Quasi-three-dimensional covalent organic framework material based on two-dimensional substrate piled functional groups, preparation method and application of quasi-three-dimensional covalent organic framework material in iodine adsorption

Abstract

The invention discloses a quasi-three-dimensional covalent organic framework material based on a two-dimensional substrate piled functional group, a preparation method and application of the quasi-three-dimensional covalent organic framework material in iodine adsorption, and the preparation method comprises the following steps: carrying out hydrothermal reaction on a mixture containing a phenyl compound, hexane (4-formylphenoxy) cyclotriphosphazene, 4-dimethylaminopyridine and water to obtain the quasi-three-dimensional covalent organic framework material based on the two-dimensional substrate piled functional group. The quasi-three-dimensional covalent organic framework material based on the two-dimensional substrate piled functional groups is obtained. According to the invention, a similar three-dimensional pore network is formed by orderly stacking two-dimensional substrates, and the three-dimensional covalent organic framework material has the characteristics of high specific surface area and strong structural stability of a three-dimensional covalent organic framework material; meanwhile, the problems that two-dimensional covalent organic framework materials are easy to peel off between layers and adsorption and mass transfer are limited are effectively solved, the defects that three-dimensional covalent organic framework materials are high in synthesis difficulty and poor in photoelectric property are avoided, and collaborative optimization of stability, adsorption efficiency and functional suitability is achieved.

Description

Technical Field

[0001] This invention belongs to the field of environmental functional materials and relates to a method for preparing iodine adsorption materials. Specifically, it relates to a quasi-three-dimensional covalent organic framework material based on a two-dimensional substrate with stacked functional groups, its preparation method, and its application in iodine adsorption. Background Technology

[0002] With the rapid development of the global nuclear energy industry, nuclear safety and radioactive waste treatment have become paramount challenges, seriously impacting environmental safety and the sustainable development of human society. Therefore, developing efficient and reliable radionuclide treatment technologies is crucial for achieving the green and safe utilization of nuclear energy and is a strategic goal for my country's nuclear energy technology field. In nuclear fuel reprocessing or nuclear accident environments, radioactive iodine, due to its high mobility, long half-life, and bioaccumulation, is one of the most challenging treatment targets. Currently, the mainstream treatment method for radioactive iodine is adsorption. Adsorption is the phenomenon of concentration enrichment of substances at the phase interface. Its core mechanism is the interaction between the adsorbent surface and adsorbate molecules. Based on the type of force, it can be divided into physical adsorption and chemical adsorption. The core principle of physical adsorption is that adsorbate molecules bind to the adsorbent surface through van der Waals forces, reducing the system energy to achieve a stable state. The core principle of chemical adsorption is that the adsorbent surface has active sites; adsorbate molecules react chemically with these active sites to form stable chemical adsorption bonds, achieving enrichment. Currently, adsorption is mainly accomplished through adsorbent materials. Among numerous types of adsorbent materials, covalent organic frameworks, as an emerging porous crystalline material, have shown great potential in the field of adsorption and separation due to their designable pore structure, high specific surface area, and excellent chemical stability, and are considered ideal adsorbents for capturing and immobilizing radioactive iodine. The core of this technology is the preparation of adsorbent materials with high adsorption capacity, high selectivity, excellent stability, and good kinetic properties.

[0003] Based on the differences in the topological structure of the building blocks, covalent organic framework materials are mainly divided into two categories: two-dimensional and three-dimensional. Two-dimensional covalent organic framework materials, while possessing excellent photoelectric properties and charge transport efficiency, have mature synthesis processes and are easily functionalized, and are readily processed into thin films, suffer from poor mechanical strength due to weak interlayer connections, making them prone to exfoliation. Their pores are mostly one-dimensional channels, resulting in limited adsorption capacity, and layered stacking can easily lead to aggregation-induced quenching. Three-dimensional covalent organic framework materials, on the other hand, possess a larger specific surface area and a rich three-dimensional pore network. Their robust three-dimensional covalent framework structure provides superior stability under extreme conditions. However, their synthesis relies on special stereo monomers, requiring stringent reaction conditions and challenging characterization. The lack of continuous π-conjugated structures leads to weak photoelectric properties and poor iodine adsorption performance, and the cost of large-scale production remains high. Summary of the Invention

