High-efficiency iodine adsorption material, preparation method and application thereof

Abstract

This application provides a high-efficiency iodine adsorbent material, its preparation method, and its application, belonging to the field of high-performance materials technology. (The following text appears to be a separate, unrelated section:) Z )-2,9-dibromo-11,12-dihydrodibenzo[ c,g [1,2] Diazacyclooctene and (4,4,5,5-tetramethyl-1,3,2-dioxaborhexacyclopentan-2-yl)aniline were dissolved in 1,4-dioxane, and a base and palladium catalyst were added. The mixture underwent a Suzuki coupling reaction in a nitrogen atmosphere to give ( Z )-4,4'-(11,12-dihydrodibenzo[ c,g [1,2]-2,9-dimethyl)diphenylamine; ( Z )-4,4'-(11,12-dihydrodibenzo[ c,g [1,2]-2,9-dimethyl)diphenylamine and 2,4,6-tricarboxymethylresorcinol were dissolved in a solvent, and a catalytic amount of trifluoroacetic acid was added. After condensation reaction, the mixture was washed to obtain an iodine adsorbent. This iodine adsorbent exhibits high adsorption efficiency and good cycling performance.

Description

Technical Field

[0001] This application relates to a highly efficient iodine adsorbent material, its preparation method, and its application, belonging to the field of high-performance materials technology. Background Technology

[0002] Nuclear contamination prevention and control is a critical issue that urgently needs to be addressed. Radioactive iodine (with an extremely long half-life) is contained in nuclear wastewater and nuclear exhaust gases. 129 I and high radioactivity 131 I) is a highly harmful pollutant, and its prevention and control work is urgent.

[0003] Organic porous framework materials have become one of the most promising materials in the field of environmental remediation due to their advantages such as high specific surface area, excellent processability, good chemical and physical stability, rich structural tunability, and ease of post-modification. For the practical needs of iodine adsorption, an ideal adsorbent should possess the following characteristics: an electron-rich structure (such as imine bonds, nitrogen heterocycles, triazine rings, etc.) to bind I2 through charge transfer; a positively charged confined space to capture polyiodine anions through electrostatic interactions; in addition, it should possess rapid adsorption kinetics, a suitable pore volume to accommodate iodine species, and good recyclability.

[0004] Among numerous organic porous framework materials, pyridine framework materials have attracted considerable attention due to their excellent adsorption capacity and adsorption rate. This is because the nitrogen atom on the pyridine ring contains a lone pair of electrons, making it a typical Lewis base (electron-rich center), while I2 is a typical electrophile (electron-deficient), and the two readily and rapidly form charge-transfer complexes. This chemical interaction is much stronger than simple physical van der Waals forces, allowing the adsorbent to maintain efficient capture capacity even in environments with low iodine partial pressures (such as under dynamic breakthrough conditions), rather than relying solely on pore filling at high concentrations. Furthermore, the charge transfer and methylation reactions involving the pyridine group also induce morphological transformations of iodine species within the pores. In electron-rich and ion-rich environments, adsorbed I2 readily transforms into polyiodine anion clusters (such as I3). - I5 - These ion clusters are more firmly confined within the pores through electrostatic interactions with the cation backbone, making them less prone to volatilization and escape, thus significantly improving the stability and capacity of iodine adsorption.

[0005] For example, BPY-COF / PAN composite fibers obtained by electrospinning exhibit high adsorption performance for gaseous iodine; ionic liquid-cellulose-based carbon materials made from cellulose fibers and ionic liquids have high efficiency and large capacity as gaseous iodine adsorbents; quasi-three-dimensional covalent organic framework materials have high iodine adsorption activity up to 6.8 g / g; and bipyridine groups have been introduced into the structure of covalent organic framework materials, enabling iodine adsorption at 75℃. However, the problem of iodine adsorption in aquatic environments remains severe. Summary of the Invention

[0006] In view of this, the first objective of this application is to provide a highly efficient iodine adsorbent material, which uses amino-functionalized bridged azobenzene as the building block to form a durable porous organic framework material that efficiently adsorbs iodine. By introducing pyridine groups with stronger electronegativity into the nitrogen-rich framework, a novel azobenzene highly efficient iodine adsorbent is formed. It not only has a high iodine vapor adsorption capacity, but can also adsorb I2 or I3 from aqueous solution in a short time (less than 10 min). - (less than 60 min).

[0007] Specifically, this application is implemented through the following scheme: A highly efficient iodine adsorbent material, having any of the following structural formulas: .

[0008] The second objective of this application is to provide a method for preparing the above-mentioned high-efficiency iodine adsorbent material, comprising the following steps: Step 1, place ( Z )-2,9-dibromo-11,12-dihydrodibenzo[ c,g [1,2] Diazacyclooctene and (4,4,5,5-tetramethyl-1,3,2-dioxaborhexacyclopentan-2-yl)aniline were dissolved in 1,4-dioxane, and a base and palladium catalyst were added. The mixture underwent a Suzuki coupling reaction in a nitrogen atmosphere to give ( Z )-4,4'-(11,12-dihydrodibenzo[ c,g [1,2]-2,9-dimethyl)diphenylamine; Step two, ( Z )-4,4'-(11,12-dihydrodibenzo[ c,g [1,2]-2,9-dimethyl)diphenylamine and 2,4,6-tricarboxymethylphloroglucinol were dissolved in a solvent, and a catalytic amount of trifluoroacetic acid was added. After condensation reaction, the mixture was washed to obtain an iodine adsorbent with structure (I).

[0009] Furthermore, as a preferred option: In step one, The alkaline agent is any one of potassium carbonate, sodium carbonate, and potassium phosphate.

[0010] The palladium catalyst is any one of Pd(PPh3)4, PdCl2(PPh3)2, and Pd(dppf)Cl2.

[0011] The Suzuki coupling reaction was carried out at a temperature of 90–120°C for a duration of 24–48 h.

