Optimizing iodine capture performance by metal–organic framework containing with bipyridine units

Abstract

Radioactive iodine exhibits medical values in radiology, but its excessive emissions can cause environmental pollution. Thus, the capture of radioiodine poses significant engineering for the environment and medical radiology. The adsorptive capture of radioactive iodine by metal–organic frameworks (MOFs) has risen to prominence. In this work, a Th-based MOF (denoted as Th-BPYDC) was structurally designed and synthesized, consisting of [Th₆(μ₃-O)₄(μ₃-OH)₄(H₂O)₆]¹²⁺ clusters, abundant bipyridine units, and large cavities that allowed guest molecules diffusion and transmission. Th-BPYDC exhibited the uptake capacities of 2.23 g·g⁻¹ and 312.18 mg·g⁻¹ towards I₂ vapor and I₂ dissolved in cyclohexane, respectively, surpassing its corresponding analogue Th-UiO-67. The bipyridine units boosted the adsorption performance, and Th-BPYDC showed good reusability with high stability. Our work thus opened a new way for the synthesis of MOFs to capture radioactive iodine.

Key words： metal–organic framework; iodine; adsorption; nuclear waste; environmental remediation

1 Introduction

As a safe and clean energy technology, nuclear energy plays an essential role in eliminating energy crises and environmental pollution in human societies [1,2]. However, the nuclear industry produces will release waste containing radionuclides during the production of nuclear fuel, which needs careful management due to their extreme and persistent toxicity [3–9]. One potentially troublesome radionuclide is radioiodine, normally exists as ¹²⁹I and ¹³¹I isotopes, which could be released into the air through volatilization and dissolved in groundwater, finally bio-accumulated to the ecological environment and humans through food-chain [10,11]. Long radioactive half-life (~1.57 × 10⁷ years for ¹²⁹I) and strong radiation (¹³¹I) of radioiodine (including elemental iodine, methyl iodide, and ethyl iodide) can bring disease to humans. In addition to these drawbacks, radioiodine showed important applications in medical science, such as treating malignant tumors, examining thyroid function [12]. Therefore, effectively extraction of solid and organic radioiodine is an important issue to address radioactive resource utilization and pollution elimination [13–15]. However, the iodine adsorption materials, such as activated carbon, silver-exchanged zeolite, and hydrotalcite, showed low adsorption capacity, which limited the application of such materials in the efficient capture of radioiodine.

Metal-organic frameworks (MOFs) are crystalline porous materials and have attracted increasing utilization in a broad range of applications, such as gas storage and separation [16,17], sensing [18,19], drug delivery, bio-therapy [20], catalysis [21–23], photoluminescence [24], sorption [25,26] and electrochemical applications [27]. Recently, MOFs with high specific surface area and modifiability have shown particular promise as adsorbents for radioiodine adsorption and capture from the air [28–30] and organic solutions [31,32] by virtue of the MOFs’ tunable structural components, long-range ordering, and controllable porosity [33,34]. Fast adsorption kinetics [35–37], high uptake [38,39], and good reusable ability are jointly necessary for high-performance adsorbents [40–42]. However, due to the weak interaction between iodine and skeleton, and the stability issues of reusability, the development of MOFs for the capable of achieving these objectives simultaneously remains a considerable challenge.

Taking the abovementioned properties and requirements into account, herein we reported a three-dimensional MOF (denoted as Th-BPYDC) with [Th₆(μ₃-O)₄(μ₃-OH)₄(H₂O)₆]¹²⁺ building blocks, bipyridine units, and large cavities that was solvothermal prepared and structurally characterized by the aid of single-crystal X-ray diffraction. Benefiting from the large cavities, abundant bipyridine units, good thermal and chemical stabilities of the framework, Th-BPYDC exhibited good iodine adsorption performances from both vapor and cyclohexane solutions [43]. In comparison, the Th-UiO-67 analogue (without bipyridine units) was also synthesized and applied to adsorb iodine under very similar conditions. The results revealed that the bipyridine units of Th-BPYDC boosted the iodine adsorption performance. This study thus offered insights into the rational development of MOFs toward the capture of radioactive iodine from nuclear waste and organic solutions.

