Ionic liquid modified MOF-808 for adsorbing radioactive iodine as well as preparation method and application of ionic liquid modified MOF-808

Abstract

The invention relates to the technical field of environmental protection, and discloses ionic liquid modified MOF-808 for adsorbing radioactive iodine as well as a preparation method and application of the ionic liquid modified MOF-808. The ionic liquid is loaded into pores of the MOF-808 by using an in-situ impregnation method to obtain the ionic liquid modified MOF-808 for adsorbing radioactive iodine, and the ionic liquid modified MOF-808 is expressed as X-IL (at) MOF. The MOF-808 has excellent removal performance on radioactive iodine, which is benefited from the excellent pore structure of the MOF-808 and abundant heteroatom adsorption sites of IL. After hydrophobic IL modification, the IL (at) MOF also shows good adsorption performance in a high-humidity environment.

Description

Technical Field

[0001] The present invention relates to the technical field of environmental protection, and particularly to an ionic liquid modified MOF-808 for adsorbing radioactive iodine, a preparation method and an application thereof. Background Art

[0002] As an efficient and clean energy form, nuclear energy is widely used to alleviate energy shortages. However, the radionuclides released from nuclear waste and nuclear leakage accidents pose potential environmental risks. Among them, radioactive iodine vapor (I2) is emitted during the exhaust gas of nuclear power plants and the nuclear fuel reprocessing process. Radioactive iodine ( 129 I) has a half-life of about 15.7 million years and is easily ingested into the human body through the food chain, posing a health risk. Therefore, there is an urgent need to design efficient environmentally friendly functional adsorbent materials to capture I2.

[0003] So far, the adsorption method has been widely used for the removal of radioactive iodine due to its high efficiency, selectivity, ease of operation, environmental friendliness and economy. Among many adsorbent materials, functional materials such as activated carbon, zeolite, aerogel, polymer compounds and metal-organic frameworks have been favored by scholars due to their strong affinity for iodine. Activated carbon and zeolite have the best application prospects due to their low price. However, low adsorption capacity and easy desorption are disadvantages.

[0004] Therefore, the design and preparation of functional materials with high adsorption capacity and adsorption stability is still a challenge. Summary of the Invention

[0005] In order to solve the above technical problems, on the one hand, the present invention provides an ionic liquid modified MOF-808 for adsorbing radioactive iodine, and its molecular formula is expressed as X-IL@MOF, where IL is an ionic liquid, MOF is a metal-organic framework MOF-88, and X represents the number of microliters of ionic liquid added per 60 mg of MOF-88.

[0006] Further, the ionic liquid is [C2min][Tf2N].

[0007] Further, X is [5, 20].

[0008] Further, X is 15.

[0009] The present invention also provides a preparation method of the ionic liquid modified MOF-808 for adsorbing radioactive iodine according to any one of the above, respectively preparing an ionic liquid and a metal-organic framework MOF-88; Then, through an impregnation method, the ionic liquid is combined with the metal-organic framework MOF-88 to obtain an ionic liquid modified MOF-808.

[0010] Further, 1-ethyl-3-methylimidazolium bromide and lithium bis(trifluoromethyl)sulfonimide are mixed, washed with deionized water and dried to obtain the ionic liquid.

[0011] Further, 1,3,5-benzenetricarboxylic acid and ZrOCl2 are respectively dissolved in a solution containing formic acid and N,N-dimethylformamide, and then the dissolved ZrOCl2 and the dissolved 1,3,5-benzenetricarboxylic acid are mixed to obtain a mixed solution. The mixed solution is heated at 120 °C for 12 hours, washed and dried to obtain the metal-organic framework MOF-88.

[0012] The present invention also provides the application of the ionic liquid-modified MOF-808 for adsorbing radioactive iodine described in any one of the above, or the ionic liquid-modified MOF-808 prepared by the preparation method described in any one of the above in the adsorption of radioactive iodine.