[0012] The (Z )-2,9-dibromo-11,12-dihydrodibenzo[ c,g The molar ratio of diazacyclooctene to (4,4,5,5-tetramethyl-1,3,2-dioxaborhecyclopentane-2-yl)aniline is 1:2.2 to 2.8.

[0013] In step two, The condensation reaction is carried out at a temperature of 110–130°C.

[0014] The ( Z )-4,4'-(11,12-dihydrodibenzo[ c,g The molar ratio of [1,2]-2,9-dimethyl)diphenylamine to 2,4,6-tricarboxymethylphloroglucinol is 3:2.

[0015] In the above process, replacing (4,4,5,5-tetramethyl-1,3,2-dioxaborhexacyclopentane-2-yl)aniline with p-aminopyridineboronic acid yields the iodine adsorbent material with structure (II).

[0016] The third purpose of this application is to provide the application of the above-mentioned high-efficiency iodine adsorbent material in the iodine adsorption process in the field of radioactive iodine pollution control.

[0017] The above scheme uses amino-functionalized bridged azobenzene as the building block and successfully prepares two azobenzene-functionalized porous organic framework materials via Schiff base condensation with 2,4,6-tricarboxyloyl-resorcinol: Azo-POF corresponding to structure (I) and Azo-POF-Py corresponding to structure (I). Both materials retain more than 80% of their adsorption capacity after five cycles. Among them, Azo-POF-Py containing pyridine groups has an adsorption capacity as high as 4.83 g / g in iodine vapor, and its adsorption rate and capacity are 300% and 150% of those of pyridine-free Azo-POF, respectively. Moreover, it can completely remove I2 from aqueous solution within 10 min and has good I3 adsorption capacity. - It also exhibits high adsorption performance and has important application prospects in the field of radioactive iodine pollution control. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application.

[0019] Figure 1 This is a synthetic route diagram for the iodine adsorbent material in this application.

[0020] Figure 2 For b-Azo-NH2 in this application 1 H NMR spectrum.

[0021] Figure 3 For b-Azo-NH2 in this application 13 C10 NMR spectrum.

[0022] Figure 4 This is the high-resolution mass spectrum of b-Azo-NH2 in this application.

[0023] Figure 5 For b-Azo-Py-NH2 in this application 1 H NMR spectrum.

[0024] Figure 6 For b-Azo-Py-NH2 in this application 13 C10 NMR spectrum.

[0025] Figure 7 This is the high-resolution mass spectrum of b-Azo-Py-NH2 in this application.

[0026] Figure 8 For chemical structure characterization, part (a) of the figure shows the FT-IR spectra of Azo-POF, TP, and b-Azo-NH2, and part (b) shows the FT-IR spectra of Azo-POF-Py, TP, and b-Azo-Py-NH2.

[0027] Figure 9 For crystallinity characterization, part (a) of the figure shows the XRD patterns of Azo-POF, TP, and b-Azo-NH2, and part (b) shows the XRD patterns of Azo-POF-Py, TP, and b-Azo-Py-NH2.

[0028] Figure 10 The figure shows the XPS spectrum of the Azo-POF in this application. Part (a) is the full spectrum, part (b) is the C 1s spectrum, part (c) is the N 1s spectrum, and part (d) is the O 1s spectrum.

[0029] Figure 11 The figure shows the XPS spectrum of Azo-POF-Py in this application. Part (a) is the full spectrum, part (b) is the C 1s spectrum, part (c) is the N 1s spectrum, and part (d) is the O 1s spectrum.

[0030] Figure 12 To characterize the microstructure of Azo-POF, part (a) is the SEM image of Azo-POF at 50µm, part (b) is the SEM image of Azo-POF at 500nm, part (c) is the TEM image of Azo-POF, and part (d) is the HR-TEM image of Azo-POF.

[0031] Figure 13 The figures show the morphological characterization of Azo-POF-Py in this application. Parts (a) to (c) are SEM images at 1µm, 2µm, and 500nm, respectively, and parts (d) to (f) are EDS-Mappings corresponding to O, N, and C, respectively.

[0032] Figure 14 For N2 adsorption-desorption tests, part (a) of the figure is the N2 adsorption-desorption isotherm of Azo-POF, part (b) is the pore size distribution of Azo-POF, part (c) is the N2 adsorption-desorption isotherm of Azo-POF-Py, and part (d) is the pore size distribution of Azo-POF-Py.

[0033] Figure 15 The static iodine adsorption capacity of Azo-POF and Azo-POF-Py in this application is shown.

[0034] Figure 16 The figure shows the adsorption performance of Azo-POF and Azo-POF-Py in static iodine vapor. Part (a) of the figure is the I2 aqueous solution (1.0 mM) after Azo-POF treatment for different times, and part (b) is the UV-Vis spectrum of the I2 aqueous solution (1.0 mM) after Azo-POF-Py treatment for different times.

[0035] Figure 17 After processing the two materials in this application for different times, I3 - The UV-Vis spectrum of the aqueous solution (1.0 mM) is shown in the figure. Part (a) represents Azo-POF, and part (b) represents Azo-POF-Py.

[0036] Figure 18 To demonstrate the recyclability of the two materials in this application, part (a) in the figure is Azo-POF, and part (b) is Azo-POF-Py. Detailed Implementation

[0037] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the technical solutions in the embodiments of this application will be further described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit the technical solutions of this application. All other embodiments obtained by those skilled in the art based on the embodiments in this application without creative effort are within the scope of protection of this application.

[0038] Table 1: Raw materials and reagents used in this embodiment .

[0039] Table 2: Characterization and testing instruments used in this embodiment .

