Role of Zeolite Structural Properties toward Iodine Capture: A Head-to-head Evaluation of Framework Type and Chemical Composition

Lignin-based porous carbon/palygorskite composites doped with different metals for efficient iodine capture: Structure, performance, and mechanism

Radioactive iodine waste from the nuclear power industry will cause air and water pollution. Here, a series of metal (Bi, Zn and Fe)-doped lignin-based porous carbon/palygorskite composites (ELC-P-X) were prepared by wet impregnation and carbonization method for enhancing the iodine capture. Their morphology, porosity, and surface functional groups of ELC-P-X were characterized in detail, these metal species showed different sizes of nanoparticles with the oxide form. Zn, Fe doping enhanced its porosity of ELC-P (247.5 m2/g), and up to 359.5 m2/g, while Bi doping had slight negative influence on the porosity. Adsorption experiments showed that the iodine vapor adsorption capacity of ELC-P-X followed an order of ELC-P-Zn > ELC-P-Fe > ELC-P-Bi> ELC-P, the highest adsorption capacity can reach 650.0 mg/g. The results suggested that above metal doping can promote iodine vapor adsorption. Meanwhile, the adsorption capacity of ELC-P-X for iodine in n-hexane solution only showed an increase on ELC-P-Fe (362.2 mg/g), compared to ELC-P (332.0 mg/g). ELC-P-Fe still had good adsorption stability, acid and alkali resistance and cycling performance. We found that the adsorption of iodine vapor could mainly depend on the porosity of ELC-P-X materials, while the surface functional groups, iodine-affinity metal species, and micro-nano structure made a major contribution synergistically to the enhanced adsorption for the iodine solution. The adsorption mechanism study revealed that the Lewis acid-base interaction, electrostatic interactions, and charge transfer action accompanied by weak chemisorption were the main driving force for the iodine molecule adsorption on ELC-P-Fe. This work provided an important reference for the rational preparation of lignin based iodine adsorbents and proposed a kind of universal strategy for enhancing iodine adsorption.

Flexible Linker Spacer Length Modulation in Cd-Based Metal-Organic Frameworks: Impact on Polarity and Sequestration Abilities

The heightening concerns over an outbreak of hazardous radioiodine from nuclear waste and carbon dioxide emissions from fossil fuels have restricted access to clean water and air. In this work, three Cd-MOFs (1-3) are self-assembled under environment-friendly conditions using i) a polypyridyl linker spanned by a flexible poly(methylene) spacer, and ii) a bent dicarboxylate linker. With a change in the length of the flexible methylene spacer, the dimensionality of the MOFs is tuned between 3D (1) and 2D (2 and 3). The microscopic images reveal that 1 displays larger particle sizes and a more pronounced morphology compared to 2 and 3. These MOFs show high thermal stability (up to 300 °C) and wettability. A controlled polar feature of 1-3 is utilized to achieve a high uptake capacity of iodine (I2 or I3 -) from water bodies (2.46-2.37 g g-1) and vapor (3.31-2.65 g g-1). With remarkable CO2 uptake by 1-3, the sorbate CO2 is further fixated into market-value products in quantitative conversions and atom economy under room temperature and solvent-free conditions. A comprehensive theoretical support is provided by configurational biased Monte Carlo (CBMC) simulations to reveal the exact locale and binding energies of the sorbates (I2, CO2, and epoxide) toward these MOFs.

Virtual Database Construction and Machine-Learning-Assisted High-Throughput Evaluation of Amorphous Porous Carbon Materials as Iodine Sorbents

We present a comprehensive approach to enable the high-throughput screening and analysis of amorphous porous carbon (APC) materials as effective I2 sorbents for the nuclear industry. A diverse virtual database of 19,599 APC models was established from scratch through liquid quenching molecular dynamics simulations. Large-scale grand canonical Monte Carlo simulation at a series of I2 concentrations was carried out for sampled APCs to generate an array of I2 adsorption capacities. Machine learning and SHapley Additive exPlanations (SHAP) analysis were employed to investigate the impact of various extracted (structural and chemical) features of the APC materials on their respective I2 adsorption behavior, revealing influential factors (surface area, pore size ranges, etc.) for APC development that varied with I2 concentrations. This work attempts to provide both fundamental databases and research frameworks to accelerate the development and enhance the understanding of APC materials.

