A polyiodine chain-functionalized covalent organic framework material, its preparation method and application

Abstract

This invention discloses a polyiodine chain-functionalized covalent organic framework material, its preparation method, and its applications. The material is formed by treating a cationic covalent organic framework (iCOF) with hydrogen peroxide. The cationic covalent organic framework contains polyiodine chain structures within its channels, and the polyiodine chain structures include I3. ‑ I5 ‑ The invention provides polyiodide-chain functionalized covalent organic framework materials with ultra-high adsorption capacity for aqueous iodide ions, ranging from 198 to 486 mg / g, significantly higher than most reported iodide ion adsorbents. The materials exhibit rapid adsorption kinetics, reaching adsorption equilibrium within 60 minutes, meeting the efficiency requirements of practical applications.

Description

Technical Field

[0001] This invention relates to the fields of materials science and environmental engineering, specifically to a polyiodine chain-functionalized cationic covalent organic framework (iCOF-Iodine) material, its preparation method, and its application in aqueous iodine ion adsorption. This material achieves a highly efficient "iodine-to-iodine adsorption" mechanism through its unique polyiodine chain structure, and can be applied to fields such as nuclear wastewater treatment, environmental remediation, and iodine resource recovery. Background Technology

[0002] Iodine, an essential trace element for the human body, has significant applications in medicine, agriculture, and the electronics industry. However, radioactive iodine isotopes (such as...) 129 I and 131 I) Iodine ions pose a serious threat to the environment and public health during nuclear accidents and nuclear waste disposal due to their volatility, water solubility, bioaccumulation, and long half-life. Meanwhile, the recovery of iodine resources from industrial wastewater and natural brine also has significant economic value. Therefore, developing efficient and highly selective iodine ion adsorption materials has important scientific and practical value. Traditional iodine adsorption materials face many challenges in practical applications. Although activated carbon has a large specific surface area, its selectivity is insufficient in multi-component systems; silver-functionalized zeolites have a high affinity for iodine ions, but they are costly, have a significant environmental impact, and low resource utilization efficiency; metal-organic frameworks (MOFs) lack stability in aquatic environments; porous organic polymers (POPs), while exhibiting improved stability, often lack structural precision and tunability, making performance optimization difficult. Covalent organic frameworks (COFs) are promising candidate materials due to their crystallinity, permanent porosity, and structural designability; however, traditional COFs typically lack functional sites for ion capture, especially in competitive aquatic environments. Integrating permanent ionic properties into COF structures is a promising but not yet fully explored strategy.

[0003] Currently, although various materials for iodine adsorption have been reported, most are aimed at gaseous molecular iodine (I₂) or iodine in organic solvents. Traditional iodide ion adsorbents mainly work through ion exchange mechanisms, and their adsorption capacity is limited by the number of cation exchange sites in the material itself. They are also susceptible to interference from coexisting ions and exhibit poor selectivity in complex environments. Especially in practical applications such as nuclear wastewater treatment, environmental remediation, and iodine resource recovery, complex ionic environments often exist, placing higher demands on the selectivity and stability of materials. Therefore, developing a novel material capable of highly efficient and selective adsorption of iodide ions in aqueous phase has significant scientific and practical value. Summary of the Invention

[0004] This invention aims to at least partially address one of the technical problems in related technologies. To this end, this invention provides a polyiodine chain-functionalized covalent organic framework material, its preparation method, and its applications. By designing and synthesizing a cationic covalent organic framework and utilizing hydrogen peroxide treatment to form the internal polyiodine chain structure, this invention successfully achieves ultra-high capacity, rapid kinetics, and excellent selective adsorption of iodide ions in aqueous phase, providing a new technical pathway for nuclear waste treatment, environmental remediation, and iodine resource recovery.

[0005] The present invention adopts the following technical solution:

[0006] Firstly,

[0007] This invention provides a polyiodine chain-functionalized covalent organic framework material, which is formed by treating a cationic covalent organic framework (iCOF) with hydrogen peroxide. The cationic covalent organic framework contains polyiodine chain structures within its channels, and these polyiodine chain structures include I3. - I5 - and higher degree of polymerization (I7) - Polyiodide anions (etc.);

[0008] The cationic covalent organic framework is synthesized from 1,2,3-triaminoguanidine hydrochloride and aromatic dialdehyde via Schiff base condensation reaction; the aromatic dialdehyde is selected from at least one of naphthalene-2,6-dicarboxaldehyde (Nap), 2,6-dihydroxynaphthalene-1,5-dicarboxaldehyde (Nap-OH), 4,4-biphenyldicarboxaldehyde (BP), and 3,3'-dihydroxy-[1,1'-biphenyl]-4,4'-dicarboxaldehyde (BP-OH).

[0009] More preferably, the aromatic dialdehyde is selected from at least one of 2,6-dihydroxynaphthalene-1,5-dicarboxaldehyde (Nap-OH) and 3,3'-dihydroxy-[1,1'-biphenyl]-4,4'-dicarboxaldehyde (BP-OH).

[0010] Secondly,

[0011] This invention provides a method for preparing the above-mentioned polyiodine chain-functionalized covalent organic framework material, comprising the following steps:

[0012] S1: 1,2,3-Triaminoguanidine hydrochloride and aromatic dialdehyde are mixed in a molar ratio of 1:(1.5-3), dissolved in a mixed solvent, and glacial acetic acid solution is added as a catalyst. Sufficient potassium iodide or sodium iodide (≥0.18 g / mL) is added as a template reagent. The aromatic dialdehyde is selected from at least one of naphthalene-2,6-dicarboxaldehyde (Nap), 2,6-dihydroxynaphthalene-1,5-dicarboxaldehyde (Nap-OH), 4,4-biphenyldicarboxaldehyde (BP), and 3,3'-dihydroxy-[1,1'-biphenyl]-4,4'-dicarboxaldehyde (BP-OH).

[0013] S2: React the mixture from step S1 in a closed reactor at 80-120°C for 24-72 hours.

[0014] S3: Filter and collect the reaction product, wash it, and then soak it in a saturated ammonium bicarbonate solution at room temperature with stirring for 4-8 hours. Add isopropanol to the saturated ammonium bicarbonate solution and continue stirring for 0.5-2 hours. Filter to separate the solid product, and then dry it at 75-100℃ for 10-24 hours to obtain iCOF-I. - (Iodide ions as cationic covalent organic frameworks for counterions);

[0015] S4: iCOF-I - Disperse in an aqueous solution containing 5%-30% hydrogen peroxide and stir at room temperature for 6-12 hours;

[0016] S5: Filter the treated product, wash it with DMF, then with deionized water until neutral, then with anhydrous ethanol, and finally dry it at 75-100℃ for 10-24 hours to obtain polyiodine chain functionalized covalent organic framework material (iCOF-Iodine).

[0017] In the present invention, in step S1, a template method is used, that is, a sufficient amount of potassium iodide or sodium iodide (≥0.18g / mL) crystals are added to the synthesis reaction system as a template to control the framework morphology and simultaneously introduce iodide ions as counter ions.

[0018] More preferably, the aromatic dialdehyde is selected from at least one of 2,6-dihydroxynaphthalene-1,5-dicarboxaldehyde (Nap-OH) and 3,3'-dihydroxy-[1,1'-biphenyl]-4,4'-dicarboxaldehyde (BP-OH). Thus, the cationic covalent organic framework contains a hydroxyl functional group, which enhances the framework's adsorption capacity for iodide ions through hydrogen bonding.

[0019] More preferably, the aromatic dialdehyde is selected from 2,6-dihydroxynaphthalene-1,5-dicarboxaldehyde (Nap-OH), and the polyiodine chain-functionalized covalent organic framework material Nap-OH-COF-Iodine prepared has a maximum adsorption capacity of 486 mg / g for iodide ions in the aqueous phase.

[0020] In some embodiments, the mixed solvent in step S1 is a mixture of 1,4-dioxane and mesitylene, more preferably, the volume ratio of the two is (1-2):1, or the mixed solvent is a mixture of o-dichlorobenzene and n-butanol, more preferably, the volume ratio of the two is (1-2):1.

