A method for preparing flexible chain quaternary phosphonium salt ion single crystals under mild conditions and application in iodine capture

Abstract

The application discloses a method for preparing a flexible chain quaternary phosphonium salt ionic single crystal under mild conditions, which comprises the following steps: respectively dissolving quaternary phosphonium salt cation monomers and sulfonic acid group anion monomers in methanol or water, and then mixing the two to obtain the quaternary phosphonium salt ionic single crystal material within 12 hours. The obtained product is dried and ground to obtain a solid adsorbent for iodine capture. Considering that the single crystal contains rich heteroatom groups (P and sulfonic acid) and rich conjugated electrons (benzene ring), the material has the ability to capture iodine. This work expands the application of new materials in the field of iodine adsorption and fills the blank of ionic single crystals in the field of iodine adsorption. In addition, the preparation process is simple, the reaction condition is mild, the reaction time is short, the synthesis efficiency is high, and the method is favorable for large-scale popularization and application.

Description

TECHNICAL FIELD

[0001] The application relates to a method for preparing a flexible chain quaternary phosphonium salt ionic single crystal under mild conditions and belongs to the single crystal material field. BACKGROUND

[0002] Efficient capture of radioactive iodine is of great significance for the management of radioactive nuclear waste and the protection of human health. As the core of iodine capture, the structural characteristics of the adsorbent material directly determine the adsorption performance of iodine. At present, a variety of porous adsorbent materials such as metal organic frameworks (MOFs), covalent organic frameworks (COFs), hydrogen-bonded organic frameworks (HOFs), porous organic polymers (POPs) and porous organic cages (POCs) have been used for efficient adsorption of iodine, but some technical problems of these materials cannot be ignored. First, due to the relatively weak van der Waals force between iodine and the porous framework, these materials face challenges in long-term storage of iodine, and the introduction of electrostatic force makes the material and the adsorbate produce stronger electrostatic interaction. Second, the rigid cross-linked macromolecular framework makes the solubility of these materials poor, which further affects their processability in solution and limits the rapid release of iodine. These problems highlight the shortcomings of existing adsorbent materials in structural flexibility and function, so there is an urgent need to develop new materials to overcome these defects. Organic ionic single crystal materials allow the design and preparation of materials with a wide variety of structures and properties by adjusting functional groups, active adsorption sites and physicochemical properties based on the charge characteristics of ionic bonds in monomers and the designability of organic groups. In addition, the successful acquisition of single crystal materials enables us to directly observe the microstructure of the material, and thus accurately reveal the interaction sites between the material and the iodine molecules and the specific relationship of the interaction. This in-depth understanding helps us further clarify the mechanism, which has extremely important theoretical and practical significance for the research and application in key fields such as nuclear industry and environmental governance. SUMMARY

[0003] The purpose of the present application is to disclose a preparation method of a flexible chain quaternary phosphonium salt ionic single crystal, so as to realize simple, mild and rapid synthesis of ionic single crystal materials.

[0004] I. Preparation of a flexible chain quaternary phosphonium salt ionic single crystal

[0005] The preparation of the flexible chain quaternary phosphonium salt ionic single crystal in the present application is to dissolve the quaternary phosphonium salt monomer and the sulfonic acid monomer in their respective solvents, mix them, shake well, and then stand at room temperature for 10-15 h to obtain the single crystal material.

[0006] The flexible chain quaternary phosphonium salt is one of ethylene bis (triphenylphosphonium bromide) (PEBTBr2) and tetramethylene bis (triphenylphosphonium bromide) (PBBTBr2), and the sulfonic acid monomer is one of 1,5-naphthalene disulfonic acid (NDSA), 1,3,6,8-pyrene tetrasulfonic acid tetrasodium salt (PTSS), and 4,4'-biphenyl disulfonic acid (BDSA).

[0007] The molar ratio of the quaternary phosphonium salt monomer and the sulfonic acid monomer is 1:1 to 2:1.