Recent Advances in Metal-Organic Frameworks and Their Derivatives for Adsorption of Radioactive Iodine

Radioactive iodine (131I) with a short half-life of ~8.02 days is one of the most commonly used nuclides in nuclear medicine. However, 131I easily poses a significant risk to human health and ecological environment. Therefore, there is an urgent need to develop a secure and efficient strategy to capture and store radioactive iodine. Metal-organic frameworks (MOFs) are a new generation of sorbents with outstanding physical and chemical properties, rendering them attractive candidates for the adsorption and immobilization of iodine. This review focuses on recent research advancements in mechanisms underlying iodine adsorption over MOFs and their derivatives, including van der Waals interactions, complexing interactions, and chemical precipitation. Furthermore, this review concludes by outlining the challenges and opportunities for the safe disposal of radioactive iodine from the perspective of the material design and system evaluation based on our knowledge. Thus, this paper aims to offer necessary information regarding the large-scale production of MOFs for iodine adsorption.

N-Heteroatom Engineered Nonporous Amorphous Self-Assembled Coordination Cages for Capture and Storage of Iodine

Radioactive iodine isotopes from nuclear-related activities, present substantial risks to human health and the environment. Developing effective materials for the capture and storage of these hazardous molecules is paramount. Traditionally, nonporous solids were historically considered ineffective for adsorbing target species. In this study, we investigate the potential of four nonporous, amorphous, self-assembled coordination cages (C1, C2, C3, and C4) featuring varying numbers of nitrogen atoms within the core (pyridyl/triazine unit) and specific cavity sizes for iodine adsorption. These coordination cages demonstrate remarkable adsorption abilities for iodine in both vapor and solution phases, facilitated by enhanced electron-pair interactions. The cages exhibit high uptake capacities of up to 3.16 g g-1 at 75 °C, the highest among metal-organic cages and up to 434.29 mg g-1 in solution, highlighting the efficiency of these materials across different phases. Even at ambient temperature, they show significant iodine capture efficiency, with a maximum value of 1.5 g g-1. Furthermore, these robust materials can be recycled, enduring at least five reusable cycles without apparent fatigue. Overall, our findings present a "N-heteroatom engineering" approach for the development of recyclable amorphous containers for the capture and storage of iodine, contributing to the mitigation of nuclear-related risks.

Metal-Encapsulated, Polymer-Containing Halide Salt Composites as Potential Long-Term Hosts for Radioiodine: Evaluating Halmets, Polyhalmets, and Halcermets

This paper presents composite waste form concepts for radioiodine immobilization including halide-metal (halmet) composites, polymer-halide-metal (polyhalmet) composites, and halide-ceramic-metal (halcermet) composites with data from experiments to evaluate these ideas. The encapsulant metal of choice for the pellets was Bi0, and a cold-press-and-sinter approach was used for creating the pellets. A polymer (i.e., polyacrylonitrile or PAN) phase was included in some composite forms because this porous, passive polymer is used as a host matrix for active chemisorption-based getters. Metals of Ag0, Bi0, and Cu0 were separately embedded into PAN beads, which were loaded with iodine in static tests. Included are details of experiments where PAN removal from the iodine-loaded composite beads was evaluated to reduce the overall volume of the final waste requiring immobilization and to improve the thermal stability of the final composite form. While these experiments demonstrate new concepts for radioiodine immobilization, more work is needed to fully understand the limitations of these approaches and further optimizations are needed before implementation at larger scales is feasible.

Synthesis and Characterization of Silver-Modified Nanoporous Silica Materials for Enhanced Iodine Removal