[0004] To overcome the problem of poor iodine adsorption performance of existing three-dimensional covalent organic framework materials, the present invention aims to provide a quasi-three-dimensional covalent organic framework material based on a two-dimensional substrate with stacked functional groups, a preparation method thereof, and its application in iodine adsorption, so as to achieve efficient iodine adsorption.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A quasi-three-dimensional covalent organic framework material based on a two-dimensional substrate with stacked functional groups, the structural formula of which is as follows: , or .

[0006] A method for preparing a quasi-three-dimensional covalent organic framework material based on a two-dimensional substrate with stacked functional groups includes the following steps: A mixture containing a phenyl compound, hexadecane(4-formylphenoxy)cyclotriphosphazene, 4-dimethylaminopyridine and water was subjected to a hydrothermal reaction to obtain a quasi-three-dimensional covalent organic framework material based on a two-dimensional substrate with stacked functional groups.

[0007] Furthermore, one of the phenyl compounds p-xylene, 4,4'-dimethylbiphenyl, and 4,4'-dimethyldiphenylamine.

[0008] Furthermore, the molar ratio of the phenyl compound to hexaalkyl(4-formylphenoxy)cyclotriphosphazene is 3:1.

[0009] Furthermore, the molar ratio of hexadecane(4-formylphenoxy)cyclotriphosphazene to 4-dimethylaminopyridine is 1:15.

[0010] Furthermore, the ratio of hexadecane(4-formylphenoxy)cyclotriphosphazene to water was 0.2 mmol:3.5 mL.

[0011] Furthermore, the hydrothermal reaction temperature is 140-180℃, and the time is 72-120h.

[0012] Furthermore, the hydrothermal reaction was carried out at a temperature of 160°C for 72 hours.

[0013] Furthermore, after the hydrothermal reaction, a filter membrane is used for filtration.

[0014] Application of a quasi-three-dimensional covalent organic framework material based on two-dimensional substrate with stacked functional groups in iodine adsorption.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention discloses a method for preparing quasi-three-dimensional covalent organic framework materials based on the stacking of functional groups on a two-dimensional substrate. This method inherits the advantages of two-dimensional covalent organic framework materials, such as ease of synthesis and flexible introduction of functional groups, while also forming a quasi-three-dimensional porous network through the orderly stacking of two-dimensional substrates. This combines the high specific surface area and strong structural stability of three-dimensional covalent organic framework materials. Simultaneously, it effectively solves the problems of easy interlayer delamination and limited adsorption mass transfer in two-dimensional covalent organic framework materials, and avoids the shortcomings of three-dimensional covalent organic framework materials, such as high synthesis difficulty and weak photoelectric performance. It achieves synergistic optimization of stability, adsorption efficiency, and functional adaptability, resulting in greater application potential. In addition to the above advantages, the quasi-three-dimensional covalent organic framework material of this invention also exhibits high iodine adsorption activity, with an iodine adsorption capacity as high as 6.8 g / g. Furthermore, this invention is simple to operate and has high reproducibility. The material integrates the advantages of both two-dimensional and three-dimensional covalent organic framework structures, providing a new solution for addressing nuclear environment remediation issues. Attached Figure Description

[0016] Figure 1 This is a chemical reaction diagram of a quasi-three-dimensional covalent organic framework material; Figure 2 This is the Fourier Transform Infrared (FTIR) spectrum of a quasi-three-dimensional covalent organic framework material; Figure 3 This is the X-ray diffraction (XRD) pattern of a quasi-three-dimensional covalent organic framework material; Figure 4 These are scanning electron microscope (SEM) images of quasi-three-dimensional covalent organic framework materials; where (a) is EBA, (b) is DYL, (c) is PXE, (d) is a magnified view of a portion of (a), (e) is a magnified view of a portion of (b), and (f) is a magnified view of a portion of (c). Figure 5 It is an adsorption spectrum of a quasi-three-dimensional covalent organic framework material. Detailed Implementation