[0013] The embodiments of the present invention have the following technical effects: In the present invention, the ionic liquid is loaded into the pores of MOF-808 by an in-situ impregnation method to obtain an ionic liquid-modified MOF-808 for adsorbing radioactive iodine, expressed as X-IL@MOF. It has excellent removal performance for radioactive iodine, which benefits from the excellent pore structure of MOF-808 and the rich heteroatom adsorption sites of IL. After being modified by hydrophobic IL, IL@MOF also shows good adsorption performance in a high-humidity environment. Description of the Drawings

[0014] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0015] Figure 1 Among them, (a) is the XRD spectrogram of 15-IL@MOF prepared in Example 1 of the present invention. Figure 1 Among them, (b) is the FT-IR spectrum of X-IL@MOF prepared in Examples 1-5 of the present invention. Figure 1 Among them, (c) is the comparison diagram of the N2 adsorption-desorption isotherms of X-IL@MOF prepared in Examples 1-4 of the present invention and MOF-808 prepared in Comparative Example 2. Figure 1 Among them, (d) is the SEM map of MOF-808 prepared in Comparative Example 2 of the present invention. Figure 1 Among them, (e) is the SEM map of 15-IL@MOF prepared in Example 1 of the present invention. Figure 1In (f), it is the EDS mapping diagram of 15-IL@MOF prepared in Example 1 of the present invention; Figure 2 In (a), it is the XPS survey diagram of MOF-808 prepared in Comparative Example 2 of the present invention, Figure 2 In (b), it is the Zr 3d diagram of 15-IL@MOF prepared in Example 1 of the present invention, Figure 2 In (c), it is the O 1s diagram of 15-IL@MOF prepared in the examples of the present invention and MOF-808 prepared in Comparative Example 2, Figure 2 In (d), it is the N 1s diagram of 15-IL@MOF prepared in the examples of the present invention, Figure 2 In (e), it is the S 2p diagram of 15-IL@MOF prepared in the examples of the present invention, Figure 2 In (f), it is the F1s diagram of 15-IL@MOF prepared in the examples of the present invention; Figure 3 In (a), it is the adsorption kinetics comparison diagram of the samples prepared in Examples 1-4 and Comparative Examples 1-2 of the present invention, Figure 3 In (b), it is the adsorption capacity comparison diagram of the samples prepared in Examples 1-4 and Comparative Examples 1-2 of the present invention, Figure 3 In (c), it is the adsorption amount comparison diagram of the samples prepared in Example 1 and Comparative Examples 1-2 of the present invention at different temperatures, Figure 3 In (d), it is the iodine vapor adsorption curve diagram of the samples prepared in Example 1 and Comparative Examples 1-2 of the present invention, Figure 3 In (e), it is the adsorption capacity comparison diagram of the samples prepared in Example 1 and Comparative Examples 1-2 of the present invention in a humid environment, Figure 3 In (f), it is the diagram of the retained adsorbed iodine of the sample prepared in Example 1 of the present invention varying with time after adsorbing iodine; Figure 4 In (a), it is the FT-IR spectrum diagram of the sample prepared in Example 1 of the present invention before and after adsorbing iodine vapor; Figure 4 In (b), it is the XRD spectrum diagram of the sample prepared in Example 1 of the present invention before and after adsorbing iodine vapor; Figure 4 In (c), it is the Raman spectrum diagram of the sample prepared in Example 1 of the present invention before and after adsorbing iodine vapor; Figure 4 In (d), it is the SEM spectrum diagram of the sample prepared in Example 1 of the present invention after adsorbing iodine vapor; Figure 4 In (e), it is the EDS mapping spectrum diagram of the sample prepared in Example 1 of the present invention after adsorbing iodine vapor; Figure 5 In (a), it is the XPS spectrum diagram of the sample prepared in Example 1 of the present invention and the sample prepared in Comparative Example 2 after adsorbing iodine vapor, Figure 5 In (b), it is the Zr 3d diagram of the sample prepared in Example 1 of the present invention before and after adsorbing iodine vapor, Figure 5In (c) is the O 1s spectrum of the sample prepared in Example 1 of the present invention before and after adsorbing iodine vapor. Figure 5 In (d) is the N 1s spectrum of the sample prepared in Example 1 of the present invention before and after adsorbing iodine vapor. Figure 5 In (e) is the S 2p spectrum of the sample prepared in Example 1 of the present invention before and after adsorbing iodine vapor. Figure 5 In (f) is the F 1s spectrum of the sample prepared in Example 1 of the present invention before and after adsorbing iodine vapor. Figure 6 is the schematic diagram of the mechanism for the sample prepared in Example 1 of the present invention to adsorb radioactive iodine. Figure 7 is the schematic diagram of the change of the specific surface area and pore volume of X-IL@MOF with the IL loading amount. Figure 8 is the schematic diagram of the contact angle of the sample prepared in Example 1 of the present invention and the sample prepared in Comparative Example 2. Detailed implementation manners