In aquatic environments, the presence of iodine species, including radioactive isotopes like 129I and I2, poses significant environmental and health concerns. Iodine can enter water resources from various sources, including nuclear accidents, medical procedures, and natural occurrences. To address this issue, the use of natural occurring nanoporous minerals, such as zeolitic materials, for iodine removal will be explored. This study focuses on the adsorption of iodine by silver-modified zeolites (13X-Ag, 5A-Ag, Chabazite-Ag, and Clinoptilolite-Ag) and evaluates their performance under different conditions. All materials were characterized using scanning electron microscopey (SEM), energy-dispersive X-ray spectroscopy (EDS), powdered X-ray diffraction (P-XRD), Fourier-transform infrared spectrometry (FTIR), and nitrogen adsorption studies. The results indicate that Chabazite-Ag exhibited the highest iodine adsorption capacity, with an impressive 769 mg/g, making it a viable option for iodine removal applications. 13X-Ag and 5A-Ag also demonstrated substantial adsorption capacities of 714 mg/g and 556 mg/g, respectively, though their behavior varied according to different models. In contrast, Clinoptilolite-Ag exhibited strong pH-dependent behavior, rendering it less suitable for neutral to slightly acidic conditions. Furthermore, this study explored the impact of ionic strength on iodine adsorption, revealing that Chabazite-Ag is efficient in low-salinity environments with an iodine adsorption capacity of 51.80 mg/g but less effective in saline conditions. 5A-Ag proved to be a versatile option for various water treatments, maintaining its iodine adsorption capacity across different salinity levels. In contrast, Clinoptilolite-Ag exhibited high sensitivity to ionic competition, virtually losing its iodine adsorption ability at a NaCl concentration of 0.1 M. Kinetic studies indicated that the pseudo-second-order model best describes the adsorption process, suggesting chemisorption mechanisms dominate iodine removal. Chabazite-Ag exhibited the highest initial adsorption rate with a k2 value of 0.002 mg g-1 h-1, emphasizing its superior adsorption capabilities. Chabazite and Clinoptilolite, naturally occurring minerals, provide eco-friendly solutions for iodine adsorption. Chabazite superior iodine removal highlights its value in critical applications and its potential for addressing pressing environmental challenges.

Engineered Nanoporous Frameworks for Adsorption Cooling Applications

The energy demand for traditional vapor-compressed technology for space cooling continues to soar year after year due to global warming and the increasing human population's need to improve living and working conditions. Thus, there is a growing demand for eco-friendly technologies that use sustainable or waste energy resources. This review discusses the properties of various refrigerants used for adsorption cooling applications followed by a brief discussion on the thermodynamic cycle. Next, sorbents traditionally used for cooling are reviewed to emphasize the need for advanced capture materials with superior properties to improve refrigerant sorption. The remainder of the review focus on studies using engineered nanoporous frameworks (ENFs) with various refrigerants for adsorption cooling applications. The effects of the various factors that play a role in ENF-refrigerant pair selection, including pore structure/dimension/shape, morphology, open-metal sites, pore chemistry and possible presence of defects, are reviewed. Next, in-depth insights into the sorbent-refrigerant interaction, and pore filling mechanism gained through a combination of characterization techniques and computational modeling are discussed. Finally, we outline the challenges and opportunities related to using ENFs for adsorption cooling applications and provide our views on the future of this technology.

Highly Efficient Capture of Volatile Iodine by Conjugated Microporous Polymers Constructed Using Planar 3- and 4-Connected Organic Monomers

The effective capture and recovery of radioiodine species associated with nuclear fuel reprocessing is of significant importance in nuclear power plants. Porous materials have been proven to be one of the most effective adsorbents for the capture of radioiodine. In this work, we design and synthesize a series of conjugated microporous polymers (CMPs), namely, TPDA-TFPB CMP, TPDA-TATBA CMP, and TPDA-TECHO CMP, which are constructed based on a planar rectangular 4-connected organic monomer and three triangular 3-connected organic monomers, respectively. The resultant CMPs are characterized using various characterization techniques and used as effective adsorbents for iodine capture. Our experiments indicated that the CMPs exhibit excellent iodine adsorption capacities as high as 6.48, 6.25, and 6.37 g g-1 at 348 K and ambient pressure. The adsorption mechanism was further investigated and the strong chemical adsorption between the iodine and the imine/tertiary ammonia of the CMPs, 3D network structure with accessible hierarchical pores, uniform micromorphology, wide π-conjugated structure, and high-density Lewis-base sites synergistically contribute to their excellent iodine adsorption performance. Moreover, the CMPs demonstrated good recyclability. This work provides guidance for the construction of novel iodine adsorbent materials with high efficiency in the nuclear power field.