[0017] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0018] The present invention discloses a method for preparing a quasi-three-dimensional covalent organic framework material based on a two-dimensional substrate with stacked functional groups, comprising the following steps: Step 1: A mixture containing 0.6 mmol of p-xylene, 4,4'-dimethylbiphenyl, or 4,4'-dimethyldiphenylamine, 172 mg of hexadecane(4-formylphenoxy)cyclotriphosphazene CTP-6-CHO (0.2 mmol), 366.5 mg of 4-dimethylaminopyridine (3 mmol), and 3.5 mL of water was stirred for 15 min, then sonicated for 10 min. The mixture was then transferred to a 5 mL reaction vessel and reacted at 140-180 °C for 72-120 h. After naturally cooling to room temperature, the reactants were vacuum filtered through a 0.22 μm filter membrane, washed five times with pure water, and then dried in a vacuum oven at 60 °C. o After drying at C for 12 h, the final sample obtained was EBA, a quasi-three-dimensional covalent organic framework material based on a two-dimensional substrate with stacked functional groups.

[0019] Step 2: Grind the EBA obtained in Step 1 until homogeneous. Place 50 mg of the ground EBA and 7 g of iodine into two separate beakers, then place both beakers into a single glass container. Repeat the above steps to prepare a total of two sets of glass containers. Also prepare two other identical sets of glass containers, one without the beaker containing the 50 mg EBA sample, and leave them at room temperature.

[0020] Step 3: Place the two sets of glass containers, each containing 50 mg of EBA sample prepared in Step 2, in an 80℃ constant temperature drying oven for static adsorption testing. The specific steps are as follows: 1) Record the initial weight, and then place both sets of glass containers into an 80℃ constant temperature drying oven at the same time.

[0021] 2) After a period of time, remove the two sets of glass containers from the 80℃ constant temperature drying oven. Immediately remove the beakers containing 50 mg of EBA sample from the two sets of glass containers and place them into the two sets of glass containers at room temperature. Let them stand at room temperature for 10 min. Then weigh and record the total mass of the two sets of beakers containing 50 mg of EBA sample. Subtract the initial weight of the beaker containing 50 mg of EBA sample from the total mass of the two sets of beakers to get the iodine adsorption capacity of the EBA sample at that time.

[0022] 3) Repeat step 2), placing two sets of glass containers containing 50 mg EBA samples in an 80℃ constant temperature drying oven. Weigh and record the total mass of the two sets of beakers containing 50 mg EBA samples every 1 hour for 8 times. Then weigh and record the total mass of the two sets of beakers containing 50 mg EBA samples every 2 hours and 4 hours respectively. Subsequently, weigh and record the total mass of the two sets of beakers containing 50 mg EBA samples every 12 hours for 3 times. If the total mass of the two sets of beakers containing 50 mg EBA samples decreases compared to the previous total mass, adsorption is considered saturated, and the static adsorption test is complete. If the total mass continues to increase compared to the previous total mass, continue the static adsorption test by weighing and recording the total mass of the two sets of beakers containing 50 mg EBA samples every 24 hours. Both sets of samples need to be tested simultaneously until both sets of samples show a decrease in total mass compared to the previous total mass, at which point the test is terminated simultaneously.

[0023] The following are specific examples.

[0024] Example 1 Step 1: A mixture containing 63.702 mg (0.6 mmol) p-xylene, 172 mg CTP-6-CHO (0.2 mmol), 366.5 mg 4-dimethylaminopyridine (3 mmol), and 3.5 mL of water was stirred for 15 min, then sonicated for 10 min. The mixture was then transferred to a 5 mL reactor and reacted at 160 °C for 72 h. After naturally cooling to room temperature, the reactants were vacuum filtered through a 0.22 μm filter membrane, washed five times with pure water, and then dried in a vacuum oven at 60 °C. o After drying at C for 12 h, the final sample obtained was a quasi-three-dimensional covalent organic framework material PXE based on a two-dimensional substrate with stacked functional groups.