[0040] In this embodiment, one of the materials used to synthesize the high-efficiency iodine adsorption material is ( Z )-2,9-dibromo-11,12-dihydrodibenzo[ c,g [1,2] Diazacyclooctene (b-Azo-Br), the synthesis process of which is as follows: Synthesis of S1,2,2'-diaminobibenzyl (M1): First, iron powder (29.0 g, 517.8 mmol) and ammonium chloride (28.0 g, 523.5 mmol) were dispersed in 650 mL of a mixed solvent (500 mL EtOH and 150 mL H2O). Then, 2,2'-dinitrobibenzyl (10.0 g, 36.7 mmol) was added, and the mixture was refluxed at 90 °C for 5 h with mechanical stirring. After the reaction was complete, the iron powder was removed by hot filtration. The resulting filtrate was extracted three times with DCM (200 mL × 3). After removing the solvent by rotary evaporation at 45 °C, a brownish-yellow powder product M1 (7.5 g, 35.4 mmol, yield 96%) was obtained. 1 H NMR (400 MHz, CDCl3): δ 7.11–7.02 (m, 2H), 6.77 (td, J =7.4, 1.3 Hz, 1H), 6.69 (dd, J =7.9, 1.2 Hz, 1H), 3.54 (s, 2H), 2.82 (s, 2H) ppm.

[0041] Synthesis of S2,2,2'-(ethane-1,2-diyl)bis(4-bromoaniline) (M2): First, M1 (8.5 g, 40.0 mmol) was dissolved in 100 mL of MeCN in a 500 mL round-bottom flask equipped with a magnetic stirrer. A solution of NBS (14.24 g, 80.0 mmol) in MeCN (150 mL) was added dropwise to the above M1 solution over 5 h with stirring at room temperature. After the NBS was completely added, the reaction mixture was stirred at room temperature for another 3 h, and then concentrated under reduced pressure. The concentrate was redissolved in EA (200 mL) and washed successively with NaOH aqueous solution (1.0 mol / L, 150 mL), saturated NaHCO3 aqueous solution (3 × 50 mL), and saturated NaCl aqueous solution (50 mL). The organic phase was dried over Na2SO4 and concentrated to obtain crude product M2. The dried crude product M2 was further purified by washing with a small amount of DCM. The light brown solid product M2 (13.38 g, 36.16 mmol, yield 90.4%) was obtained.1 H NMR (400 MHz, CDCl3): δ 7.15 (d, J =8.4 Hz, 2H), 6.56 (d, J =8.1 Hz, 1H), 3.62 (s, 2H), 2.72 (s, 2H) ppm. 13 C NMR (100 MHz, CDCl3): δ 143.37, 132.00, 130.15, 127.94, 117.48,110.74, 77.41, 77.09, 76.77, 30.60 ppm.

[0042] S3, First, in a 1000 mL beaker equipped with a magnetic stir bar, M2 (7.5 g, 20.0 mmol) was dissolved in 400 mL of a mixed solvent of DCM and AcOH (3:1, v:v). m-chloroperoxybenzoic acid (6.9 g, 40.0 mmol) was dissolved in 100 mL of AcOH, and the resulting solution was added dropwise to the M2 solution over 3 h with stirring at room temperature. After the addition was complete, the reaction mixture was stirred at room temperature for another 3 h. Subsequently, the reaction was stopped, and the solution was concentrated under reduced pressure. The crude product was further purified by column chromatography (eluent, DCM / PE = 1 / 3, v / v). A yellow powdery solid product, β-Azo-Br (3.8 g, 10.23 mmol, yield 50.5%), was obtained. 1 HNMR (400 MHz, DMSO- d 6): δ 7.43–7.35 (m, 2H), 6.85 (d, J =8.2 Hz, 1H), 2.89–2.75(m, 2H) ppm. 13 C NMR (100 MHz, DMSO-) d 6): δ 154.49, 132.83, 131.05, 130.32, 121.19,120.26, 40.68, 40.47, 40.26, 40.05, 39.84, 39.63, 39.42, 30.74 ppm.

[0043] Example 1

[0044] This embodiment provides a highly efficient iodine adsorbent material, which is a compound corresponding to structural formula (I). The embodiments of this application are described below with reference to the accompanying drawings.

[0045] See Figure 1, Figure 1 A schematic diagram of the preparation process of the high-efficiency iodine adsorbent material in this embodiment is shown.

[0046] Step 1, ( Z )-4,4'-(11,12-dihydrodibenzo[ c,g Synthesis of [1,2]-2,9-diyl)diphenylamine (b-Azo-NH2) β-Azo-NH₂ was synthesized via a Suzuki coupling reaction. First, β-Azo-Br (3.6 g, 10.0 mmol) and (4,4,5,5-tetramethyl-1,3,2-dioxaborhexacyclopentan-2-yl)aniline (5.2 g, 24 mmol) were dissolved in 1,4-dioxane (15 mL) in a 50 mL two-necked flask equipped with a magnetic stirrer and a condenser. 10 mL of aqueous K₂CO₃ (6.9 g, 50.0 mmol) solution and the catalyst Pd(PPh₃)₄ (0.115 g, 0.1 mmol) were added to the flask. The mixture was then stirred at 95 °C for 24–48 h under a nitrogen atmosphere. The crude product was purified by column chromatography (eluent, DCM / PE = 99 / 1, v / v). The brown solid b-Azo-NH2 was obtained (2.6 g, 6.67 mmol, yield 66.7%).

[0047] 1 H NMR (400 MHz, DMSO-) d 6. See Figure 2 ): δ 7.35 (dd, J =8.2, 2.0 Hz, 1H), 7.32–7.25(m, 2H), 6.88 (d, J =8.2 Hz, 1H), 6.61–6.54 (m, 1H), 5.22 (s, 1H), 2.88 (d, J =2.9 Hz, 1H) ppm.

[0048] 13 C NMR (100 MHz, DMSO- d 6. See Figure 3 ): δ 153.63, 149.04, 139.86, 128.85,127.54, 126.79, 126.60, 123.96, 120.02, 114.65, 40.70, 40.49, 40.28, 40.07,39.87, 39.66, 39.45, 31.81 ppm.