[0008] The solvent of the quaternary phosphonium salt monomer is methanol, the solvent of the sulfonic acid monomer is water, and the volume ratio of methanol and water is 1:3 to 3:1.

[0009] The synthesis mechanism of the application is as follows:

[0010] Based on the principle of anion-cation self-assembly, by designing and selecting multiple anion and cation monomers with different charge characteristics, under room temperature conditions, the anion and cation monomers form an ionic single crystal material with a highly ordered structure through a spontaneous and ordered ionic self-assembly process.

[0011] II. Characterization of flexible chain quaternary phosphonium salt ionic single crystal

[0012] 1. Crystal structure

[0013] Figure 1 The structure schematic diagrams of the four single crystals are shown in the table 1, PEBT-NDS belongs to triclinic system, point group, space group. As can be seen from Figure 1 a, NDS has four arrangement modes in the crystal, and PEBT has four arrangement modes and presents two-to-two center symmetry; PEBT-PTS belongs to monoclinic system, 2 / m point group, P21 / n space group, and PTS and PEBT present two-to-two center symmetric structure ( Figure 1 b). PBBT-PTS is the same as PEBT-PTS, which presents the same unit cell structure and arrangement mode ( Figure 1 c); PBBT-BDS also belongs to triclinic system, point group, space group, BDS and PBBT each present two center symmetric structures ( Figure 1 d). In addition, the anion and cation of the four single crystals each present a lamellar structure.

[0014] Table 1 Crystal lattice data of four single crystals prepared in examples 1-4

[0015]

[0016] 2. Optical microscope

[0017] As Figure 2 (a-d) are the images of the four single crystals under optical microscope, from which it can be seen that the shapes of the four single crystals are all regular. Among them, PEBT-NDS is a rhombus with diagonal of 2495.6 μm and 966.8 μm; PEBT-PTS is a square with side length of about 1282.4 μm; PBBT-PTS is a hexagonal crystal with length of 2099.2 μm and width of 1492.0 μm; and PBBT-BDS presents a rod-like structure with length of about 1718.0 μm.

[0018] 3. X-ray diffraction (PXRD)

[0019] The crystallinity of the four materials was studied by PXRD analysis. As Figure 3 (a-d) shows, the results of XRD of the four single crystal powders are in good agreement with the simulated PXRD results given by the single crystal structure, indicating that the four single crystals all have high crystallinity and phase purity.

[0020] 4. Specific surface area analysis (BET)

[0021] As Figure 4 (a-d) shows, according to the CO2 adsorption-desorption test, the micropore surface areas of the four materials calculated are PEBT-NDS 16.041 m 2 / g, PEBT-PTS 10.179 m 2 / g, PBBT-PTS 15.682 m 2 / g, and PBBT-BDS 26.951 m 2 / g, respectively. The small specific surface areas indicate that the four single crystals all have relatively dense structures. From the isothermal adsorption curves, it can be seen that the adsorption curves of PEBT-NDS, PEBT-PTS and PBBT-PTS are similar, at low relative pressure, the adsorption amount increases sharply, which belongs to monolayer adsorption, i.e. chemical adsorption, and gradually changes into multilayer adsorption, i.e. physical adsorption process with the increase of pressure. While the adsorption amount of PBBT-BDS only increases slightly at low pressure, i.e. chemical adsorption process, and gradually increases with the increase of pressure.

[0022] 5. Thermogravimetric analysis (TGA)

[0023] The thermal stability of a compound is one of the important properties of the compound, especially for an organic-inorganic hybrid compound formed by supramolecular interaction, the strength of the interaction between the components has a great influence on the thermal stability. From Figure 5(a-d) It can be seen that the heat resistance of the four single crystals is good, all above 299 ℃, which lays a foundation for the iodine adsorption test in high temperature environment. In addition, the thermal weight loss starting temperature of the single crystal with PBBT as the monomer is about 100 ℃ higher than that of the single crystal with PEBT as the monomer, which shows that with the extension of the intermediate alkyl chain in the quaternary phosphonium salt monomer, the heat resistance of the material is improved.