[0025] Step 2: Grind the PXE obtained in Step 1 until homogeneous. Place 50 mg of the ground PXE and 7 g of iodine into two separate beakers, then place both beakers together in a single glass container. Repeat the above steps to prepare a total of two sets of glass containers. Also prepare two other identical sets of glass containers, one without the beaker containing the 50 mg PXE sample, and leave them at room temperature.

[0026] Step 3: Place the two sets of glass containers, each containing 50 mg of PXE sample prepared in Step 2, in an 80℃ constant temperature drying oven for static adsorption testing. The specific steps are as follows: 1) Record the initial weight, and then place both sets of glass containers into an 80℃ constant temperature drying oven at the same time.

[0027] 2) After a period of time, remove the two sets of glass containers from the 80℃ constant temperature drying oven. Immediately remove the beakers containing 50 mg of PXE sample from the two sets of glass containers and place them into the two sets of glass containers at room temperature. Let them stand at room temperature for 10 min. Then weigh and record the total mass of the two sets of beakers containing 50 mg of PXE sample. Subtract the initial weight of the beaker containing 50 mg of PXE sample from the total mass of the two sets of beakers to get the iodine adsorption capacity of the PXE sample at that time.

[0028] 3) Repeat step 2), placing two sets of glass containers containing 50 mg PXE samples in an 80℃ constant temperature drying oven. Weigh and record the total mass of the two sets of beakers containing 50 mg PXE samples every hour for 8 times. Then weigh and record the total mass of the two sets of beakers containing 50 mg PXE samples every 2 and 4 hours for 1 time each. Subsequently, weigh and record the total mass of the two sets of beakers containing 50 mg PXE samples every 12 hours for 3 times. If the total mass of the two sets of beakers containing 50 mg PXE samples decreases compared to the previous total mass, adsorption is considered saturated, and the static adsorption test is complete. If the total mass continues to increase compared to the previous total mass, continue the static adsorption test by weighing and recording the total mass of the two sets of beakers containing 50 mg PXE samples every 24 hours. Both sets of samples should be tested simultaneously until both sets of samples show a decrease in total mass compared to the previous total mass, at which point the test is terminated simultaneously.

[0029] Example 2 Step 1: A mixture containing 109.356 mg (0.6 mmol) of 4,4'-dimethylbiphenyl, 172 mg of CTP-6-CHO (0.2 mmol), 366.5 mg of 4-dimethylaminopyridine (3 mmol), and 3.5 mL of water was stirred for 15 min, then sonicated for 10 min. The mixture was then transferred to a 5 mL reactor and reacted at 160 °C for 72 h. After naturally cooling to room temperature, the reactants were vacuum filtered through a 0.22 μm filter membrane, washed five times with pure water, and then dried in a vacuum oven at 60 °C. o After drying at C for 12 h, the final sample obtained was a quasi-three-dimensional covalent organic framework material DYL based on a two-dimensional substrate with stacked functional groups.

[0030] Step 2: Grind the DYL obtained in Step 1 until homogeneous. Place 50 mg of the ground DYL and 7 g of iodine into two separate beakers, then place both beakers into the same glass container. Repeat the above steps to prepare a total of two sets of glass containers. Also prepare two other identical sets of glass containers, one without the beaker containing the 50 mg DYL sample, and leave them at room temperature.

[0031] Step 3: Place the two sets of glass containers, each containing 50 mg of DYL sample prepared in Step 2, into an 80℃ constant temperature drying oven for static adsorption testing. The specific steps are as follows: 1) Record the initial weight, and then place both sets of glass containers into an 80℃ constant temperature drying oven at the same time.

[0032] 2) After a period of time, remove the two sets of glass containers from the 80℃ constant temperature drying oven. Immediately remove the beakers containing 50 mg DYL samples from the two sets of glass containers and place them into the two sets of glass containers at room temperature. Let them stand at room temperature for 10 min. Then weigh and record the total mass of the two sets of beakers containing 50 mg DYL samples. Subtract the initial weight of the beaker containing 50 mg DYL samples from the total mass of the two sets of beakers to get the iodine adsorption capacity of the DYL sample at that time.