2 Experimental

2.1 Syntheses of MOFs

Th-BPYDC and Th-UiO-67 were synthesized by a solvothermal method employing Th(NO₃)₄·xH₂O, 2,2' Bipyridine-5,5' dicarboxylic acid (BPYDC) or biphenyl dicarboxylic acid (BPDC), and nitric acid in N,N-dimethylformamide (DMF) at 120 °C for 3 d. This was attributed to the fact that the coordination of tetravalent metal thorium with carboxylic acid ligands required a strong Lewis acid for its rapid nucleation. In a 5 mL glass vial, 48 mg of Th(NO₃)₄·xH₂O and 24.5 mg of BPYDC were dissolved in 2 mL of DMF, and then added 0.25 mL of nitric acid. After 3 days of heating at 120 °C, the colorless crystals were washed several times with DMF and collected by filtration (yield MOF Th-BPYDC). MOF Th-BPYDC analogue (Th-UiO-67) was synthesized by a similar procedure under same conditions, only replacing the BPYDC ligand with BPDC (24.2 mg).

2.2 Materials activation

Before the iodine adsorption experiment, Th-BPYDC and Th-UiO-67 immersed in DMF were solvent-exchanged with fresh dichloromethane every 12 h for 3 days, then the materials were filtered and washed, and then vacuum-dried at 60 °C for 24 h to remove solvent guest molecules in the pores. The results of elemental analyses of Th-BPYDC and Th-UiO-67 were tabulated in Table S1 (cf. Electronic Supplementary Material, ESM).

2.3 Iodine vapor adsorption experiments

First, 20 mg of each MOF adsorbent was put in a 5 mL glass vial, and then the excess iodine was placed in the inner container of a hydrothermal kettle. Afterward, the packaged kettle was put in an oven at 75 °C for 24 h. After cooling down to room temperature, the mass of the sample in the vial was weighed, and the adsorption capacity was calculated from the mass difference. The iodine uptake capacity was calculated according to Eq. (1):

(1)\alpha =\frac{w_3-w_2}{w_2-w_1},

where α is the equilibrium adsorption capacity of iodine vapor, w₁ is the quality of 5 mL glass vial, w₂ and w₃ are the quality of MOF adsorbent before and after adsorption of iodine vapor in 5 mL glass vial, respectively.

2.4 Iodine adsorption from cyclohexane solutions

Iodine adsorption isotherms. All the experiments were conducted at 25 °C using the batch adsorption method. MOF adsorbent was added into a cyclohexane solution containing iodine at a particular concentration (the adsorbent/liquid ratio was fixed at 2 mg∙mL^–1). After sharking for a certain contact time, the iodine concentration in the filtrate was quantified by ultra–violet-visible (UV)-spectrophotometry. Langmuir isotherm model was applied to fit the sorption isotherm data by Eq. (2) [44]:

(2)\frac{C_{\mathrm{e}}}{q_{\mathrm{e}}}=\frac{1}{K_{\mathrm{L}}{q}_{\mathrm{m}}}+\frac{C_{\mathrm{e}}}{q_{\mathrm{m}}},

where q_m is the maximum adsorption capacity of iodine, K_L is the constant of Langmuir model. The iodine uptake capacity was calculated according to Eq. (3):

(3)q_{\mathrm{e}}=\frac{\left(C_0-C_{\mathrm{e}}\right)\times V}{m},

where C₀ is the initial iodine concentration, and C_e is the equilibrium iodine concentration. V is the volume of the solution and m is the amount of adsorbent.

Iodine adsorption kinetics. To determine the iodine adsorption kinetics, MOF adsorbent was dispersed in a cyclohexane solution containing 200 ppm (10⁻⁶) iodine (with an adsorbent/liquid ratio of 2 mg∙mL^–1). The resulting dispersion was stirred at 180 r·min⁻¹, with aliquots of the dispersion being collected at regular time intervals. The aliquots were filtered through a 0.22 μm membrane filter and iodine in the filtrates was quantified by UV-spectrophotometry. Pseudo-first-order and pseudo-second-order kinetic models were used to fit the kinetic adsorption data by following the equations:

(4)\mathrm{l}\mathrm{n}\left(q_{\mathrm{e}}-q_{\mathrm{t}}\right)=\mathrm{l}\mathrm{n}{q}_{\mathrm{e}}-k_{1}t,

(5)\frac{t}{q_{\mathrm{t}}}=\frac{1}{k_2{q}_{\mathrm{e}}^2}+\frac{t}{q_{\mathrm{e}}},

where k₁ and k₂ are the rate constants for the pseudo-first-order and pseudo-second-order kinetic models, respectively, and q_t is the adsorption capacity at a given contact time.

