A porous polymer and a method for preparing and using the same

Abstract

The present application relates to the field of photocatalysis and polymer materials, in particular to a novel porous polymer and a preparation method and application thereof.The porous polymer material is obtained by reaction of naphthalene tetracarboxylic anhydride as an acceptor unit and tri(4-aminophenyl)amine as a donor unit; the porous polymer has a structural unit shown in formula 3: formula 3.The porous polymer can precipitate U(VI) in the form of solid (UO2)O2(H2O)2 under light conditions and thus remove U(VI), and can be used in the field of removing uranium from nuclear waste water.

Description

Technical Field

[0001] This invention relates to the fields of photocatalysis and polymer materials, and in particular to a novel porous polymer, its preparation method, and its applications. Background Technology

[0002] With the increasing severity of environmental pollution and the energy crisis, photocatalysis technology, as a green and sustainable solution, has shown great potential in the fields of environmental governance and energy conversion. Among them, polymeric photocatalytic materials have received widespread attention in recent years due to their unique structure and properties.

[0003] In the field of environmental remediation, some polymer materials have been reported for photocatalytic removal of pollutants. However, these materials have several limitations in photocatalytic reactions: First, their specific surface area is relatively low, which limits the number of effective reaction sites that can act on the photocatalytic reaction, thus adversely affecting the overall catalytic efficiency. Second, in terms of molecular structure, these materials lack an effective conjugated system, resulting in insufficient electron transport capacity, which in turn reduces the separation and migration efficiency of photogenerated carriers, thus restricting photocatalytic performance. Finally, from the perspective of material stability, these materials usually exhibit low chemical and photostable stability, and are prone to degradation or structural damage during practical applications.

[0004] Therefore, proposing a novel porous polymer material that can achieve higher specific surface area, better light absorption capacity and stability is of great significance for the field of photocatalytic uranium removal. Summary of the Invention

[0005] Based on the above, the present invention provides a porous polymer, its preparation method, and its application.

[0006] To achieve the above objectives, the present invention provides the following solution: One of the technical solutions of the present invention is a porous polymer (PNDI-TAPA) comprising a donor unit as shown in Formula 1 and an acceptor unit as shown in Formula 2: Formula 1; Formula 2; The donor unit and the acceptor unit form a porous polymer with a cross-linked structure through a dehydration condensation reaction.

[0007] The porous polymer has the structural unit shown in Formula 3: Formula 3.

[0008] The second technical solution of the present invention is a method for preparing the above-mentioned porous polymer, comprising the following steps: The donor unit and acceptor unit are mixed with an organic solvent and subjected to a dehydration condensation reaction under an inert atmosphere to obtain the porous polymer.

[0009] The third technical solution of the present invention is the application of the above-mentioned porous polymer in the photocatalytic removal of U(VI).

[0010] The fourth technical solution of the present invention is a method for photocatalytic removal of U(VI) from wastewater, wherein the above-mentioned porous polymer is added to the wastewater containing U(VI) as a photocatalyst and a hole sacrificial agent, and U(VI) is reduced to (UO2)O2(H2O)2 precipitate under light conditions.

[0011] Compared with the prior art, the present invention has the following beneficial effects: The porous polymer (PNDI-TAPA) of the present invention can precipitate U(VI) in the form of solid (UO2)O2(H2O)2 under light irradiation, thereby removing it, and can be used in the field of uranium removal from nuclear wastewater.

[0012] In terms of structural design, this invention utilizes tris(4-aminophenyl)amine (TAPA) and 1,4,5,8-naphthalenetetracarboxylic anhydride (NDI) to construct a polymer PNDI-TAPA with a porous network structure. This structure contributes to UO2 2+ It rapidly diffuses onto the PNDI-TAPA network backbone, enabling UO2 to... 2+ It can be efficiently reduced. Regarding material structure verification, SEM images confirm its porous network structure, and PXRD shows no obvious characteristic peaks, consistent with its amorphous state. In terms of cycling and performance, PNDI-TAPA maintained an 88% uranium removal rate after 5 adsorption-desorption cycles. Regarding environmental benefits, the material achieved a 99% removal rate of 50 ppm uranium solution at pH 5, and in Na+... + Cr 3+ The removal rate fluctuates by less than 5% in the presence of interfering ions, making it suitable for the treatment of uranium-containing wastewater and seawater. During the photocatalytic process, U(VI) is converted into (UO2)O2(H2O)2 precipitate, avoiding secondary pollution caused by traditional reduction methods and achieving efficient treatment of uranium pollution. This provides an innovative solution for the treatment of radioactive wastewater that combines selectivity and cycle stability. Attached Figure Description

[0013] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0014] Figure 1The Fourier transform infrared spectrum of PNDI-TAPA is shown.

