Multi-Functionalization Integration into the Electrospun Nanofibers Exhibiting Effective Iodine Capture from Water

Local Charge Density Enhancement Strategy in Nitrogen-rich Covalent Organic Framework for Boosted Iodine Removal From Water

The leakage of nuclear pollution highlights the critical importance of effectively separating radioactive pollutants. Radioactive iodine, a high-yield fission product of nuclear reactions, poses serious environmental and health risks. However, the lack of efficient adsorbents makes the management of aqueous radioactive iodine pollution a significant challenge. N-doped materials are among the most recognized adsorbents for iodine removal, but their weak binding affinity and limited number of iodine-binding N-sites hinder their practical application. Herein, a covalent organic framework (COFs) named phen-TPA is synthesized, featuring an increased number and optimized local chemical environment of iodine-binding N-sites. This material demonstrates record-breaking iodine removal kinetics, with a kinetic constant of 14.64 g g-1 min-1 for aqueous iodine (I2), and the highest-reported iodine adsorption capacity of 11.9 g g-1 for aqueous triiodide (I3 -). Large-scale flow-through adsorption experiments show that phen-TPA can remove 99.5% aqueous I2 and I3 - from high-salinity aqueous environments, highlighting its potential for practical applications.

Porous Aromatic Framework with Multifunctional Sites for Effective Recovery of Various Trace Iodine Species From Water

Recovery of environmental iodine is of great significance for both recycling iodine resources and addressing iodine pollution. However, iodine is highly sensitive to environmental factors and exists in various chemical species, which complicates the recovery of trace iodine in aqueous systems. Here a porous aromatic framework (iPAF-TEPT) is presented with multifunctional adsorption sites for efficient recovery of various iodine species, including molecular iodine (I2), iodide (I- and I3 -). The material utilizes a synergistic strategy combining charge-transfer interactions and Coulomb interactions to effectively adsorb different iodine species. Thanks to its high density of accessible ion exchange sites for I⁻ and I3⁻, and nitrogen-rich sites for I2, iPAF-TEPT demonstrates an unprecedented adsorption capacity for various iodine forms. Notably, iPAF-TEPT achieves exceptional removal efficiency for trace iodine pollutants, even at concentrations as low as 100 ppb, making it the first promising single-framework material for highly efficient treatment of aqueous iodine contamination.

Nitrogen-rich and core-sheath polyamide/polyethyleneimine@Zr-MOF for iodine adsorption and nerve agent simulant degradation

Radioactive nuclides and highly toxic organophosphates are typical deadly threats. Materials with the function of radioactive substances adsorption and organophosphates degradation provide double protection. Herein, dual-functional polyamide (PA)/polyethyleneimine (PEI)@Zr-MOF fiber composite membranes, fabricated by in-situ solvothermal growth of Zr-MOF on PA/PEI electrospun fiber membranes, are designed for protection against two typical model compounds of iodine and dimethyl 4-nitrophenyl phosphate (DMNP). Benefiting from the unique core-sheath structure composed of inner nitrogen-rich fibers and outer porous Zr-MOF, the composite membranes rapidly enrich iodine through abundant active sites of the outer sheath and form complexes with the amine of inner PEI, exhibiting a highly competitive adsorption capacity of 609 mg g-1. Moreover, it can adsorb and degrade DMNP with the synergy of PEI component and Zr-MOF, achieving an 80 % removal of DMNP within 7 min without any additional co-catalyst. This work provides a feasible strategy to fabricate dual-functional materials that protect against radioactive and organophosphorus contaminants.

Scavenging Radionuclide by Shapeable Porous Materials

Nuclear energy is a competitive and environmentally friendly low-carbon energy source. It is seen as an important avenue for satisfying energy demands, responding to the energy crisis, and mitigating global climate change. However, much attention has been paid to achieving the effective treatment of radionuclide ions produced in nuclear waste. Initially, advanced adsorbents were mainly available in powder form, which meant that additional purification processes were usually required for separation and recovery in industrial applications. Therefore, to meet the practical requirements of industrial applications, materials need to be molded and processed into forms such as beads, membranes, gels, and resins. Here, we summarize the fabrication of porous materials used for capturing typical radionuclide ions, including UO2 2+, TcO4 -, IO3 -, SeO3 2-, and SeO4 2-.