Adsorption–desorption cycles of iodine in cyclohexane. Th-BPYDC (20 mg) after the adsorption of the iodine/cyclohexane solution was put into ethanol (10 mL) and sonicated to make the iodine in the material released rapidly. The eluted solid was then filtered and then re-placed into a 200 ppm iodine/cyclohexane solution to perform the adsorption experiment again, repeated multiple times.

3 Results and discussion

3.1 Characterization

Subsequent single-crystal X-ray diffraction analysis revealed that Th-BPYDC was crystallized in a cubic space group Fm-3m and possessed an extended 3D framework (Fig.1). One prominent structural feature of Th-BPYDC was the presence of [Th₆(μ₃-O)₄(μ₃-OH)₄(H₂O)₆]¹²⁺ clusters (Fig.1(a)), which served as nodes to bind twelve BPYDC linear ligands and form cavities. Th₆(μ₃-O)₄(μ₃-OH)₄(H₂O)₆ cluster contained six Th⁴⁺ cations, four μ₃-O and four μ₃-OH groups, and six terminal water molecules were coordinated to form a square inverse prism geometry structure. Interestingly, two types of cavities were observed. Four [Th₆(μ₃-O)₄(μ₃-OH)₄(H₂O)₆]¹²⁺ clusters were connected by six BPYDC ligands to form a tetrahedral cavity that could be filled by a ball with a diameter of 5 nm (Fig.1(b)). The other one was an octahedral cavity, which was formed through six [Th₆(μ₃-O)₄(μ₃-OH)₄(H₂O)₆]¹²⁺ clusters connected by eight BPYDC linkers (Fig.1(c)). Each octahedral cavity was surrounded by eight tetrahedral cavities, thus forming the cubic packing 3D fcu frameworks (Fig.1(d) and Fig.1(e)).

Fig.1 (a) View of the [Th₆(μ₃-O)₄(μ₃-OH)₄(H₂O)₆]¹²⁺ SBU, and the BPYDC ligand; (b) the tetrahedral cavity substructure in Th-BPYDC; (c) the octahedral cavity substructure in Th-BPYDC; (d) the 3D framework of Th-BPYDC; (e) displaying the 12-connected fcu topology of Th-BPYDC.

Full size|PPT slide

The prepared Th-BPYDC and Th-UiO-67 were characterized in detail (Fig.2). The powder X-ray diffraction (PXRD) patterns were well matched with the calculated results, revealing the phase high purities of Th-BPYDC and Th-UiO-67 (Fig.2(a) and Fig.2(b)). It was also revealed that Th-BPYDC and Th-UiO-67 had similar structures. Thermogravimetric analysis (TGA) test results showed that Th-BPYDC and Th-UiO-67 had high thermal stability, and their structures remained unchanged at temperatures as high as 486 and 517 °C, respectively (Fig.2(c)). Subsequently, the dichloromethane exchanged sample was heated under a vacuum at 60 °C for 24 h to remove the guest molecules. The desolvated samples were used for determining the N₂ adsorption–desorption isotherms at 77 K. The adsorption isotherm conformed to type I type and was characterized by micropore distribution (Fig.2(d)). The Brunner–Emmett–Teller surface areas of Th-BPYDC and Th-UiO-67 were calculated to be 648 and 845 m²∙g^–1, respectively, revealing the high porosity. Pore size distribution analysis revealed that the average diameters of both Th-BPYDC and Th-UiO-67 MOFs samples were approximately 1.73 nm (Figs. S1 and S2, cf. ESM). Scanning electron microscopy (SEM) images revealed the polyhedral morphology of both MOFs (Fig.2(e) and Fig.2(f)), consistent with the structures from single-crystal diffraction analysis.

Fig.2 (a) XRD patterns of Th-BPYDC before and desolvated sample, together with calculated result; (b) XRD patterns of Th-UiO-67 and desolvated sample, together with calculated result; (c) TGA diagrams of Th-BPYDC and Th-UiO-67 after activation; (d) N₂ adsorption (filled symbols) and desorption (open symbols) isotherms measured at 77 K for Th-BPYDC and Th-UiO-67; SEM image of (e) Th-BPYDC and (f) Th-UiO-67.

