid-liquid ratio was 10, and 350 mg of the material was placed in 35 ml of 56 ppm ReO4 solution.- The solution was vigorously shaken in a shaker for 24 h, and then filtered through a 0.22 μm nylon membrane for ICP analysis. Figure 5 As shown, the irradiated sample still exhibits good adsorption performance. The material demonstrates rapid adsorption kinetics, achieving over 90% ReO4 adsorption in just 5 minutes of contact time. - Removal efficiency: When the system reaches adsorption equilibrium, the maximum removal rate can reach 97.78%.

[0038] (5) CB8-CSP on ReO4 under high alkalinity conditions - Adsorption removal rate Currently, a large number of cationic organic polymers have been used in ReO4. - Adsorption occurs, but its active sites are easily affected by OH groups. - The attack of these substances limits their practical application under extreme conditions. Different masses (4 mg, 8 mg, 20 mg, 40 mg, or 80 mg) of CB8-CSP material were placed in 8 ml of ReO4 containing 50 ppm. - The solution was dissolved in 3M NaOH and shaken vigorously for 24 hours. Then, it was filtered through a 0.22 μm nylon membrane and subjected to ICP analysis to calculate the effect of CB8-CSP on ReO4 under strongly alkaline conditions. - The adsorption removal rate. For example... Figure 6 As shown, a removal rate of 96.02% can be achieved when the solid-liquid ratio is 1, while the residual ReO4 is lower when the solid-liquid ratio is 5. - Below the detection limit, it can be completely removed. This indicates that CB8-CSP can completely remove ReO4 under strongly alkaline conditions. - It has a high adsorption and removal rate.

[0039] (6) TcO4 - Removal Experiment Place 30 mg of sample in an unadjusted solution containing 0.1 ppm of [a specific solution]. 99 TcO4 - Adsorption kinetics experiments were conducted using a 60 ml solution containing 0.1 ppm of HNO3 in 1 M HNO3. 99 TcO4 - Simplified simulated waste liquid (NO3) - initial concentration ratio 99 TcO4 - Height approximately 1.63 × 10 6 (times), CB8-CSP material was irradiated with 200 kGy of gamma rays and then subjected to... 99 TcO4 - Ion exchange experiments were conducted. The solid-liquid ratio was 10, meaning 300 mg of CB8-CSP material was placed in 30 ml of...99 TcO4 - The mixture was stirred with a magnetic rod for the required contact time (1 minute to 4 hours) and then separated using a 0.22-micron nylon membrane filter. The concentration of the liquid in the aqueous solution was measured using a liquid scintillation counting system (Perkin Elmer Quantulus 1220). 99 TcO4 - The concentration. According to Figure 7 In a solution without pH adjustment, CB8-CSP adsorbed 99.4% of the [substance / property] within 3 minutes. 99 TcO4 - The adsorption of [the substance] achieved a removal rate of 99.79% within 20 minutes. In an adsorption experiment conducted in 1M HNO3, 92.9% of [the substance] was adsorbed within 3 minutes. 99 TcO4 - The adsorption of CB8-CSP achieved a removal rate of 98.29% after 8 hours. This indicates that CB8-CSP effectively removes 98.29% of the pollutants. 99 TcO4 - It has excellent removal capabilities.

[0040] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A supramolecular organic framework material based on cucurbituril, characterized in that, Its building blocks are based on cucurbita[8] CB8 as the main body and terephthalocyanine ligand 1,1''-(1,4-phenylene)bis([4,4'-bipyridine]-1-onium) salt PBV·2X as the guest, and are constructed through host-guest bonding; wherein X is chloride ion or hexafluorophosphate ion; In the molecular structure of the supramolecular organic framework material, the building units are spatially misaligned and stacked in parallel, NO3 - It is located in the gap between adjacent CB8.

2. The supramolecular organic framework material according to claim 1, characterized in that, Each of the said host molecules encloses two said guests; in terms of molecular configuration, the two said guests are arranged in a parallel J-shape; the host molecules are nested outside the pyridine units of the said guests; the two pyridine rings on the said guest molecules are connected by benzene rings.

3. The supramolecular organic framework material according to claim 1 or 2, characterized in that, The molecular formula of the supramolecular organic framework material is C. 74 H 68 N 38 O 22 It has a molecular weight of 1841.57, and the crystals are orange-yellow and elongated, exhibiting a photochromic phenomenon from yellow to green under ultraviolet light.

4. The method for preparing the supramolecular organic framework material according to any one of claims 1-3, characterized in that, Includes the following steps: Step (1): Using CB8 and PBV·2X as reaction raw materials, mix them with water, nitric acid aqueous solution and copper nitrate hexahydrate aqueous solution to prepare a reaction mixture; Step (2): The reaction mixture prepared in step (1) is subjected to a self-assembly reaction to obtain a supramolecular organic framework material.

5. The preparation method according to claim 4, characterized in that, In step (1), the molar ratio of CB8 and PBV·2X is 1:(1-2).

6. The preparation method according to claim 4 or 5, characterized in that, In step (1), the molar ratio of CB8 to copper nitrate in the copper nitrate hexahydrate aqueous solution is 1:(2-6).

7. The preparation method according to any one of claims 4-6, characterized in that, The volume ratio of the water to the aqueous solution of copper nitrate hexahydrate is (5-8):

1.

8. The preparation method according to claim 4, characterized in that, In step (1), the pH value of the reaction mixture is <4.

9. The preparation method according to claim 4, characterized in that, In step (2), the self-assembly reaction is carried out under hydrothermal conditions, with a reaction temperature of 100-180 ℃ and a reaction time of 6-48 h.

10. The application of the supramolecular organic framework material according to any one of claims 1-3 or the supramolecular organic framework material prepared by the preparation method according to any one of claims 4-9 in nuclear waste treatment.

Images