Investigation of bismuth-based metal-organic frameworks for effective capture and immobilization of radioiodine gas

In this study, we investigated the use of Bi-mna, a specific type of bismuth metal organic framework (MOF) for the capture and disposal of iodine, a key nuclide of concern in nuclear fuel reprocessing plants and nuclear power plants. To find the suitable form of Bi-mna for the purpose, experiments were performed by synthesizing four different Bi-mna with varying reagent ratios and connecting iodine adsorption and conversion for immobilization. After iodine adsorption and characterization to investigate their adsorption mechanisms, the Bi-mna samples went through conversion for immobilization to fix captured iodine into the adsorbents. The converted materials are characterized to examine their thermal stability. The Bi-2mna, showing the best performance of adsorption and thermal stability after the conversion, was selected to explore its chemical stability. According to the test results, the converted compound showed relatively low leaching rate (3.06 ×10-5 g/m2∙day) compared with other iodine containing waste forms for disposal. Based on the results, we proposed the Bi-2mna as a candidate material as iodine adsorbent as well as waste form precursor. ENVIRONMENTAL IMPLICATION: Radioiodine a key nuclide of concern in nuclear fuel reprocessing plants and nuclear power plants. Once ingested, it is accumulated in thyroid grand, causing negative health effects. Currently, a typical radioiodine adsorbent is silver-based zeolites. Despite a strong affinity to iodine of silver, it has a chemical toxicity that causes a potential issue in disposal. Therefore, it is substantially required to develop new type of adsorbents which are both good for capture and disposal of radioiodine. In this respect, we suggested a bismuth-based metal-organic framework as an alternative adsorbent to manage the life cycle of radioiodine.

Enhancing Iodine Capture of Porous Organic Cages through N-Heteroatom Engineering

Iodine radioisotopes, produced or released during nuclear-related activities, severely affect human health and the environment. The efficient removal of radioiodine from both aqueous and vapor phases is crucial for the sustainable development of nuclear energy. In this study, we propose an "N-heteroatom engineering" strategy to design three porous organic cages with N-containing functional groups for efficient iodine capture. Among the molecular cages investigated, FT-Cage incorporating tertiary amine groups and RT-Cage with secondary amine groups show higher adsorption capacity and much faster iodine release compared to IT-Cage with imine groups. Detailed investigations demonstrate the superiority of amine groups, along with the influence of crystal structures and porosity, for iodine capture. These findings provide valuable insights for the design of porous organic cages with enhanced capabilities for capturing iodine.

Hierarchical Porous Activated Carbon from Wheat Bran Agro-Waste: Applications in Carbon Dioxide Capture, Dye Removal, Oxygen and Hydrogen Evolution Reactions

This work reports an efficient method for facile synthesis of hierarchically porous carbon (WB-AC) utilizing wheat bran waste. Obtained carbon showed 2.47 mmol g-1 CO2 capture capacity with good CO2 /N2 selectivity and 27.35 to 29.90 kJ mol-1 isosteric heat of adsorption. Rapid removal of MO dye was observed with a capacity of ~555 mg g-1 . Moreover, WB-AC demonstrated a good OER activity with 0.35 V low overpotential at 5 mA cm-2 and a Tafel slope of 115 mV dec-1 . It also exhibited high electrocatalytic HER activity with 57 mV overpotential at 10 mA cm-2 and a Tafel slope of 82.6 mV dec-1 . The large SSA (757 m2  g-1 ) and total pore volume (0.3696 cm3  g-1 ) result from N2 activation contributing to selective CO2 uptake, high and rapid dye removal capacity and superior electrochemical activity (OER/HER), suggesting the use of WB-AC as cost effective adsorbent and metal free electrocatalyst.

Enhanced Iodine Capture Using a Postsynthetically Modified Thione-Silver Zeolitic Imidazole Framework

Efficient management of radionuclides that are released from various processes in the nuclear fuel cycle is of significant importance. Among these nuclides, radioactive iodine (mainly 129I and 131I) is a major concern due to the risk it poses to the environment and to human health; thus, the development of materials that can capture and safely store radioactive iodine is crucial. Herein, a novel silver-thione-functionalized zeolitic imidazole framework (ZIF) was synthesized via postsynthetic modification and assessed for its iodine uptake capabilities alongside the parent ZIF-8 and intermediate materials. A solvent-assisted ligand exchange procedure was used to replace the 2-methylimidazole linkers in ZIF-8 with 2-mercaptoimidazole, forming intermediate compound ZIF-8 = S, which was reacted with AgNO3 to yield the ZIF-8 = S-Ag+ composite for iodine uptake. Despite possessing the lowest BET surface area of the derivatives, the Ag-functionalized material demonstrated superior I2 adsorption in terms of both maximum capacity (550 g I2/mol) and rapid kinetics (50% loading achieved in 5 h, saturation in 50 h) compared to that of our pristine ZIF-8, which reached 450 g I2/mol after 150 h and 50% loading in 25 h. This improvement is attributed to the presence of the Ag+ ions, which provide a strong chemical driving force to form a stable Ag-I species. The results of this study contribute to a broader understanding of the strategies that can be employed to engineer adsorbents with robust iodine uptake behavior.