[0049] HRMS (ESI) m / z: C 26 H 22 N4 + Calculated value: 390.1845; Measured value: 390.1832 (see...) Figure 4 ).

[0050] Step 2: Synthesis of Azo-POF framework materials

[0051] First, in a 50 mL flask equipped with a magnetic stirrer and a condenser, b-Azo-NH2 (117 mg, 0.3 mmol) and TP (42 mg, 0.2 mmol) were dissolved in DMF (10 mL) under sonication, followed by the addition of a catalytic amount of TFA (0.2 mL). The reaction mixture was then heated at 120 °C for 48 h with stirring. After the reaction was complete, the precipitate was collected by filtration and washed successively with DMF and DCM. The product was dried under vacuum overnight at 120 °C to obtain a brown powder of Azo-POF (143.1 mg, yield 90.2%).

[0052] Example 2

[0053] This embodiment provides a highly efficient iodine adsorbent material, which is a compound corresponding to structural formula (II). The embodiments of this application are described below with reference to the accompanying drawings.

[0054] See Figure 1 , Figure 1 A schematic diagram of the preparation process of the high-efficiency iodine adsorbent material in this embodiment is shown.

[0055] Step 1, ( Z )-5,5'-(11,12-dihydrodibenzo[ c,g Synthesis of [1,2]diazaoct-2,9)bis(pyridin-2-amine) (b-Azo-Py-NH2) First, in a 100 mL two-necked flask equipped with a magnetic stirrer and a condenser, 3.6 g (10.0 mmol) of b-Azo-Br and 3.5 g (25 mmol) of p-aminopyridineboronic acid were dissolved in 25 mL of 1,4-dioxane. 25 mL of aqueous Na₂CO₃ (3.2 g, 30 mmol) solution and the catalyst Pd(PPh₃)₄ (0.115 g, 0.1 mmol) were added to the flask. The mixture was then stirred at 110 °C for 24–48 h under a nitrogen atmosphere. After the reaction was complete, the flask was cooled to room temperature, and the resulting filter cake was obtained by vacuum filtration. The filter cake was repeatedly washed with DCM and EA, and finally collected and dried under vacuum at 60 °C to give the yellowish-brown product b-Azo-Py-NH₂ (2.89 g, yield 73.7%).

[0056] 1 H NMR (400 MHz, DMSO-) d 6. See Figure 5 ): δ 8.18 (s, J =2.5 Hz, 1H), 7.62 (d, J =8.7, 2.6 Hz, 1H), 7.40 (d, J =8.2, 1.9 Hz, 1H), 7.34 (s, J =1.9Hz, 1H), 6.92 (d, J =8.2Hz, 1H), 6.46 (d, J =8.6 Hz, 1H), 6.07 (s, 2H), 2.89 (d, J =5.6 Hz, 2H) ppm.

[0057] 13 C NMR (101 MHz, DMSO-) d 6. See Figure 6 ): δ 159.77, 154.00, 146.22, 137.34,135.62, 129.01, 126.83, 124.01, 123.10, 120.14, 108.36, 31.69 ppm.

[0058] HRMS (ESI) m / z: C 24 H 20 N7 + Calculated value: 393.1783, measured value: 393.1791 (see...) Figure 7 ).

[0059] Step 2: Synthesis of Azo-POF-Py framework material

[0060] First, in a 50 mL flask equipped with a magnetic stirrer and a condenser, b-Azo-Py-NH2 (116 mg, 0.3 mmol) and TP (42 mg, 0.2 mmol) were dissolved in DMF (10 mL) under sonication, followed by the addition of a catalytic amount of TFA (0.2 mL). The reaction mixture was then heated at 120 °C for 48 h with stirring. After the reaction was complete, the precipitate was collected by filtration and washed sequentially with DMF and DCM. The product was then heated at 120 °C. o Vacuum dried overnight at C. A brown powder of Azo-POF-Py (120.8 mg, yield 76.4%) was obtained.

[0061] Application Example 1

[0062] This application example is a static iodine vapor adsorption experiment, using Azo-POF prepared in Example 1 and Azo-POF-Py prepared in Example 2 as adsorbents. The process is as follows: Iodine vapor adsorption assays were performed in 250 mL wide-mouth bottles containing three 10 mL open sample vials. Two of the vials contained iodine granules (600 mg) and adsorbent (30 mg), respectively, while the third vial served as a blank control. First, the initial masses of the sample vials containing the adsorbent and the blank control were recorded. Then, the wide-mouth bottles were placed in a 75 °C oven. At regular intervals, the bottles were removed, cooled to room temperature, and the masses of the adsorbent sample vial and the control vial were re-weighed. Iodine adsorption capacity (… Q t The calculation formula is as follows: Q t =[( m at - m a0 )-( m ct - m c0 )] / 0.03.

[0063] Q t (g / g) represents the iodine adsorption capacity per unit mass of adsorbent at time t. m a0 , m at Let represent the initial mass and the mass at time t of the sample vial containing the adsorbent, respectively. m c0 , m ct t represents the initial mass and the mass at time t of the blank control sample bottle, respectively, and 0.03 represents the amount of adsorbent added (g).

[0064] Application Example 2

[0065] This application example involves I2 or I3 in an aqueous solution. - The adsorption experiment was conducted using Azo-POF prepared in Example 1 and Azo-POF-Py prepared in Example 2 as adsorbents. The process is as follows: Add the adsorbent (30 mg) to a container of I2 or I3. -The aqueous solution (1 mM, 30 mL) was placed in a 50 mL Erlenmeyer flask. The flask was then placed on a magnetic stirrer and stirred continuously. Equal volumes of the supernatant were collected for analysis at predetermined time intervals. Preparation of competing anion solutions: Stoichiometric amounts of NaCl, NaBr, NaNO3, or Na2SO4 were weighed and dissolved in pre-prepared 1 mM I2 / I3 solutions. - In solution, after complete dissolution, it yields anion containing interfering ions (Cl). - ,Br - NO3 - or SO4 2- ( ) solution.

