Multifunctional site porous aromatic framework adsorbent for adsorbing trace iodine and preparation method thereof

Abstract

The invention discloses a multifunctional site porous aromatic framework adsorbent for adsorbing trace iodine, and the adsorbent is synthesized by carrying out copolymerization reaction on 3-(2, 5-dibromobenzyl)-1-methyl-1H-imidazole-3-ammonium salt and 2, 4, 6-tri (4-acetylene phenyl)-1, 3, 5-triazine. According to the multifunctional-site porous aromatic framework adsorbent iPAF-TEPT provided by the invention, multifunctional sites with a synergistic effect are adopted, and charge transfer and coulomb interaction are combined, so that iodine pollutants in various forms are efficiently recovered. Especially in an environment with extremely low concentration of iodide ions (such as 100ppb), the adsorbent still shows excellent iodine removal capability. Based on the excellent performance, the adsorbent disclosed by the invention is expected to become a preferred material for treating various iodine pollutants in water, and can realize efficient adsorption through a single frame.

Description

Technical Field

[0001] The invention relates to the field of new material applications, and in particular to a multifunctional site porous aromatic framework adsorbent for adsorbing trace iodine and a preparation method thereof. Background Art

[0002] Iodine is an important and scarce resource, widely used in many fields such as medicine, industry, agriculture and food. With the continuous development of the global economy, the demand for iodine is increasing. Although seawater is rich in iodine resources, the existing iodine recovery technology still has many shortcomings and cannot fully meet the growing demand. Therefore, it is necessary to develop new and efficient recovery processes to meet this challenge. In addition, the problem of iodine pollution is particularly serious in many fields, especially in chemical industrial wastewater, ore leakage, disinfectant use, etc. The release of iodine often leads to water pollution and threatens the ecological environment and human health. Effectively recovering iodine resources in the environment not only helps to reduce pollution, but also can meet the continued growth of the growing demand for iodine resources, which has important social and environmental significance.

[0003] In view of the above problems, designing efficient iodine capture materials has become the key to solving the problems of iodine pollution and recovery. By optimizing the structure and functional design of the adsorbent, combined with the charge transfer effect and the construction of high affinity sites, the iodine capture efficiency can be significantly improved. For example, aromatic networks (such as triazines, pyridines and amines) and cationic functional groups doped with heteroatoms or heterocycles have been proven to effectively improve the affinity of materials for iodine molecules and iodide ions, thereby improving the capture efficiency. However, existing adsorbents such as metal organic frameworks (MOFs), covalent organic frameworks (COFs), hydrogen bonded organic frameworks (HOFs) and porous organic polymers (POPs) are more effective in capturing high-concentration iodine pollutants, but their effects are poor in low-concentration environments. In practical applications, the iodine concentration in chemical industrial wastewater, contaminated seawater and groundwater is usually less than 10 ppm, and the capture effect of existing materials in these low-concentration environments is limited.

[0004] Iodine exists in water as molecular iodine (I2), triiodide ion (I3 - ) and iodide ion (I - ) and other forms, the ratio of which is affected by pH and redox potential, making it difficult for existing adsorbents to effectively capture different types of iodine species at the same time. In addition, competitive anions and extreme pH values ​​increase the complexity of operation, which in turn limits the stability and effectiveness of existing materials. Therefore, it is necessary to develop a multifunctional site porous aromatic framework adsorbent for adsorbing trace iodine and a preparation method thereof. Summary of the invention

[0005] In view of this, the present invention provides a multifunctional site porous aromatic framework adsorbent for adsorbing trace iodine, which solves the problem that the existing iodine adsorbent has limited capture effect at low concentrations.

[0006] In one aspect, the present invention uses a multifunctional site porous aromatic framework adsorbent for adsorbing trace iodine, characterized in that the adsorbent is obtained by copolymerization of 3-(2,5-dibromobenzyl)-1-methyl-1H-imidazole-3-ammonium salt and 2,4,6-tris(4-ethynylphenyl)-1,3,5-triazine. Preferably, the amount of 3-(2,5-dibromobenzyl)-1-methyl-1H-imidazole-3-ammonium salt is 3 mmol, and the amount of 2,4,6-tris(4-ethynylphenyl)-1,3,5-triazine is 2 mmol.

[0007] On the other hand, the present invention adopts a preparation method of a multifunctional site porous aromatic framework adsorbent for adsorbing trace iodine, comprising the following steps: weighing 3-(2,5-dibromobenzyl)-1-methyl-1H-imidazole-3-ammonium salt, 2,4,6-tris(4-ethynylphenyl)-1,3,5-triazine, Pd[P(C6H5)3]4 and CuI and adding them into a reaction bottle; slowly adding a mixed solvent of N,N-dimethylformamide and triethylamine, and performing ultrasonic dispersion treatment; stirring and heating the reaction under nitrogen protection; after the reaction is completed, cooling to room temperature, filtering to obtain a crude product; and finally purifying and drying to obtain the porous aromatic framework adsorbent.