Synthesis of a Novel Zwitterionic Hypercrosslinked Polymer for Highly Efficient Iodine Capture from Water

Cationic porous organic polymers have a unique advantage in removing radioactive iodine from the aqueous phase because iodine molecules exist mainly in the form of iodine-containing anions. However, halogen anions will inevitably be released into water during the ion-exchange process. Herein, we reported a novel and easy-to-construct zwitterionic hypercrosslinked polymer (7AIn-PiP)-containing cationic pyridinium-type group, uncharged pyridine-type group, pyrrole-type group, and even an electron-rich phenyl group, which in synergy effectively removed 94.2% (456 nm) of I2 from saturated I2 aqueous solution within 30 min, surpassing many reported iodine adsorbents. Moreover, an I2 adsorption efficiency of ~95% can still be achieved after three cyclic evaluations, indicating a good recycling performance. More importantly, a unique dual 1,3-dipole was obtained and characterized by 1H/13C NMR, HRMS, and FTIR, correlating with the structure of 7AIn-PiP. In addition, the analysis of adsorption kinetics and the characterization of I2@7AIn-PiP indicate that the multiple binding sites simultaneously contribute to the high affinity towards iodine species by both physisorption and chemisorption. Furthermore, an interesting phenomenon of inducing the formation of HIO2 in unsaturated I2 aqueous solution was discovered and explained. Overall, this work is of great significance for both material and radiation protection science.

Fabrication of bimetallic MOF-74 derived materials for high-efficiency adsorption of iodine

Owing to their high porosity, open metal sites, and huge surface area, metal-organic framework (MOF) materials are commonly employed in iodine adsorption processes. Bimetallic MOFs have drawn a lot of attention since mono-metal MOFs have been unable to keep up with the demand. Bimetallic MOF materials still have drawbacks, including limited adsorption capacity, extended adsorption time, poor stability, and poor selectivity, despite their positive performance in radioactive iodine capture. It has been therefore difficult to develop adsorbents with quick iodine adsorption rates and high iodine adsorption efficiency. This study investigated the adsorption properties of a series of bimetallic MOF-74 materials (Mn-Co-MOF-74, Mn-Zn-MOF-74, and Mn-Ni-MOF-74) for radioactive iodine, as well as their design and synthesis utilizing the reflux approach. It was discovered that the adsorption performance of Mn-Ni-MOF-74 for radioiodine was superior to that of the other two bimetallic MOF-74 materials. Using the bimetallic Mn-Ni-MOF-74 as a precursor, a variety of bimetallic MOF-74 derived carbon compounds (Mn-Ni-CX) were prepared by high-temperature pyrolysis. Simultaneously, the structure of the material and the iodine adsorption characteristics have been thoroughly studied.

One-Step Prepared Multifunctional Polyacrylonitrile/MIL-100(Fe) Membrane with High-Density Porous Fibers for Efficient Dye/Oil Wastewater Remediation