[0024] III. Application of quaternary phosphonium salt ionic single crystal in iodine adsorption

[0025] The iodine capture performance of the quaternary phosphonium salt ionic single crystal materials prepared in Examples 1-4 of the present application in iodine-cyclohexane solution and iodine vapor was evaluated.

[0026] 1. Evaluation of iodine adsorption performance in iodine-cyclohexane

[0027] In order to evaluate the adsorption performance of the material to the iodine solution, the adsorption capacity was investigated by taking cyclohexane as the solvent of iodine. The concentration of all iodine-cyclohexane solutions was tested by UV-Vis, and the absorbance of the solution at 525 nm was taken as the standard for quantification. The corresponding relationship between absorbance and concentration was obtained by testing the absorbance corresponding to different concentrations (0, 0.39, 0.78, 1.56, 3.13, 6.25, 12.5, 25, 50 ppm) of samples, so as to quantify the unknown samples, and the standard curve is as shown in Figure 6 Figure 7 ​The adsorption of iodine in different concentrations of iodine-cyclohexane solution on four single crystal materials is shown in the figure. In order to study the effect of the concentration of iodine-cyclohexane solution on the adsorption of iodine, the adsorption experiments of cyclohexane solution with initial concentrations of 25 ppm and 50 ppm were carried out respectively. The four materials show similar properties, and the adsorption of iodine in cyclohexane solution is fast within 12 h. After more than 12 h, the adsorption rate slows down with the decrease of the remaining active sites, and the adsorption equilibrium is reached around 80 h, and the adsorption capacity remains basically unchanged thereafter. The equilibrium adsorption capacity of PEBT-NDS, PEBT-PTS, PBBT-PTS and PBBT-BDS for iodine in cyclohexane solution is 22.9 mg / g (25 ppm) and 31.5 mg / g (50 ppm), 27.5 mg / g (25 ppm) and 34.4 mg / g (50 ppm), 23.5 mg / g (25 ppm) and 32.1 mg / g (50 ppm), and 23.5 mg / g (25 ppm) and 38.4 mg / g (50 ppm) respectively. Experimental data show that the adsorption of iodine in cyclohexane solution on four single crystals increases with the increase of initial concentration, which is due to the increase of mass transfer driving force, so that the adsorption capacity can be significantly increased in high concentration solution. In order to further evaluate the adsorption kinetics of iodine on the material, the experimental data were fitted by pseudo-first-order and pseudo-second-order kinetic models. The results show that the fitting degree of the four materials to the two kinetic models is very similar, indicating that the adsorption process is a mixed mechanism of physical and chemical. The fitting degree of pseudo-second-order kinetic model is slightly higher than that of pseudo-first-order kinetic model, so the chemical adsorption plays a dominant role in the adsorption process.

[0028] 2. Evaluation of iodine adsorption performance in iodine vapor

[0029] In order to evaluate the adsorption capacity of the four invented materials for iodine vapor, the four materials were placed in 4 mL vials and exposed to iodine vapor at 70°C. With the increase of time, the color of the sample gradually deepened from white or light yellow to black, indicating that iodine molecules diffused into the sample. As shown in the figure, the color of the sample gradually deepened from white or light yellow to black, indicating that iodine molecules diffused into the sample. As shown in the figure, Figure 8The adsorption amount-time change graph of four single crystals is shown, and the four single crystals reach adsorption equilibrium within 145h (PEBT-NDS), 24h (PEBT-PTS), 60h (PBBT-PTS) and 36h (PBBT-BDS) respectively, and the maximum adsorption amounts are 1620, 1410, 1190 and 590mg / g respectively. In combination with the BET data, although PBBT-BDS has the largest specific surface area, the adsorption effect is not as good as that of the other three single crystals, which may be because the adsorption effect of the material is not only related to the specific surface area of the material, but also related to the orientation of the active sites of the functional groups in the pore. In addition, the adsorption process of the four adsorbents is subjected to adsorption kinetics fitting, and from the data, the fitting degrees of the pseudo-first-order and pseudo-second-order kinetics of the four materials are very similar, so it belongs to a physical and chemical mixed adsorption process.