[0016] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

[0017] Radioactive iodine (I2) poses a potential risk to environmental safety and human health. Designing efficient and stable functional materials for I2 capture is an urgent problem to be solved.

[0018] Metal-organic frameworks (MOFs) are porous crystalline materials formed by the self-assembly of metal ions and organic ligands through ligand bonds. MOFs have been widely used in gas separation, hydrogen storage and CO2 capture due to their high specific surface area, high porosity and hierarchical pore structure. Functional groups or metal sites on the surface of MOFs can form hydrogen bonds, Lewis acid-base interactions or coordination bonds with I2 to achieve highly selective adsorption. A two-dimensional assembly composed of ZIF-8 particles achieved an I2 adsorption capacity of 200 wt%. However, MOFs composed of soft Lewis acidic metal ions (such as Zn 2+ and Cu 2+ ) are not very stable. Zr 4+ is considered to be a tough Lewis acid with more organic linkers that can be connected. Although MOF-808 achieved a high I2 adsorption capacity based on its ultra-high specific surface area and affinity. It still faces the problems of insufficient and single adsorption sites.

[0019] Ionic liquids (ILs) are typically composed of organic cations and organic / inorganic anions and are used in high-temperature catalysis, separation, and other applications due to their design flexibility, functionalization modification, high boiling point, and extremely low vapor pressure. Imidazolium cationic ILs are the most widely studied and applied IL category. Among them, [C2mim] + The imidazole ring of - [Tf2N] contains two nitrogen atoms and has an aromatic and conjugated electron system, which gives the cation high overall stability and makes it resistant to decomposition. The length of its side chain enhances hydrophobicity and helps improve the effect of humidity on I2 adsorption. [Tf2N]

[0020] Due to its high stability, unique molecular structure, low viscosity, and strong hydrophobicity, it is one of the anions with the most balanced comprehensive performance among ionic liquids. However, the high viscosity hinders the diffusion of I2 into the interior of the IL, resulting in low utilization of effective adsorption sites. Combining [C2mim][Tf2N] rich in adsorption sites with MOF-808 with a high specific surface area can overcome the disadvantages of both in I2 adsorption.

[0021] In some embodiments, the ionic liquid is [C2min][Tf2N].

[0022] In some embodiments, X is [5, 20].

[0023] In some embodiments, X is 15.

[0024] The present invention also provides a method for preparing the ionic liquid-modified MOF-808 for adsorbing radioactive iodine described in any one of the above, respectively preparing an ionic liquid and a metal-organic framework MOF-88; Then, through an impregnation method, the ionic liquid is combined with the metal-organic framework MOF-88 to obtain the ionic liquid-modified MOF-808.

[0025] In some embodiments, 1-ethyl-3-methylimidazolium bromide and lithium bis(trifluoromethyl)sulfonamide are mixed, washed with deionized water, and dried to prepare the ionic liquid.

[0026] In some embodiments, 1,3,5-benzenetricarboxylic acid and ZrOCl2 are respectively dissolved in a solution containing formic acid and N,N-dimethylformamide, and then the dissolved ZrOCl2 and the dissolved 1,3,5-benzenetricarboxylic acid are mixed to obtain a mixed solution; After heating the mixed solution at 120 °C for 12 hours, it was washed and dried to obtain the metal-organic framework MOF-88.