[0021] In some embodiments, when the aromatic dialdehyde is selected as naphthalene-2,6-dicarboxaldehyde (Nap) or 2,6-dihydroxynaphthalene-1,5-dicarboxaldehyde (Nap-OH), the mixed solvent is a mixture of 1,4-dioxane and mesitylene in a volume ratio of (1-2):1; when the aromatic dialdehyde is selected as 4,4-biphenyldicarboxaldehyde (BP) or 3,3'-dihydroxy-[1,1'-biphenyl]-4,4'-dicarboxaldehyde (BP-OH), the mixed solvent is a mixture of o-dichlorobenzene and n-butanol in a volume ratio of (1-2):1.

[0022] In some embodiments, the concentration of the glacial acetic acid solution is 6-9M, and the volume ratio of the glacial acetic acid solution to the mixed solvent is 1:(3-10).

[0023] In some embodiments, when the aromatic dialdehyde is selected as naphthalene-2,6-dicarboxaldehyde (Nap) or 2,6-dihydroxynaphthalene-1,5-dicarboxaldehyde (Nap-OH), the mixed solvent is a mixture of 1,4-dioxane and mesitylene, the glacial acetic acid solution concentration is 6M, and the volume ratio of 1,4-dioxane, mesitylene, and 6M glacial acetic acid solution is 6:3:1.

[0024] In some embodiments, when the aromatic dialdehyde is selected as 4,4-biphenyldicarboxaldehyde (BP) or 3,3'-dihydroxy-[1,1'-biphenyl]-4,4'-dicarboxaldehyde (BP-OH), the mixed solvent is a mixture of o-dichlorobenzene and n-butanol, the glacial acetic acid solution concentration is 6M, and the volume ratio of o-dichlorobenzene, n-butanol, and 6M glacial acetic acid solution is 5:5:1.

[0025] In some embodiments, in step S3, the washing refers to washing the reaction product sequentially with N,N-dimethylformamide (DMF), deionized water, tetrahydrofuran (THF), and dichloromethane.

[0026] In some embodiments, the concentration of the hydrogen peroxide solution in step S4 is 10%.

[0027] Thirdly,

[0028] This invention also provides the application of the above-mentioned polyiodine chain-functionalized covalent organic framework material in the adsorption (removal) of iodine ions in water.

[0029] In the above applications, the material captures iodide ions in water through the following adsorption mechanism:

[0030] (a) The pre-formed polyiodide chains within the cationic covalent organic framework serve as adsorption sites, oxidizing iodide ions in the water to generate more polyiodide anions through redox reactions.

[0031] (b) Cationic covalent organic frameworks adsorb iodide ions through electrostatic interactions;

[0032] (c) When hydroxyl groups are present in a cationic covalent organic framework, the hydroxyl groups in the cationic covalent organic framework adsorb iodide ions through hydrogen bonding;

[0033] (d) Polyiodide chains and iodide ions form specific bonds through charge transfer reactions and halogen bonds.

[0034] In some embodiments of the application, the adsorption process employs either batch adsorption or continuous flow adsorption.

[0035] In some embodiments of the application, the batch adsorption refers to directly adding the above-mentioned polyiodine chain functionalized covalent organic framework material to an aqueous solution containing iodide ions, stirring and adsorbing at room temperature, and separating after adsorption is completed.

[0036] In some embodiments of the application, the continuous flow adsorption refers to preparing the above-mentioned polyiodine chain functionalized covalent organic framework material into a membrane, and adsorbing an aqueous solution containing iodine ions through the membrane using a continuous flow system.

[0037] Specifically, the material is prepared into a membrane for use in a continuous flow iodine ion adsorption system; the membrane is prepared by suspending polyiodine chain functionalized covalent organic framework material powder in water to form a uniform suspension, filtering the suspension onto a nylon membrane substrate by vacuum filtration to form a uniform self-supporting membrane, and drying to obtain a composite membrane; the flow rate of the continuous flow system is 0.5-5 mL / min.

[0038] In some embodiments of the application, the water body includes one of the following: iodine-containing wastewater, spiked tap water, salt lake brine, and seawater.

[0039] In some embodiments of the application, after the iodine ions in the water body are adsorbed, the material is regenerated by hydrogen peroxide solution, then washed with DMF, deionized water and anhydrous ethanol in sequence, and dried at 75°C for 8-24 hours to achieve the regeneration of the adsorbent.

[0040] The present invention has the following beneficial effects:

[0041] (1) This invention adopts a biomimetic strategy to simulate the mechanism of iodine enrichment by seaweed, and realizes an innovative adsorption strategy of "iodine-to-iodine adsorption", which breaks through the limitations of traditional ion exchange materials in terms of capacity and selectivity.

[0042] (2) The polyiodine chain functionalized covalent organic framework material prepared in this invention has an ultra-high adsorption capacity for aqueous iodide ions, with an adsorption capacity of 198-486 mg / g, which is much higher than most reported iodide ion adsorbents.

[0043] (3) The material of the present invention has rapid adsorption kinetics and can reach adsorption equilibrium within 60 minutes, which meets the efficiency requirements in practical applications.

[0044] (4) The material of the present invention has excellent selectivity for iodide ions, even in F - ,Cl - ,Br - NO3 - HCO3 - AC - SO4 2- CO3 2- SiO3 2- ,PO4 3- Even in the presence of coexisting ions, it can still maintain high adsorption efficiency for iodide ions (in a multi-ion solution containing 100 mg / L of each of the above ions, the removal efficiency of iodide ions exceeds 90%).

[0045] (5) The material of the present invention exhibits excellent practical application performance in complex environments such as salt lake brine and seawater, with an iodine ion removal rate of up to 65% or more, providing strong support for practical environmental applications.

[0046] (6) The material of the present invention can be easily prepared into a film for use in a continuous flow adsorption system to achieve continuous and efficient removal of iodine ions, and has good engineering application prospects.

[0047] (7) The material of the present invention has good regeneration performance. After five cycles, it can still maintain more than 85% of the initial adsorption capacity, which reflects the economic efficiency and sustainability of the material.

[0048] (8) The preparation method of the present invention is simple, mild and environmentally friendly. It can be completed using common organic reagents and aqueous solution systems, and is suitable for large-scale production and practical application. Attached Figure Description

[0049] Figure 1 The present invention iCOF-Cl - iCOF-I - A schematic diagram of the synthetic route. Wherein:

[0050] (a): Synthesis of chlorinated cationic covalent organic frameworks (iCOF-Cl) using different aromatic dialdehyde building blocks - The synthetic route of ) demonstrates the formation of four different iCOF-Cl by Schiff base condensation reactions of 1,2,3-triaminoguanidine hydrochloride with different dialdehyde monomers. - (Nap-COF-Cl - Nap-OH-COF-Cl - BP-COF-Cl - and BP-OH-COF-Cl - The process;

[0051] (b): Potassium iodide template-assisted synthesis of iodine-containing cationic covalent organic frameworks (iCOF-I) - The route demonstrates a strategy of adding potassium iodide as a template to the synthetic reaction system to achieve framework morphology control and simultaneously introduce iodide ions as counterions.

[0052] Figure 2 iCOF-I - The structural characterization results of the material are shown in the figure. Among them:

[0053] (a): Nap-COF-I - (a) X-ray powder diffraction (PXRD) pattern; (b) Nap-OH-COF-I - X-ray powder diffraction (PXRD) pattern; (c): BP-COF-I - X-ray powder diffraction (PXRD) pattern; (d): BP-OH-COF-I - X-ray powder diffraction (PXRD) patterns; (e) shows four iCOF-I - The Fourier transform infrared (FT-IR) spectrum of the material shows the characteristic absorption peaks of key functional groups in the material.

[0054] Figure 3 iCOF-Cl - X-ray powder diffraction (PXRD) pattern of the material. Among them:

[0055] (a): Nap-COF-Cl - (b): Nap-OH-COF-Cl - (c): BP-COF-Cl - (d): BP-OH-COF-Cl - .

[0056] Figure 4 Four types of iCOF-Cl - FT-IR spectrum of the material. Wherein:

[0057] (a): Nap-COF-Cl - (b): Nap-OH-COF-Cl - (c): BP-COF-Cl - (d): BP-OH-COF-Cl - .