[0066] The collected supernatant was analyzed using UV-Vis. I2 / I3 - The removal rate (R) is calculated as follows: R (%) = ( C 0 - C t ) / C 0 ×100%.

[0067] C 0 (mM) represents I2 or I3 - The initial concentration of the aqueous solution, C t This represents I2 or I3 at the corresponding time point t. - Concentration of aqueous solution.

[0068] Detection and characterization results

[0069] 1) Structural and morphological characterization of Azo-POFs (1) FT-IR characterization results are as follows Figure 8 As shown: By comparing the spectra with those of monomers TP and b-Azo-NH2, it was found that the characteristic absorption peak at 3500 cm⁻¹ in TP-b-Azo, which originally existed in the monomer, was present. -1 The amino vibration peak at 1700 cm⁻¹ -1 The aldehyde stretching vibration peak at [location] completely disappeared after the reaction. Simultaneously, a new peak at 1540 cm⁻¹ appeared in the spectrum. -1 The vibrational peak of the unsaturated carbon-carbon double bond at 1200 cm⁻¹ and the peak at 1200 cm⁻¹ -1 C–N bond vibration peak at (see) Figure 8 (see part (a) in the text). The above results indicate that in Example 1, a condensation reaction successfully occurred between the aldehyde group and the amino monomer, followed by an irreversible enol-keto tautomerism, thereby forming the target chemical structure of Azo-POF.

[0070] In Azo-POF-Py, the characteristic vibrational peaks of the aldehyde and amino groups corresponding to the monomers TP and b-Azo-Py-NH2 have completely disappeared, indicating that the condensation reaction proceeded fully. Notably, the pyridine ring at 1580 cm⁻¹... -1 The characteristic absorption peaks at that location were well preserved in the product. Meanwhile, the Azo-POF-Py spectrum also showed the same unsaturated carbon-carbon double bond vibration peaks and C–N bond vibration peaks as Azo-POF (see...). Figure 8 (see part (b) above). The results above demonstrate that Example 2 successfully constructed Azo-POF-Py with the target chemical structure.

[0071] (2) XRD characterization results are as follows Figure 9 As shown: Both monomers TP and b-Azo-NH2 exhibited sharp diffraction peaks, indicating their good crystallinity. The polymerized Azo-POF, however, showed two relatively broad diffraction peaks near 5° and 25° (see...). Figure 9 Part (a) in the figure indicates that a framework material with a certain degree of crystallinity has been formed. It is speculated that this is because the original flexible TAEA nodes were replaced by rigid TP, which enhanced the rigidity of the overall material, making the framework exhibit a more orderly periodic arrangement and the interlayer stacking more regular.

[0072] The absence of obvious diffraction peaks in the small-angle region of Azo-POF-Py indicates its poor crystallinity and amorphous state (see...). Figure 9 (See part (b)). This result is closely related to the increased conformational complexity of the molecular building blocks and the interlayer molecular interactions after the introduction of pyridine groups. Compared to the structurally regular phenyl units, pyridine groups not only introduce additional dipole moments and potential coordination capabilities of nitrogen atoms, but may also increase the conformational freedom of molecular building blocks during self-assembly due to their spatial orientation diversity. This complexity disrupts the original ordered stacking based on β-keto-enamine covalent bonding and π–π stacking interactions, causing pyridine-induced hydrogen bonds or dipole interactions to compete with the main driving force for framework formation, thereby destroying the precision of the periodic arrangement. In addition, the basicity of pyridine may also affect the equilibrium or nucleation rate of Schiff base condensation reactions, further inhibiting the formation of long-range ordered structures, ultimately leading to materials tending to form amorphous rather than crystalline states.

[0073] (3) XPS characterization results are as follows Figure 10 , 11 As shown: XPS characterization results of Azo-POF are as follows: Figure 10 As shown. From Figure 10As can be seen from the XPS full spectrum in part (a), Azo-POF is mainly composed of three elements: C, N, and O. Further peak fitting analysis was performed on the high-resolution spectrum: Figure 10 In the C 1s spectrum of part (b), the peaks with binding energies at 288.5 eV, 286.4 eV, and 284.8 eV are attributed to C=O, C–N, and C–C / C=C / C–H, respectively; Figure 10 In the N 1s spectrum of part (c), the signals at 399.5 eV and 409.8 eV correspond to N=N and N–C, respectively; Figure 10 In the O 1s spectrum of part (d), the peak at 532.2 eV is attributed to O=C. The above XPS analysis results fully confirm the successful formation of the β-ketoenamine linkage structure in Azo-POF.

[0074] XPS characterization results of Azo-POF-Py are as follows: Figure 11 As shown. From Figure 11 The XPS full spectrum in part (a) shows that the Azo-POF-Py framework is mainly composed of three elements: C, N, and O. Figure 11 In the C 1s spectrum of part (b), the signals of the pyridine carbon and the benzene ring carbon are difficult to distinguish; however, through Figure 11 In the N 1s spectrum of part (c), a characteristic peak of pyridine nitrogen can be observed at 398.5 eV. Furthermore, characteristic peaks for N=N, N–C, and O=C are also present (see...). Figure 11 The (d) part was also well preserved.

[0075] (4) Microscopic morphology and pore characteristics, such as Figures 12 to 14 As shown: The SEM characterization results of Azo-POF are as follows: Figure 12 As shown: Azo-NAF exhibits a relatively uniform spherical packing morphology, with a particle diameter of approximately 10 μm and a relatively regular surface (see...). Figure 12 (See parts (a) and (b) in the document). To corroborate the crystallinity results revealed by XRD, this application further utilized TEM to analyze the internal microstructure of Azo-POF. High-resolution TEM images show (see...) Figure 12 In sections (c) and (d), regular and periodically arranged moiré fringes are present at both the particle edges and internal regions, indicating that the material has good local order. Furthermore, selected area electron diffraction analysis reveals that some regions exhibit clear, discrete diffraction spots (see...). Figure 12 The (d) part corresponds to a typical single-crystal electron diffraction pattern. This result fully confirms that although Azo-POF exhibits a micron-scale spherical aggregate morphology, its micro-regions possess a highly ordered crystal structure.