[0030] In summary, the present application has the following advantages over the prior art:

[0031] 1. The present application relies on ionic action to self-assemble two kinds of quaternary phosphonium salt cations and three kinds of sulfonic acid (salt) anions, which is different from the direction-fixed covalent bond and coordination bond. The flexibility of electrostatic force can bring the possibility of multiple structures to the system, and the existence of single crystals makes the structure composition of the material visualized. In addition, quaternary phosphonium salt has not been used in the field of ionic self-assembly as an ionic liquid, so the quaternary phosphonium salt ionic single crystal material proposed in the present application fills the gap in this field.

[0032] 2. The quaternary phosphonium salt ionic single crystal material prepared by the present application has mild preparation process conditions, simple process flow and short required time, and has the feasibility of large-scale production. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 The crystal structure diagrams of the four single crystals prepared in Examples 1-4 of the present application are: (a) PEBT-NDS, (b) PEBT-PTS, (c) PBBT-PTS, (d) PBBT-BDS.

[0034] Figure 2 The optical microscope photos of the four single crystals prepared in Examples 1-4 of the present application are: (a) PEBT-NDS, (b) PEBT-PTS, (c) PBBT-PTS, (d) PBBT-BDS.

[0035] Figure 3 The PXRD characterization diagrams of the four single crystals prepared in Examples 1-4 of the present application are: (a) PEBT-NDS, (b) PEBT-PTS, (c) PBBT-PTS, (d) PBBT-BDS.

[0036] Figure 4BET characterization plots of four single crystals prepared in Examples 1-4 of the present application: (a) PEBT-NDS, (b) PEBT-PTS, (c) PBBT-PTS, (d) PBBT-BDS.

[0037] Figure 5 TGA characterization plots of four single crystals prepared in Examples 1-4 of the present application: (a) PEBT-NDS, (b) PEBT-PTS, (c) PBBT-PTS, (d) PBBT-BDS.

[0038] Figure 6 Standard curves for the adsorption of four single crystals prepared in Examples 1-4 of the present application in iodine-cyclohexane at different concentrations.

[0039] Figure 7 Kinetic fitting curves of four single crystals prepared in Examples 1-4 of the present application in iodine-cyclohexane at different concentrations: (a) PEBT-NDS, (b) PEBT-PTS, (c) PBBT-PTS, (d) PBBT-BDS.

[0040] Figure 8 Kinetic fitting curves of four single crystals prepared in Examples 1-4 of the present application in iodine vapor: (a) PEBT-NDS, (b) PEBT-PTS, (c) PBBT-PTS, (d) PBBT-BDS. DETAILED DESCRIPTION

[0041] The method for preparing flexible chain quaternary phosphonium salt ion single crystals under mild conditions and the application thereof in the study of iodine adsorption will be further described below through specific examples. The examples are only used to illustrate the present application, and are not intended to limit the present application.

[0042] Example 1

[0043] 0.0356 g of PEBTBr2 was weighed and dissolved in a mixed solution of 0.9 mL of methanol and 0.1 mL of water, and 0.0144 g of NDSA was dissolved in 1 mL of water. The mixture was placed in a 25 °C oven for 12 h to obtain PEPT-NDS. After the PEPT-NDS was taken out, it was washed with ultrapure water for 3 times and centrifuged, and then dried in a 45 °C oven and ground into powder with a mortar.

[0044] 10 mg of iodine was weighed and dissolved in 10 mL of cyclohexane to obtain a 1000 ppm iodine-cyclohexane solution; 1 mL of the 1000 ppm iodine-cyclohexane solution was taken and diluted with 19 mL of cyclohexane to obtain a 50 ppm iodine-cyclohexane solution; 4 mL of the 50 ppm iodine-cyclohexane solution was taken and diluted with 4 mL of cyclohexane to obtain a 25 ppm iodine-cyclohexane solution.