[0033] 3) Repeat step 2), placing the two sets of glass containers containing 50 mg DYL samples in an 80℃ constant temperature drying oven. Weigh and record the total mass of the two sets of beakers containing 50 mg DYL samples every 1 hour for 8 times. Then weigh and record the total mass of the two sets of beakers containing 50 mg DYL samples every 2 and 4 hours for 1 time each. Subsequently, weigh and record the total mass of the two sets of beakers containing 50 mg DYL samples every 12 hours for 3 times. If the total mass of the two sets of beakers containing 50 mg DYL samples decreases compared to the previous total mass, adsorption is considered saturated, and the static adsorption test is complete. If the total mass continues to increase compared to the previous total mass, continue the static adsorption test by weighing and recording the total mass of the two sets of beakers containing 50 mg DYL samples every 24 hours. Both sets of samples need to be tested simultaneously until both sets of samples show a decrease in total mass compared to the previous total mass, at which point the test is terminated simultaneously.

[0034] Example 3 Step 1: A mixture containing 118.369 mg (0.6 mmol) of 4,4'-dimethyldiphenylamine, 172 mg of CTP-6-CHO (0.2 mmol), 366.5 mg of 4-dimethylaminopyridine (3 mmol), and 3.5 mL of water was stirred for 15 min, then sonicated for 10 min. The mixture was then transferred to a 5 mL reaction vessel and reacted at 160 °C for 72 h. After naturally cooling to room temperature, the reactants were vacuum filtered through a 0.22 μm filter membrane, washed five times with pure water, and then dried in a vacuum oven at 60 °C. o The sample was dried at C for 12 h and the final sample was EBA.

[0035] Step 2: Grind the EBA obtained in Step 1 until homogeneous. Place 50 mg of the ground EBA and 7 g of iodine into two separate beakers, then place both beakers into the same glass container. Repeat the above steps to prepare a total of two sets of glass containers. Also prepare two other identical sets of glass containers, one without the beaker containing the 50 mg EBA sample, and leave them at room temperature.

[0036] Step 3: Place the two sets of glass containers, each containing 50 mg of EBA sample prepared in Step 2, in an 80℃ constant temperature drying oven for static adsorption testing. The specific steps are as follows: 1) Record the initial weight, and then place both sets of glass containers into an 80℃ constant temperature drying oven at the same time.

[0037] 2) After a period of time, remove the two sets of glass containers from the 80℃ constant temperature drying oven. Immediately remove the beakers containing 50 mg of EBA sample from the two sets of glass containers and place them into the two sets of glass containers at room temperature. Let them stand at room temperature for 10 min. Then weigh and record the total mass of the two sets of beakers containing 50 mg of EBA sample. Subtract the initial weight of the beaker containing 50 mg of EBA sample from the total mass of the two sets of beakers to get the iodine adsorption capacity of the EBA sample at that time.

[0038] 3) Repeat step 2), placing two sets of glass containers containing 50 mg EBA samples in an 80℃ constant temperature drying oven. Weigh and record the total mass of the two sets of beakers containing 50 mg EBA samples every hour for 8 times. Then weigh and record the total mass of the two sets of beakers containing 50 mg EBA samples every 2 and 4 hours for 1 time each. Subsequently, weigh and record the total mass of the two sets of beakers containing 50 mg EBA samples every 12 hours for 3 times. If the total mass of the two sets of beakers containing 50 mg EBA samples decreases compared to the previous total mass, adsorption is considered saturated, and the static adsorption test is complete. If the total mass continues to increase compared to the previous total mass, continue the static adsorption test by weighing and recording the total mass of the two sets of beakers containing 50 mg EBA samples every 24 hours. Both sets of samples should be tested simultaneously until both sets of samples show a decrease in total mass compared to the previous total mass, at which point the test is terminated simultaneously.

[0039] Figure 1 These are chemical reaction diagrams for all samples in Examples 1-3, which provide a more intuitive understanding of the reaction mechanisms of each sample.