[0076] Morphological characterization of Azo-POF-Py as follows Figure 13 As shown: Unlike the regular spherical stacking of Azo-POF, Azo-POF-Py exhibits an irregular sheet-like stacking morphology, with a relatively loose overall structure. This may be related to the increased conformational freedom of the molecules and the decreased orderliness of the framework self-assembly after the introduction of the pyridine group (see...). Figure 13 (a), (b), and (c) in the text). EDS surface scanning analysis results show that the Azo-POF-Py surface is mainly composed of three elements: C, N, and O, and the elements are evenly distributed (see...). Figure 13 (d), (e), and (f) in the text).

[0077] N2 adsorption-desorption tests were performed on Azo-POF and Azo-POF-Py at 77 K, and the results are as follows: Figure 14 As shown: According to the IUPAC classification, Azo-POF exhibits a typical Type IV adsorption isotherm, indicating the presence of a mesoporous structure in the material (see...). Figure 14 (Part (a) of the text). The specific surface area of ​​Azo-POF, calculated using the BET model, is 25 m². 2 / g. Analysis of its pore size distribution using the DFT method showed that the pore size is mainly concentrated around 5 nm (see...). Figure 14 Part (b) further confirms the formation of the mesoporous structure. This result indicates that although Azo-POF has a low specific surface area, it possesses well-ordered mesoporous channels, providing a foundation for subsequent adsorption applications. The BET specific surface area of ​​Azo-POF-Py is 30 m². 2 / g see Figure 14 In part (c), the pore size is slightly higher than that of Azo-POF. Its adsorption isotherm also belongs to the typical Type IV isotherm, indicating the dominance of the mesoporous structure in the material. Compared with Azo-POF, the pore size distribution of Azo-POF-Py is significantly wider, with its pore size mainly concentrated around 15 nm (see [reference needed]). Figure 14 The (d) part of the diagram may be attributed to the fact that the introduction of pyridine groups increases the complexity of the molecular conformation, leading to a looser or more irregular framework stacking, thus forming larger and more widely distributed mesoporous channels. This result indicates that although the introduction of pyridine units did not significantly increase the specific surface area, it altered the pore structure characteristics of the material, providing a structural basis for subsequent studies on the influence of different nitrogen sites on adsorption performance.

[0078] 2) Iodine adsorption performance of Azo-POFs Based on the structural features of both Azo-POF and Azo-POF-Py, which are rich in nitrogen adsorption sites (containing azo bonds, imine bonds, and sp), respectively, 3(-N or pyridine groups), this application systematically investigated the adsorption performance of these two framework materials in iodine vapor.

[0079] (1) Static iodine vapor adsorption performance: The results of the iodine vapor adsorption experiment under static adsorption conditions at 75 ℃ are as follows: Figure 15 As shown, Azo-POF without pyridine sites gradually reaches equilibrium after 120 h of adsorption, with a maximum iodine adsorption capacity of 3.21 g / g. In contrast, Azo-POF-Py with pyridine sites exhibits significantly improved adsorption performance: it reaches adsorption equilibrium in only about 40 h, with a maximum adsorption capacity as high as 4.83 g / g.

[0080] From an adsorption kinetics perspective, the adsorption rate of Azo-POF-Py is approximately three times that of Azo-POF. This significant difference strongly suggests that the pyridine nitrogen sites play a crucial role in iodine adsorption, potentially accelerating the process by enhancing the electron affinity between I2 and the framework or providing more effective adsorption sites. In terms of adsorption capacity, the saturated adsorption capacity of Azo-POF-Py reaches 150% of that of Azo-POF. This improvement can be partly attributed to its slightly higher specific surface area (30 m²). 2 / g vs. 25m 2 However, the main reason may be that the pyridine nitrogen atom itself has a strong electron-donating ability and a higher polarizability, which can form a stronger charge-transfer complex with I2, thereby significantly improving the framework's ability to capture iodine.

[0081] (2) Adsorption performance of I2 in aqueous solution Given that both Azo-POF and Azo-POF-Py rigid porous framework materials exhibit excellent adsorption capacity in static iodine vapor adsorption, we further investigated their adsorption performance for I₂ in aqueous solution. The results are as follows: Figure 16 As shown, the adsorption effect of Azo-POF on I2 in aqueous solution is relatively limited; after 15 minutes of adsorption, its iodine removal rate is only about 40% (see...). Figure 16 (a) of the text indicates that the adsorption efficiency is relatively low. In contrast, Azo-POF-Py exhibits extremely rapid and efficient iodine capture: it can completely adsorb I2 from a 1.0 mM I2 aqueous solution in less than 10 min, with a removal rate close to 100% (see [reference]). Figure 16 (part (b) of the text).

[0082] From the perspective of adsorption kinetics, the iodine capture rate of Azo-POF-Py is significantly better than that of Azo-POF. This significant difference fully demonstrates that the introduction of pyridine groups plays a crucial role in improving the iodine adsorption performance in aqueous phase. On the one hand, the introduction of pyridine nitrogen atoms enhances the overall hydrophilicity of the material, making it easier for the framework to contact and interact with I2 in aqueous solution. On the other hand, the pyridine group itself has a strong electron-donating ability, and compared with Azo-POF, it is more likely to form charge-transfer complexes with I2, thereby accelerating the iodine adsorption process. The above results indicate that pyridine functionalization modification not only significantly improves the affinity of the material for I2, but also greatly enhances its iodine capture capacity in aqueous environment.