[0008] Preferably, the heating reaction condition is specifically 120° C. and stirring for 48 hours.

[0009] Preferably, the purification is performed by washing with hydrochloric acid, methanol, dichloromethane and ethanol in sequence.

[0010] Preferably, the volume ratio of N,N-dimethylformamide to triethylamine is 1:1.

[0011] The multifunctional site porous aromatic framework adsorbent iPAF-TEPT provided by the present invention for adsorbing trace iodine can efficiently recover various forms of iodine pollutants (I2, I - and I3 - ).

[0012] Furthermore, iPAF-TEPT has an important role in the regulation of I2, I3 - and I - The equilibrium adsorption capacities of I2 and I3 were 15.59, 14.68 and 0.22 g·g-1, respectively. - The adsorption capacity in aqueous solution exceeds that of most other adsorbents reported so far.

[0013] Furthermore, iPAF-TEPT was found to be highly active in complex aqueous environments (e.g., solutions with a pH range of 1 to 9, or solutions containing 1000 times more competing ions, such as Cl - Br - 、NO3 - 、CO3 2- 、SO4 2- 、CH3COO - etc.) can still maintain an iodine pollutant removal efficiency of over 97%, showing excellent stability and adaptability.

[0014] Furthermore, iPAF-TEPT still exhibits excellent removal ability at extremely low concentrations (such as 100 ppb), and is able to remove I2, I - and I3 - The residual concentrations of were all reduced to below 10 ppb, showing its great potential in removing trace iodine pollution.

[0015] The multifunctional site-based porous aromatic framework adsorbent (iPAF-TEPT) provided by the present invention can efficiently remove various iodine pollutants in water by virtue of its excellent adsorption performance and wide applicability, and can still maintain excellent removal efficiency in low concentrations and complex water environments. Therefore, the adsorbent of the present invention is expected to become the first single framework adsorbent that can efficiently treat various forms of iodine pollutants in water. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Schematic diagrams of preparing porous aromatic framework adsorbents of Example 1 and Comparative Example 1 respectively;

[0017] Figure 2 This is the infrared spectrum of the porous aromatic framework adsorbent iPAF-TEPT of Example 1;

[0018] Figure 3 This is a scanning electron microscope image of the porous aromatic framework adsorbent iPAF-TEPT of Example 1;

[0019] Figure 4 The adsorption capacity of the porous aromatic framework adsorbent iPAF-TEPT and the porous aromatic framework adsorbent PAF-TEPT in three different iodine aqueous solutions of Example 1;

[0020] Figure 5 The adsorption capacity of the porous aromatic framework adsorbent iPAF-TEPT of Example 1 on three iodine aqueous solutions under different pH conditions;

[0021] Figure 6 The porous aromatic framework adsorbent iPAF-TEPT of Example 1 was prepared in the presence of 1000 times the competitive ion (Cl - Br -、NO3 - 、CO3 2- 、SO4 2- 、CH3COO - ) environment for the adsorption capacity of three iodine aqueous solutions;

[0022] Figure 7 The porous aromatic framework adsorbent iPAF-TEPT of Example 1 contains 10 times more competitive ions (Cl - Br - 、NO3 - 、SO4 2- )The adsorption capacity of the mixture in iodine solution. DETAILED DESCRIPTION

[0023] The principles and features of the present invention are described below in conjunction with the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0024] 3-(2,5-Dibromobenzyl)-1-methyl-1H-imidazole-3-ammonium salt (i-DBB) was prepared according to the method disclosed in the literature (Angew. Chem. Int. Ed. 2022, 61, e202113682).

[0025] Embodiment 1: Figure 1 A method for preparing a multifunctional site porous aromatic framework adsorbent for adsorbing trace iodine comprises the following steps: weighing 3 mmol 3-(2,5-dibromobenzyl)-1-methyl-1H-imidazole-3-ammonium salt (i-DBB), 2 mmol 2,4,6-tris(4-ethynylphenyl)-1,3,5-triazine (TEPT), 0.12 mmol Pd[P(C6H5)3]4 and 0.12mmolCuI were added to a two-necked flask; 100mL of a mixed solvent of ultra-dry N,N-dimethylformamide and triethylamine (the volume ratio of N,N-dimethylformamide to triethylamine was 1:1) was slowly added, and ultrasonic dispersion treatment was performed; the air in the solution was removed by a cyclic freeze-thaw process; under nitrogen protection, the reaction system was heated to 120°C and stirred for 48 hours; after the reaction was completed, it was cooled to room temperature and filtered to obtain a crude product; the crude product was washed three times with 6M hydrochloric acid, methanol, dichloromethane and ethanol respectively; finally, the product was placed at 80°C and vacuum dried overnight to obtain a brown powdery porous aromatic framework adsorbent iPAF-TEPT.

