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Chemically Stable and Heteroatom Containing Porous Organic Polymers for Efficient Iodine Vapor Capture and its Storage
... The development of porous organic polymer for halogen adsorption guided several principles and mechanisms for structural design, but most porous material has been reported for iodine adsorption. [18][19][20][21][22][23][24][25][26][27][28][29] Halogens are electrophilic and have an affinity towards electron-rich species. [30] According to the recent literature incorporating electron-rich binding sites and electron-rich heteroatom-containing monomers like nitrogen and sulfur units in the structure of moiety efficiently adsorbed iodine. ...
Bromine is a significant environmental threat due to its corrosive nature and contribution to ozone layer depletion. It often coexists with iodine and forms interhalogen complexes (IBr), which require an effective and selective bromine adsorption strategy. Leveraging the electrophilic nature of bromine, we designed an electron‐rich thiophene‐based porous organic polymer (POF‐2). This material exhibits exceptional efficiency for bromine adsorption (2.86 g g⁻¹) and rapid uptake kinetic from aqueous solutions, driven by noncovalent charge transfer interactions. POF‐2 also demonstrates selective capture of bromine from a bromine‐iodine mixture in cyclohexane. The material's electron‐rich sites exhibit a stronger orbital interaction with the σ* orbital of bromine compared to iodine, leading to the observed selectivity in cyclohexane.
... Several studies on catalysis and adsorption by various POPs were reported, focusing mainly on the catalytic efficiency [25][26][27] and adsorption capacity. [28][29][30][31][32][33][34] However, correlation studies are very limited and not generalized. Thus, herein, we attempted to establish a correlation between adsorption capacity and catalytic efficiency with these above-mentioned structural features of isoreticular POPs. ...
The impact of surface area, pore volume, and heteroatom type on the performance of porous organic polymers (POPs) in various applications remains unclear. To investigate this, three isoreticular POPs were employed having one common building block, resulting in varying surface areas, pore volumes, and heteroatom compositions. This study aimed to establish a correlation between the structural features of POPs (surface area, pore volume, and heteroatom type) with their adsorption capacity, and catalytic efficiency. To explore this relationship, the Knoevenagel condensation reaction was used as a model system, testing various substituted aldehydes to further validate our findings. Additionally, the capture of radioactive iodine vapor at 75 °C was simulated to examine the correlation with adsorption capacity, comparing the gravimetric iodine uptake capacity of each POP to gain insights into this relationship.
... To gain further insights into iodine adsorption, we conducted FT-IR, SEM, BET, and PXRD studies for I 2 @CTPB and I 2 @STPB. [47][48] In FT-IR spectra, there has been a shift in the secondary amine (À NH) bands from 3300 cm À 1 to 3378 cm À 1 for CTPB and from 3200 cm À 1 to 3230 cm À 1 for STPB. Additionally, the stretching frequencies of À C=O and À C=N shifted from 1710 cm À 1 and 1520 cm À 1 to 1702 cm À 1 and 1503 cm À 1 for CTPB and from 1715 cm À 1 and 1590 cm À 1 to 1701 cm À 1 and 1570 cm À 1 for STPB, respectively ( Figure S22). ...
Given the rapid growth of the nuclear sector, effective treatment of radioactive iodine is critical. Herein, we report the synthesis and the iodine adsorption properties of croconic acid (CTPB) and squaric acid (STPB) containing π‐conjugated novel zwitterionic conjugated porous polymers (CPPs). The CPPs have been synthesized through a condensation reaction of tris(4‐aminophenyl)benzene with croconic acid or squaric acid in high yields (~95 %). The ionic nature of the polymers promoted high iodine/polyiodide vapour adsorption capacity of up to 4.6 g/g for CTPB and 3.5 g/g for STPB under ambient pressure at 80 °C. The zwitterionic framework (croconic acid or squaric acid units) coupled with the aromatic units is expected to effectively capture molecular iodine (I2) and polyiodides (I3⁻ and I5⁻). The iodine adsorption properties of the polymers have been studied using Fourier‐Transform Infrared Spectroscopy (FT‐IR), Scanning Electron Microscopy (SEM), Brauner‐Emmett‐Teller (BET) analysis, and Raman Spectroscopy. Besides this work, there are only three ionic units for effective iodine adsorption. This work demonstrates the importance of zwitterionic units in the porous network reported for iodine adsorption and separation.
The development of highly efficient materials for trapping radioactive iodine is essential for the safe use of nuclear energy. Herein, we present a strategy to synergistically enhance iodine capture by exploiting the flexible building blocks with the affinity properties of electrically rich heteroatoms by combining the cyclic triphosphonitrile derivative with amine linkers of different molecular lengths and constructing triangular pore‐structured flexible cyclotriphosphonitrile‐based covalent organic frameworks. A series of cyclotriphosphonitrile‐based COFs (CTP‐X‐COF, X = PDA, ODA, BPY, DPT) with triangular pore topology were synthesized using CTP‐6 as the node and connection point of p‐phenylenediamine (PDA), 4,4‐diaminodiphenyl ether (ODA), 5,5‐diamino2,2‐bipyridine (BPY), and 4,4‐diaminotribiphenyl (DPT) with different molecular lengths. It was found that the adsorption capacities of CTP‐PDA‐COF, CTP‐ODA‐COF, CTP‐BPY‐COF, and CTP‐DPT‐COF for iodine vapor were 4.65 g g⁻¹, 4.18 g g⁻¹, 2.38 g g⁻¹, and 3.57 g g⁻¹, respectively. The results showed that the adsorption capacities of CTP‐PDA‐COF, CTP‐ODA‐COF, CTP‐BPY‐COF, and CTP‐DPT‐COF for iodine in cyclohexane were 281.50 mg g⁻¹, 221.67 mg g⁻¹, 161.14 mg g⁻¹, and 222.67 mg g⁻¹, respectively. It was found that the four COFs adsorbed iodine in cyclohexane solution was a mixed adsorption process with chemical adsorption playing a predominant role and physical adsorption as an auxiliary mechanism.
The thiol-aldehyde polycondensation reaction was employed to synthesize novel spiro-thioketal-based porous organic polymers. At 75 °C, iodine uptake capacities of POPSPs were measured as 4.13, 5.25, and 5.65 g g ⁻¹ , respectively.
Organic X‐ray sensors are a promising new class of detectors with the potential to revolutionize medical imaging, security screening, and other applications. However, the development of high‐performance organic X‐ray sensors is challenged by low sensitivity. This paper reports on the development of nine X‐ray sensors based on new organic materials. It is demonstrated that the incorporation of bromine atoms into the sidechains of carbazolyl‐containing organic molecules significantly enhances their X‐ray sensitivity. This research suggests that incorporating a variety of high‐atomic‐number chemical elements into well‐established organic semiconductors is a promising strategy for designing efficient X‐ray sensor materials.