[0083] (3) I3 in aqueous solution - Adsorption performance To further investigate the adsorption selectivity of the two framework materials for different iodine forms, we also examined the adsorption of I3 in aqueous solution by Azo-POF and Azo-POF-Py. - The adsorption performance, the results are as follows Figure 17 As shown: Both are related to I3 - The adsorption capacity of each exhibits more significant differences.

[0084] For Azo-POF lacking pyridine sites, after adsorption for up to 60 min, the I3 in the aqueous solution... - The concentration of [unspecified substance] did not decrease significantly (see [unspecified source]). Figure 17 (a) indicates that it has almost no ability to adsorb I3. - This result is closely related to the electroneutrality of its framework itself; due to the lack of sites for interaction with anions, it is difficult to capture negatively charged I3+ through electrostatic attraction or coordination. - .

[0085] In contrast, Azo-POF-Py exhibits superior I3 performance. - Adsorption performance: When adsorption proceeds for approximately 40 minutes, the I3 in the aqueous solution... - It can be completely removed (see) Figure 17 (See part (b)). This significant difference clearly demonstrates that the introduction of the pyridine group transforms the framework from an electrically neutral state to a polar state. The pyridine nitrogen atom not only possesses a certain electron-donating ability but can also undergo protonation or form a localized positively charged center in aqueous solution, thereby effectively capturing I3 in anionic form through electrostatic interactions. - .

[0086] The above results indicate that pyridine functionalization not only enhances the affinity for neutral I2, but also endows the framework with efficient adsorption capacity for iodide anions. Azo-POF-Py has the potential to be used as a multifunctional iodine adsorbent material.

[0087] 3) Recyclability of Azo-POFs To evaluate the practical application potential of the materials, their recycling performance in iodine adsorption was investigated using Azo-POF and Azo-POF-Py as adsorbents: The specific operation of the iodine adsorption-desorption cycle experiment of Azo-POF or Azo-POF-Py framework materials is as follows: During adsorption, Azo-POF / Azo-POF-Py (30 mg) is added to the sample vial, and iodine vapor is adsorbed using the aforementioned method. After adsorption saturation, the sample vial is cooled to room temperature and weighed. During desorption, I2@Azo-POF / I2@Azo-POF-Py is collected, placed on a glass petri dish, spread evenly, and then placed in a vacuum oven at 120 °C for 12 h. The desorption rate is calculated according to the following formula and denoted as . E (%).

[0088] E (%) = ( m 0 - m t ) / 0.03×100%. m 0 (g) m t (g) represents the initial mass of the sample vial containing iodine adsorbent (or iodine particles) and the mass at time t, respectively. The sample requires no further processing and is used directly in the next adsorption-desorption cycle following the same procedure.

[0089] After completing one iodine adsorption cycle, the adsorbed I₂ was removed by vacuum heating at 120 °C to regenerate the adsorbent. Five adsorption-desorption cycles were then performed consecutively, and the results are as follows: Figure 18 As shown in the figure. Experiments show that both materials exhibit good cycling stability: after five cycles, the iodine adsorption capacity of Azo-POF and Azo-POF-Py remains above 80% of the initial adsorption capacity. This result indicates that although the introduction of pyridine groups significantly improves the adsorption rate and capacity, it does not impair the structural stability and regeneration capability of the framework. High-temperature vacuum treatment can effectively remove adsorbed I2, and the main framework structure remains intact after multiple cycles, with active sites not irreversibly occupied or destroyed. The excellent cycling and regeneration performance further confirms the potential of these two Azo-POF materials as reusable iodine adsorbents.

[0090] The microstructure and elemental distribution of Azo-POF and Azo-POF-Py after iodine adsorption were characterized. The results showed that after iodine adsorption, Azo-POF particles agglomerated and the interface became blurred, presumably due to iodine enrichment on the surface and within the pores. In contrast, the morphology of Azo-POF-Py remained largely unchanged after adsorption, maintaining a loosely packed structure and exhibiting good structural stability. EDS-Mapping analysis revealed that iodine was uniformly distributed in both materials and highly overlapped with the distribution of potential adsorption sites such as nitrogen and oxygen, further confirming the crucial role of these sites in the iodine adsorption process.

[0091] Comparing the infrared spectra before and after Azo-POF adsorption, it can be found that the adsorption is located at 1200 cm⁻¹. -1 The vibrational peak attributable to the C–N bond showed a significant blue shift and broadened considerably after iodine adsorption. This change indicates that electronic interactions occurred between the C–N bond and I₂, forming a charge transfer intermediate. Simultaneously, the broadening of the peak also indicates a change in the chemical environment of the nitrogen atom after adsorption, further confirming that I₂ was effectively captured near the nitrogen-containing site. A comparative analysis of the infrared spectra of Azo-POF-Py before and after iodine adsorption showed that the peak at 1580 cm⁻¹ after adsorption... -1 The characteristic absorption peak at 1200 cm⁻¹ exhibited a significant blue shift, indicating the formation of a charge-transfer complex between the pyridine nitrogen atom and I₂. The pyridine nitrogen, acting as an electron donor, donated lone pairs of electrons to iodine, leading to a decrease in the electron cloud density on the pyridine ring and thus shifting its characteristic vibrational frequency towards higher wavenumbers. Simultaneously, the peak at 1200 cm⁻¹... -1 The vibrational peaks at the C–N bond also showed a slight blue shift, suggesting that the chemical bonds connected to the nitrogen atom were also disturbed by iodine adsorption, further confirming that nitrogen-containing sites jointly participated in the iodine capture process.

[0092] Comparing the XRD patterns before and after adsorption reveals similar trends in both materials after iodine adsorption: the intensity of the broad peak originally located around 25° significantly increases. Notably, the characteristic diffraction peaks attributed to crystalline iodine are absent from the post-adsorption spectra. This result strongly suggests that I₂ is not simply attached to the material surface in a crystalline form, but rather is trapped within the pores of the framework in an amorphous or highly dispersed state.