[0058] Figure 5 Four types of iCOF-I - Solid-state carbon NMR spectrum of the material. Among them:

[0059] (a): Nap-COF-I - (b): Nap-OH-COF-I - (c): BP-COF-I - (d): BP-OH-COF-I - .

[0060] Figure 6 Four types of iCOF-I - The N2 adsorption-desorption isotherm of the material. Among them:

[0061] (a): Nap-COF-I - (b): Nap-OH-COF-I - (c): BP-COF-I - (d): BP-OH-COF-I - .

[0062] Figure 7 Four types of iCOF-Cl - and four iCOF-I - Thermogravimetric curve of the material.

[0063] (a): Nap-COF-Cl - and Nap-COF-I - Thermogravimetric curve, (b): Nap-OH-COF-Cl - and Nap-OH-COF-I - Thermogravimetric curve, (c): BP-COF-Cl - and BP-COF-I - Thermogravimetric curve, (d): BP-OH-COF-Cl - and BP-OH-COF-I - Thermogravimetric curve.

[0064] Figure 8 Nap-OH-COF-I - and BP-OH-COF-I - PXRD patterns before and after treatment with different reagents for 3 days, including:

[0065] (a): Nap-OH-COF-I - PXRD patterns before and after treatment with 0.5M HCl, 0.5M NaOH, DMF, THF, ethanol, and cyclohexane for 3 days.

[0066] (b): BP-OH-COF-I - PXRD patterns before and after treatment with 0.5M HCl, 0.5M NaOH, DMF, THF, ethanol, and cyclohexane for 3 days.

[0067] Figure 9 Nap-OH-COF-I - and BP-OH-COF-I - FT-IR spectra before and after treatment with different reagents for 3 days, including:

[0068] (a): Nap-OH-COF-I - FT-IR spectra before and after treatment with 0.5M HCl, 0.5M NaOH, DMF, THF, ethanol, and cyclohexane for 3 days.

[0069] (b): BP-OH-COF-I - FT-IR spectra before and after treatment with 0.5M HCl, 0.5M NaOH, DMF, THF, ethanol, and cyclohexane for 3 days.

[0070] Figure 10 This describes the morphology and elemental composition of iCOF. Specifically:

[0071] (a): Nap-COF-Cl - Scanning electron microscope image, (b): Nap-OH-COF-Cl - Scanning electron microscope image, (c): BP-COF-Cl - Scanning electron microscope image, (d): BP-OH-COF-Cl - Scanning electron microscope image, (e): Nap-COF-I - Scanning electron microscope image, (f): Nap-OH-COF-I - Scanning electron microscope image, (g): BP-COF-I - Scanning electron microscope image, (h): BP-OH-COF-I - Scanning electron microscope image, (i): iCOF-Cl - X-ray photoelectron spectroscopy (XPS), (j): iCOF-I - X-ray photoelectron spectroscopy (XPS), (k): Nap-OH-COF-Cl - Transmission electron microscopy energy dispersive spectroscopy elemental mapping (TEM-EDX), (l): Nap-OH-COF-I - Transmission electron microscopy energy dispersive spectroscopy elemental mapping (TEM-EDX).

[0072] Figure 11 This represents the adsorption performance of iCOF for iodide ions in water. Among them:

[0073] (a): Nap-COF-Cl - and Nap-OH-COF-Cl -pH-dependent removal of iodide ions; (b): iCOF-Cl - Adsorption kinetics of materials; (c): iCOF-Cl - (d): Schematic diagram of iCOF-Iodine adsorbent preparation and iodine ion capture; (e): Adsorption kinetics of iCOF-Iodine material; (f): Adsorption isotherm of iCOF-Iodine material; (g): Elemental analysis and scanning electron microscopy energy dispersive spectroscopy mapping of Nap-OH-COF-Iodine after iodine ion adsorption.

[0074] Figure 12 iCOF-Cl in aqueous dispersion - The zeta potential and particle size distribution of the material.

[0075] Figure 13 This refers to the selective adsorption of iodide ions in water by iCOFs. Specifically:

[0076] (a): Performance comparison with other reported materials; (b): Iodine ion removal efficiency of Nap-OH-COF-Iodine in the presence of competing ions; (c): Iodine ion removal efficiency in actual environmental samples; (d): iCOF-Cl - (e) Saturated adsorption capacity in a high-concentration chloride environment; (f) Saturated adsorption capacity of iCOF-Iodine in a high-concentration chloride environment; - Saturated adsorption capacity in a high-concentration chloride environment; (g): Breakthrough curve of triiodide ion dynamic flow adsorption; (h): UV-Vis absorption spectrum of Nap-OH-COF-Iodine after adsorption of triiodide ions; (i) UV-Vis absorption spectrum of BP-OH-COF-Iodine after adsorption of triiodide ions.

[0077] Figure 14 For I after 5 cycles - Reusability of iCOFs after adsorption-desorption cycles.

[0078] Figure 15 The removal efficiency of iCOF-Iodine for iodine ions in samples coexisting with other interfering ions or in actual environmental samples was determined.

[0079] Figure 16 The water contact angles are for four types of iCOF-Iodine materials.

[0080] Figure 17 This describes the adsorption mechanism of iodide ions. Specifically:

[0081] (a): Raman spectrum of Nap-OH-COF-Iodine; (b): Raman spectrum of BP-OH-COF-Iodine; (c): I 3d X-ray photoelectron spectrum of Nap-OH-COF-Iodine; (d): I 3d X-ray photoelectron spectrum of BP-OH-COF-Iodine; (e): I 3d X-ray photoelectron spectrum of Nap-OH-COF-Iodine. - Convert to I2 / I3 - / I5 - Energy change diagram; (f): I in Nap-OH-COF - Convert to I2 / I3 - / I5 - Energy change diagram; (g): I in BP-COF - Convert to I2 / I3 - / I5 - Energy change diagram; (h): I in BP-OH-COF - Convert to I2 / I3 - / I5 - Energy variation diagrams: (i): N1s X-ray photoelectron spectrum before iodide ion adsorption; (j): N1s X-ray photoelectron spectrum after iodide ion adsorption; (k): O1s X-ray photoelectron spectrum before iodide ion adsorption; (l): O1s X-ray photoelectron spectrum after iodide ion adsorption.

[0082] Figure 18 The image shows the 3d XPS spectrum of iCOF-Iodine after iodine ion adsorption.

[0083] Figure 19 The N1s and O1s XPS spectra of iCOF-Iodine before and after iodine ion adsorption are shown. Detailed Implementation

[0084] To make the objectives, technical solutions, and beneficial effects of the embodiments of the present invention clearer, the embodiments of the present invention will now be described in further detail. Obviously, the described embodiments are only a part of the present invention, but not all embodiments. Based on this specification, those skilled in the art can obtain various other implementation forms without creative effort, all of which fall within the protection scope of the present invention.

[0085] Unless otherwise stated, all raw materials and reagents used in the examples were purchased from legitimate commercial sources or are available by known methods. Definitions of scientific and technical terms follow generally accepted conventions in the field. "About" means a value fluctuating within 10%, better by 5%, or optimally by 1%. "Range" also includes all subranges and their specific upper and lower limits (whether specifically stated or not).

[0086] The core mechanism by which biological systems (such as seaweed) efficiently enrich iodide ions is through specific redox reactions and the formation of polyiodide chain structures, achieving efficient capture and concentration of iodide ions. This invention can form adsorbent materials with special polyiodide chains within their structure, potentially overcoming the performance bottlenecks of traditional adsorbents. Cationic covalent organic frameworks (iCOFs), due to their permanent pore structure, tunable functional groups, and intrinsic positive charge, provide an ideal platform for designing novel iodide ion adsorbents. Functional modification, particularly the introduction of hydrophilic functional groups such as hydroxyl groups, can further enhance the interaction between the material and iodide ions in water. However, effectively integrating the "iodine-to-iodine adsorption" mechanism from biological systems into synthetic materials to form stable polyiodide chain structures for efficient adsorption of iodide ions in aqueous phases still faces many scientific challenges. During redox processes, polyiodide anions (I... n - The formation of polyiodine chains is a crucial step, as these polyiodine species interact strongly with additional iodine ions through halogen bonds and charge transfer. Such polyiodine chain structures are difficult to stabilize in conventional inorganic materials, but carefully designed porous organic frameworks may provide an ideal microenvironment for this purpose.