The syntheses of ionic porous organic polymers (iPOP) via ionothermal strategy or using solvents with high boiling points are not environmentally friendly approaches. Further, the green synthesis of an ionic porous organic polymer is not reported till date. Azo-coupling reaction is considered as a green synthetic strategy that has been used to obtain a new ionic porous organic polymer (iPOP-6) wherein water is used as a solvent. The iPOP-6 turns out to be a useful adsorbent that can scavenge toxic water pollutants (MnO4- and I3-) in an energy efficient manner via ion exchange based adsorption process. The partition coefficients associated with the removal of MnO4- and I3- are greater than 105 mL/g - a desirable feature observed in a superior adsorbent. The iPOP-6 can remove such pollutants from water samples collected from different water bodies with good capture efficiency. The removal mechanism was also ratified by theoretical studies. Overall, this work presents a new ionic POP with improved features and performance for water purification applications.
Porous polymeric nanoreactors capable of multitasking are attractive and require judicious design strategy. Herein, an unusual approach for the synthesis of a porous polymer, SBF-BINOL-6 by in-situ formation of the...
The uses and production of radionuclides in nuclear energy production and medical therapy are becoming more significant in today's world. While these applications have many benefits, they can produce harmful pollutants, such as radioactive iodine, that need to be sequestered. Effective capture and storage of radioactive iodine waste remains a major challenge for nuclear energy generation and nuclear medicine. Here we report the highly efficient capture of iodine in a series of mesoporous, two-dimensional (2D) covalent organic frameworks, called COFamides, which contain amide sidechains in their pores. COFamides are capable of rapidly removing iodine from aqueous solution at concentrations as low as 50 ppm, with total capacities greater than 650 wt%. In order to explain the high affinity of the COFamide series for iodine and iodide species in water, we performed a computational analysis of the interactions between the COFamide framework and iodine guests. These studies suggest that the origin of the large iodine capacity in these materials can be explained by the presence of multiple, cooperative, non-covalent interactions between the framework and both iodine, and iodide species.
A set of two unique hybrid POPs (HPOP-1 and HPOP-2) bearing triptycene and phosphazene units has been developed for their use as strategic materials capable of sensing HCl acid vapor and capturing/storing iodine. The materials were synthesized via the well-known Schiff base reaction, leading to the inclusion of ample imine linkages in the resultant HPOPs that were characterized thoroughly using various techniques. High thermal stability of HPOPs was evident from the TGA plots. The protonation of phosphazene and imine moieties in HPOPs, upon exposure to corrosive HCl vapors, acts like a chemical trigger that could be perceived not only by a “turn-on” fluorescence response but also by a color change visible to the unaided (naked) eye. The optical and electronic response of the HPOPs in the presence of HCl vapors is fully reversible using NH3 vapors as a chemical switch. These HPOPs were also found to be suitable for trapping iodine vapors and iodine species present in water or hexane solutions. This additional utility of HPOPs arises due to the presence of ample N, O, and P heteroatoms and imine linkages in the polymeric network. HPOPs can trap up to 4.90 g g–1 of iodine at 75 °C. The iodine removal efficiency at ambient temperature (25 °C) under dry as well as humid conditions is also quite promising, and performances are better than that of previously reported porous materials under similar experimental conditions. HPOPs can also efficiently remove iodine dissolved in water and hexane. All of these results indicate that HPOP-1 and HPOP-2 are potential materials for versatile environmental applications.
Over the last few decades, considering the impending global energy and environmental crisis, paramount development in nuclear energy has been widely observed as an alternative high power density and low-carbon...
A novel synthetic strategy for p -di(bis-indolylmethane)benzene was proposed and three derived porous organic polymers with unique mophologies were obtained.
The main contaminants in aqueous solutions that bio-magnify in living organisms include (but are not limited to) heavy metal-based toxic oxo-anions (CrO42—, MnO4—, ReO4—, HAsO4— etc.), anionic radioactive pollutants (such...
Since Russia invaded Ukraine in February 2022, the possibility of reducing Europe’s energy dependence on Russian resources has been hotly debated. The fossil fuel industries received most attention as European Union leaders first introduced gradual sanctions on Russian coal and later on oil and gas, while Russia responded with supply cuts. However, Russia’s role as a major player in the global nuclear power sector has remained largely below the sanctions radar, despite dependencies on Russian nuclear technology, uranium supplies and handling of spent nuclear fuel. Here we analyse the state nuclear company Rosatom and its subsidiaries as tools of Russian energy statecraft. We map the company’s global portfolio, then categorize countries where Russia is active according to the degree and intensity of dependence. We offer a taxonomy of long-term energy dependencies, highlighting specific security risks associated with each of them. We conclude that the war and Russia’s actions in the energy sector will undermine Rosatom’s position in Europe and damage its reputation as a reliable supplier, but its global standing may remain strong.
Nuclear energy is a sustainable low-carbon energy source that plays an increasingly important role in supporting the progress of human society. However, there are safety issues associated with the operation...
The Russia–Ukraine conflict has triggered an energy crisis that directly affected household energy costs for heating, cooling and mobility and indirectly pushed up the costs of other goods and services throughout global supply chains. Here we bridge a global multi-regional input–output database with detailed household-expenditure data to model the direct and indirect impacts of increased energy prices on 201 expenditure groups in 116 countries. On the basis of a set of energy price scenarios, we show that total energy costs of households would increase by 62.6–112.9%, contributing to a 2.7–4.8% increase in household expenditures. The energy cost burdens across household groups vary due to differences in supply chain structure, consumption patterns and energy needs. Under the cost-of-living pressures, an additional 78 million–141 million people will potentially be pushed into extreme poverty. Targeted energy assistance can help vulnerable households during this crisis. We emphasize support for increased costs of necessities, especially for food.
Nowadays, the demand for nuclear power is continue increasing due to its safety, cleanliness, and high economic benefits. Radioactive iodine from nuclear accidents and nuclear waste treatment processes poses a threat to humans and the environment. Therefore, the capture and storage of radioactive iodine are vital. Bismuth-based (Bi-based) materials have drawn much attention as low-toxicity and economical materials for removing and immobilizing iodine. Recent advances in adsorption and immobilization of vapor iodine by the Bi-based materials are discussed in this review, in addition with the removal of iodine from solution. It points out the neglected areas in this research topic and provides suggestions for further development and application of Bi-based materials in the removal of radioactive iodine.
In case of pollutant segregation, fast mass diffusion is a fundamental criterion in order to achieve improved performance. The rapid mass transport through porous materials can be achieved by availing large open pores followed by easy and complete accessibility of functional sites. Inducing macroporosity into such materials could serve as ideal solution providing access to large macropores that offer unhindered transport of analyte and full exposure to interactive sites. Moreover, the challenge to configure the ionic‐functionality with macroporosity could emerge as an unparalleled avenue toward pollutants separation. Herein, we strategized a synthetic protocol for construction of a positively charged hierarchically‐porous ordered interconnected macro‐structure of organic framework where the size and number of macropores can easily be tuned. The ordered macropores with strong electrostatic interaction synergistically exhibited ultrafast removal efficiency towards various toxic pollutants.