Full size|PPT slide

The chemical stabilities of Th-BPYDC and Th-UiO-67 were then investigated by immersing both materials in different concentrations of HCl, NaOH, and different organic solutions for at least 24 h (Fig.3). Remarkably, Th-BPYDC and Th-UiO-67 showed good crystal stability in aqueous solutions with pH values ranging from 1 to 10 (Fig.3(a) and Fig.3(c)). The XRD patterns further showed that the frameworks of Th-BPYTC and Th-UiO-67 remained high stable after immersion in various organic solvents (Fig.3(b) and Fig.3(d)). Based on the above structural benefits, such as permanent porosity, high stability, and suitable pore size, Th-BPYDC and Th-UiO-67 demonstrate potential applications such as radioiodine capture from radioactive wastes and organic reagents.

Fig.3 (a) XRD patterns of Th-BPYDC after treatment in aqueous solution with pH from 1–10; (b) XRD patterns of Th-BPYDC after treatment in various organic solvents; (c) XRD patterns of Th-UiO-67 after treatment in aqueous solution with pH from 1–10; (d) XRD patterns of Th-UiO-67 after treatment in various organic solvents.

Full size|PPT slide

3.2 Iodine adsorption

We next performed a series of experiments to evaluate the iodine adsorption properties of Th-BPYDC and Th-UiO-67 (Fig.4). We firstly evaluated the iodine adsorption abilities of Th-BPYDC and Th-UiO-67 in cyclohexane solutions at room temperature (25 °C). Equilibrium adsorption isotherms were obtained using initial iodine concentrations ranging from 50 to ~1200 ppm with a solid to liquid ratio of 2 mg∙mL^–1. The adsorption capacity of Th-BPYDC was determined to be 312.18 mg∙g^–1, much higher than that of its analogue Th-UiO-67 (196.7 mg∙g^–1) under similar conditions (Fig.4(a)). The adsorption curves are well simulated with the Langmuir model (Table S2, cf. ESM). Subsequently, the adsorption kinetics were studied in 200 ppm cyclohexane solution for 1 to 21 h. Th-BPYDC showed fast adsorption kinetics with an adsorption removal rate of over 99.9% in 21 h (Fig.4(b)). At the same time, after the two materials adsorbed iodine in cyclohexane solution, the UV spectra of the solution showed that the characteristic peak of iodine (400–600 nm) gradually weakened with an increase of contact time (Figs. S3 and S4, cf. ESM). The kinetic adsorption data could be well fitted by the pseudo-second-order model, with R² values > 0.99 (Table S3, cf. ESM).

Fig.4 (a) Equilibrium adsorption isotherms for iodine adsorption on different MOF materials in cyclohexane solutions (iodine concentrations ranging from 50 to ~1200 ppm; fit lines for the Langmuir model are shown); (b) iodine adsorption kinetics on different MOF materials at an initial iodine concentration of ~200 ppm in cyclohexane solutions; (c) iodine vapor adsorption kinetics on different MOF materials at 75 °C; (d) recyclability of Th-BPYDC for iodine adsorption from cyclohexane solution.