[Sn2S6]4- Anion-Intercalated Layered Double Hydroxides for Highly Efficient Capture of Iodine

The development of low-cost and high-efficiency iodine sorbents is of great significance for the control of nuclear pollution. In this work, we intercalate the tin sulfide cluster of [Sn2S6]4- to Mg/Al-type layered double hydroxides to obtain Sn2S6-LDH, which exhibits highly efficient capture performance of iodine vapor and iodine in solutions. The dispersion effect of the positively charged LDH layers contributes to the adequate exposure of [Sn2S6]4- anions, providing plentiful adsorption sites. For iodine vapor, Sn2S6-LDH showed an extremely large iodine capture capacity of 2954 mg/g with a large contribution from physisorption. For iodine in solutions, a significantly large sorption capacity of 1308 mg/g was achieved. During iodine capture, I2 molecules were reduced to I- ions (by S2- in [Sn2S6]4-), which then reacted with Sn4+ to form SnI4, where the molar amount of captured iodine is 4-fold that of Sn. Besides, the as-reduced I- combined with I2 again to generate [I3]-, which then entered the LDH interlayers to maintain electric neutrality. While reducing iodine, S2- itself in [Sn2S6]4- was oxidized to S8, which further combined with SnI4 to form a novel compound of SnI4(S8)2. The excellent iodine capture capability endows Sn2S6-LDH with a promising application in trapping radioactive iodine.

In situ growth of UiO-66-NH2 in wood-derived cellulose for iodine adsorption

The capture of radioactive iodine is an inevitable requirement in nuclear industry for environmental protection. Metal-organic frameworks (MOFs) are a new generation of sorbents that have wide applications for iodine adsorption and recovery. Although the loading of MOFs on wood can avoid the drawbacks of the powder form of MOFs in implementation, the dense structure of wood results in the lower loading, even after delignification, which limits the adsorption capacity. Herein, a hierarchically porous UiO-66-NH₂ @WCA composite was fabricated by in-situ synthesis of UiO-66-NH₂ in wood-derived cellulose aerogel (WCA) that was further removed hemicellulose from delignified wood. UiO-66-NH₂ @WCA exhibited a high loading (36 wt%) of UiO-66-NH₂ crystals and a high adsorption capacity of 704 mg/g for iodine vapor and 248 mg/g for iodine aqueous solution. The adsorption behavior in iodine aqueous solution was well predicted by the Freundlich isotherm and pseudo-second-order kinetic model. The adsorption capacity of UiO-66-NH₂ @WCA was highest in solution when the pH was 6, while the ionic strength had little effect. The hydroxyl groups on the WCA matrix had a charge transfer effect with iodine, providing additional sites for iodine capture. Furthermore, a packed column system was applied to demonstrate the excellent recyclability and potential for practical application.

Review of recent developments in iodine wasteform production

Radioiodine capture and immobilization is not only important to consider during the operation of reactors (i.e., I-131), during nuclear accidents (i.e., I-131 and I-129) or nuclear fuel reprocessing (i.e., I-131 and I-129), but also during disposal of nuclear wastes (i.e., I-129). Most disposal plans for I-129-containing waste forms (including spent nuclear fuel) propose to store them in underground repositories. Here, iodine can be highly mobile and, given its radiotoxicity, needs to be carefully managed to minimize long-term environmental impacts arising from disposal. Typically, any process that has been used to capture iodine from reprocessing or in a reactor is not suitable for direct disposal, rather conversion into a wasteform for disposal is required. The objectives of these materials are to use either chemical immobilization or physical encapsulation to reduce the leaching of iodine by groundwaters. Some of the more recent ideas have been to design capture materials that better align with disposal concepts, making the industrial processing requirements easier. Research on iodine capture materials and wasteforms has been extensive. This review will act as both an update on the state of the research since the last time it was comprehensively summarized, and an evaluation of the industrial techniques required to create the proposed iodine wasteforms in terms of resulting material chemistry and applicability.