Leveraging metal–organic framework (MOF) to eliminate radioactive contaminants has invariably received much attention, but low preparation efficiency and poor selectivity have still limited its actual application. Herein, it is found that a fourfold interpenetrated cationic MOF (Ag‐TPPE) can be rapidly synthesized by only mixing, stirring, or sonication at room temperature. More impressively, the preparation process can be completed in <1 min. Up to now, this is the first report that cationic MOFs can be obtained by directly mixing the corresponding raw materials at room temperature. In addition to holding the rare merits of structural stability in extremely strong bases (8 m NaOH), Ag‐TPPE can selectively remove TcO4⁻ in the presence of large excess SO4²⁻ or NO3⁻. Based on its ultra‐high selectivity, Ag‐TPPE exhibits exceptional removal rate for TcO4⁻ from simulated Hanford and Savannah River Site waste streams, which refreshes the record of selective sorption of TcO4⁻ at low solid/liquid ratio, overcoming the drawback of overused sorbent in treatment of radioactive waste solution. Such superior sorption capabilities are thoroughly elucidated by the density functional theory calculations on a molecular level, clearly disclosing that TcO4⁻ can enter into the framework through breathing effect and is trapped in the large cavity through dense hydrogen bonds.
The effective and efficient capture as well as storage of radioisotopes of iodine is of significant importance in the treatment of nuclear waste. Further, the use of radioisotopes of iodine in medical therapy requires proper capture of radioactive iodine. Thus, there is a pressing need to develop novel adsorbents obtained using easy and simple methods that can capture iodine from various media with good uptake capacity. With this target, a new triptycene-based porous organic network (TP_POP-7) was designed and synthesized using a flexible trialdehyde with a triazine core and a rigid three-dimensional triptycene triamine as monomers. The two trifunctional monomers were covalently linked using the Schiff base reaction. TP_POP-7 is a porous organic polymer with good thermal and chemical stability. Due to the presence of abundant electron rich arene rings and N centers in the polymeric framework, efficient interaction with iodine was anticipated. Indeed, TP_POP-7 proved to be a promising material for capturing iodine from various media/conditions such as iodine vapor at elevated temperature (75 °C: 4215 mg g⁻¹) and room temperature (25 °C: 2040 mg g⁻¹), iodide ions from aqueous solution (2312 mg g⁻¹) and molecular iodine from organic solution (865 mg g⁻¹). Further, TP_POP-7 is a recyclable adsorbent without much compromise in its capture performance. Considering the high iodine uptake values under different conditions with good retention capability, TP_POP-7 emerges as one of the best materials for reliable capture and storage of iodine.
Radioactive molecular iodine (I2) and organic iodides, mainly methyl iodide (CH3I), coexist in the off-gas stream of nuclear power plants at low concentrations, whereas few adsorbents can effectively adsorb low-concentration I2 and CH3I simultaneously. Here we demonstrate that the I2 adsorption can occur on various adsorptive sites and be promoted through intermolecular interactions. The CH3I adsorption capacity is positively correlated with the content of strong binding sites but is unrelated to the textural properties of the adsorbent. These insights allow us to design a covalent organic framework to simultaneously capture I2 and CH3I at low concentrations. The developed material, COF-TAPT, combines high crystallinity, a large surface area, and abundant nucleophilic groups and exhibits a record-high static CH3I adsorption capacity (1.53 g·g−1 at 25 °C). In the dynamic mixed-gas adsorption with 150 ppm of I2 and 50 ppm of CH3I, COF-TAPT presents an excellent total iodine capture capacity (1.51 g·g−1), surpassing various benchmark adsorbents. This work deepens the understanding of I2/CH3I adsorption mechanisms, providing guidance for the development of novel adsorbents for related applications. Radioactive molecular iodine (I2) and methyl iodide (CH3I) coexist in the off-gas stream of nuclear power plants at low concentrations and only few adsorbents can effectively adsorb low-concentration I2 and CH3I simultaneously. Here, the authors demonstrate simultaneous capture of I2 and CH3I at low concentrations by exploiting different adsorptive sites in a covalent organic framework.
Nuclear power will continue to provide energy for the foreseeable future, but it can pose significant challenges in terms of the disposal of waste and potential release of untreated radioactive substances. Iodine is a volatile product from uranium fission and is particularly problematic due to its solubility. Different isotopes of iodine present different issues for people and the environment. 129I has an extremely long half-life of 1.57 × 107 years and poses a long-term environmental risk due to bioaccumulation. In contrast, 131I has a shorter half-life of 8.02 days and poses a significant risk to human health. There is, therefore, an urgent need to develop secure, efficient and economic stores to capture and sequester ionic and neutral iodine residues. Metal-organic framework (MOF) materials are a new generation of solid sorbents that have wide potential applicability for gas adsorption and substrate binding, and recently there is emerging research on their use for the selective adsorptive removal of iodine. Herein, we review the state-of-the-art performance of MOFs for iodine adsorption and their host-guest chemistry. Various aspects are discussed, including establishing structure-property relationships between the functionality of the MOF host and iodine binding. The techniques and methodologies used for the characterisation of iodine adsorption and of iodine-loaded MOFs are also discussed together with strategies for designing new MOFs that show improved performance for iodine adsorption.
Porous materials have recently attracted much attention owing to their fascinating structures and broad applications. Moreover, exploring novel porous polymers affording the efficient capture of iodine is of significant interest. In contrast to the reported porous polymers fabricated with small molecular blocks, we herein report the preparation of porous polymer frameworks using rigid polyisocyanides as building blocks. First, tetrahedral four-arm star polyisocyanides with predictable molecular weight and low dispersity were synthesized; the chain-ends of the rigid polyisocyanide blocks were then crosslinked, yielding well-defined porous organic frameworks with a designed pore size and narrow distribution. Polymers of appropriate pore size were observed to efficiently capture radioactive iodine in both aqueous and vapor phases. More than 98% of iodine could be captured within 1 minute from a saturated aqueous solution (capacity of up to 3.2 g g-1), and an adsorption capacity of up to 574 wt% of iodine in vapor was measured within 4 hours. Moreover, the polymers could be recovered and recycled for iodine capture for at least six times, while maintaining high performance.