[0087] All adsorption experiments in this invention were repeated three times and the average value was taken. The entire reaction was conducted in the dark to eliminate interference from photodegradation.

[0088] Cationic covalent organic frameworks (iCOFs) are synthesized through two different methods: one is a chlorine-containing framework (iCOF-Cl). - One is the traditional solvothermal method (iCOF-I series), and the other is the iodine-containing framework (iCOF-I). - An innovative potassium iodide crystal template method (series), as shown in the attached document. Figure 1 As shown.

[0089] Example 1

[0090] iCOF-Cl - The synthesis method includes the following steps:

[0091] Synthesis of Nap-COF-Cl -In one reaction, 1,2,3-triaminoguanidine hydrochloride (28.2 mg, 0.2 mmol) and naphthalene-2,6-dicarboxaldehyde (55.3 mg, 0.3 mmol) were mixed in a solvent mixture consisting of 1,4-dioxane (3 mL) and mesitylene (1.5 mL), followed by the addition of 6M acetic acid (0.5 mL) as a catalyst. The reaction mixture was transferred to a PTFE-lined stainless steel autoclave, sealed, and heated at 120 °C for 72 hours. Following a similar procedure, Nap-OH-COF-Cl was synthesized by reacting 1,2,3-triaminoguanidine hydrochloride (28.2 mg, 0.2 mmol) with 2,6-dihydroxynaphthalene-1,5-dicarboxaldehyde (64.9 mg, 0.3 mmol) under the same conditions. - .

[0092] For BP-COF-Cl - 1,2,3-Triaminoguanidine hydrochloride (28.2 mg, 0.2 mmol) was combined with [1,1'-biphenyl]-4,4'-dicarboxaldehyde (63.1 mg, 0.3 mmol) in a mixture of o-dichlorobenzene (2.5 mL) and n-butanol (2.5 mL), using 6M acetic acid (0.5 mL) as a catalyst. The reaction mixture was transferred to a PTFE-lined stainless steel autoclave, sealed, and maintained at 120 °C for 72 hours. Similarly, BP-OH-COF-Cl... - It was prepared by reacting 1,2,3-triaminoguanidine hydrochloride (28.2 mg, 0.2 mmol) with 3,3'-dihydroxy-[1,1'-biphenyl]-4,4'-dicarboxaldehyde (72.7 mg, 0.3 mmol) under the same reaction conditions.

[0093] After synthesis, all crude products underwent thorough purification to remove unreacted monomers and residual solvent molecules. The specific purification steps were as follows: the solid product was collected by filtration and washed in a solvent filtration apparatus with 50 mL of DMF, 50 mL of THF, and 50 mL of dichloromethane, respectively. The purified iCOF-Cl... - The sample was immersed in 50 mL of saturated ammonium bicarbonate solution at room temperature and stirred for 6 hours. Then, 20 mL of isopropanol was added and the mixture was stirred for 1 hour to induce recrystallization of ammonium bicarbonate within the COF pores. This method effectively prevents framework collapse due to capillary forces during solvent evaporation. The material was then dried overnight at 100 °C to obtain activated iCOF-Cl. - The product is stored in sealed glass bottles for further characterization and application.

[0094] Example 2

[0095] iCOF-I - The synthesis method includes the following steps:

[0096] iCOF-I - The series was synthesized using a novel crystal template method that uses potassium iodide as both a template and an iodine source.

[0097] Synthesis of Nap-COF-I - In one reaction, 1,2,3-triaminoguanidine hydrochloride (28.2 mg, 0.2 mmol) and naphthalene-2,6-dicarboxaldehyde (55.3 mg, 0.3 mmol) were mixed in a solvent mixture consisting of 1,4-dioxane (3 mL) and mesitylene (1.5 mL), followed by the addition of 6M acetic acid (0.5 mL) as a catalyst and potassium iodide crystals (1 g) as a template agent. The reaction mixture was transferred to a PTFE-lined stainless steel autoclave, sealed, and heated at 120 °C for 72 hours. Following a similar procedure, Nap-OH-COF-I was synthesized by reacting 1,2,3-triaminoguanidine hydrochloride (28.2 mg, 0.2 mmol) with 2,6-dihydroxynaphthalene-1,5-dicarboxaldehyde (64.9 mg, 0.3 mmol) under the same conditions. - .

[0098] For BP-COF-I - 1,2,3-Triaminoguanidine hydrochloride (28.2 mg, 0.2 mmol) was combined with [1,1'-biphenyl]-4,4'-dicarboxaldehyde (63.1 mg, 0.3 mmol) in a mixture of o-dichlorobenzene (2.5 mL) and n-butanol (2.5 mL), using 6M acetic acid (0.5 mL) as a catalyst and potassium iodide crystals (1 g) as a template agent. The reaction mixture was transferred to a PTFE-lined stainless steel autoclave, sealed, and maintained at 120 °C for 72 hours. Similarly, BP-OH-COF-I - It was prepared by reacting 1,2,3-triaminoguanidine hydrochloride (28.2 mg, 0.2 mmol) with 3,3'-dihydroxy-[1,1'-biphenyl]-4,4'-dicarboxaldehyde (72.7 mg, 0.3 mmol) under the same reaction conditions.

[0099] After synthesis, all crude products underwent thorough purification to remove unreacted monomers and residual solvent molecules. The specific purification steps were as follows: the solid product was collected by filtration and washed in a solvent filtration apparatus with 50 mL of DMF, 50 mL of deionized water, 50 mL of THF, and 50 mL of dichloromethane, respectively. The purified iCOF-I... -The sample was immersed in 50 mL of saturated ammonium bicarbonate solution at room temperature for 6 hours, followed by the addition of 20 mL of isopropanol and stirring for 1 hour to induce recrystallization of ammonium bicarbonate in the COF pores. This method effectively prevents framework collapse caused by capillary forces during solvent evaporation. The material was then dried overnight at 100 °C to obtain activated iCOF-I. - The product is stored in sealed glass bottles for further characterization and application.

[0100] iCOF-I - The reaction conditions of the framework are the same as those in Example 1 for iCOF-Cl - The corresponding substances are exactly the same, but there is one key change: the addition of 1 gram of potassium iodide crystals to each reaction vessel. (See attached image.) Figure 1 As shown in (b), this template strategy facilitates the controlled assembly of the COF network through three stages: (1) monomers are initially adsorbed onto the surface of potassium iodide crystals; (2) an ordered framework grows along the lattice structure; and (3) the potassium iodide template subsequently dissolves, releasing the templated COF nanosheets. After the reaction, the remaining bulk potassium iodide crystals were carefully removed with tweezers, followed by a standard washing process. An additional deionized water washing step was also performed to ensure complete removal of residual potassium iodide. This crystal template method not only promotes the incorporation of iodide ions as counterions into the framework but also significantly improves the structural order of the resulting material.

[0101] Due to iCOF-I - The inherent iodine counterion in the framework prevents it from being used directly as an iodine ion adsorbent. To overcome the limitations of iodine-containing iCOF-I... - To address the limitations of materials in iodide ion adsorption, this invention utilizes a 10% hydrogen peroxide solution to treat freshly synthesized iCOF-I. - The material oxidizes the iodide ions inherent within the framework to form polyiodide chains (I-) within the one-dimensional channels of the COF. n - The resulting modified material (iCOF-Iodine) exhibited a significantly enhanced iodine ion capture ability.