With environmental pollution becoming more serious, developing efficient treatment technologies for all kinds of organic wastewater has become the focus of current research. In this work, the coaxial electrospinning technology was used to one-step fabricate a porous and underwater superoleophobic polyacrylonitrile nanofibrous membrane with an Fe-based metal-organic framework (MIL-100(Fe)). Benefiting from the synergistic effect of two jets, the nanofibers are smaller and denser, which prompt the exposure of more nanomaterial additives (MIL-100(Fe)). The BET surface area increased to 202.888 m2/g, and the membranes demonstrated outstanding underwater superoleophobicity. Moreover, compared with traditional blended matrix membranes by the single-axis method, separation of the modifier and membrane matrix material by coaxial methods also maintained excellent mechanical properties, which enhanced Young's modulus 3.4 times (∼1.34 MPa). As a result, facing soluble dyes, the porous C-PAN/MIL-100(Fe) membrane can demonstrate outstanding and fast adsorptive property (the Qm of MB and CR reached 44.71 and 88.74 mg g-1, respectively). For oily emulsion, the hydrophilic and oleophobic nanofibrous reticular surface provided excellent separation performance (flux: 1124.0-1549.3 L m-2 h-1, R > 98%). Moreover, the porous and underwater superoleophobic C-PAN/MIL-100(Fe)-0.5 membrane can synchronously purify the dye/oil mixture emulsions by one-step filtration. Based on the above performance, we believe that the modified nanofibrous membrane prepared by one-step coaxial electrospinning technology can promote more studies of the development of membrane preparation technology in the field of oily wastewater treatment.

σ-Hole Effect-Induced Electroluminescence of Halogen Cocrystals for Determination of Iodide in Seawater

Developing new electrochemiluminescence (ECL) luminators with high stability, wide applicability, and strong designability is of great strategic significance to promote the ECL field to the frontier. Here, driven by the I···N bond, 1,3,5-trifluoro-2,4,6-triiodobenzene (TFTI) and 2,4,6-trimethyl-1,3,5-triazine (TMT) self-assembled into a novel halogen cocrystal (TFTI-TMT) through slow solution volatilization. Significant difference of charge density existed between the N atoms on TMT and the σ-hole of the I atoms on TFTI. Upon the induction of σ-hole effect, high-speed and spontaneous charge transferring from TMT to the σ-hole of TFTI occurred, stimulating exciting ECL signals. Besides, the σ-hole of the I atoms could capture iodine ions specifically, which blocked the original charge transfer from the N atoms to the σ-hole, causing the ECL signal of TFTI-TMT to undergo a quenching rate as high as 92.9%. Excitingly, the ECL sensing of TFTI-TMT toward I- possessed a wide linear range (10-5000 nM) and ultralow detection limit (3 nM) in a real water sample. The halogen cocrystal strategy makes σ-hole a remarkable new viewpoint of ECL luminator design and enables ECL analysis technology to contribute to addressing the environmental and health threats posed by iodide pollution.

Efficient capture of iodine in steam and water media by hydrogen bond-driven charge transfer complexes

Untreated radioactive iodine (129I and 131I) released from nuclear power plants poses a significant threat to humans and the environment, so the development of materials to capture iodine from water media and steam is critical. Here, we report a charge transfer complex (TCNQ-MA CTC) with abundant nitrogen atoms and π-conjugated system for adsorption of I2 vapor and I3- from aqueous solutions. Due to the synergistic binding mechanism of benzene/triazine rings and N-containing groups with iodine, special I-π and charge transfer interaction can be formed between the guest and the host, and thus efficient removal of I2 and I3- can be realized by TCNQ-MA CTC with the adsorption capacity up to 2.42 g/g and 800 mg/g, respectively. TCNQ-MA CTC can capture 92% of I3- within 2.5 min, showing extremely fast kinetics, excellent selectivity and high affinity (Kd = 5.68 × 106 mL/g). Finally, the TCNQ-MA CTC was successfully applied in the removal of iodine from seawater with the efficiency of 93.71%. This work provides new insights in the construction of charge transfer complexes and lays the foundation for its environmental applications.