Full size|PPT slide

Adsorption performance was further determined under iodine vapor conditions. As shown in Fig.4, the maximum saturated adsorption capacities of Th-BPYDC and Th-UiO-67 were 2.23 and 2.10 g∙g^–1, respectively after 24 h. Then, in order to explore the recycling performance of the materials, the cycling experiments of iodine in cyclohexane solution were performed on Th-BPYDC. As shown in Fig.4(d), the adsorption percentage of iodine still remained at 70% after four cycles, indicating that Th-BPYDC had high stability with good reusability (Fig. S5, cf. ESM). With the increase in the number of cycles, the decreased removal rate was derived from the mass loss of the material during the elution process. The Th-BPYDC and Th-UiO-67 before and after iodine adsorption were characterized and the results were shown in Fig.5. The PXRD of Th-BPYDC and Th-UiO-67 after adsorption in iodine cyclohexane solution and iodine vapor matched the PXRD of the two materials before adsorption, implying that the structures of the two materials did not change before and after the adsorption, which further indicated that the two materials were very stable (Fig.5(a) and Fig.5(b)). The iodine attached to the crystal surface and entered the pore, resulting in the disappearance of the diffraction peaks at 5° to 7° of the Th-UiO-67 (Fig. S6, cf. ESM). TGA analysis further revealed that iodine occupied the cavities of the Th-UiO-67 and Th-BPYDC (Fig. S7, cf. ESM). To further demonstrate the stability of the two materials, Fourier transform infrared spectroscopy (FTIR) was applied to characterize the Th-BPYDC and Th-UiO-67 before and after absorbing iodine vapor or iodine cyclohexane, and we found that the functional groups of Th-BPYDC and Th-UiO-67 did not change after adsorption (Fig.5(c) and Fig.5(d)). The above complementary analysis confirms that the structures of Th-BPYDC and Th-UiO-67 are very stable. In order to evaluate the adsorption mechanism of iodine cyclohexane and iodine vapor by Th-BPYDC and Th-UiO-67, the analysis was carried out by X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. The XPS spectra clearly showed the existence of iodine signals after adsorption, including I₃^– and I₂, indicating that charge transfer was formed between the MOFs framework and iodine, and part of the guest molecular iodine entered the pores of the MOFs (Fig.5(e), Fig.5(f), S8, S9, cf. ESM) [28]. The adsorption of I₃^– and I₂ on the two MOFs was further confirmed by Raman spectroscopy by the appearance of peaks at 110 cm^–1 (I₂ stretching vibration) and 160 cm^–1 (I₃^– stretching vibration) (Figs. S10 and S11, ESM) [29]. The above characterizations demonstrated that the bipyridine units enhanced the binding affinity towards I₂ and I₃⁻ anions, thus significantly boosting the adsorption uptake capacity and kinetics. The high uptake capacity of Th-BPYDC is comparable to other reported MOFs [28,29,36,45] (Tab.1). One can see that the Th-BPYDC shows higher adsorption capacity than other materials.

Tab.1 Comparison of the performance of different adsorbents for iodine adsorption in cyclohexane

Material	Conditions	Capacity for I2 (mg·g−1)	Temp.	Adsorption strategy	Ref.
MIL-53 (Al)	0.01 mol·L−1 solution I2 in cyclohexane	9.7	RT	Physisorption	[45]
MIL-100 (Al)	0.01 mol·L−1 solution I2 in cyclohexane	63	RT	Physisorption	[45]
CAU-1	0.01 mol·L−1 solution I2 in cyclohexane	290	RT	Pore surface functionalization	[45]
MIL-101-NH2	0.01 mol·L−1 solution I2 in cyclohexane	311	RT	Pore surface functionalization	[45]
MIL-120 (Al)	0.01 mol·L−1 solution I2 in cyclohexane	155	RT	Pore surface functionalization	[45]
Tb(Cu4I4)(ina*)3 (DMF)	0.69 mmol·L−1 solution I2 in cyclohexane	226	RT	Halide-halide interaction	[36]
Th-SINAP-7	200 mg·L−1 solution I2 in cyclohexane	107	RT	Charge transfer	[29]
Th-SINAP-8	200 mg·L−1 solution I2 in cyclohexane	258	RT	Charge transfer	[29]
Th-SINAP-10	200 mg·L−1 solution I2 in cyclohexane	292.4	RT	Charge transfer	[28]
Th-SINAP-12	200 mg·L−1 solution I2 in cyclohexane	298.5	RT	Charge transfer	[28]
Th-BPYDC	200 mg·L−1 solution I2 in cyclohexane	312.18	RT	Charge transfer	This Work
Th-UiO-67	200 mg·L−1 solution I2 in cyclohexane	196.7	RT	Charge transfer	This Work

Fig.5 (a) XRD patterns of Th-BPYDC after iodine adsorption studies; (b) XRD patterns of Th-UiO-67 after iodine adsorption studies; FTIR spectra of (c) Th-BPYDC and (d) Th-UiO-67 before and after iodine adsorption studies; I_3d XPS spectra for (e) Th-BPYDC and (f) Th-UiO-67 after iodine adsorption studies.

Full size|PPT slide

4 Conclusions

In conclusion, we successfully constructed a Th-based microporous metal-organic framework by utilizing a bipyridine substituted dicarboxylic linker. Th-BPYDC exhibited good iodine capture abilities in solution and vapor owing to the advantage of ordered porosity, good thermal and chemical stability. The bipyridine units of the host framework improved the binding affinity toward iodine, thus showing enhanced uptake and kinetic performances, which provides a new approach for iodine treatment through MOFs with thorium as the metal source. This study ultimately shows that bipyridine-functionalized Th-MOFs have great potential for capturing radioactive iodine from nuclear waste, organic solutions, and environmental pollution regulation.