[0102] The synthesis method of iCOF-Iodine includes the following steps:

[0103] Accurately weigh 500 mg of pre-synthesized iCOF-I into a clean, dry 100 mL beaker. - Then, carefully add 50 mL of freshly prepared 10% hydrogen peroxide solution using a pipette. Simultaneously, place the stir bar in the beaker and position it on a magnetic stirrer. Turn on the magnetic stirrer and set it to a stirring speed of 300 rpm to ensure the iCOF-I... - The material was fully dispersed in solution and then reacted at room temperature for 12 hours to promote iCOF-I- The oxidation reaction between iodide ions and hydrogen peroxide in the solution is observed, during which the solution color gradually changes from colorless to brownish-yellow, indicating the formation of polyiodide chains. After the reaction is complete, the solid product is collected using a vacuum filtration device. The collected solid product is then washed sequentially with the following solvents: first with 30 mL of DMF, then with 30 mL of deionized water, and finally with 30 mL of anhydrous ethanol. The solid should be thoroughly dispersed during each wash to ensure complete cleaning. The washed solid product is then dried overnight in a vacuum drying oven at 75°C to remove all residual solvent. After drying, the product iCOF-Iodine is stored in a dry, light-protected, sealed glass bottle, avoiding exposure to air.

[0104] like Figure 1 As shown, a series of ionic covalent organic frameworks (iCOFs) with different structural features were successfully synthesized via Schiff base condensation reactions between guanidine triaminohydrochloride and various aromatic dialdehydes. Using naphthyl or biphenyl building blocks, and functionalized with or without hydroxyl groups, four different frameworks (labeled Nap-COF, Nap-OH-COF, BP-COF, and BP-OH-COF, respectively) were prepared. Each framework is further functionalized using chloride ions (Cl... - ) or iodide ions (I - As counter ions, eight different iCOF materials were obtained. Powder X-ray diffraction (PXRD) analysis confirmed the successful formation of the crystal framework. Figure 2 As shown in (a)-(d), Nap-COF-I - Nap-OH-COF-I - BP-COF-I - and BP-OH-COF-I - The sample exhibits a strong diffraction pattern with strong peaks corresponding to the (100) reflector at approximately 4.18°, 4.46°, 3.56°, and 3.65°. Additional peaks at higher 2θ values ​​further indicate the formation of an ordered structure. The experimental PXRD pattern closely matches the simulated pattern derived from the predicted AA stacking model, suggesting that this stacking mode dominates the synthetic framework. The refined cell parameters and lower R0... p The values ​​(3.81%-4.30%) further validated the structural model. Similarly, iCOFs-Cl - They show similar diffraction patterns. Figure 3 This confirms that counterion exchange does not significantly alter the crystal framework structure. Fourier transform infrared spectroscopy (FT-IR) provides strong evidence for the successful formation of imine bonds in these frameworks. Figure 2 (e) and Figure 4 As shown, all iCOFs are at approximately 1610-1617 cm⁻¹ -1The characteristic C=N stretching vibration is observed at this point, confirming the successful condensation reaction between the aldehyde and amine functional groups. Compared to their respective monomers, the aldehyde C=O stretching band in the iCOF spectra (~1680 cm⁻¹) is significantly larger. -1 The disappearance of ) and the stretching signal of primary amine NH (~3200-3300cm) -1 The significant reduction in [something] further confirms the formation of imine bonds. Solid state 13 C nuclear magnetic resonance spectrum ( Figure 5 The molecular structure of the synthesized framework was further validated. All spectra showed characteristic signals at approximately 150–160 ppm, which can be attributed to the carbon atoms in the newly formed C=N bonds. The remaining resonance signals corresponded well to the aromatic carbon environment of the naphthalene or biphenyl moiety. The spectral assignments were consistent with the proposed structural model, providing further confirmation of the successful framework formation.

[0105] The porosity characteristics of the iCOF material were evaluated by nitrogen adsorption-desorption isotherms at 77 K. Figure 6 Nap-COF-I - Nap-OH-COF-I - BP-COF-I - and BP-OH-COF-I - The specific surface area of ​​Brunauer-Emmett-Teller (BET) is 127.3 m². 2 / g, 108.5m 2 / g, 142.4m 2 / g and 243.5m 2 / g, with pore size distribution mainly concentrated at 1.71nm, 1.69nm, 1.92nm, and 1.88nm. Thermogravimetric analysis (TGA) confirmed that these iCOF materials possess excellent thermal stability. Figure 7 All skeletal structures remain intact at least up to 247°C. Notably, the counter ion type (Cl...) - Or I - The effect on thermal stability is minimal, indicating that skeletal decomposition is primarily determined by the organic framework rather than the ionic components. The representative iCOF (Nap-OH-COF-I) was evaluated by exposing the material to various chemical environments, including acidic (0.5M HCl), alkaline (0.5M NaOH), and various organic solvents (DMF, THF, ethanol, and cyclohexane). - and BP-OH-COF-I - The chemical stability of ) such as Figure 8 and Figure 9 As shown in the figure. Notably, the PXRD and FT-IR spectra of the treated sample remained essentially unchanged compared to the original material, demonstrating its excellent chemical stability.

[0106] The synthesized iCOFs exhibited a unique morphology as observed by scanning electron microscopy (SEM). Figure 10 (a)-(h)). Most of the frameworks form a three-dimensional network with interconnected fibrous structures, creating a hierarchical porous structure. Notably, Nap-OH-COF exhibits a unique petal-like morphology, composed of interwoven nanosheets (20-50 nm thick), which assemble into a multilayer structure. Figure 10 (b) and (f)). This unique structure likely originates from the enhanced π-π stacking between naphthalene rings and the interhydroxyl hydrogen bond network, which enhances the interlayer interactions. X-ray photoelectron spectroscopy (XPS) analysis confirmed the elemental composition of all framework components, revealing characteristic peaks (C 1s, N 1s, O 1s) of the framework components, as well as iCOF-Cl. - Cl 2p (~198.5 eV) or iCOF-I in the material - The I 3d in the material (~619.0 eV, ~630.0 eV) ( Figure 10 (i) and (j)). The absence of a chlorine signal in the iCOF-I- spectrum confirms the completeness of the counterion exchange performed using the potassium iodide template method. Transmission electron microscopy energy-dispersive X-ray spectroscopy (TEM-EDX) mapping ( Figure 10 The results (k) and (l) show that all elements are uniformly distributed within the framework, confirming that guanidine hydrochloride is successfully integrated into the framework structure, rather than being limited to the surface.

[0107] Example 3

[0108] The adsorption experiment of iodide ions in aqueous phase includes the following steps:

[0109] The adsorption behavior of iodide ions on the synthesized iCOFs was systematically studied through batch equilibrium experiments. A potassium iodide stock solution (500 mg / L) was prepared using distilled water and subsequently diluted to obtain a series of iodide ion solutions with concentrations ranging from 2 to 250 mg / L. For pH-dependent adsorption studies, 10 mg of iCOF adsorbent was added to 20 mL of iodide ion solution (100 mg / L), and the pH was adjusted to between 2 and 11 using 0.5 mol of hydrochloric acid or sodium hydroxide solution. The suspension was continuously stirred at room temperature for 60 minutes to reach adsorption equilibrium. After centrifugation, the concentration of residual iodide ions in the supernatant was measured, and the removal efficiency was calculated using the following formula:

[0110]

[0111] Where c0 and c e (mg / L) represent the initial and equilibrium concentrations of iodide ions, respectively.

[0112] Adsorption kinetics experiments were conducted by dispersing 25 mg iCOF in 50 mL of iodide ion solution (250 mg / L, pH = 7) with continuous stirring at room temperature. At predetermined time intervals, aliquots of the suspension were extracted, centrifuged, and the residual iodide ion concentration was analyzed. Similar experimental procedures were used for adsorption isotherm studies, but the initial iodide ion concentration varied from 20 to 250 mg / L, while other experimental parameters remained constant. The equilibrium adsorption capacity (q...) was determined. e (mg / g) is calculated using the following formula:

[0113]

[0114] Where V(L) is the solution volume and m(g) is the mass of the iCOF adsorbent. All batch adsorption experiments were performed three times to ensure reproducibility, and the average values ​​were reported. Iodine ion concentration was mainly determined by UV-Vis absorption spectroscopy, which involves monitoring the characteristic absorption peak at approximately 226 nm. However, for complex matrices containing multiple ion species, inductively coupled plasma optical emission spectrometry / mass spectrometry (ICP-OES / MS) was used for more accurate quantitative analysis.