Iodine-129 poses a significant challenge in the drive towards lowering radionuclide emissions from used nuclear fuel recycling operations. Various techniques are employed for capture of gaseous iodine species, but it is also present, mainly as iodide anions, in problematic residual aqueous wastestreams, which have stimulated research interest in technologies for adsorption and retention of the radioiodine. This removal effort requires specialised adsorbents, which use soft metals to create selectivity in the challenging chemical conditions. A review of the literature, at laboratory scale, reveals a number of organic, inorganic and hybrid adsorbent matrices have been investigated for this purpose. They are functionalised principally by Ag metal, but also Bi, Cu and Pb, using numerous synthetic strategies. The iodide capacity of the adsorbents varies from 13 to 430 mg g⁻¹, with ion-exchange resins and titanates displaying the highest maximum uptakes. Kinetics of adsorption are often slow, requiring several days to reach equilibrium, although some ligated metal ion and metal nanoparticle systems can equilibrate in < 1 h. Ag-loaded materials generally exhibit superior selectivity for iodide verses other common anions, but more consideration is required of how these materials would function successfully in industrial operation; specifically their performance in dynamic column experiments and stability of the bound radioiodine in the conversion to final wasteform and subsequent geological storage.
Article highlights
Metallated adsorbents for the capture and retention of radioiodine in the nuclear industry are assessed.
The strengths and weaknesses of organic, inorganic and hybrid support matrices and loading mechanisms are discussed.
Pathways for progression of this technology are proposed.
Graphic abstract
Parties to the 2015 Paris Agreement pledged to limit global warming to well below 2 °C and to pursue efforts to limit the temperature increase to 1.5 °C relative to pre-industrial times¹. However, fossil fuels continue to dominate the global energy system and a sharp decline in their use must be realized to keep the temperature increase below 1.5 °C (refs. 2, 3, 4, 5, 6–7). Here we use a global energy systems model⁸ to assess the amount of fossil fuels that would need to be left in the ground, regionally and globally, to allow for a 50 per cent probability of limiting warming to 1.5 °C. By 2050, we find that nearly 60 per cent of oil and fossil methane gas, and 90 per cent of coal must remain unextracted to keep within a 1.5 °C carbon budget. This is a large increase in the unextractable estimates for a 2 °C carbon budget⁹, particularly for oil, for which an additional 25 per cent of reserves must remain unextracted. Furthermore, we estimate that oil and gas production must decline globally by 3 per cent each year until 2050. This implies that most regions must reach peak production now or during the next decade, rendering many operational and planned fossil fuel projects unviable. We probably present an underestimate of the production changes required, because a greater than 50 per cent probability of limiting warming to 1.5 °C requires more carbon to stay in the ground and because of uncertainties around the timely deployment of negative emission technologies at scale.
Adsorption‐based iodine (I2) capture has great potential for the treatment of radioactive nuclear waste. In this study, we apply a “multivariate” synthetic strategy to construct ionic covalent organic frameworks (iCOFs) with a large surface area, high pore volume, and abundant binding sites for I2 capture. The optimized material iCOF‐AB‐50 exhibits a static I2 uptake capacity of 10.21 g g⁻¹ at 75 °C and a dynamic uptake capacity of 2.79 g g⁻¹ at ≈400 ppm I2 and 25 °C, far exceeding the performances of previously reported adsorbents under similar conditions. iCOF‐AB‐50 also exhibits fast adsorption kinetics, good moisture tolerance, and full reusability. The promoting effect of ionic groups on I2 adsorption has been elucidated by experimentally identifying the iodine species adsorbed at different sites and calculating their binding energies. This work demonstrates the essential role of balancing the textural properties and binding sites of the adsorbent in achieving a high I2 capture performance.
To safeguard the development of nuclear energy, practical techniques for capture and storage of radioiodine are of critical importance but remain a significant challenge. Here we report the synergistic effect of physical and chemical adsorption of iodine in tetrathiafulvalene-based covalent organic frameworks (COFs), which can markedly improve both iodine adsorption capacity and adsorption kinetics due to their strong interaction. These functionalized architectures are designed to have high specific surface areas (up to 2359 m2 g-1) for efficient physisorption of iodine, and abundant tetrathiafulvalene functional groups for strong chemisorption of iodine. We demonstrate that these frameworks achieve excellent iodine adsorption capacity (up to 8.19 g g-1), which is much higher than those of other materials reported so far, including silver-doped adsorbents, inorganic porous materials, metal-organic frameworks, porous organic frameworks, and other COFs. Furthermore, a combined theoretical and experimental study, including DFT calculations, electron paramagnetic resonance spectroscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy, reveals the strong chemical interaction between iodine and the frameworks of the materials. Our study thus opens an avenue to construct functional COFs for a critical environment-related application.
Constructing three‐dimensional (3D) structural characteristics on two‐dimensional (2D) covalent organic frameworks (COFs) is a good approach to effectively improve the permeability and mass transfer rate of the materials and realize the rapid adsorption for guest molecules, while avoiding the high cost and monomer scarcity in preparing 3D COFs. Herein, we report for the first time a series of colyliform crystalline 2D COFs with quasi‐three‐dimensional (Q‐3D) topologies, consisting of unique “stereoscopic” triangular pores, large interlayer spacings and flexible constitutional units which makes the pores elastic and self‐adaptable for the guest transmission. The as‐prepared QTD‐COFs have a faster adsorption rate (2.51 g h⁻¹) for iodine than traditional 2D COFs, with an unprecedented maximum adsorption capacity of 6.29 g g⁻¹. The excellent adsorption performance, as well as the prominent irradiation stability allow the QTD‐COFs to be applied for the rapid removal of radioactive iodine.
High-energy demands due to globalization have led to the proliferation of nuclear technology as an alternative greener energy source to meet these demands. With this proliferation comes the release of large amounts of radionuclides into the environment. Zeolitic imidazolate frameworks (ZIFs) with tunable porous structures and numerous active sites have proved to be excellent at removing these radionuclides from various environmental media. These active sites due to the presence of functional groups allow for favorable sorptive interactions between ZIF-based materials and radionuclides. With their excellent chemical stability in refluxing organic and aqueous media, ZIFs hold a special place among metal-organic framework materials with respect to capturing various types of radionuclides. Moreover, other favorable characteristics such as high thermal stability, high framework porosities (ZIF-8 surface area as high as 1970 m² g⁻¹) and abundant functional groups, make them suitable for capturing radionuclides. In this review, recent advances in the sequestration of radionuclides with ZIFs and their derived materials (composites, derivatives) are highlighted. The challenges and prospects in this fast-growing branch of coordination chemistry are briefly discussed. This work, being the first of its kind to the best of our knowledge will serve as grounding for the future development of ZIF-based materials for radionuclide removal from the environment.
The number of studies on the capture of radioactive iodine compounds by porous sorbents has regained major importance in the last few years. In fact, nuclear energy is facing major issues related to operational safety and the treatment and safe disposal of generated radioactive waste. In particular during nuclear accidents, such as that in 2011 at Fukushima, gaseous radionuclides have been released in the off-gas stream. Among these, radionuclides that are highly volatile and harmful to health such as long-lived ¹²⁹I, short-lived ¹³¹I and organic compounds such as methyl iodide (CH3I) have been released. Immediate and effective means of capturing and storing these radionuclides are needed. In the present review, we focus on porous sorbents for the capture and storage of radioactive iodine compounds. Concerns with, and limitations of, the existing sorbents with respect to operating conditions and their capacities for iodine capture are discussed and compared.