[0027] The present invention also provides the application of the ionic liquid-modified MOF-808 for adsorbing radioactive iodine described in any one of the above, or the ionic liquid-modified MOF-808 prepared by the preparation method described in any one of the above, in the adsorption of radioactive iodine.

[0028] The following is elaborated with specific examples: Example 1 (1) Preparation of ionic liquid [C2mim][Tf2N] First, 10 mmol of 1-ethyl-3-methylimidazolium bromide ([C2mim]Br) and 10 mmol of lithium bis(trifluoromethyl)sulfonimide (Li[Tf2N]) were added to a beaker containing 50 mL of deionized water. The solution was stirred at room temperature for 2 hours. Subsequently, the ionic liquid phase was washed several times with deionized water. Finally, the water was removed from the sample by rotary evaporation and dried at 60 °C for 12 hours.

[0029] (2) Preparation of MOF-808 First, 2 mmol of 1,3,5-benzenetricarboxylic acid was dissolved in beaker A containing 40 mL of formic acid and 40 mL of N,N-dimethylformamide, and continuously stirred until completely dissolved. 2 mmol of ZrOCl2 was dissolved in beaker B containing 40 mL of formic acid and 40 mL of N,N-dimethylformamide, and continuously stirred until completely dissolved. Subsequently, the solution in beaker B was slowly added dropwise to beaker A and continuously stirred for 0.5 hour. The mixed solution was transferred to a 200 mL Teflon-lined tube and heated at 120 °C for 12 hours. Finally, the sample was washed several times with deionized water and ethanol and dried at 60 °C for 12 hours.

[0030] (3) Preparation of X-IL@MOF for adsorbing radioactive iodine First, 60 mg of MOF-808 was added to a beaker containing 20 mL of ethanol and 10 mL of deionized water, and continuously stirred until completely dispersed. Subsequently, 15 μL of [C2mim][Tf2N] was slowly added dropwise to the beaker. The solution was continuously stirred at 60 °C until the solvent was completely evaporated. Finally, the sample was dried in an oven at 60 °C to obtain 15-IL@MOF.

[0031] Example 2 The preparation of the ionic liquid [C2mim][Tf2N] and the preparation of MOF-808 were the same as in Example 1, except that 5 μL of [C2mim][Tf2N] was added when preparing X-IL@MOF to obtain 5-IL@MOF.

[0032] Example 3 The preparation of the ionic liquid [C2mim][Tf2N] and the preparation of MOF-808 were the same as in Example 1, except that when preparing X-IL@MOF, 10 μL of [C2mim][Tf2N] was added to obtain 10-IL@MOF.

[0033] Example 4 The preparation of the ionic liquid [C2mim][Tf2N] and the preparation of MOF-808 were the same as in Example 1, except that when preparing X-IL@MOF, 20 μL of [C2mim][Tf2N] was added to obtain 20-IL@MOF.

[0034] Example 5 The preparation of the ionic liquid [C2mim][Tf2N] and the preparation of MOF-808 were the same as in Example 1, except that when preparing X-IL@MOF, 30 μL of [C2mim][Tf2N] was added to obtain 30-IL@MOF.

[0035] Comparative Example 1 Preparation of the ionic liquid [C2mim][Tf2N]: First, 10 mmol of 1-ethyl-3-methylimidazolium bromide ([C2mim]Br) and 10 mmol of lithium bis(trifluoromethyl)sulfonamide (Li[Tf2N]) were added to a beaker containing 50 mL of deionized water. The solution was stirred at room temperature for 2 hours. Subsequently, the ionic liquid phase was washed several times with deionized water. Finally, the water was removed from the sample by rotary evaporation and dried at 60 °C for 12 hours.

[0036] Comparative Example 2 Preparation of MOF-808: First, 2 mmol of 1,3,5-benzenetricarboxylic acid was dissolved in beaker A containing 40 mL of formic acid and 40 mL of N,N-dimethylformamide and continuously stirred until completely dissolved. 2 mmol of ZrOCl2 was dissolved in beaker B containing 40 mL of formic acid and 40 mL of N,N-dimethylformamide and continuously stirred until completely dissolved. Subsequently, the solution in beaker B was slowly added dropwise to beaker A and continuously stirred for 0.5 hour. The mixed solution was transferred to a 200 mL Teflon-lined tube and heated at 120 °C for 12 hours. Finally, the sample was washed several times with deionized water and ethanol and dried at 60 °C for 12 hours.