[0115] This invention investigated the removal of iodide ions in aqueous phase using two cationic iCOF materials: iCOF-Cl - Conventional anion exchange method and the use of modified iCOF-I for materials - Biomimicry strategies for materials. pH-dependent studies ( Figure 11 (a) indicates that iCOF-Cl - The material performed best in the pH range of 2–7, with the hydroxyl-functionalized variant maintaining high removal efficiency over a wider pH range, indicating enhanced iodide ion stability through the addition of hydrogen bonds. This behavior is consistent with Zeta potential measurements ( Figure 12 Consistent with the latter, which shows a transition from positive to negative values ​​at approximately pH = 8-9. Adsorption kinetics ( Figure 11 (b) reveals a two-stage process: rapid adsorption within 15 minutes, followed by equilibrium reaching within 60 minutes. Nap-OH-COF-Cl - It exhibited the highest adsorption capacity (281.9 mg / g), followed by BP-OH-COF-Cl. - (223.6 mg / g), BP-COF-Cl - (151.8 mg / g) and Nap-COF-Cl - (124.5 mg / g). The kinetic model best matches the pseudo-second-order kinetic model (R0). 2 >0.99 (Table 1), indicating that chemisorption is the rate-limiting step. Adsorption isotherms ( Figure 11(c) conforms to the Langmuir model (R 2 >0.999 (Table 2) indicates that iodine ions undergo monolayer adsorption on a uniform surface.

[0116] Despite iCOF-Cl - The material exhibits excellent adsorption properties. The iCOF-I synthesized in this invention... - The inherent iodine counterions within the framework prevent them from being used directly as iodine ion adsorbents. To overcome this, iodine-containing iCOF-I... - To address the limitations of materials in iodine ion adsorption, this invention develops a biomimetic method. For example... Figure 11 As shown in (d), iCOF-I - The material is treated with 10% hydrogen peroxide to oxidize the iodide ions inherent in the framework, forming polyiodide chains (I-) within the COF channels. n - These modified materials (iCOF-Iodine) exhibit significantly enhanced iodide ion capture capabilities. The iCOF-Iodine material demonstrates an accelerated adsorption rate. Figure 11 In the middle (e) group, the equilibrium adsorption capacity almost doubled: Nap-OH-COF-Iodine (486.1 mg / g), BP-OH-COF-Iodine (385.0 mg / g), Nap-COF-Iodine (207.2 mg / g), and BP-COF-Iodine (198.4 mg / g). The kinetic model confirmed the pseudo-second-order kinetic model (R0). 2 >0.99 (Table 3), a higher intraparticle diffusion constant indicates improved mass transfer efficiency. Adsorption isotherms ( Figure 11 Table 4 shows a good agreement with the Langmuir model (Rf). 2 >0.998), with maximum adsorption capacities of: 500.0 mg / g for Nap-OH-COF-Iodine, 400.0 mg / g for BP-OH-COF-Iodine, 243.9 mg / g for Nap-COF-Iodine, and 212.8 mg / g for BP-COF-Iodine. This superior performance stems from a charge-transfer-driven "snowball" effect, where polyiodide chains promote the continuous enrichment of additional iodide ions by forming extended polyiodide species. Elemental analysis and mapping ( Figure 11 The study (g) confirmed the increased iodine content and its uniform distribution within the framework. The superior performance of hydroxyl-functionalized materials stems from synergistic factors: the creation of nucleation sites by the polyiodide chains, the strong electrostatic interactions generated by the cationic framework, the additional hydrogen bonding provided by the hydroxyl groups, and the optimized pore structure. This biomimetic "iodine-capturing" approach transforms structural constraints into functional advantages for advanced iodine-capturing materials.

[0117] Table 1 Iodide ions in iCOF-Cl - Adsorption kinetic fitting parameters

[0118]

[0119]

[0120] Table 2 Iodide ions in iCOF-Cl - Adsorption isotherm fitting parameters

[0121]

[0122] Table 3. Adsorption kinetics fitting parameters of iodide ions on iCOF-Iodine

[0123]

[0124] Table 4. Fitting parameters for the adsorption isotherm of iodide ions on iCOF-Iodine

[0125]

[0126] Example 4

[0127] The selective adsorption study of iodide ions in aqueous phase includes the following steps:

[0128] To evaluate the adsorption selectivity of iCOF for iodide ions, batch adsorption experiments were conducted in the presence of competing anions, using F... - Cl - ,Br - NO3 - HCO3 - AC - (acetate), SO4 2- CO3 2- SiO3 2- PO4 3-A multi-anion solution (100 mg / L for each concentration, pH = 7) was prepared. Furthermore, the effect of chloride ions on iodide ion adsorption was specifically investigated using a binary solution containing iodide ions (250 mg / L) and chloride ions (1000 mg / L) at neutral pH. To evaluate the practical applicability of the synthesized iCOF in removing iodide ions from complex environmental matrices, adsorption experiments were conducted using real-world environmental samples, including brine from the Qarhan Salt Lake and seawater from the Bohai Sea. Prior to the adsorption experiments, these environmental samples were filtered through a 0.22 μm nylon membrane to remove insoluble impurities. Typically, 25 mg of iCOF was dispersed in 50 mL of the filtered environmental sample and stirred at room temperature for 60 min. The suspension was then centrifuged, and the supernatant was analyzed using ICP-OES / MS to determine the residual concentrations of iodide ions and other competing ions, thereby evaluating the selective adsorption performance of iCOF under real-world conditions.

[0129] With record-breaking capacity, exceptional reusability, and rapid dynamic characteristics ( Figure 13 (a), Table 5, and Figure 14 Nap-OH-COF-Iodine has emerged as a promising candidate material for nuclear waste treatment and environmental remediation applications. After adsorbing iodide ions, iCOF-Iodine was regenerated by immersing it in a 10% hydrogen peroxide solution for 24 hours, thereby fully oxidizing the adsorbed iodide ions into elemental iodine and iodine oxides. After filtration to separate the solid, the material was washed sequentially with DMF, deionized water, and anhydrous ethanol to remove residual iodine species from the surface. The washed iCOF-Iodine material was then dried overnight at 75°C for reuse in the next adsorption cycle. After five consecutive adsorption-desorption cycles, Nap-OH-COF-Iodine retained 94.8% of its original adsorption capacity for iodide ions. This invention tested the adsorption selectivity of the material under conditions where various interfering ions coexisted with iodide ions to evaluate its practical application value. When compared with common competing anions (F... - Cl - ,Br - NO3 - HCO3 - AC - SO4 2- CO3 2- SiO3 2- PO4 3- When tested at concentrations equivalent to iodide ions, Nap-OH-COF-Iodine maintained consistently high removal efficiency (>90%) in all cases. Figure 13 (b)). Similar results were also observed in other iCOF-Iodine materials. Figure 15This remarkable selectivity stems from a polyiodide-mediated capture mechanism, in which the strong affinity between the grown polyiodide chains and the incoming iodide ions creates an energy-advantaged species that can outcompete other anions. In complex real-world environments (… Figure 13 (c) Figure 15 The samples included brine from the Qarhan Salt Lake, tap water spiked with iodine ions, and real Bohai Sea water. All iCOF-Iodine materials maintained satisfactory removal efficiencies (65.8-95.2%). The poorer efficiencies in the salt lake samples reflect the impact of the extremely high concentrations of chlorides and sulfates typical of salt lake environments.

[0130] Given that chloride ions are the most abundant and potentially disruptive anions in natural water bodies, we conducted a detailed comparative study of the chloride ion resistance of the materials. The comparative study of chloride ion resistance showed that when the chloride ion concentration was four times that of the iodide ion concentration (C... I - =250mg / L), iCOF-Cl - The material exhibited a significant reduction in capacity (42.5-58.1%). Figure 13 (d)). In contrast, iCOF-Iodine materials exhibited significantly enhanced resistance with minimal capacity reduction: Nap-OH-COF-Iodine reduced by 7.5%, BP-OH-COF-Iodine by 8.3%, BP-COF-Iodine by 15.1%, and Nap-COF-Iodine by 14.6% (d). Figure 13 (e)). This improvement highlights the advantages of a polyiodide-mediated capture mechanism that relies on specific iodine-iodine interactions, rather than just electrostatic attraction. Furthermore, Nap-OH-COF-I, which pre-captures I2 vapor and desorbs it via ethanol, is also improved. - It also exhibited a significant iodine ion adsorption capacity (304.2 mg / g), achieving approximately 85% of the saturation adsorption capacity observed in chlorine-free solutions without H2O2 treatment. Figure 13 (f) This reveals that residual iodine species can also promote the "iodine uptake" mechanism, highlighting the potential of these materials for continuous gas-phase and aqueous-phase iodine capture.