[0015] Figure 2 The image is a scanning electron microscope (SEM) image of the PNDI-TAPA prepared in Example 1.

[0016] Figure 3 PXRD images of PNDI-TAPA prepared in Example 1 and PNDI-TPDA prepared in Comparative Example 1.

[0017] Figure 4 The UV-Vis absorption spectra of PNDI-TAPA prepared in Example 1 and PNDI-TPDA prepared in Comparative Example 1 are shown.

[0018] Figure 5 Photocatalytic U(VI) removal performance of PNDI-TAPA prepared in Example 1 and PNDI-TPDA prepared in Comparative Example 1 at pH=5, with methanol, ethanol and isopropanol as hole sacrificial agents respectively; where (a) is Comparative Example 1 and (b) is Example 1.

[0019] Figure 6 The uranium removal efficiency of PNDI-TAPA prepared in Example 1 and PNDI-TPDA prepared in Comparative Example 1 at different pH values.

[0020] Figure 7 The optical band gaps of PNDI-TAPA prepared in Example 1 and PNDI-TPDA prepared in Comparative Example 1 are shown.

[0021] Figure 8 The graph shows the cycle performance test results of the PNDI-TAPA prepared in Example 1.

[0022] Figure 9 The graph shows the uranium removal rate of PNDI-TAPA prepared in Example 1 in the presence of different competing ions.

[0023] Figure 10 The XPS high-resolution full spectrum of the PNDI-TAPA prepared in Example 1 before and after the photocatalytic reaction is shown.

[0024] Figure 11 The PXRD spectra of the PNDI-TAPA prepared in Example 1 before and after the photocatalytic reaction are shown.

[0025] Figure 12 The N2 adsorption-desorption isotherms of PNDI-TAPA prepared in Example 1 and PNDI-TPDA prepared in Comparative Example 1 are shown.

[0026] Figure 13 Pore ​​size distribution curves of PNDI-TAPA prepared in Example 1 and PNDI-TPDA prepared in Comparative Example 1. Detailed Implementation

[0027] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0028] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0029] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0030] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0031] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0032] Tris(4-aminophenyl)amine (TAPA), as an organic compound, can be used as an intermediate in organic synthesis. The amino group (-NH2) on each phenyl group is a strong electron donor group. These amino groups transfer electron density from the nitrogen atom to the benzene ring through a resonance effect, thereby enhancing the electron density of the benzene ring. This electron donor effect makes the molecule more reactive in certain reactions. Based on this, this invention uses 1,4,5,8-naphthalenetetracarboxylic anhydride (NDI) as the acceptor unit (as shown in Formula 2) and tris(4-aminophenyl)amine (TAPA) as the donor unit (as shown in Formula 1) to synthesize a novel porous polymer material, named PNDI-TAPA, through a dehydration condensation reaction, and investigates its application in photocatalytic uranium removal.

[0033] The donor element is shown in Equation 1: Formula 1; The receptor unit is shown in Equation 2: Formula 2; Reacting the compounds shown in Formula 1 and Formula 2 yields the porous polymer PNDI-TAPA. The repeating unit structure of PNDI-TAPA is shown in Formula 3. It exists in the form of cross-linked network polymerization and has no defined end groups. Formula 3.

[0034] The first aspect of the present invention provides a porous polymer (PNDI-TAPA) comprising a donor unit as shown in Formula 1 and an acceptor unit as shown in Formula 2: Formula 1; Formula 2; The donor unit and the acceptor unit form a cross-linked structure through a dehydration condensation reaction.

[0035] Scanning electron microscopy and nitrogen adsorption-desorption curve analysis revealed that PNDI-TAPA possesses a porous network structure with numerous 0.43 nm pores within the material, resulting in a specific surface area as high as 1054.5 m². 2 ·g -1 At this location, this structure helps to expand the interaction with UO2. 2+ They come into contact and undergo a catalytic reaction.