Acknowledgements

We gratefully acknowledge funding support from the Science Challenge Project (Grant No. TZ2016004) and the Hunan Provincial Natural Science Foundation of China (Grant No. 2021JJ30565).

Electronic Supplementary Material

Supplementary material is available in the online version of this article at https://dx.doi.org/10.1007/s11705-022-2218-3 and is accessible for authorized users.

References

1 Adamantiades A, Kessides I. Nuclear power for sustainable development: current status and future prospects. Energy Policy, 2009, 37(12): 5149–5166

2 Mayer K, Wallenius M, Lutzenkirchen K, Horta J, Nicholl A, Rasmussen G, van Belle P, Varga Z, Buda R, Erdmann N, Kratz J V, Trautmann N, Fifield L K, Tims S G, Fröhlich M B, Steier P. Uranium from German nuclear power projects of the 1940s—a nuclear forensic investigation. Angewandte Chemie International Edition, 2015, 54(45): 13452–13456

3 Yang H, Liu X, Hao M, Xie Y, Wang X, Tian H, Waterhouse G I N, Kruger P E, Telfer S G, Ma S. Functionalized iron-nitrogen-carbon electrocatalyst provides a reversible electron transfer platform for efficient uranium extraction from seawater. Advanced Materials, 2021, 33(51): 2106621

4 Cheng G, Zhang A, Zhao Z, Chai Z, Hu B, Han B, Ai Y, Wang X. Extremely stable amidoxime functionalized covalent organic frameworks for uranium extraction from seawater with high efficiency and selectivity. Science Bulletin, 2021, 66(19): 1994–2001

5 Shen N, Yang Z, Liu S, Dai X, Xiao C, Taylor-Pashow K, Li D, Yang C, Li J, Zhang Y, Zhang M, Zhou R, Chai Z, Wang S. ⁹⁹TcO₄⁻ removal from legacy defense nuclear waste by an alkaline-stable 2D cationic metal organic framework. Nature Communications, 2020, 11(1): 1–12

6 Li J, Chen L, Shen N, Xie R, Sheridan M, Chen X, Sheng D, Zhang D, Chai Z, Wang S. Rational design of a cationic polymer network towards record high uptake of ⁹⁹TcO₄⁻ in nuclear waste. Science China. Chemistry, 2021, 64(7): 1251–1260

7 Li J, Li B, Shen N, Chen L, Guo Q, Chen L, He L, Dai X, Chai Z, Wang S. Task-specific tailored cationic polymeric network with high base-resistance for unprecedented ⁹⁹TcO₄^– cleanup from alkaline nuclear waste. ACS Central Science, 2021, 7(8): 1441–1450

8 Zhang J, Chen L, Dai X, Chen L, Zhai F, Yu W, Guo S, Yang L, Chen L, Zhang Y, He L, Chen C, Chai Z, Wang S. Efficient Sr-90 removal from highly alkaline solution by an ultrastable crystalline zirconium phosphonate. Chemical Communications, 2021, 57(68): 8452–8455

9 Hao M, Chen Z, Yang H, Waterhouse G I N, Ma S, Wang S. Pyridinium salt-based covalent organic framework with well-defined nanochannels for efficient and selective capture of aqueous ⁹⁹TcO₄^–. Science Bulletin, 2022, 67(9): 924–932

10 He L, Chen L, Dong X, Zhang S, Zhang M, Dai X, Liu X, Lin P, Li K, Chen C, Pan T, Ma F, Chen J, Yuan M, Zhang Y, Chen L, Zhou R, Han Y, Chai Z, Wang S. A nitrogen-rich covalent organic framework for simultaneous dynamic capture of iodine and methyl iodide. Chem, 2021, 7(3): 699–714

11 Soelberg N R, Garn T G, Greenhalgh M R, Law J D, Jubin R, Strachan D M, Thallapally P K. Radioactive iodine and krypton control for nuclear fuel reprocessing facilities. Science and Technology of Nuclear Installations, 2013, 2013: 1–12

12 Pryma D A, Mandel S J. Radioiodine therapy for thyroid cancer in the era of risk stratification and alternative targeted therapies. Journal of Nuclear Medicine, 2014, 55(9): 1485–1491

13 Liu X, Zhang A, Ma R, Wu B, Wen T, Ai Y, Sun M, Jin J, Wang S, Wang X. Experimental and theoretical insights into copper phthalocyanine-based covalent organic frameworks for highly efficient radioactive iodine capture. Chinese Chemical Letters, 2022, 33(7): 3549–3555