Covalent organic frameworks (COFs) are crystalline porous polymers formed by a bottom‐up approach from molecular building units having a predesigned geometry that are connected through covalent bonds. They offer positional control over their building blocks in two and three dimensions. This control enables the synthesis of rigid porous structures with a high regularity and the ability to fine‐tune the chemical and physical properties of the network. This Feature Article provides a comprehensive overview over the structures realized to date in the fast growing field of covalent organic framework development. Different synthesis strategies to meet diverse demands, such as high crystallinity, straightforward processability, or the formation of thin films are discussed. Furthermore, insights into the growing fields of COF applications, including gas storage and separations, sensing, electrochemical energy storage, and optoelectronics are provided.
Owing to their chemical and thermal stabilities, high uptake capacities, and easy recyclability, covalent organic polymers (COPs) have shown promise as pollutant sponges. Here, we describe the use of diazo coupling to synthesize two cationic COPs, COP1++ and COP2++, that incorporate a viologen‐based molecular switch and an organic macrocycle, calix[4]arene. Both COPs form nanosheets with height profiles of 6.00 and 8.00 nm, respectively, based on AFM measurements. The sheets remain morphologically intact upon one‐ or two‐electron reductions of their viologen subunits. MD simulations of the dicationic COPs indicate that calix[4]arene adopts a partial cone conformation and that, in height, the individual 2D polymer layers are 5.48 Å in COP1++ and 5.65 Å in COP2++, which, together with the AFM measurements, suggests that the nanosheets are composed of 11 and 14 layers, respectively. The COPs, in either dicationic, radical cationic, or neutral form exhibit high affinity for iodine, reaching up to 200% mass increase when exposed to iodine vapor at 70 °C, which makes the materials among the best‐performing nanosheets for iodine capture reported in the literature. In addition, the COPs effectively remove Congo red from solution in the pH range of 2 ‐ 10, reaching nearly 100% removal within 15 minutes at acidic pH.
Two unique ionic covalent organic networks (iCONs) incorporated with guanidinium motifs were obtained and characterized by various techniques. Upon 8 h of treatment with iCON-HCCP (250 μg/mL), >97% killing of Staphylococcus aureus, Candida albicans, and Candida glabrata strains was observed. Antimicrobial efficacies against bacteria and fungi were also evident from FE-SEM studies. High antifungal efficacies also correlated well with >60% reduction of ergosterol content, high lipid peroxidation, and membrane damage leading to necrosis.
Fashioning microporous covalent organic frameworks (COFs) into single crystals with ordered macropores allows for an effective reduction of the mass transfer resistance and the maximum preservation of their intrinsic properties but remains unexplored. Here, we report the first synthesis of three-dimensional (3D) ordered macroporous single crystals of the imine-linked 3D microporous COFs (COF-300 and COF-303) via a template-assisted modulated strategy. In this strategy, COFs crystallized within the sacrificial colloidal crystal template, assembled from monodisperse polystyrene microspheres, and underwent an aniline-modulated amorphous-to-crystalline transformation to form large single crystals with 3D interconnected macropores. The effects of the introduced macroporous structure on the sorption performances of COF-300 single crystals were further probed by iodine. Our results indicate that iodine adsorption occurred in micropores of COF-300 but not in the introduced macropores. Accordingly, the iodine adsorption capacity of COF single crystals was governed by their micropore accessibility. The relatively long diffusion path in the non-macroporous COF-300 single crystals resulted in a limited micropore accessibility (48.4%) and thus a low capacity in iodine adsorption (1.48 g·g-1). The introduction of 3D ordered macropores can greatly shorten the microporous diffusion path in COF-300 single crystals and thus render all their micropores fully accessible in iodine adsorption with a capacity (3.15 g·g-1) that coincides well with the theoretical one.
The reaction of 5,5'-([2,2'-bipyridine]-5,5'-diyl)diisophthalaldehyde (BPDDP) with cyclohexanediamine and [benzidine (BZ)/[2,2'-bipyridine]-5,5'-diamine (BPDA)], respectively, affords a nitrogen-rich porous organic cage BPPOC and two two-dimensional (2D) covalent organic frameworks (COFs), USTB-1 and USTB-2 (USTB = University of Science and Technology Beijing), under suitable conditions. Interestingly, BPPOC with a single-crystal X-ray diffraction structure is able to successfully transform into USTB-1 and USTB-2 (newly converted COFs denoted as USTB-1c and USTB-2c, respectively) upon exchange of the imine unit of cyclohexanediamine in the cage by BZ and BPDA. Such a transformation also enables the isolation of analogous COFs (USTB-3c and USTB-4c) on the basis of an isostructural organic cage, BTPOC, which is derived from 5,5'-([2,2'-bithiophene]-4,4'-diyl)diisophthalaldehyde (BTDDP) and cyclohexanediamine. However, the conventional solvothermal reaction between BTDDP and BPDA leads to an impure phase of USTB-4 containing incompletely converted aldehyde groups due to the limited solubility of the building block. The newly prepared COFs have been characterized by nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy, and transmission electron microscopy. In particular, BPPOC is able to absorb the iodine vapor with an uptake of 5.64 g g-1, breaking the porous organic cage's (POC's) record value of 3.78 g g-1. Nevertheless, the cage-derived COFs exhibit improved iodine vapor adsorption capability in comparison with the directly synthesized counterparts, with the highest uptake of 5.80 g g-1 for USTB-1c. The mechanism investigation unveils the superiority of nitrogen atoms to sulfur atoms for POCs in iodine vapor capture with the assistance of definite crystal structures. This, in combination with porosity, synergistically influences the iodine vapor capture capacity of COFs.
Supramolecular organic frameworks (SOFs) and covalent organic frameworks (COFs) have been the focus of researchers for a long time because of their regular periodic structure and good crystalline morphology. However, the relatively limited stability of SOFs and the slightly insufficient functionality of COFs have restricted the further applications of these materials to some extent. Herein, we report for the first time a COF & SOF bicrystalline composite based on a triazine COF and a bisbenzimidazole SOF, which combines the excellent stability and uniform pore support of COFs with the advantage of abundant and diverse active functional sites of SOFs. The as-produced composite has better stability, adsorption performance for gaseous iodine and recycling utilization rate than the single COF and SOF materials, with the highest adsorption capacity of up to 4.46 g g⁻¹, which benefits from the abundant active adsorption sites brought about by the SOF. The design and construction strategy of bicrystalline composites in this study can not only effectively solve the problem of poor stability of traditional SOFs which makes it difficult to meet the practical application requirements, but also greatly improve the variety and number of functional sites of COFs, which creates the conditions for the improvement and enhancement of the application properties of the materials and has great popularization and application value.