[0045] Take 4 mg PEPT-NDS, add 8 mL of 25 ppm and 50 ppm iodine-cyclohexane solution respectively, stand at room temperature of 25 ℃, test the absorbance of iodine-cyclohexane solution at 0, 3, 6, 12, 24, 36, 60, 84, 108 h by UV-Vis, take the absorbance value at 525 nm as the quantitative standard, bring into the standard curve, and calculate the adsorption amount of iodine. As shown in Figure 7 a, the adsorption reaches equilibrium at 84 h and no longer increases, and the adsorption amount is 22.9 mg / g (25 ppm) and 31.5 mg / g (50 ppm). In addition, the data can be used to calculate the kinetic model of the adsorption process, which shows that the pseudo-first-order and pseudo-second-order kinetics of the adsorption process are very similar, so it belongs to a physical-chemical mixed adsorption process. And the fitting degree of the pseudo-second-order kinetic model is slightly higher than that of the pseudo-first-order kinetic model, so the chemical adsorption dominates the adsorption process.

[0046] Take 10 mg PEPT-NDS powder and place it in a 4 mL sample bottle, record the total weight of the adsorbent and sample bottle as the initial weight, place the 4 mL sample bottle in a 20 mL sample bottle containing 0.1 g of iodine element in a 70 ℃ oven for adsorption, and weigh the total weight of the adsorbent and sample bottle at 0, 0.167, 0.5, 1, 2, 4, 7, 13, 25, 37, 49, 61, 73, 85, 97, 109, 121, 133, 145, 157 h, calculate the adsorption amount of iodine, and thus obtain the adsorption amount of PEPT-NDS to iodine with time, as shown in Figure 8 a. As can be seen from the figure, the material reaches adsorption equilibrium at 145 h, and the adsorption amount of iodine is 1620 mg / g. In addition, the fitting of the kinetic model shows that the pseudo-first-order and pseudo-second-order kinetics of the adsorption process are very similar, so the adsorption in the gas iodine also belongs to a physical-chemical mixed adsorption process.

[0047] Example 2

[0048] Take 0.0356 g PEBTBr2 and dissolve it in 2 mL of methanol, take 0.0152 g PTSS and dissolve it in 1.2 mL of water, then add 0.8 mL of methanol, and stand in a 25 ℃ oven for 12 h to obtain PEPT-PTS.

[0049] Take 10 mg of iodine element, dissolve in 10 mL of cyclohexane to obtain a 1000 ppm iodine-cyclohexane solution; take 1 mL of 1000 ppm iodine-cyclohexane solution and dilute with 19 mL of cyclohexane to obtain a 50 ppm iodine-cyclohexane solution; take 4 mL of 50 ppm iodine-cyclohexane solution and dilute with 4 mL of cyclohexane to obtain a 25 ppm iodine-cyclohexane solution.

[0050] Take 4 mg of PEPT-PTS and add to 8 mL of 25 ppm and 50 ppm iodine-cyclohexane solutions respectively, and stand at room temperature of 25°C, and test the absorbance of the iodine-cyclohexane solution at 0, 3, 6, 12, 24, 36, 60, 84, 108 h with UV-Vis, and take the absorbance value at 525 nm as the quantitative standard, and input into the standard curve to calculate the adsorption amount of iodine by the material. As shown in Figure 7 b, the adsorption reaches equilibrium at 24 h and no longer increases, and the adsorption amount is 27.5 mg / g (25 ppm) and 34.4 mg / g (50 ppm). In addition, the data can be used to calculate the kinetic model of the adsorption process, and the model shows that the fitting degrees of the first-order and second-order kinetics of the adsorption process are very similar, so it belongs to a physical-chemical mixed adsorption process. And the fitting degree of the pseudo-second-order kinetic model is slightly higher than that of the pseudo-first-order kinetic model, so the chemical adsorption action dominates the adsorption process.