[0093] To theoretically elucidate the differences in iodine adsorption performance between the two framework materials, we performed geometric optimization of the structures of Azo-POF and Azo-POF-Py based on DFT and calculated their electrostatic potential distributions. The results show that the nitrogen and oxygen heteroatom sites all exhibit electron-rich characteristics, playing a crucial role as potential-affinity sites in the iodine adsorption process. Further comparison revealed that the overall charge density of Azo-POF-Py is significantly higher than that of Azo-POF, mainly attributed to the enhanced electron-donating ability of the framework due to the introduction of pyridine nitrogen atoms. The higher charge density implies a stronger charge transfer interaction between the framework and I₂, thereby improving the affinity and trapping capacity for iodine. These results are highly consistent with experimental observations, providing molecular-level theoretical support for the significant advantages of Azo-POF-Py in iodine adsorption capacity and rate.

[0094] To further quantify the affinity of the two framework materials for I2, we calculated the binding energies between I2 and different adsorption sites in Azo-POF and Azo-POF-Py using DFT. The results showed that in Azo-POF, the binding energy of the b-Azo unit for I2 was -6.49 kJ / mol, indicating that the azobenzene framework itself has a certain affinity for iodine. In contrast, the binding energies of Azo-POF-Py with I2 at all adsorption sites after the introduction of pyridine groups were significantly higher than those of Azo-POF. This improvement is mainly attributed to the strong electron-donating ability of the pyridine nitrogen atom, which can form a more stable charge-transfer complex with I2, thereby enhancing the interaction strength between the framework and I2.

[0095] The above process systematically investigated the adsorption performance of the two materials in iodine vapor and aqueous solution. Static iodine vapor adsorption experiments showed that Azo-POF-Py reached adsorption equilibrium within 40 h, with a maximum adsorption capacity as high as 4.83 g / g. Its adsorption rate and saturated adsorption capacity were 300% and 150% of those of Azo-POF without pyridine groups, respectively, fully demonstrating the crucial role of the pyridine nitrogen site in enhancing iodine adsorption kinetics and capacity. More importantly, Azo-POF-Py also exhibited excellent iodine capture ability in the aqueous phase: it could completely remove I₂ from aqueous solution within 10 min and capture I₃. - Anions achieve efficient adsorption, while Azo-POF has almost no I3 content. - Adsorption capacity. Cyclic performance tests show that both materials retain more than 80% of their initial adsorption capacity after five adsorption-desorption cycles, demonstrating good regeneration performance and structural stability.

[0096] The above-described embodiments are merely illustrative of several feasible implementations of the present invention, and their descriptions are relatively specific and detailed. However, they should not be construed as limiting the scope of the present invention, nor are the embodiments intended to limit the scope of protection in the claims of the present invention. For those skilled in the art, various modifications and improvements can be made without departing from the concept of the present invention. All equivalent implementations or changes that do not depart from the present invention should be included in the technology of the present invention.

Claims

1. A high-efficiency iodine adsorbent material, characterized in that, The iodine adsorbent material has a structural formula of any of the following: 。 2. A method for preparing the high-efficiency iodine adsorbent material according to claim 1, characterized in that, The steps are as follows: Step 1, place ( Z )-2,9-dibromo-11,12-dihydrodibenzo[ c,g [1,2] Diazacyclooctene and (4,4,5,5-tetramethyl-1,3,2-dioxaborhexacyclopentan-2-yl)aniline were dissolved in 1,4-dioxane, and a base and palladium catalyst were added. The mixture underwent a Suzuki coupling reaction in a nitrogen atmosphere to give ( Z )-4,4'-(11,12-dihydrodibenzo[ c,g [1,2]-2,9-dimethyl)diphenylamine; Step two, ( Z )-4,4'-(11,12-dihydrodibenzo[ c,g [1,2]-2,9-dimethyl)diphenylamine and 2,4,6-tricarboxymethylphloroglucinol were dissolved in a solvent, and a catalytic amount of trifluoroacetic acid was added. After condensation reaction, the mixture was washed to obtain an iodine adsorbent with structure (I).

3. The method for preparing a high-efficiency iodine adsorbent material according to claim 2, characterized in that: The alkaline agent is any one of potassium carbonate, sodium carbonate, and potassium phosphate.

4. The method for preparing a high-efficiency iodine adsorbent material according to claim 2, characterized in that: The palladium catalyst is any one of Pd(PPh3)4, PdCl2(PPh3)2, and Pd(dppf)Cl2.

5. The method for preparing a high-efficiency iodine adsorbent material according to claim 2, characterized in that: In step one, the temperature of the Suzuki coupling reaction is 90–120°C, and the duration is 24–48 h.

6. The method for preparing a high-efficiency iodine adsorbent material according to claim 2, characterized in that: In step one, ( Z )-2,9-dibromo-11,12-dihydrodibenzo[ c,g The molar ratio of diazacyclooctene to (4,4,5,5-tetramethyl-1,3,2-dioxaborhecyclopentane-2-yl)aniline is 1:2.2 to 2.

8.

7. The method for preparing a high-efficiency iodine adsorbent material according to claim 2, characterized in that: In step two, the temperature of the condensation reaction is 110–130°C.

8. The method for preparing a high-efficiency iodine adsorbent material according to claim 2, characterized in that: ( Z )-4,4'-(11,12-dihydrodibenzo[ c,g The molar ratio of [1,2]-2,9-dimethyl)diphenylamine to 2,4,6-tricarboxymethylresorcinol is 3:

2.

9. The method for preparing the high-efficiency iodine adsorbent material according to any one of claims 2 to 8, characterized in that: In step one, (4,4,5,5-tetramethyl-1,3,2-dioxaborhecyclopentane-2-yl)aniline is replaced with p-aminopyridineboronic acid to obtain an iodine adsorbent with structure (II).

10. The application of the high-efficiency iodine adsorbent material according to claim 1 in iodine adsorption.

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