[0131] Table 5 Comparison of the materials in this application with reported adsorbents

[0132]

[0133] (1)Lefèvre,G.;Walcarius,A.;Ehrhardt,J.-J.;Bessière,J.Sorptionofiodide on cuprite(Cu2O).Langmuir 2000,16(10),4519-4527.

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[0146] (14)Liu,S.;Wang,N.;Zhang,Y.;Li,Y.;Han,Z.;Na,P.Efficient removal ofradioactive iodide ions from water by three-dimensional Ag2O–Ag / TiO2composites under visible light irradiation.Journal of hazardous materials2015,284,171-181.

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[0152] (20) Bo, A.; Sarina, S.; Zheng, Z.; Yang, D.; Liu, H.; Zhu, H.Removalofradioactive iodine from water using Ag2O grafted titanate nanolamina as efficient adsorbent. Journal of Hazardous Materials 2013, 246, 199-205. Example 5

[0153] The adsorption experiment of triiodide ions in aqueous phase includes the following steps:

[0154] To evaluate the adsorption efficiency of iCOF under dynamic breakthrough conditions, a series of studies using triiodide ions (I3) were designed and conducted. -Experiments with aqueous solutions. First, a stock solution of triiodide ions (1.5 mmol) was prepared by dissolving 225 mg sodium iodide (1.5 mmol) and 381 mg iodine (1.5 mmol) in 1000 mL of deionized water. Successful formation of triiodide ions was confirmed by UV-Vis absorption spectroscopy, with characteristic absorption bands observed at 287 nm and 351 nm, consistent with the spectral characteristics of triiodide ions in aqueous solution. For dynamic filtration experiments, the iCOF membrane was prepared using a vacuum-assisted in-situ deposition method. Specifically, 100 mg of synthesized iCOF powder was uniformly dispersed in 50 mL of deionized water under gentle sonication to form a homogeneous suspension. This suspension was then filtered through a 50 mm diameter nylon membrane substrate using vacuum filtration to form a homogeneous, self-supporting iCOF membrane. After formation, the membrane was thoroughly rinsed with deionized water to remove any loosely bound particles and then air-dried at room temperature for 12 hours. The prepared iCOF membrane was carefully fixed between the intermediate layers of a stainless steel filter apparatus to ensure that the entire solution could pass through the membrane during filtration. The experimental setup was constructed by connecting the outlet of a peristaltic pump to the inlet of the filter housing via appropriate tubing, with the pump inlet immersed in a 1.5 mmol triiodide ion stock solution. The dynamic adsorption process was initiated by activating the peristaltic pump at a controlled flow rate of 5 mL / min. To monitor breakthrough behavior, effluent samples were collected every five minutes and analyzed immediately using UV-Vis absorption spectroscopy. The absorbance at 286 nm was measured to determine the residual triiodide ion concentration in the filtered solution, used to calculate the removal efficiency over time and the volume of the treated solution. This experimental configuration allows for evaluation of the iCOF membrane performance under conditions closer to real-world applications, where continuous flow and rapid adsorption kinetics are crucial for efficient contaminant removal. The dynamic breakthrough experiment provides information on the adsorption capacity, selectivity, and stability of the iCOF membrane under flow conditions.

[0155] For continuous flow applications, hydroxyl-functionalized materials exhibit enhanced hydrophilicity. Figure 16 This facilitates water permeation and contaminant contact. This invention evaluates the effect of these materials on triiodide ions (I3). - Triiodide ions often form in environmental water bodies when iodide ions and iodine coexist. (Breakthrough curve) Figure 13 The BP-OH-COF-Iodine membrane exhibited excellent triiodine ion retention capacity, with permeation occurring after approximately 550 mL, while the Nap-OH-COF-Iodine membrane showed permeation after approximately 800 mL. UV-Vis absorption spectra ( Figure 13 (h) and Figure 13(i) confirms that the triiodide ion concentration gradually increases with increasing solution volume (peaking at 287 nm and 351 nm). These results indicate that the material of this invention is suitable not only for batch adsorption but also for continuous flow applications in water treatment processes. This combination of high capacity, rapid kinetics, excellent selectivity, and robust performance in complex matrices makes iodine-based iCOF materials one of the most promising candidates for practical iodide ion remediation. Its superior selectivity stems from specific affinity sites created by the polyiodide chains, which preferentially bind to iodide ions through halogen bonding and charge transfer interactions, forming a self-amplified capture system similar to the bio-iodine concentration mechanism in algae. Hydroxyl-functionalized variants further enhance selectivity by providing additional hydrogen bonding interactions that stabilize growing polyiodide species.

[0156] To elucidate the microscopic interaction between iCOF-Iodine, which exhibits superior iodine ion-trapping capabilities, and iodine ions, this invention employed spectroscopic studies combined with theoretical calculations. Raman spectra of Nap-OH-COF-Iodine and BP-OH-COF-Iodine were obtained. Figure 17 (a) and Figure 17 (b) shows 104-135cm -1 (belonging to I3) - (stretching vibration) and 151-175cm -1 (attributable to I) n - The characteristic peak at the stretching vibration (n≥3) confirms the presence of multiple polyiodides within the frame channels. XPS analysis of the 3d region ( Figure 17 (c) Figure 17 (d) and Figure 18 These findings were confirmed. These spectra can be deconvolved into three distinct chemical environments: a peak at approximately 619 eV (I5). - The peak at 630 eV (I3) - ), and 617.27-618.08 eV (I 3d 5 / 2 ) and 628.79-629.44eV (I 3d 3 / 2 The additional peak at () indicates the presence of extended polyiodides. The hydroxyl-functionalized framework exhibits a higher proportion of extended polyiodides, consistent with its superior adsorption properties.

[0157] Density functional theory (DFT) calculations Figure 17 The (e)-(h)) method reveals a thermodynamically favorable pathway for iodide ion capture, primarily through I -It is oxidized to I₂, and then combines with additional iodide ions to form an extended polyiodide chain. The hydroxyl-functionalized framework exhibits more favorable energy properties in both the oxidation and chain-forming steps. For Nap-OH-COF( Figure 17 (f)), I - The energy barrier for conversion to I2 (-0.291 eV) is significantly lower than that for Nap-COF (0.105 eV), while the subsequent formation of I3... - and I5 - It is also more energy-efficient. BP-OH-COF( Figure 17 (h) and BP-COF ( Figure 17 A similar trend was observed when comparing the N1s and O1s regions (g). XPS analysis of the N1s and O1s regions (g) Figure 17 The electronic interactions between the framework components and adsorbed polyiodide species were investigated in (i)-(l). N 1s spectra showed a significant shift in the binding energy of the C=N component after iodide ion adsorption (Nap-OH-COF from 399.87 eV to 399.23 eV), with a new peak at approximately 398.15 eV attributable to charge transfer interactions. Similar shifts were observed in all materials. Figure 19 ), and the hydroxyl-functionalized variants exhibit more pronounced changes. The O 1s spectrum also shows a binding energy shift after iodide ion adsorption (Nap-OH-COF-Iodine from 532.0 eV to 531.6 eV), indicating that the hydroxyl group is involved in stabilizing the polyiodide chain. Based on these studies, this invention provides a multi-step capture mechanism: (1) iodide ion (I - (1) Iodine molecules are oxidized to iodine molecules (I2) by residual iodine species within the framework, a process promoted by a cationic environment; (2) The formed iodine molecules combine with additional iodide ions to generate triiodide ions (I3). - (3) These further interactions form extended polyiodide chains (I5) that are stable within the framework channels. - I7 - (etc.). The hydroxyl group enhances this process by providing hydrogen bonding sites, increasing the hydrophilicity of the framework, and promoting charge transfer interactions with polyiodine species. This "iodine-to-iodine" mechanism is fundamentally different from traditional ion exchange. It achieves higher capture capacity through extended polyiodine chains, imparts inherent selectivity for iodide ions through specific iodine-iodine interactions, and gradually improves capture efficiency through thermodynamically favorable iodine species conversion.