Nuclear energy is considered as the best alternative to fossil fuel to meet the ever-increasing global electricity demand. Nuclear electricity generation is not associated with direct emission of greenhouse gases unlike thermal power plants. On the flipside, tackling nuclear waste and spent fuel is a major issue, which becomes even more challenging due to the presence of volatile radionuclides such as ¹³¹I and ¹²⁹I. In unfortunate events of accidental release of fission products in the environment, ¹³¹I and ¹²⁹I are considered as the most dreaded air pollutants. Therefore, development of materials for efficient and rapid uptake/storage of ¹²⁹I or ¹³¹I, is a research topic of utmost importance in this context. Herein, we report unique triptycene based covalent organic polymers (T_COPs) derived from benzene-1,3,5-tricarbaldehyde derivatives possessing varying number of hydroxy groups. The microporous T_COPs feature presence of abundant imine groups and π-rich environment. Interestingly, we observed that varying the number of hydroxy groups in T_COPs alter their surface area as well as their iodine uptake capacity. T_COPs exhibited ultra-high iodine uptake up to 4860 mg/g, which is superior compared to previously reported COPs. For practical applications, the T_COPs can be reused up to five cycles with smaller loss in the uptake performance - a desirable feature expected in a superior adsorbent. Our results reflect immense potential of these triptycene based COPs for environmental remediation.
The explosion at the Chernobyl Nuclear Power Plant in Ukraine 35 years ago forged a strong safety culture that underpins nuclear energy today. At a time when the world was divided profoundly by distrust, the accident prompted nations to collaborate and communicate as they became more transparent and open about their nuclear power programs. After the tsunami of 2011 hit the Fukushima Daiichi Nuclear Power Plant in northern Japan, the international community came together again to reinforce the global nuclear safety regime. These anniversaries are reminders of the ever-evolving efforts to strengthen nuclear safety. This is especially important today because public trust is a prerequisite for nuclear power to play its part in mitigating climate change. Too often, the debate about how to move the world onto a more sustainable energy path is framed in the false dichotomy of “either we invest in solar and wind power, or in nuclear energy.” Reaching netzero carbon emissions will require investment in all of them.
Developing an efficient and cheap iodine sorbent is of great practical significance in the modern nuclear industry. In this work, novel bismuth and silver functionalized Ni foam composites as iodine sorption materials (Bi-Ni foam and Ag-Ni foam) were successfully prepared via a simple solvothermal method. Through a series of iodine sorption experiments and characterization methods, iodine capture properties and corresponding sorption mechanism were comprehensively compared and thoroughly revealed. The results show that the core-sheath structure formed by the solvothermal reaction can supply more active sites (Bi⁰ or Ag⁰ particles) for the contact of radioactive iodine gas, thereby improving the sorption capacity of sorbents. Compared with Ag-Ni foam (456 mg/g), Bi-Ni foam exhibits a higher iodine capture capacity (658 mg/g), whereas silver-based material has a faster sorption kinetics. Such excellent sorption performances were attributed to the chemical reaction between Bi⁰/Ag⁰ particles and iodine gas, generating stable BiI3/AgI. In addition, this type of sorbents inherits the external structure of the Ni foam skeleton, decreasing the physically sorbed iodine, and can be prepared in different shapes and sizes, which is of great practical significance.
A new and innovative class of calixarene-based polymers emerged as adsorbents for a variety of compounds and ions in solution and vapor media. These materials take advantage of the modifiable rims and hydrophobic cavities of the calixarene monomers, in addition to the porous nature of the polymeric matrix. With main-chain calixarenes' function as supramolecular hosts and the polymers' high surface areas, polycalixarenes can effectively encapsulate target analytes. This feature is particularly useful for environmental remediation as dangerous and toxic molecules reversibly bind to the macrocyclic cavity, which facilitates their removal and enables repeated use of the polymeric sorbent. This Spotlight touches on the unique characteristics of the calixarene monomers and discusses the synthetic methods of our reported calixarene-based porous polymers, including Sonogashira-Hagihara coupling, and diazo and imine bond formation. It then discusses the promising applications of these materials in adsorbing dyes, micropollutants, iodine, mercury, paraquat, and perfluorooctanoic acid (PFOA) from water. In most cases, these reports cover materials that outperform others in terms of recyclability, rates of adsorption, or uptake capacities of specific pollutants. Finally, this Spotlight addresses the current challenges and future aspects of utilizing porous polymers in pollution treatment.
Radioactive materials of nuclear waste would be hazardous to human health such as the reproductive and metabolic system. How to design a radioactive material adsorbent quickly and efficiently is still a great challenge. In this study, a strategy for the efficient design of a high-potential radioactive iodine uptake adsorbent by theoretical screening is proposed. The following experiments which use covalent organic frameworks (COFs) as demonstration have great agreement with the theoretical screening prediction. Three screened COFs show ultrahigh iodine adsorption, which reaches up to 6.4 g/g (640% in mass) in vapor and 99.9 mg/g in solution, owing to the pore size and the functional groups in COFs.
Air, water, and soil pollution devastate countless ecosystems and deteriorate human health. Adsorption has commonly been used as a pollutant removal technique, but ongoing materials science research is still searching for more efficient, cheaper, and scalable sorbent materials. Herein, we discuss the synthesis and pollutant-capturing abilities of covalent polymeric structures, including covalent organic polymers and covalent organic frameworks that contain organic macrocycles in the backbone of their structures. These organic macrocycles (cyclodextrin, calixarene, cucurbituril, pillararene, and porphyrin) possess cavities and functional groups that can sequester pollutants by forming supramolecular interactions. The insolubility of these materials prominently aids in their regeneration and recyclability potentials. Following a discussion on the synthetic strategies used in the polymerization of each type of macrocycle, environmental applications of these materials are presented. Here, we focus on the removal of micropollutants, charged species, metal ions, oils and organic solvents, perfluorinated substances, iodine, and volatile organic compounds.
Porous polymers have been widely used as adsorbents to cope with environmental issues. Two parallel series of hybrid silsesquioxane-based phosphazene functionalized porous polymers (PCS-OP-1, 2, 3 and PCS-CP-1, 2, 3) have been prepared by varying the molar ratio of hexaphenoxycyclotriphosphazene (OP) or hexaphenylcyclotriphosphazene (CP) with octavinylsilsesquioxane (OVS) in the Friedel-Crafts reaction, respectively. PCS-OP-3 and PCS-CP-3 with hierarchical micropore/mesopore coexisting structures and high surface areas are chosen to absorb I2 vapor, dyes and CO2. The adsorption capacity of PCS-OP-3 is higher than PCS-CP-3, which is 1.51 g g⁻¹ for iodine vapor, 731 mg g⁻¹ for Congo red (CR), 151 mg g⁻¹ for Methylene Blue (MB) and 1.74 mmol g⁻¹ for CO2. This study provides a feasible method to prepare and tune phosphazene functionalized silsesquioxane-based porous polymers.