Efficient Removal of Iodine from Water by a Calix[4]pyrrole-Based Nanofilm

The efficient removal of radioactive iodine from an aqueous solution is largely dependent on the adsorbent materials employed. In this work, we report a calix[4]pyrrole-based nanofilm and its application for the rapid removal of iodine from water. The nanofilm was synthesized through a confined dynamic condensation of tetra hydrazide calix[4]pyrrole with 1,3,5-tri-(4-formylphenyl) aldehyde at the air/dimethyl sulfoxide (DMSO) interface. The thickness of the obtained nanofilm is ∼35 nm, enabling fast mass transfer and a high ratio of accessible binding sites for iodine. The pseudo-second-order rate constant of the nanofilm for iodine is ∼0.061 g g-1 min-1, 3 orders of magnitude higher than most reported adsorbent materials. Flow-through nanofiltration tests demonstrated that the nanofilm has an adsorption capacity of 1.48 g g-1, a high removal efficiency, and good reusability. The mechanism study revealed that the moieties of Schiff base, pyrrole, and aromatic rings play a key role for binding iodine. We believe this work provides not only a new strategy for the efficient removal of radioactive iodine from water but also new ideas for designing efficient iodine adsorbents.

Construction of Ketoenamine-Based Covalent Organic Frameworks with Electron-Rich Sites for Efficient and Rapid Removal of Iodine from Solution

Porous covalent organic frameworks (COFs) have been widely used for the efficient removal of iodine from solution due to their abundance of electron-rich sites. In this study, two kinds of ketoenamine-based COFs, TpBD-(OMe)2 and TpBD-Me2, are successfully synthesized via Schiff base reaction under solvothermal conditions using 1, 3, 5-triformylphoroglucinol as aldehyde monomer, o-tolidine and o-dianisidine as amino monomers. The ability of TpBD-(OMe)2 and TpBD-Me2 to adsorb iodine in cyclohexane or aqueous solutions has been quantitatively analyzed and interpreted in terms of adsorption sites. TpBD-Me2 possesses two adsorption sites, -NH- and -C=O, and exhibits an adsorption capacity of 681.67 mg/g in cyclohexane, with an initial adsorption rate of 0.6 g/mol/min with respect to COF unit cell. The adsorption capacity of TpBD-(OMe)2 can be as high as 728.77 mg/g, and the initial adsorption rate of TpBD-(OMe)2 can reach 1.2 g/mol/min in the presence of oxygen atoms between the methyl group and the benzene ring. Compared with TpBD-Me2, the higher adsorption capacity and adsorption rate of TpBD-(OMe)2 towards iodine are not only reflected in organic solvents, but also in aqueous solutions. It is proven through X-ray photoelectron spectroscopy and Raman spectroscopy that iodine exists in the form of I2, I3-, and I5- within TpBD-(OMe)2 and TpBD-Me2 after adsorption. This work not only expands the application of COFs in the field of iodine adsorption, but also provides research ideas and important an experimental basis for the optimization of iodine adsorption sites.

[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.

Synthesis of Tröger's base-based [3]arenes for efficient iodine adsorption

Enantiomers of Tröger's base-based [3]arenes R6N-E[3] and S6N-E[3] were synthesized successfully as two optically pure Tröger's base-based macrocycles in which three Tröger's base subunits were incorporated. Among these Tröger's base-based[3]arenes, M[3] showed high absorption of iodine up to 4.02 g g-1 in vapor.

Ratiometric fluorescent detection of exosomal piRNA-823 based on Au NCs/UiO-66-NH2 and target-triggered rolling circle amplification

piR-823 is a newly discovered colorectal cancer marker with high diagnostic efficacy. However, the current quantification methods have complicated operations and high cost, which restrict its clinical application. Herein, a metal-organic framework (MOF) with a UiO-66 prototype structure which supports gold nanoclusters (Au NCs), Au NCs/UiO-66-NH₂, were prepared as a model nanobiosensing platform for ratiometric detection of exosomal piR-823. The rolling circle amplification process provides high sensitivity and the ratiometric detection process ensures good accuracy of the sensor. Such biosensor showed a wide linear range of 0.04-4 pM, and a low detection limit of 10.2 fM towards piR-823. In addition, piR-823 can be used as an effective supplement to carcinoembryonic antigen (CEA) in clinical diagnosis of colorectal cancer. This study not only provides a potentially valuable ratio fluorescence platform involving enzyme catalytic reaction, but also offers a design blueprint for further expansion of nanotechnology in the diverse biological analysis.