[0158] It should be understood that although specific embodiments of the present invention have been shown and described in detail above, these embodiments are merely illustrative and should not be considered as limiting the scope of protection of the present invention. Those skilled in the art can make various adjustments, optimizations, equivalent substitutions, or improvements to the above embodiments without departing from the spirit and scope of the present invention.

Claims

1. A polyiodine chain-functionalized covalent organic framework material, characterized in that, The material is formed by treating a cationic covalent organic framework with hydrogen peroxide. The cationic covalent organic framework contains polyiodide chain structures within its channels, and these polyiodide chain structures include I3. - I5 - and I7 - Polyiodide anions; The cationic covalent organic framework is synthesized from 1,2,3-triaminoguanidine hydrochloride and aromatic dialdehyde via Schiff base condensation reaction; the aromatic dialdehyde is selected from at least one of naphthalene-2,6-dicarboxaldehyde, 2,6-dihydroxynaphthalene-1,5-dicarboxaldehyde, 4,4-biphenyldicarboxaldehyde, and 3,3'-dihydroxy-[1,1'-biphenyl]-4,4'-dicarboxaldehyde.

2. The polyiodine chain-functionalized covalent organic framework material according to claim 1, characterized in that: The aromatic dialdehyde is selected from at least one of 2,6-dihydroxynaphthalene-1,5-dicarboxaldehyde and 3,3'-dihydroxy-[1,1'-biphenyl]-4,4'-dicarboxaldehyde.

3. A method for preparing a polyiodine chain-functionalized covalent organic framework material, characterized in that, Includes the following steps: S1: 1,2,3-Triaminoguanidine hydrochloride and aromatic dialdehyde are mixed in a molar ratio of 1:(1.5-3), dissolved in a mixed solvent, and glacial acetic acid solution is added as a catalyst, and potassium iodide or sodium iodide at a concentration of ≥ 0.18 g / mL is added as a template reagent; the aromatic dialdehyde is selected from at least one of naphthalene-2,6-dicarboxaldehyde, 2,6-dihydroxynaphthalene-1,5-dicarboxaldehyde, 4,4-biphenyldicarboxaldehyde, and 3,3'-dihydroxy-[1,1'-biphenyl]-4,4'-dicarboxaldehyde; S2: React the mixture from step S1 in a closed reactor at 80-120°C for 24-72 hours. S3: Filter and collect the reaction product, wash it, and then soak it in a saturated ammonium bicarbonate solution at room temperature with stirring for 4-8 hours. Add isopropanol to the saturated ammonium bicarbonate solution and continue stirring for 0.5-2 hours. Filter to separate the solid product, and then dry it at 75-100℃ for 10-24 hours to obtain iCOF-I. - ; S4: iCOF-I - Disperse in an aqueous solution containing 5%-30% hydrogen peroxide and stir at room temperature for 6-12 hours; S5: Filter the treated product, wash it with DMF, then wash it with deionized water until neutral, then wash it with anhydrous ethanol, and finally dry it at 75-100℃ for 10-24 hours to obtain polyiodine chain functionalized covalent organic framework material.

4. The method for preparing a polyiodine chain-functionalized covalent organic framework material according to claim 3, characterized in that, The aromatic dialdehyde is selected from at least one of 2,6-dihydroxynaphthalene-1,5-dicarboxaldehyde and 3,3'-dihydroxy-[1,1'-biphenyl]-4,4'-dicarboxaldehyde.

5. The method for preparing a polyiodine chain-functionalized covalent organic framework material according to claim 4, characterized in that, The aromatic dialdehyde is selected from 2,6-dihydroxynaphthalene-1,5-dicarboxaldehyde.

6. The method for preparing a polyiodine chain-functionalized covalent organic framework material according to claim 3, characterized in that, The mixed solvent in step S1 is a mixture of 1,4-dioxane and mesitylene in a volume ratio of (1-2):1, or the mixed solvent is a mixture of o-dichlorobenzene and n-butanol in a volume ratio of (1-2):

1.

7. The method for preparing a polyiodine chain-functionalized covalent organic framework material according to claim 6, characterized in that, When the aromatic dialdehyde is selected as naphthalene-2,6-dicarboxaldehyde or 2,6-dihydroxynaphthalene-1,5-dicarboxaldehyde, the mixed solvent is a mixture of 1,4-dioxane and mesitylene in a volume ratio of (1-2):1; when the aromatic dialdehyde is selected as 4,4-biphenyldicarboxaldehyde or 3,3'-dihydroxy-[1,1'-biphenyl]-4,4'-dicarboxaldehyde, the mixed solvent is a mixture of o-dichlorobenzene and n-butanol in a volume ratio of (1-2):

1.

8. The method for preparing a polyiodine chain-functionalized covalent organic framework material according to claim 6, characterized in that, The concentration of the glacial acetic acid solution is 6-9 M, and the volume ratio of the glacial acetic acid solution to the mixed solvent is 1:(3-10).

9. The method for preparing a polyiodine chain-functionalized covalent organic framework material according to claim 8, characterized in that, When the aromatic dialdehyde is selected as naphthalene-2,6-dicarboxaldehyde or 2,6-dihydroxynaphthalene-1,5-dicarboxaldehyde, the mixed solvent is a mixture of 1,4-dioxane and mesitylene, the glacial acetic acid solution concentration is 6 M, and the volume ratio of 1,4-dioxane, mesitylene and 6 M glacial acetic acid solution is 6:3:

1. When the aromatic dialdehyde is selected as 4,4-biphenyldicarboxaldehyde or 3,3'-dihydroxy-[1,1'-biphenyl]-4,4'-dicarboxaldehyde, the mixed solvent is a mixture of o-dichlorobenzene and n-butanol, the glacial acetic acid solution has a concentration of 6 M, and the volume ratio of o-dichlorobenzene, n-butanol, and 6 M glacial acetic acid solution is 5:5:

1.

10. The method for preparing a polyiodine chain-functionalized covalent organic framework material according to claim 3, characterized in that, In step S3, the washing refers to washing the reaction product sequentially with N,N-dimethylformamide, deionized water, tetrahydrofuran, and dichloromethane.

11. The application of polyiodide chain-functionalized covalent organic framework materials for adsorbing iodide ions in water, characterized in that, The polyiodine chain-functionalized covalent organic framework material is the polyiodine chain-functionalized covalent organic framework material according to claim 1 or 2, or the polyiodine chain-functionalized covalent organic framework material prepared by the method according to any one of claims 3-10.

12. The application according to claim 11, characterized in that, The adsorption process employs either batch adsorption or continuous flow adsorption.

13. The application according to claim 12, characterized in that, The batch adsorption refers to the direct addition of the polyiodine chain-functionalized covalent organic framework material to an aqueous solution containing iodine ions, followed by adsorption with stirring at room temperature, and separation after adsorption is complete.

14. The application according to claim 12, characterized in that, The continuous flow adsorption refers to preparing a membrane from the polyiodine chain-functionalized covalent organic framework material, and then adsorbing an aqueous solution containing iodine ions through the membrane using a continuous flow system.

15. The application according to claim 14, characterized in that, The polyiodine chain-functionalized covalent organic framework material is used to prepare a membrane for a continuous flow iodine ion adsorption system. The membrane is prepared by suspending the polyiodine chain-functionalized covalent organic framework material powder in water to form a uniform suspension, filtering the suspension onto a nylon membrane substrate by vacuum filtration to form a uniform self-supporting membrane, and drying it to obtain a composite membrane. The flow rate of the continuous flow system is 0.5-5 mL / min.

16. The application according to claim 11, characterized in that, The water bodies include one of the following: iodine-containing wastewater, spiked tap water, salt lake brine, and seawater; And / or, after the iodine ions in the water body are adsorbed, the material is regenerated by hydrogen peroxide solution, and then washed with DMF, deionized water and anhydrous ethanol in sequence, and dried at 75°C for 8-24 hours to achieve the regeneration of the adsorbent.

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