[0037] Results and Analysis: FTIR was used to study the functional groups and chemical structures of MOF-808 and 15-IL@MOF. As Figure 1 shown in (a) below, 1169, 1133 and 1052 cm -1The three characteristic peaks nearby are respectively attributed to the asymmetric stretching vibration of the C-F bond, the symmetric stretching vibration of the O=S=O bond, and the asymmetric stretching vibration of the S-N-S bond. The peak located at 1346 cm -1 The peak nearby is attributed to the stretching vibration of the C-N bond on the imidazole ring. The characteristic peaks at 1627, 1557, and 1449 cm -1 The characteristic peaks nearby are attributed to the asymmetric stretching vibration of the carboxyl group in MOF-808

[36] . While the peak at 1384 cm -1 The peak nearby is attributed to the symmetric stretching vibration peak of the carboxyl group. In addition, the peaks at 754 and 650 cm -1 The peaks nearby may be attributed to the out-of-plane bending vibration of the C-H bond on the benzene ring and the breathing vibration of the benzene ring.

[0038] It should be noted that in X-IL@MOF, the peak intensity attributed to [C2mim][Tf2N] gradually increases with the increase of IL loading. The peaks of MOF and [C2mim][Tf2N] coexist in the spectrum of X-IL@MOF, indicating good binding.

[0039] Figure 1 In (b) is the FT-IR spectrum of X-IL@MOF prepared in Examples 1-5 of the present invention, (c) is the comparison chart of N2 adsorption-desorption isotherms of X-IL@MOF prepared in Examples 1-4 of the present invention and MOF-808 prepared in Comparative Example 2, and (f) is the EDS mapping of 15-IL@MOF prepared in Example 1 of the present invention. The morphologies and surface element distributions of MOF-808 and X-IL@MOF were studied using SEM. The SEM mapping results show that the elements Zr, O, C, N, S, and F are uniformly distributed on the surface of IL@MOF. In Figure 1 In (d) is the SEM pattern of MOF-808 prepared in Comparative Example 2 of the present invention. MOF-808 exhibits a regular octahedral morphology and excellent crystallization below 1 μm. Figure 1 In (e) is the SEM pattern of 15-IL@MOF prepared in Example 1 of the present invention. By comparison, it is known that IL is uniformly distributed on the surface of MOF-808 and binds well. These results confirm the successful preparation of IL@MOF.

[0040] The crystal structures of MOF-808 and X-IL@MOF were studied using XRD. As Figure 2As shown in (b), the four strong characteristic peaks at 8.63, 9.02, 10.33, and 11.26° are attributed to MOF-808, confirming the successful preparation of MOF-808. Importantly, the characteristic peaks of MOF-808 were observed in the XRD spectra of X-IL@MOF. As the IL loading increased, the intensities of the characteristic peaks at 8.63° and 9.02° gradually decreased. This may be due to the scattering and absorption of X-rays by IL on the surface of MOF-808. Figure 2 The XRD pattern results in (a) confirmed the formation of the IL@MOF composite phase.

[0041] The specific surface area and pore size distribution characteristics of MOF-808 and X-IL@MOF were studied using N2 adsorption-desorption isotherms, and the results are as Figure 2 shown in (c). The adsorption type of MOF-808 belongs to the typical type I. This adsorption type is accompanied by the presence of micropores. In addition, the hysteresis loop of MOF-808 belongs to the typical H4 type. It is worth noting that the adsorption type and hysteresis loop of IL@MOF do not change significantly with the loading of IL. IL does not have a specific surface area or pore size in the traditional sense. From Figure 7 it can be seen that the specific surface area and pore volume of X-IL@MOF gradually decrease with the increase of IL loading, indicating that IL is present in the pores of MOF-808.