[0026] (1) The porous aromatic framework adsorbent iPAF-TEPT was characterized by infrared spectroscopy, such as Figure 2 As shown in the infrared spectrum of iPAF-TEPT, the characteristic vibration of the CH bond of the TEPT terminal acetylenic group disappears, and the acetylenic bond shows a blue shift from 2107cm-1 to 2218 cm in iPAF-TEPT -1 and 2210 cm in PAF-TEPT -1 , indicating that the terminal alkynyl group is coupled with i-DBB to form a porous aromatic framework structure. In addition, all vibrations of the imidazole and triazine groups are retained, indicating that these functional groups remain unchanged during the synthesis process and still retain multiple potential binding functional sites.

[0027] (2) The porous aromatic framework adsorbent iPAF-TEPT was tested by scanning electron microscopy. The results are as follows Figure 3 As shown, the adsorbent is a porous aromatic framework with nano-sized spherical particles, which is beneficial for its practical application.

[0028] Comparative Example 1: Figure 1 The difference between Comparative Example 1 and Example 1 is that p-dibromobenzene (DBB) is used to replace 3-(2,5-dibromobenzyl)-1-methyl-1H-imidazole-3-ammonium salt (i-DBB) to obtain a porous aromatic framework adsorbent PAF-TEPT.

[0029] Example 2: The iodine adsorption capacity of the porous aromatic framework adsorbent iPAF-TEPT was studied, and the results are as follows:

[0030] (1) Study on the iodine adsorption capacity of porous aromatic framework adsorbents in aqueous solution

[0031] 5 mg of the prepared porous aromatic framework adsorbents iPAF-TEPT and PAF-TEPT were weighed and added to 500 mL of 1.2 mM I2 aqueous solution (or 0.4 mM I2 - Aqueous solution, or 0.4 mM I3 - ), stirred at room temperature, sampled and filtered at regular intervals, and the collected filtrate was subjected to UV spectroscopy analysis. Figure 4 As shown, iPAF-TEPT has an effect on I2, I3 - and I - The equilibrium adsorption capacities of I2 and I3 were 15.59, 14.68 and 0.22 g·g-1, respectively. - The adsorption capacity in aqueous solution exceeds that of other existing adsorbents including PAF-TEPT.

[0032] (2) Study on the iodine adsorption capacity of porous aromatic framework adsorbents in water environments with different pH values

[0033] Weigh 50 mg of the prepared porous aromatic framework adsorbent iPAF-TEPT, add 50 mL of 1.2 mM I2 aqueous solution (or 0.4 mM I -Aqueous solution, or 0.4 mM I3 - ), adjusting the solution pH to 1 to 9, stirring at room temperature and periodically sampling and filtering, collecting the filtrate and performing inductively coupled plasma mass spectrometry analysis. Figure 5 As shown, iPAF-TEPT can still maintain more than 97% iodine pollutant removal efficiency in complex water environments (such as pH values ​​ranging from 1 to 9).

[0034] (3) Study on the iodine adsorption capacity of porous aromatic framework adsorbents in an environment with excess competing ions

[0035] Weigh 50 mg of the prepared porous aromatic framework adsorbent iPAF-TEPT, add 50 mL of 1.2 mM I2 aqueous solution (or 0.4 mM I - Aqueous solution, or 0.4 mM I3 - ), 1000 times the concentration of competing ions (Cl - Br - 、NO3 - 、CO3 2- 、SO4 2- 、CH3COO - The mixture was stirred at room temperature, samples were taken and filtered at regular intervals, and the filtrate was collected and analyzed by inductively coupled plasma mass spectrometry. Figure 6 As shown, iPAF-TEPT can still maintain more than 92% iodine pollutant removal efficiency in a complex water environment, indicating that iPAF-TEPT has high selectivity for the adsorption of iodine pollutants.