14 Liu X, Pang H, Liu X, Li Q, Zhang N, Mao L, Qiu M, Hu B, Yang H, Wang X. Orderly porous covalent organic frameworks-based materials: superior adsorbents for pollutants removal from aqueous solutions. Innovation, 2021, 2(1): 100076

15 Xie W, Cui D, Zhang S R, Xu Y H, Jiang D L. Iodine capture in porous organic polymers and metal–organic frameworks materials. Materials Horizons, 2019, 6(8): 1571–1595

16 Li J R, Kuppler R J, Zhou H C. Selective gas adsorption and separation in metal–organic frameworks. Chemical Society Reviews, 2009, 38(5): 1477–1504

17 Murray L J, Dincă M, Long J R. Hydrogen storage in metal-organic frameworks. Chemical Society Reviews, 2009, 38(5): 1294–1314

18 Xue D X, Wang Q, Bai J. Amide-functionalized metal–organic frameworks: syntheses, structures and improved gas storage and separation properties. Coordination Chemistry Reviews, 2019, 378: 2–16

19 Dolgopolova E A, Rice A M, Martin C R, Shustova N B. Photochemistry and photophysics of MOFs: steps towards MOF-based sensing enhancements. Chemical Society Reviews, 2018, 47(13): 4710–4728

20 He C, Liu D, Lin W. Nanomedicine applications of hybrid nanomaterials built from metal-ligand coordination bonds: nanoscale metal–organic frameworks and nanoscale coordination polymers. Chemical Reviews, 2015, 115(19): 11079–11108

21 Drake T, Ji P, Lin W. Site isolation in metal–organic frameworks enable novel transition metal catalysis. Accounts of Chemical Research, 2018, 51(9): 2129–2138

22 Hao M, Qiu M, Yang H, Hu B, Wang X. Recent advances on preparation and environmental applications of MOF-derived carbons in catalysis. Science of the Total Environment, 2021, 760: 143333

23 Chen T, Yu K, Dong C, Yuan X, Gong X, Lian J, Cao X, Li M, Zhou L, Hu B, He R, Zhu W, Wang X. Advanced photocatalysts for uranium extraction: elaborate design and future perspectives. Coordination Chemistry Reviews, 2022, 467: 214615

24 Cui Y, Yue Y, Qian G, Chen B. Luminescent functional metal–organic frameworks. Chemical Reviews, 2012, 112(2): 1126–1162

25 Yu S, Pang H, Huang S, Tang H, Wang S, Qiu M, Chen Z, Yang H, Song G, Fu D, Hu B, Wang X. Recent advances in metal–organic frameworks membranes for water treatment: a review. Science of the Total Environment, 2021, 800: 149662

26 Zhang S, Wang J, Zhang Y, Ma J, Huang L, Yu S, Chen L, Song G, Qiu M, Wang X. Applications of water-stable metal–organic frameworks in the removal of water pollutants: a review. Environmental Pollution, 2021, 291: 118076

27 Liu X, Xie Y, Hao M, Chen Z, Yang H, Waterhouse G I N, Ma S, Wang X K. Highly efficient electrocatalytic uranium extraction from seawater over an amidoxime-functionalized In-N-C catalyst. Advanced Science, 2022, 9(23): 2201735

28 Li Z J, Ju Y, Yu B, Wu X, Lu H, Li Y, Zhou J, Guo X, Zhang Z H, Lin J, Wang J Q, Wang S. Modulated synthesis and isoreticular expansion of Th-MOFs with record high pore volume and surface area for iodine adsorption. Chemical Communications, 2020, 56(49): 6715–6718

29 Li Z J, Yue Z, Ju Y, Wu X, Ren Y, Wang S, Li Y, Zhang Z H, Guo X, Lin J, Wang J Q. Ultrastable thorium metal–organic frameworks for efficient iodine adsorption. Inorganic Chemistry, 2020, 59(7): 4435–4442

30 Sava D F, Chapman K W, Rodriguez M A, Greathouse J A, Crozier P S, Zhao H, Chupas P J, Nenoff T M. Competitive I₂ sorption by Cu-BTC from humid gas streams. Chemistry of Materials, 2013, 25(13): 2591–2596