[0042] The elemental composition and chemical state of MOF-808 and 15-IL@MOF were studied using XPS. As Figure 2 shown in (a), the XPS survey of MOF-808 mainly consists of O1s, Zr3p, C1s, and Zr3d. In addition, the XPS survey of 15-IL@MOF contains F1s, O1s, N1s, C1s, and S2p attributed to [C2mim][Tf2N]. In Figure 2 (b), the two peaks near 185.2 and 182.8 eV are attributed to Zr3d3 / 2 and Zr3d5 / 2. In Figure 2 (c), the two peaks near 531.9 and 529.9 eV are attributed to Zr-OH and Zr-O-Zr bonds

[40] . Compared with MOF-808, the O1s peaks of Zr3d and 15-IL@MOF are shifted, which may be caused by the migration of free electrons on the surface of IL and MOF-808. In Figure 2 (d), the two peaks at 402.2 and 399.7 eV are attributed to C-N and C=N bonds in the imidazole ring. In Figure 2 (e), the two peaks at 170.2 and 169.1 eV are attributed to S-F and S=O bonds respectively. The peaks in the high-resolution spectrum of F1s are attributed to S-F bonds (as Figure 2in (f)).

[0043] The present invention uses an adsorption kinetics system to study the adsorption rate and adsorption capacity of samples. As Figure 3 shown in (a) and (b), the adsorption capacity of MOF-808 for I2 is about 1.49 g / g. In contrast, the adsorption capacity of [C2mim][Tf2N] for I2 is only 0.12 g / g, which may be attributed to the liquid nature of the IL itself, which results in less exposure of active sites. In addition, the adsorption capacities of 5-IL@MOF, 10-IL@MOF, 15-IL@MOF, and 20-IL@MOF for I2 are 1.85, 2.19, 2.61, and 2.38 g / g, respectively. It is worth noting that as the IL loading increases, the adsorption capacity of X-IL@MOF for I2 gradually increases. This is mainly because the large specific surface area and pore size of MOF-808 provide an excellent loading substrate for the IL. However, excessive IL loading tends to block the internal pores of MOF-808 and affect the diffusion of I2 inside MOF-808. The pseudo-first-order and pseudo-second-order models were used to study the adsorption type of the samples for I2. As Figure 3 shown in (a), the adsorption kinetics was fitted with the pseudo-first-order model with a relatively high correlation coefficient (R2), indicating that the adsorption of I2 by MOF-808, [C2mim][Tf2N], and 15-IL@MOF is mainly physical adsorption.

[0044] The effect of temperature on the adsorption performance of the samples was studied through adsorption thermodynamics experiments. As Figure 3 shown in (c), the adsorption capacities of MOF-808, [C2mim][Tf2N], and 15-IL@MOF decrease with increasing temperature, indicating that the adsorption process of MOF-808, [C2mim][Tf2N], and 15-IL@MOF for iodine is exothermic. The adsorption capacities of MOF-808, [C2mim][Tf2N], and 15-IL@MOF at 160 °C are 1.21, 0.102, and 2.15 g / g, respectively. These represent decreases of 19.4%, 15.1%, and 17.6%, respectively.

[0045] The effect of water vapor on the adsorption ability of the samples was studied. The water vapor was sourced from a saturated aqueous solution of calcium chloride. As Figure 3 shown in (d), the adsorption capacities of MOF-808, [C2mim][Tf2N], and 15-IL@MOF for water molecules are 0.21, 0.02, and 0.12 g / g, respectively. Subsequently, I 2 adsorption experiments were carried out on the samples after water molecule adsorption. MOF-808, [C2mim][Tf2N], and 15-IL@MOF for I 2The adsorption capacities are 0.864, 0.110, and 1.879 g / g, respectively. These are reduced by 42%, 8%, and 28% respectively ( Figure 3 in (e)). This may be due to the higher specific surface area and pore size of MOF-808, making it easier for water molecules to occupy the adsorption sites. The hydrophilicity of the samples was examined by measuring the contact angle. As Figure 8 shown, the contact angle of MOF-808 is 32.5°, demonstrating that MOF-808 is very hydrophilic. The contact angle of 15-IL@MOF is 90°, indicating that IL is hydrophobic and the hydrophobicity of MOF-808 is further enhanced after loading IL. It is worth noting that MOF-808 after loading IL is less affected by water vapor, which is beneficial for gaseous iodine adsorption. The desorption experiment was carried out on 15-IL@MOF at room temperature for up to 7 days. As Figure 3 shown in (f), after being placed in air for 7 days, the I2 retention rate of 15-IL@MOF is 88.9%, indicating that the capture of I 2 by the sample is stable.