[0051] Take 10 mg of PEPT-PTS powder and place it in a 4 mL sample bottle, record the total weight of the adsorbent and sample bottle as the initial weight, place the 4 mL sample bottle in a 20 mL sample bottle containing 0.1 g of iodine element in a 70°C oven for adsorption, and weigh the total weight of the adsorbent and sample bottle at 0, 0.5, 1.5, 3, 6, 12, 24, 36, 48, 60 h, and calculate the adsorption amount of iodine to obtain the change curve of the adsorption amount of iodine by PEPT-PTS with time, as shown in Figure 8 b. As can be seen from the figure, the material reaches adsorption equilibrium at 24 h, and the adsorption amount of iodine is 1430 mg / g. In addition, the fitting of the kinetic model shows that the fitting degrees of the first-order and second-order kinetics of the adsorption process are very similar, so the adsorption in the gas iodine also belongs to a physical-chemical mixed adsorption process.

[0052] Example 3

[0053] Take 0.0370 g of PBBTBr2 and dissolve in 2 mL of methanol, take 0.0152 g of PTSS and dissolve in 1 mL of methanol, and mix with 1 mL of methanol to obtain a mixed solution, and stand in a 25°C oven for 12 h to obtain PEPT-PTS.

[0054] Take 10 mg of iodine element, dissolve in 10 mL of cyclohexane to obtain a 1000 ppm iodine-cyclohexane solution; take 1 mL of 1000 ppm iodine-cyclohexane solution and dilute with 19 mL of cyclohexane to obtain a 50 ppm iodine-cyclohexane solution; take 4 mL of 50 ppm iodine-cyclohexane solution and dilute with 4 mL of cyclohexane to obtain a 25 ppm iodine-cyclohexane solution.

[0055] Take 4 mg of PBBT-PTS and add to 8 mL of 25 ppm and 50 ppm iodine-cyclohexane solution respectively, and stand at room temperature of 20 °C, and test the absorbance of the iodine-cyclohexane solution at 0, 3, 6, 12, 24, 36, 60, 84, 108 h with UV-Vis, and take the absorbance value at 525 nm as the quantitative standard, and input into the standard curve to calculate the adsorption amount of iodine by the material. As shown in Figure 7 c, the adsorption reaches equilibrium at 84 h and no longer increases, and the adsorption amount is 23.5 mg / g (25 ppm) and 32.1 mg / g (50 ppm). In addition, the data can be used to calculate the kinetic model of the adsorption process, which shows that the fitting degrees of the first-order and second-order kinetics of the adsorption process are very similar, so it belongs to a physical-chemical mixed adsorption process. And the fitting degree of the pseudo-second-order kinetics model is slightly higher than that of the pseudo-first-order kinetics model, so the chemical adsorption dominates the adsorption process.

[0056] Take 10 mg of PBBT-PTS powder and place it in a 4 mL sample bottle, record the total weight of the adsorbent and sample bottle as the initial weight, place the 4 mL sample bottle in a 20 mL sample bottle containing 0.1 g of iodine element in a 70 °C oven for adsorption, and weigh the total weight of the adsorbent and sample bottle at 0, 0.5, 1.5, 3.5, 12, 36, 60, 84, 108 h, and calculate the adsorption amount of iodine to obtain the adsorption amount of iodine by PBBT-PTS with time, as shown in Figure 8 c. As can be seen from the figure, the material reaches adsorption equilibrium at 60 h, and the adsorption amount of iodine is 1190 mg / g. In addition, the fitting of the kinetic model shows that the fitting degrees of the first-order and second-order kinetics of the adsorption process are very similar, so the adsorption in the gas iodine also belongs to a physical-chemical mixed adsorption process.