Radioiodine is one of the main fission products in the nuclear industry. Due to its strong volatility and radiotoxicity, it must be filtered and purified before being released into the environment. In this work, we reported three novel bismuth-based iodine sorption materials coated with Bi and/or Bi2O3 on the surface of electrospinning carbon nanofibers (HT-Bi2O3-ESCNF, HT-Bi-Bi2O3-ESCNF and HT-Bi-ESCNF). These materials were obtained by adding a hydrothermal step on the basis of electrospinning, pre-oxidation and carbonization process. The benefit of hydrothermal load was that active sites appeared on the outer surface of the fiber, making the contact with iodine gas more convenient and effective, and was no longer restricted by the concentration of Bi³⁺ in the solution like before. Finally, iodine capture tests were also conducted on these three sorbents and the property changes were investigated before and after iodine exposure. The results showed that the coating on the surface of the fiber did greatly improve the iodine capture capacity, and elemental bismuth had a greater effective atomic utilization rate of iodine than bismuth oxide, whose sorption capacity reached a record high of 732 mg/g among all the bismuth-based sorbents. The capture mechanism was thoroughly elucidated by a combination of PXRD, SEM, TEM, BET, XPS, Raman spectra and TGA characterizations.
The capture of radioiodine species during nuclear fuel reprocessing and nuclear accidents is crucial for nuclear safety, environmental protection, and public health. Previously reported emerging materials for iodine uptake cannot outperform commercial zeolites and active carbon under the practical dynamic scenario. Herein, we present a new design philosophy aiming at significantly enhanced specific host-guest interactions and obtain a nitrogen-rich covalent organic framework material by introducing a bipyridine group into the building block for the simultaneous capture of both iodine gas through enhanced electron-pair effect and organic iodide via the methylation reaction. These efforts give rise to not only an ultrahigh uptake capacity of 6.0 g g⁻¹ for iodine gas and a record-high value of 1.45 g g⁻¹ for methyl iodide under static sorption conditions but also, more importantly, a record-high iodine loading capability under dynamic conditions demonstrated from the breakthrough experiments.
Radioactive iodine isotopes that are discharged into environment have been of significant concern due to its long-term impact on public health. In this work, a new bismuth-based composite named Bi@ESCNF (bismuth-decorated electrospinning carbon nanofibers) was prepared and investigated for capturing iodine-129 (129 I). This material used an electrospinning carbon nanofiber membrane as the substrate and metallic Bi nanoparticles were uniformly inlaid on the fibers, providing a rich active site to capture iodine gas. Due to the strong affinity of bismuth and iodine, Bi@ESCNF exhibited a very high iodine uptake capacity up to 559 mg/g after exposure to iodine for 4 h at 200 °C which could reach approximately twofold higher than that of the commercial silver exchanged zeolite and even larger than other reported bismuth-based adsorbents. The uptake mechanism was also unraveled by the combined BET, PXRD, SEM, TEM, XPS, and Raman spectra characterizations. It is found that such excellent iodine capture property by this material was attributed to the chemical reaction between bismuth and iodine, which will generate a stable phase of BiI 3 , and possess a huge specific surface area of 537 m 2 /g. Thus, our results showed that the new and highly efficient Bi@ESCNF would be a promising adsorbent for radioactive iodine removal.
Capturing volatile radioactive nuclides including iodine (I129 or I131) is one of the major problems to be solved for environmental sustainability. Multiple types of functional microporous materials such as metal organic frameworks and covalent organic frameworks have been constructed for iodine emission control. However, most of the microporous materials are limited by their weak binding force with iodine and low stability, leading to low capture efficiencies. Herein, the synthesis of pyridyl conjugated microporous polymer networks with large surface areas (PCMP‐Y) up to 1304 m2 g−1 and high yields up to 95% via a simple Yamamoto cross‐coupling reaction, is reported. The PCMP‐Y carries amine and pyridine N groups which have stronger interactions with iodine molecules. The high specific surface areas and porosities of PCMP‐Y facilitate iodine capture, delivering a maximum adsorption capacity of 4.75 g g−1 in a short time (3 h), which is superior to a majority of porous materials reported. Moreover, the reversible desorption nature of PCMP‐Y capturing iodine imparts a platform for metal‐free heterogeneous catalyst, which can be applied to synthesize aminobenzothiazole medicines via O2‐promoted cascade reactions. A series of pyridine‐ and triphenylamine‐functionalized conjugated microporous polymers are simply synthesized via a Yamamoto coupling reaction. Adjusting pyridine and triphenylamine molar ratio enables high specific surface areas up to 1304 m2 g−1 to be achieved. Such porous polymers exhibit a high iodine adsorption capacitance of 475 wt%, which can be applied to synthesize aminobenzothiazole medicines via O2‐promoted cascade reactions.
Triptycene based polymeric networks are rapidly emerging as porous organic polymers (POPs) for efficient capture of small gas molecules. Further, such triptycene based frameworks are also being explored as adsorbents for radioactive iodine. Herein, a group of three unique “Triptycene based and Nitrogen-rich Hyper Crosslinked Polymers” (TNHCPs) have been easily obtained via the well-known Friedel-Craft alkylation reactions of triptycene with six-membered N-rich heterocycles. In these TNHCPs, the presence of triptycene motifs yields contorted and rigid polymeric frameworks with plenty of micropores and ultramicropores. Further, the presence of N-rich heterocycles increases their efficiency to selectively capture carbon dioxide and adsorb iodine vapours as well as iodide ions from aqueous solutions. Comparison with data in recent literature reveals that TNHCPs are better in these domains than several previously reported POPs in general and HCPs in particular.
This paper develops an automated fault detection tool to detect very small LOCAs in pressurized water reactors that would be difficult for operators to detect manually. One of the primary challenges with previous automated fault detection methods, which are data-driven, is that they require data from LOCAs; however, it may be difficult to capture real operational data from LOCA scenarios. This work uses a physics-inspired approach that equates the physical effects of a LOCA to changes in known variables. This approach enables the detection of very small LOCAs using data-driven approaches that use nominal operating data without the need for LOCA data. The approach combines data-driven modeling with control-theoretic estimation techniques to detect LOCAs and estimate their magnitudes in real-time. First, simulated process data for a variety of nominal operating conditions is collected using a generic pressurized water reactor simulator. Then, that data is used to train an artificial neural network regression model that captures the nonlinear plant dynamics. Finally, the regression model is used in a particle filter to detect the onset and estimate the magnitude of the leak. These methods are successfully verified using LOCA simulations that would be hard to manually distinguish from normal operating transients.
The environmental issues associated with the fast advancement of nuclear energy are of great concern due to the radiological and chemical toxicity of some radionuclides which may be potentially released into the environment in different stages of nuclear fuel cycle. Advanced versatile materials and techniques are thus critically needed to efficiently eliminate radionuclides from environmental media with respect to pollution control and environmental remediation. Recently, plenty of novel layered structure-based materials were ingeniously fabricated and widely applied in radionuclide sequestration from aqueous solutions. Up to now, however, comprehensive categorical summarization with new insights into this topic are still quite limited. Herein, this paper systematically reviewed recent research progress upon new materials with layered structures for radionuclide sequestration or removal. Particular attention was paid to graphene-, MXene-based materials and their composites. Important methodologies for this topic of research, with emphasis on computational and X-ray absorption spectroscopic methods were also discussed. In addition, future challenges and basic research needs about fabricating and utilizing tailored functional materials with layered structures for environment remediation are also given.