[0046] FTIR was used to study the functional groups and chemical structures of 15-IL@MOF before and after adsorption. As Figure 4 shown in (a), the blue and red lines are the FT-IR spectra of the sample prepared in Example 1 of the present invention before and after adsorbing iodine vapor, respectively. The characteristic peaks attributed to MOF-808 and [C2mim][Tf2N] are retained in the spectrum of 15-IL@MOF-I. It is worth noting that the peak intensities at 1169, 1133, and 1052 cm -1 significantly decrease after adsorption. This indicates that the F and S sites interact with I2 during the adsorption process. In addition, after adsorption, the peak intensity of the C-N bond on the imidazole ring at 1346 cm -1 also significantly decreases. This indicates that the N site also interacts with I2 during the adsorption process. The peaks attributed to MOF-808 do not change significantly, except that the OH- near 3400 cm -1 significantly weakens. Therefore, OH - may play a role in the adsorption process.

[0047] The crystalline phase of 15-IL@MOF before and after adsorption was examined by XRD. As Figure 4 shown in (b), the blue and red lines are the XRD spectra of the sample prepared in Example 1 of the present invention before and after adsorbing iodine vapor, respectively. The characteristic peak intensity attributed to MOF-808 significantly attenuates, which may be due to the interaction between I2 and the pore wall after entering the pore channels, resulting in the disordered arrangement of atoms on the pore wall surface.

[0048] The adsorption product of 15-IL@MOF on I2 was explored in depth. As Figure 4As shown in (c), the blue and red lines are the F Raman spectra of the sample prepared in Example 1 of the present invention before and after adsorbing iodine vapor. In the spectrum of 15-IL@MOF-I, two characteristic peaks of I3 -1 at 112 cm -1 and I2 at 143 cm - are observed. This indicates that I2 is mainly adsorbed by 15-IL@MOF in the forms of I2 and I3 - .

[0049] SEM was used to detect the morphology and elemental distribution of 15-IL@MOF after adsorption. As shown in (d), the morphology of 15-IL@MOF-I has no significant change compared with that before adsorption (as shown in (e)), and the regular octahedral morphology is relatively intact. Figure 4 As shown in (d), the morphology of 15-IL@MOF-I has no significant change compared with that before adsorption (as shown in (e)), and the regular octahedral morphology is relatively intact. Figure 1 in (e)). Figure 4 Figure (e) is the EDS mapping spectrum of the sample prepared in Example 1 of the present invention after adsorbing iodine vapor.