[0036] In a preferred embodiment of the present invention, the porous polymer has the structural unit shown in Formula 3: Formula 3.

[0037] A second aspect of the present invention provides a method for preparing the above-mentioned porous polymer, comprising the following steps: The donor unit and acceptor unit are mixed with an organic solvent and subjected to a dehydration condensation reaction under an inert atmosphere to obtain the porous polymer.

[0038] In a preferred embodiment of the present invention, the molar ratio of the donor unit to the acceptor unit is 1:1.2 to 1:1.8.

[0039] In a preferred embodiment of the present invention, the organic solvent is anhydrous N,N-dimethylformamide (DMF).

[0040] In a preferred embodiment of the present invention, the temperature of the dehydration condensation reaction is 100~140℃ and the reaction time is 24~72 h.

[0041] In a preferred embodiment of the present invention, the dehydration condensation reaction is further complicated by separation, purification and drying steps.

[0042] A third aspect of the present invention provides the application of the above-described porous polymer in the photocatalytic removal of U(VI).

[0043] The fourth aspect of the present invention provides a method for photocatalytic removal of U(VI) from wastewater, wherein the above-mentioned porous polymer is added to the wastewater containing U(VI) as a photocatalyst and a hole sacrificial agent, and U(VI) is reduced to (UO2)O2(H2O)2 precipitate under light irradiation.

[0044] In a preferred embodiment of the present invention, the hole sacrificial agent is selected from at least one of isopropanol, methanol or ethanol (the volume fraction of the hole sacrificial agent in the photocatalyst degradation system is 3% to 5%); the illumination conditions are natural light or external light source with a wavelength ≥ 420 nm; and the pH of the wastewater containing U(VI) is 3 to 7.

[0045] Unless otherwise specified, the technical solutions described in this invention are all conventional solutions in the field, and the reagents or raw materials used are all purchased from commercial channels or are publicly available unless otherwise specified.

[0046] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0047] Example 1 The synthesis method of PNDI-TAPA is as follows: Tris(4-aminophenyl)amine (TAPA) (116 mg, 0.4 mmol) and 1,4,5,8-naphthalenetetracarboxylic anhydride (NDI) (161 mg, 0.6 mmol) were added to a flask, followed by 15 mL of anhydrous DMF. The mixture was degassed and heated to 120 °C for 48 h under a nitrogen atmosphere. After the reaction was complete, the mixture was added dropwise to methanol, resulting in the precipitation of a purple solid. The solid was filtered, and the polymer was extracted sequentially with petroleum ether, dichloromethane, tetrahydrofuran, and acetone using a Soxhlet extractor. After vacuum drying for 24 h, a purplish-brown solid (204 mg, yield 73.6%) was obtained.

[0048] The synthesis route is as follows: The Fourier transform infrared spectrum of PNDI-TAPA prepared in Example 1 is as follows: Figure 1 As shown in the figure; the characteristic peaks indicate that the material contains C═O and C─N─C characteristic peaks, proving that the final polymer synthesis was successful.

[0049] The SEM image of PNDI-TAPA prepared in Example 1 is shown below. Figure 2 As shown; by Figure 2 It can be seen that PNDI-TAPA materials all have a porous network structure, which is conducive to UO2 2+ It spreads rapidly to the PNDI-TAPA network skeleton.

[0050] Comparative Example 1 The only difference from Example 1 is that the donor unit tris(4-aminophenyl)amine (TAPA) is replaced with an equimolar amount of N1,N1'-(1,4-phenylene)bis(N1-(4-aminophenyl)phenyl-1,4-diamine) (TPDA); the resulting product is denoted as PNDI-TPDA.

[0051] The synthesis route is as follows: PXRD images of PNDI-TAPA prepared in Example 1 and PNDI-TPDA prepared in Comparative Example 1, by... Figure 3 It can be seen that neither Example 1 nor Comparative Example 1 has obvious characteristic peaks, but rather exhibits a bulging shape, which is amorphous and consistent with the typical amorphous XRD peaks of porous polymer materials.

[0052] Figure 4 The UV-Vis absorption spectra of PNDI-TAPA prepared in Example 1 and PNDI-TPDA prepared in Comparative Example 1 are obtained from... Figure 4 It can be seen that, compared with the absorption edge of Comparative Example 1, the absorption edge of Example 1 is red-shifted by about 20 nm, which enhances the light absorption ability of the material.