[0036] (4) Study on the adsorption capacity of trace iodine in aqueous solution by porous aromatic framework adsorbent

[0037] Weigh 20 mg of the prepared porous aromatic framework adsorbent iPAF-TEPT and add it to 5 mL of 100 ppb containing 10 times the competitive ion (Cl - Br - 、NO3 - 、SO4 2- ) of I2 aqueous solution (or replaced by I - Aqueous solution, or replace with I3 - ); stirring at room temperature, sampling and filtering at regular intervals, and the collected filtrate was subjected to inductively coupled plasma mass spectrometry and ion chromatography analysis. The results are as follows Figure 7 As shown in Figure 2, iPAF-TEPT still exhibits excellent removal ability at extremely low concentrations (such as 100 ppb), and is able to remove I2, I - and I3 -The residual concentrations of iodine pollutants in water were reduced to less than 10 ppb. This adsorbent is expected to become the first single-frame adsorbent that can effectively treat multiple iodine pollutants in water.

[0038] (5) Comparison of different adsorbents in I2 or I3 - Adsorption capacity in aqueous solution

[0039] Under the same conditions, the iPAF-TEPT of Example 1 and the PAF-TEPT of Comparative Example 1 were compared to determine the effects of I2 or I3 on ​​the - The adsorption capacity of iPAF-TEPT was tested. As shown in the results of Table 1, compared with similar porous aromatic frameworks, the adsorbent iPAF-TEPT has a significant trace iodine adsorption capacity.

[0040] Table 1 Adsorption capacity of different adsorbents in iodine aqueous solution

[0041]

[0042] In summary, the present invention provides a multifunctional site porous aromatic framework adsorbent iPAF-TEPT for adsorbing trace iodine. The material adopts the synergistic effect of multifunctional sites, combines charge transfer and Coulomb interaction, and achieves the adsorption of various forms of iodine pollutants (I2, I - and I3 - ) is highly efficient in the recovery of I2 and I3. - and I - The equilibrium adsorption capacities of I2 and I3 were 15.59, 14.68 and 0.22 g·g-1, respectively. - The adsorption capacity of iPAF-TEPT in aqueous solution exceeds that of most other adsorbents reported so far. In addition, iPAF-TEPT has good adsorption performance in complex aqueous environments (such as solutions with a pH range of 1 to 9, or solutions containing 1000 times more competitive ions such as Cl - Br - 、NO3 - 、CO3 2- 、SO4 2- 、CH3COO - More importantly, iPAF-TEPT still exhibits excellent removal ability at extremely low concentrations (such as 100 ppb), and can remove I2, I - and I3 - The residual concentrations of iodine pollutants in water were reduced to less than 10 ppb. Therefore, the iPAF-TEPT adsorbent provided by the present invention is expected to become the first single-frame adsorbent that can efficiently treat multiple iodine pollutants in water.

[0043] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A multifunctional site porous aromatic framework adsorbent for adsorbing trace iodine, characterized in that: The adsorbent is obtained by copolymerizing 3-(2,5-dibromobenzyl)-1-methyl-1H-imidazole-3-ammonium salt and 2,4,6-tris(4-ethynylphenyl)-1,3,5-triazine.

2. A method for preparing a multifunctional site porous aromatic framework adsorbent for adsorbing trace iodine, characterized in that The following steps are involved: Weigh 3-(2,5-dibromobenzyl)-1-methyl-1H-imidazole-3-ammonium salt, 2,4,6-tri(4-ethynylphenyl)-1,3,5-triazine, Pd[P(C6H5)3]4 and CuI and add them into a reaction bottle; slowly add a mixed solvent of N,N-dimethylformamide and triethylamine for ultrasonic dispersion treatment; under nitrogen protection, stir and heat to react; after the reaction is completed, cool to room temperature and filter to obtain a crude product; finally, purify and dry to obtain a porous aromatic framework adsorbent.

3. The method for preparing a multifunctional site porous aromatic framework adsorbent for adsorbing trace iodine according to claim 2, characterized in that: The amount of 3-(2,5-dibromobenzyl)-1-methyl-1H-imidazole-3-ammonium salt used was 3 mmol, and the amount of 2,4,6-tris(4-ethynylphenyl)-1,3,5-triazine used was 2 mmol.

4. The method for preparing a multifunctional site porous aromatic framework adsorbent for adsorbing trace iodine according to claim 2, characterized in that: The heating reaction condition is 120° C. and stirring for 48 hours.

5. The method for preparing a multifunctional site porous aromatic framework adsorbent for adsorbing trace iodine according to claim 2, characterized in that: The purification step comprises washing with hydrochloric acid, methanol, dichloromethane and ethanol in sequence.

6. The method for preparing a multifunctional site porous aromatic framework adsorbent for adsorbing trace iodine according to claim 2, characterized in that: The volume ratio of the N,N-dimethylformamide to triethylamine is 1:1.

Images