[0057] Example 4

[0058] Take 0.0370 g of PBBTBr2 and dissolve it in a mixture of 1 mL of methanol and 1 mL of water, and take 0.0158 g of BDSS and dissolve it in 1.2 mL of water and then add 0.8 mL of methanol, and stand in a 25 °C oven for 12 h to obtain PEPT-PTS.

[0059] Take 10 mg of iodine element, dissolve in 10 mL of cyclohexane to obtain 1000 ppm iodine-cyclohexane solution; take 1 mL of 1000 ppm iodine-cyclohexane solution and dilute with 19 mL of cyclohexane to obtain 50 ppm iodine-cyclohexane solution; take 4 mL of 50 ppm iodine-cyclohexane solution and dilute with 4 mL of cyclohexane to obtain 25 ppm iodine-cyclohexane solution.

[0060] Take 4 mg of PBBT-BDS and add to 8 mL of 25 ppm and 50 ppm iodine-cyclohexane solution respectively, and stand at room temperature of 20 °C, and measure the absorbance of iodine-cyclohexane solution at 0, 3, 6, 12, 24, 36, 60, 84, 108 h by UV-Vis, and take the absorbance value at 525 nm as the quantitative standard, and input into the standard curve to calculate the adsorption amount of iodine. As shown in Figure 7 d, the adsorption reaches equilibrium at 84 h and no longer increases, and the adsorption amount is 23.5 mg / g (25 ppm) and 38.4 mg / g (50 ppm). In addition, the data can be used to calculate the kinetic model of the adsorption process, and the model shows that the first-order and second-order kinetics fitting degrees of the adsorption process are very similar, so it belongs to a physical-chemical mixed adsorption process. And the fitting degree of the pseudo-second-order kinetic model is slightly higher than that of the pseudo-first-order kinetic model, so the chemical adsorption action dominates the adsorption process.

[0061] Take 10 mg of PBBT-BDS powder and place it in a 4 mL sample bottle, record the total weight of the adsorbent and sample bottle as the initial weight, place the 4 mL sample bottle in a 20 mL sample bottle containing 0.1 g of iodine element and adsorb in a 70 °C oven, and weigh the total weight of the adsorbent and sample bottle at 0, 0.5, 1.5, 3.5, 6.5, 12, 24, 36, 48, 72, 96 h, and calculate the adsorption amount of iodine to obtain the change curve of the adsorption amount of PBBT-BDS to iodine with time, as shown in Figure 8 d. As can be seen from the figure, the material reaches adsorption equilibrium at 36 h, and the adsorption amount of iodine is 590 mg / g. In addition, the fitting of the kinetic model shows that the first-order and second-order kinetics fitting degrees of the adsorption process are very similar, so the adsorption in the gas iodine also belongs to a physical-chemical mixed adsorption process.

Claims

1. A method for preparing flexible chain quaternary phosphonium salt ionic single crystals under mild conditions, characterized by, The quaternary phosphonium salt monomer and the sulfonic acid monomer are weighed and dissolved in respective solvents, mixed, shaken up, and left to stand at room temperature for 10-15 hours to obtain the flexible chain quaternary phosphonium salt ionic single crystal material; The structure of the quaternary phosphonium salt monomer is: ， wherein n is one of 2 or 4; The structure of the sulfonic acid monomer is one of the following three: , or .

2. The method for preparing flexible chain quaternary phosphonium salt ion single crystals under mild conditions as described in claim 1, characterized in that, The molar ratio of the quaternary phosphonium salt monomer to the sulfonic acid monomer is 1:1-2:

1.

3. The method of claim 1, wherein the flexible chain quaternary phosphonium salt is prepared under mild conditions. The solvent of the quaternary phosphonium salt monomer is methanol, and the solvent of the sulfonic acid monomer is water, and the volume ratio of methanol to water is 1:3-3:

1.

4. The flexible chain quaternary phosphonium salt ionic single crystal prepared by the method of claim 1 is used for adsorption of iodine in iodine-cyclohexane and iodine vapor.

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