[0053] Example 1 of effect verification Using PNDI-TAPA prepared in Example 1 or PNDI-TPDA prepared in Comparative Example 1 as catalysts for photocatalytic reduction of uranium(VI) in uranium-containing wastewater: 10 mg of catalyst was uniformly dispersed in 50 mL of 50 ppm uranium (VI) aqueous solution, and 2 mL of hole sacrificial agent (isopropanol, methanol, or ethanol) was added. The mixture was then stirred in the dark for 60 minutes to reach adsorption-desorption equilibrium. Immediately afterwards, the sample was irradiated with a 300 W xenon lamp under a 420 nm cutoff filter. Samples were taken every 30 minutes, and the UO2 of the samples was analyzed at a wavelength of 650 nm. 2+ The absorbance; converting the absorbance intensity at different irradiation times into UO2. 2+ Removal rate.

[0054] Figure 5Photocatalytic U(VI) removal performance of PNDI-TAPA prepared in Example 1 and PNDI-TPDA prepared in Comparative Example 1 at pH=5, using methanol, ethanol, and isopropanol as hole sacrificial agents, respectively; where (a) is Comparative Example 1 and (b) is Example 1. Figure 5 It can be seen that both Example 1 and Comparative Example 1 showed the best results when isopropanol was used as a sacrificial agent. In Example 1, the removal rate of U(VI) reached 99% after 3 hours of light irradiation with isopropanol as a sacrificial agent (reaction rate constant k = 0.02045 min). -1 In contrast, under the same conditions, the removal rate of U(VI) by Comparative Example 1 after 3 hours of illumination was only 87%.

[0055] Figure 10 The XPS high-resolution full spectrum of the PNDI-TAPA prepared in Example 1 before and after the photocatalytic reaction is shown below. Figure 10 High-resolution full-spectrum analysis revealed a distinct U 4f peak on PNDI-TAPA after the photocatalytic reaction, demonstrating the successful catalytic reduction of uranium on the PNDI-TAPA surface.

[0056] Figure 11 The PXRD spectra of the PNDI-TAPA prepared in Example 1 before and after the photocatalytic reaction are shown below. Figure 11 It can be seen that the characteristic peak of (UO2)O2(H2O)2 appeared after photocatalysis, which is the precipitate product after the photocatalytic reduction of uranyl ions in aqueous solution.

[0057] Figure 6 PNDI-TAPA was prepared in Example 1, and PNDI-TPDA was prepared in Comparative Example 1. The solution was irradiated with a 300W xenon lamp source with a 420 nm cutoff filter to provide simulated sunlight. Isopropanol was used as a hole sacrificial agent, and the uranium removal efficiency was tested at different pH values ​​after 4 hours of illumination. Figure 6 It can be seen that both Comparative Example 1 and Example 1 showed the best results at pH 5.

[0058] The optical band gaps of PNDI-TAPA prepared in Example 1 and PNDI-TPDA prepared in Comparative Example 1 were calculated using Tauc Plot, as follows: Figure 7 As shown, the band gap of Comparative Example 1 is 2.88 eV, which is higher than that of Example 1 (2.78 eV), indicating that PNDI-TAPA has better charge separation capability.

[0059] Cyclic performance tests were performed on the PNDI-TAPA prepared in Example 1. After photocatalysis, the photocatalytic material was filtered, washed with 0.2 mol / L Na₂CO₃ solution with stirring for 6 h, and then washed with ethanol and deionized water and dried for the next experiment. The results are as follows: Figure 8 As shown, by Figure 8 It can be seen that after elution with Na2CO3 solution for five cycles of photocatalysis, the PNDI-TAPA prepared in Example 1 still achieved a removal rate of 88% for U(VI), indicating that the material has good stability.

[0060] The PNDI-TAPA prepared in Example 1 was tested for its resistance to ion interference, and the results are as follows: Figure 9 As shown, the concentration of U(VI) is 50 ppm (solvent is water), in Na + K + Mg 2+ Ca 2+ Cr 3+ Zn 2+ Cu 2+ or Pd 2+ The influence of different ions on the photoreduction activity of uranium was investigated in the presence of competing ion M, with a molar concentration ratio of M:U(VI) = 50:1. The examples still showed a high removal rate of U(VI) (≥95%), indicating that the material has good resistance to ion interference.