In Situ Confined Synthesis of a Copper-Encapsulated Silicalite-1 Zeolite for Highly Efficient Iodine Capture

Effective capture of radioactive iodine is highly desirable for decontamination purposes in spent fuel reprocessing. Cu-based adsorbents with a low cost and high chemical affinity for I2 molecules act as a decent candidate for iodine elimination, but the low utilization and stability remain a significant challenge. Herein, a facile in situ confined synthesis strategy is developed to design and synthesize a copper-encapsulated flaky silicalite-1 (Cu@FSL-1) zeolite with a thickness of ≤300 nm. The maximum iodine uptake capacity of Cu@FSL-1 can reach 625 mg g-1 within 45 min, which is 2 times higher than that of a commercial silver-exchanged zeolite even after nitric acid and NOX treatment. The Cu nanoparticles (NPs) confined within the zeolite exert superior iodine adsorption and immobilization properties as well as high stability and fast adsorption kinetics endowed by the all-silica zeolite matrix. This study provides new insight into the design and controlled synthesis of zeolite-confined metal adsorbents for efficient iodine capture from gaseous radioactive streams.

Synthesis of Iron(II) Clathrochelate-Based Poly(vinylene sulfide) with Tetraphenylbenzene Bridging Units and Their Selective Oxidation into Their Corresponding Poly(vinylene sulfone) Copolymers: Promising Materials for Iodine Capture

The development of a simple and efficient synthetic methodology to engineer functional polymer materials for gas adsorption is necessary due to its relevance for various applications. Herein, we report the synthesis of metalorganic poly(vinylene sulfide) copolymers CTP1-3 with iron(II) clathrochelate of various side groups connected by tetraphenylbenzene units. CTP1-3 were subsequently oxidized into their respective poly(vinylene sulfone) copolymers CTP4-6 under green reaction conditions. The target copolymers CTP1-6 were characterized using various instrumental analysis techniques. Examination of the iodine adsorption properties of the copolymers revealed high iodine uptake properties, reaching 2360 mg g−1 for CTP2, and whose reusability tests proved its efficient regeneration, thus proving the importance of iron(II) clathrochelate polymers in iodine capture.

Radioiodine sorbent selection criteria

Methods for preventing radioiodine from entering the environment are needed in processes related to nuclear energy and medical isotope production. The development and performance of many different types of sorbents to capture iodine have been reported on for decades; however, there is yet to be a concise overview on the important parameters that should be considered when selecting a material for chemically capturing radioiodine. This paper summarizes several criteria that should be considered when selecting candidate sorbents for implementation into real-world systems. The list of selection criteria discussed are 1) optimal capture performance, 2) kinetics of adsorption, 3) performance under relevant process conditions, 4) properties of the substrate that supports the getter, and 5) environmental stability and disposition pathways for iodine-loaded materials.

Synthesis of Electron-Rich Porous Organic Polymers via Schiff-Base Chemistry for Efficient Iodine Capture

As one of the main nuclear wastes generated in the process of nuclear fission, radioactive iodine has attracted worldwide attention due to its harm to public safety and environmental pollution. Therefore, it is of crucial importance to develop materials that can rapidly and efficiently capture radioactive iodine. Herein, we report the construction of three electron-rich porous organic polymers (POPs), denoted as POP-E, POP-T and POP-P via Schiff base polycondensations reactions between Td-symmetric adamantane knot and four-branched “linkage” molecules. We demonstrated that all the three POPs showed high iodine adsorption capability, among which the adsorption capacity of POP-T for iodine vapor reached up to 3.94 g·g⁻¹ and the removal rate of iodine in n-hexane solution was up to 99%. The efficient iodine capture mechanism of the POP-T was investigated through systematic comparison of Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) before and after iodine adsorption. The unique π-π conjugated system between imine bonds linked aromatic rings with iodine result in charge-transfer complexes, which explains the exceptional iodine capture capacity. Additionally, the introduction of heteroatoms into the framework would also enhance the iodine adsorption capability of POPs. Good retention behavior and recycling capacity were also observed for the POPs.