[0040] Figure 2 These are the Fourier Transform Infrared (FTIR) spectra of the quasi-three-dimensional covalent organic framework materials from Examples 1-3. All samples have a peak value at 810 cm⁻¹.-1 The presence of a characteristic peak representing CH at this location indicates the presence of a para-disubstituted benzene, while the peak at 1180 cm⁻¹ indicates the presence of a para-disubstituted benzene. -1 1730cm -1 and 3420 cm -1 This indicates that the compound containing the activated methyl group (attached to the benzene ring) underwent cross-aldol condensation with the aldehyde and was further oxidized to an ester.

[0041] Figure 3 The images show the X-ray diffraction (XRD) patterns of the quasi-three-dimensional covalent organic framework materials in Examples 1-3, demonstrating that all synthesized samples are quasi-three-dimensional covalent organic framework structures based on functional groups stacked on a two-dimensional substrate.

[0042] Figure 4 Images (a)-(f) are scanning electron microscope (SEM) images of the quasi-three-dimensional covalent organic framework materials of Examples 1-3. The topological networks and pore structures of the synthesized PXE, DYL, and EBA can be observed.

[0043] Figure 5 These are the adsorption spectra of the quasi-three-dimensional covalent organic framework materials in Examples 1-3. The adsorption spectra are made based on the static adsorption data of all samples, which can more intuitively represent the high capacity of EBA for iodine adsorption.

[0044] The above description only illustrates the preferred embodiments of the present invention and should not be construed as limiting the scope of the claims. The present invention is not limited to the above embodiments, and variations in its specific structure are permitted. All modifications made within the scope of the independent claims of this invention are also within the scope of protection of this invention.

[0045] Unless otherwise defined, 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. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

Claims

1. A quasi-three-dimensional covalent organic framework material based on a two-dimensional substrate with stacked functional groups, characterized in that, The structural formula of the quasi-three-dimensional covalent organic framework material is as follows: , or .

2. A method for preparing a quasi-three-dimensional covalent organic framework material based on a two-dimensional substrate with stacked functional groups, characterized in that, Includes the following steps: A mixture containing a phenyl compound, hexadecane(4-formylphenoxy)cyclotriphosphazene, 4-dimethylaminopyridine and water was subjected to a hydrothermal reaction to obtain a quasi-three-dimensional covalent organic framework material based on a two-dimensional substrate with stacked functional groups.

3. The method for preparing quasi-three-dimensional covalent organic framework materials based on two-dimensional substrate stacked functional groups according to claim 2, characterized in that, One of the phenyl compounds p-xylene, 4,4'-dimethylbiphenyl, and 4,4'-dimethyldiphenylamine.

4. The method for preparing quasi-three-dimensional covalent organic framework materials based on two-dimensional substrate stacked functional groups according to claim 2, characterized in that, The molar ratio of the phenyl compound to hexadecane(4-formylphenoxy)cyclotriphosphazene is 3:

1.

5. The method for preparing quasi-three-dimensional covalent organic framework materials based on two-dimensional substrate stacked functional groups according to claim 2, characterized in that, The molar ratio of hexadecane(4-formylphenoxy)cyclotriphosphazene to 4-dimethylaminopyridine is 1:

15.

6. The method for preparing quasi-three-dimensional covalent organic framework materials based on two-dimensional substrate stacked functional groups according to claim 2, characterized in that, The ratio of hexadecane(4-formylphenoxy)cyclotriphosphazene to water was 0.2 mmol: 3.5 mL.

7. The method for preparing quasi-three-dimensional covalent organic framework materials based on two-dimensional substrate stacked functional groups according to claim 2, characterized in that, The hydrothermal reaction temperature is 140-180℃, and the time is 72-120h.

8. The method for preparing quasi-three-dimensional covalent organic framework materials based on two-dimensional substrate stacked functional groups according to claim 2, characterized in that, The hydrothermal reaction was carried out at a temperature of 160℃ for 72 hours.

9. The method for preparing a quasi-three-dimensional covalent organic framework material based on a two-dimensional substrate with stacked functional groups according to claim 2, characterized in that, After the hydrothermal reaction, a filter membrane is used for filtration.

10. The application of a quasi-three-dimensional covalent organic framework material based on a two-dimensional substrate with stacked functional groups as described in claim 1 in iodine adsorption.

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