Radioactive iodine-129 (129I) and technetium-99 (99Tc) pose a risk to groundwater due to their long half-lives, toxicity, and high environmental mobility. Based on literature reviewed in Moore et al. (2019) and Pearce et al. (2019), natural and engineered materials, including iron oxides, low-solubility sulfides, tin-based materials, bismuth-based materials, organoclays, and metal organic frameworks, were tested for potential use as a deployed technology for the treatment of 129I and 99Tc to reduce environmental mobility. Materials were evaluated with metrics including capacity for IO3- and TcO4- uptake, selectivity and long-term immobilization potential. Batch testing was used to determine IO3- and TcO4- sorption under aerobic conditions for each material in synthetic groundwater at different solution to solid ratios. Material association with IO3- and TcO4- was spatially resolved using scanning electron microscopy and X-ray microprobe mapping. The potential for redox reactions was assessed using X-ray absorption near edge structure spectroscopy. Of the materials tested, bismuth oxy(hydroxide) and ferrihydrite performed the best for IO3-. The commercial Purolite A530E anion-exchange resin outperformed all materials in its sorption capacity for TcO4-. Tin-based materials had high capacity for TcO4-, but immobilized TcO4- via reductive precipitation. Bismuth-based materials had high capacity for TcO4-, though slightly lower than the tin-based materials, but did not immobilize TcO4- by a redox-drive process, mitigating potential negative re-oxidation effects over longer time periods under oxic conditions. Cationic metal organic frameworks and polymer networks had high Tc removal capacity, with TcO4- trapped within the framework of the sorbent material. Although organoclays did not have the highest capacity for IO3- and TcO4- removal in batch experiments, they are available commercially in large quantities, are relatively low cost and have low environmental impact, so were investigated in column experiments, demonstrating scale-up and removal of IO3- and TcO4- via sorption, and reductive immobilization with iron- and sulfur-based species.
Porous organic polymers (POPs) have received great attention worldwide and become attractive for capture and storage of carbon dioxide (CO2) and radioactive iodine (¹²⁹I or ¹³¹I). Here we present modified tetraphenylmethane (TPM)-based POPs i.e. mPTPMs (synthesized via Buchwald-Hartwig cross-coupling of a tetrakis(4-bromophenyl) methane core and selected aryl diamine linkers, followed by a crosslinking alkylation strategy using diiodomethane as a crosslinker). This new strategy offers mPTPMs with high surface areas up to 640 m²/g and uniform ultramicropore size of 0.6 nm, where porous properties are readily controlled by the substitutions of linkers and the crosslinker. Finally, as-synthesized mPTPMs exhibit good CO2 uptake capacities (0.106 g/g at 273 K and 1 bar) and high iodine uptake capacities up to 3.94 g/g within only 2.5 h, representing fast and efficient adsorbents for wider environmental applications.
Enrichment of radioactive iodine in the waste of nuclear industries threatens the health of humans, and efficient capture of iodine has attracted a great deal of attention in recent years. Porous organic polymers (POPs) and metal-organic frameworks (MOFs), new classes of porous materials, act as outstanding candidate adsorbent materials in this field based on their high surface areas, permanent tunable porosities, controllable structures, high thermal/chemical stabilities, versatility in molecular design and potential for post-synthetic modification. Herein, this review focuses on the research progress of the two kinds of porous materials POPs and MOFs for highly efficient iodine capture. We analysis and discuss some valid strategies for enhancing iodine uptakes including increasing surface areas and pore volumes, using organic building units with unique configurations and functions, introducing chemical functional groups to provide high-enthalpy binding sites, further processing of POPs and MOFs materials and so on. Indeed, there are many special structural and functional features found in the porous POPs and MOFs materials which make them really unique and merit further exploration. And we expect to see their usage grow as the field progresses.
Nuclear power is critical in addressing the growing energy demand required for an improved quality of life. Its sustainable development, however, rests on the accessibility of fuel material and the ability to manage a nuclear fuel cycle safely and efficiently. Recently, porous organic polymers (POPs) have been shown to provide improved radionuclide sequestration performance over traditional porous materials in terms of both uptake capacity and selectivity. These materials also exhibit improved stability and are readily functionalized, rendering them promising materials for a number of emergent applications. This Opinion demonstrates achievements in engineered POPs for nuclear fuel mining and remediation of representative radioactive species, along with discussions of the underlying design strategies and principles. Future research opportunities and implementation barriers are also discussed with the hope of inspiring additional scientists to engage in this emerging area of research.
Although designs abound, reactors that can breed fuel remain mostly a dream.
Rich heteroatom-doped conjugated nanoporous polymers with uniform microspherical morphology exhibit remarkablly high capacity up to 450 wt% in removing iodine from vapor phase (at 348 K and atmosphere pressure).
The effective control of crystallinity of covalent organic frameworks (COFs) and the optimization of their performances related to the crystallinity have been considered as big challenges. COFs bearing flexible building blocks (FBBs) generally own larger lattice sizes and broader monomer sources, which may endow them with unprecedented application values. Herein, we report the oriented synthesis of a series of two-dimensional (2D) COFs from FBBs with different content of intralayer hydrogen bonds. Studies of H-bonding effects on the crystallinity and adsorption properties indicate that partial structure of the COFs is “locked” by the H-bonding interaction, which consequently improves their microscopic order degree and crystallinity. Thus, the regulation of crystallinity can be effectively realized by controlling the content of hy-drogen bonds in COFs. Impressively, the as-prepared COFs show excellent and reversible adsorption performance for volatile iodine with capacities up to 543 wt%, much higher than all previously reported adsorbents, although the variation tendency of adsorption capacities is opposite to their crystallinity. This study provides a general guidance for the design and construction of highly/appropriately crystalline COFs and ultrahigh-capacity iodine adsorbents.
Two-dimensional (2D) imine-linked covalent organic frameworks (COFs) have attracted great interest for gas uptake, catalysis, drug delivery, electronic devices, and photocatalytic applications. The synthetic methodologies involved in imine-linked COF formations such as solvothermal synthesis usually require harsh experimental conditions. In this work, we show for the first time how highly crystalline COFs with very high surface areas (3.6 times higher than using conventional approaches) can be prepared by combining a mechanochemical and crystallization approach. More importantly, this facile method is a general route to novel composites of COF and metal oxides including Fe3O4, Co3O4, and NiO. The composites can be used as magnetically recoverable adsorbents and show a strong redox-activity making them interesting for applications in electrochemical energy storage.