31 Li B, Dong X, Wang H, Ma D, Tan K, Jensen S, Deibert B J, Butler J, Cure J, Shi Z, Thonhauser T, Chabal Y J, Han Y, Li J. Capture of organic iodides from nuclear waste by metal–organic framework-based molecular traps. Nature Communications, 2017, 8(1): 1–9

32 Zhang X, da Silva I, Godfrey H G W, Callear S K, Sapchenko S A, Cheng Y, Vitorica-Yrezabal I, Frogley M D, Cinque G, Tang C C, Giacobbe C, Dejoie C, Rudić S, Ramirez-Cuesta A J, Denecke M A, Yang S, Schröder M. Confinement of iodine molecules into triple-helical chains within robust metal–organic frameworks. Journal of the American Chemical Society, 2017, 139(45): 16289–16296

33 Valizadeh B, Nguyen T N, Smit B, Stylianou K C. Porous metal–organic framework@polymer beads for iodine capture and recovery using a gas-sparged column. Advanced Functional Materials, 2018, 28(30): 1801596

34 Banerjee D, Chen X, Lobanov S S, Plonka A M, Chan X, Daly J A, Kim T, Thallapally P K, Parise J B. Iodine adsorption in metal organic frameworks in the presence of humidity. ACS Applied Materials & Interfaces, 2018, 10(13): 10622–10626

35 Leloire M, Walshe C, Devaux P, Giovine R, Duval S, Bousquet T, Chibani S, Paul J F, Moissette A, Vezin H, Nerisson P, Cantrel L, Volkringer C, Loiseau T. Capture of gaseous iodine in isoreticular zirconium-based UiO-n metal–organic frameworks: influence of amino functionalization, DFT calculations, Raman and EPR spectroscopic investigation. Chemistry, 2022, 28(14): e202104437

36 Hu Y Q, Li M Q, Wang Y, Zhang T, Liao P Q, Zheng Z, Chen X M, Zheng Y Z. Direct observation of confined I⁻···I₂···I⁻ interactions in a metal-organic framework: iodine capture and sensing. Chemistry, 2017, 23(35): 8409–8413

37 Wang L, Li T, Dong X, Pang M, Xiao S, Zhang W. Thiophene-based MOFs for iodine capture: effect of pore structures and interaction mechanism. Chemical Engineering Journal, 2021, 425: 130578

38 Ju Y, Li Z J, Lu H, Zhou Z, Li Y, Wu X L, Guo X, Qian Y, Zhang Z H, Lin J, Wang J Q, He M Y. Interpenetration control in thorium metal–organic frameworks: structural complexity toward iodine adsorption. Inorganic Chemistry, 2021, 60(8): 5617–5626

39 Munn A S, Millange F, Frigoli M, Guillou N, Falaise C, Stevenson V, Volkringer C, Loiseau T, Cibin G, Walton R I. Iodine sequestration by thiol-modified MIL-53 (Al). CrystEngComm, 2016, 18(41): 8108–8114

40 Mehlana G, Ramon G, Bourne S A. A 4-fold interpenetrated diamondoid metal–organic framework with large channels exhibiting solvent sorption properties and high iodine capture. Microporous and Mesoporous Materials, 2016, 231: 21–30

41 Jia M W, Li J T, Che S T, Kan L, Li G H, Liu Y L. Two Cu_xI_y-based copper-organic frameworks with multiple secondary building units (SBUs): structure, gas adsorption and impressive ability of I₂ sorption and release. Inorganic Chemistry Frontiers, 2019, 6(5): 1261–1266

42 Xu T, Li J T, Jia M W, Li G H, Liu Y L. Contiguous layer-based metal–organic framework with conjugated π-electron ligand for high iodine capture. Dalton Transactions, 2021, 50(37): 13096–13102

43 Luo D, He Y, Tian J, Sessler J L, Chi X D. Reversible iodine capture by nonporous adaptive crystals of a bipyridine cage. Journal of the American Chemical Society, 2022, 144(1): 113–117

44 HaoMLiuXLiuXZhangJYangHWaterhouseG I NWangXMaS. Converging cooperative functions into the nanospace of covalent organic frameworks for efficient uranium extraction from seawater. CCS Chemistry, 2022, 4: 2294–2307

45 Falaise C, Volkringer C, Facqueur J, Bousquet T, Gasnot L, Loiseau T. Capture of iodine in highly stable metal–organic frameworks: a systematic study. Chemical Communications, 2013, 49(87): 10320–10322