[0050] XPS was used to study the elemental composition and chemical state of 15-IL@MOF before and after adsorption. Figure 5 Figure (a) is the XPS spectrum of the sample prepared in Example 1 of the present invention and MOF-808 prepared in Comparative Example 2 after adsorbing iodine vapor, Figure 5 Figure (b) is the Zr 3d map of the sample prepared in Example 1 of the present invention before and after adsorbing iodine vapor, Figure 5 Figure (c) is the O 1s map of the sample prepared in Example 1 of the present invention before and after adsorbing iodine vapor, Figure 5 Figure (d) is the N 1s map of the sample prepared in Example 1 of the present invention before and after adsorbing iodine vapor, Figure 5 Figure (e) is the S 2p map of the sample prepared in Example 1 of the present invention before and after adsorbing iodine vapor, Figure 5 Figure (f) is the F 1s map of the sample prepared in Example 1 of the present invention before and after adsorbing iodine vapor. Among them, 15-IL@MOF-1 represents the sample prepared in Example 1 after adsorbing iodine vapor, 15-IL@MOF represents the sample prepared in Example 1 before adsorbing iodine vapor, and MOF-808-1 represents the sample prepared in Comparative Example 2 after adsorbing iodine vapor. As shown in Figure 5 Figure (a), the two peaks near 632.3 and 620.8 eV are attributed to I2, while the two peaks at 630.5 and 618.9 eV are attributed to I3 - . It should be noted that the percentage of I3 - in the I2 adsorption product of MOF-808 is 60.7%. In contrast, the percentage of I3 - in the I2 adsorption product of 15-IL@MOF is 85%. This indicates that the percentage of I3 -The percentage is higher than that of MOF-808, which may be the reason for the enhanced adsorption capacity of MOF-808 after loading [C2mim][Tf2N]. As Figure 5 shown in (b) below, the characteristic peak of Zr3d shifts to a higher binding energy of about 0.3 eV after adsorption, indicating that charge migration occurs in Zr during adsorption and electrons are lost. In Figure 5 shown in (c) below, the peak of the Zr-OH bond located near 532.6 eV also shifts significantly and its intensity decreases, indicating that the terminal OH- of MOF-808 is an important adsorption site. In Figure 5 shown in (d) below, the peaks of the C-N and C=N bonds located near 402.2 and 399.7 eV also shift significantly and their intensity weakens, indicating that the N sites in the imidazole ring interact with I2. In addition, similar shifts are also observed for the characteristic peaks attributed to S and F, indicating an interaction between I2 and heteroatoms.

[0051] Based on these results and analyses, as Figure 6 shown below, the possible mechanism for the adsorption of radioactive iodine by X-IL@MOF-808 may be divided into two parts: (i) When I2 molecules enter the pores of IL@MOF, the I2 molecules are electrostatically adsorbed by the highly unsaturated Zr nodes, terminal OH-, S, F, and N sites; (ii) The I2 captured by the above adsorption sites may form a charge complex through charge transfer between lone pair orbitals (n). Subsequently, the charge complex captures more I2 molecules to form I3 - .

[0052] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the technical solutions of the embodiments of the present invention.

Claims

1. Ionic liquid modified MOF-808 for adsorbing radioactive iodine, characterized in that, The molecular formula is expressed as X-IL@MOF, where IL is an ionic liquid, MOF is the metal-organic framework MOF-88, and X represents the number of microliters of ionic liquid added per 60 mg of MOF-88.

2. The ionic liquid-modified MOF-808 for adsorbing radioactive iodine according to claim 1, wherein The ionic liquid is [C2min][Tf2N].

3. The ionic liquid-modified MOF-808 for adsorbing radioactive iodine according to claim 1, wherein The X is [5, 20].

4. The ionic liquid-modified MOF-808 for adsorbing radioactive iodine according to claim 3, wherein, The X is 15.

5. The preparation method of the ionic liquid-modified MOF-808 for adsorbing radioactive iodine according to any one of claims 1-4, characterized in that, Prepare the ionic liquid and the metal-organic framework MOF-88 respectively; Then, through the impregnation method, combine the ionic liquid with the metal-organic framework MOF-88 to obtain the ionic liquid-modified MOF-808.

6. The preparation method according to claim 5, wherein Mix 1-ethyl-3-methylimidazolium bromide and lithium bis(trifluoromethyl)sulfonimide, wash with deionized water and dry to obtain the ionic liquid.

7. The preparation method according to claim 5, characterized in that, Dissolve 1,3,5-benzenetricarboxylic acid and ZrOCl2 in a solution containing formic acid and N,N-dimethylformamide respectively, and then mix the dissolved ZrOCl2 and the dissolved 1,3,5-benzenetricarboxylic acid to obtain a mixed solution; After heating the mixed solution at 120 °C for 12 hours, wash and dry to obtain the metal-organic framework MOF-88.

8. Use of the ionic liquid-modified MOF-808 for adsorbing radioactive iodine according to any one of claims 1-4 or the ionic liquid-modified MOF-808 prepared by the preparation method according to any one of claims 5-7 in the adsorption of radioactive iodine.

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