[0061] Figure 12 The N2 adsorption-desorption isotherms of PNDI-TAPA prepared in Example 1 and PNDI-TPDA prepared in Comparative Example 1 are obtained by... Figure 12 It can be seen that the specific surface area of ​​Example 1 is 1054.5 m². 2 ·g -1 Compared to the specific surface area of ​​Comparative Example 1 (494.5 m²), 2 ·g -1 The larger size indicates that Example 1 can access more reaction sites in the photocatalytic reaction.

[0062] Figure 13 Pore ​​size distribution curves of PNDI-TAPA prepared in Example 1 and PNDI-TPDA prepared in Comparative Example 1. Figure 13 It can be seen that the pore size distribution of Comparative Example 1 and Example 1 is concentrated at 0.43 and 0.43 nm, indicating that their pore sizes are similar.

[0063] Comparative Example 2 The only difference from Example 1 is that the acceptor unit 1,4,5,8-naphthalenetetracarboxylic anhydride (NDI) is replaced with an equimolar amount. (That is, the bonds between the donor and the acceptor are different).

[0064] The synthesis route is as follows: The difference between Comparative Example 2 and Example 1 lies in the different bonding between the donor and acceptor. This change will greatly weaken the electron transfer ability between the donor and acceptor, which is not conducive to the generation of photogenerated carriers. This will greatly reduce the photocatalytic performance of the material. The photochemical band gap of Comparative Example 2 is 3.06 eV (higher than Example 1 and Comparative Example 1). It can be seen that the bonding mode between the donor and acceptor has a huge impact on the photocatalytic performance of the material.

[0065] Comparative Example 3 The only difference from Example 1 is that the acceptor unit 1,4,5,8-naphthalenetetracarboxylic anhydride (NDI) is replaced with an equal amount of pyromellitic diimide. .

[0066] The synthesis route is as follows: Compared to Example 1 and Comparative Examples 1 and 2, Comparative Example 3 not only changed the bonding between the donor and acceptor, but also further altered the structure of the donor. This change further reduced its photogenerated carrier generation capability, and the connection method significantly reduced the rigidity of the material structure. Under the same experimental conditions as Example 1, Comparative Example 3 exhibited structural disintegration and damage from free radical attacks. Furthermore, its structural integrity and regularity were worse than those of Example 1, resulting in a significant weakness in both structural strength and photocatalytic performance compared to the Example.

[0067] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A porous polymer, characterized in that, Includes the donor unit shown in Equation 1 and the acceptor unit shown in Equation 2: Formula 1; Formula 2; The donor unit and the acceptor unit form a porous polymer with a cross-linked structure through a dehydration condensation reaction.

2. The porous polymer according to claim 1, characterized in that, It has the structural unit shown in Equation 3: Formula 3.

3. A method for preparing the porous polymer according to claim 1 or 2, characterized in that, Includes the following steps: The donor unit and acceptor unit are mixed with an organic solvent and subjected to a dehydration condensation reaction under an inert atmosphere to obtain the porous polymer.

4. The preparation method according to claim 3, characterized in that, The molar ratio of the donor unit to the acceptor unit is 1:1.2 to 1:1.

8.

5. The preparation method according to claim 3, characterized in that, The organic solvent is anhydrous N,N-dimethylformamide.

6. The preparation method according to claim 3, characterized in that, The dehydration condensation reaction is carried out at a temperature of 100~140℃ for a reaction time of 24~72 h.

7. The preparation method according to claim 3, characterized in that, The dehydration condensation reaction is followed by separation, purification, and drying steps.

8. The application of the porous polymer as described in claim 1 or 2 in the photocatalytic removal of U(VI).

9. A method for photocatalytic removal of U(VI) from wastewater, characterized in that, Add the porous polymer described in claim 1 or 2 as a photocatalyst and hole sacrificial agent to wastewater containing U(VI), and reduce U(VI) to (UO2)O2(H2O)2 precipitate under light irradiation.

10. The method according to claim 9, characterized in that, The hole sacrificial agent is selected from at least one of isopropanol, methanol, or ethanol; the illumination conditions are natural light or external light source with a wavelength ≥420 nm; the pH of the wastewater containing U(VI) is 3~7.

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