Ionic covalent organic framework for selective detection and adsorption of TcO4-/ReO4. Chem Commun (Camb) 2023. [PMID: 37455640 DOI: 10.1039/d3cc02429f]

Membrane-based adsorbent materials for uranium extraction from seawater: recent progress and future prospects

The global energy shortage is becoming increasingly severe, making it urgent to address the energy deficit. Nuclear energy is considered a green, efficient and clean energy source. The reserves of uranium, an essential strategic nuclear fuel resource, have become pivotal in addressing the energy crisis. Compared to uranium resources on land, the ocean is rich in uranium. Therefore, uranium extraction from seawater has become an ideal choice. However, the variety of competing ions in seawater, its high salinity and the complex marine environment make uranium extraction from seawater a huge challenge. In the context of assessing the economics and sustainability of the entire uranium separation process, membrane-based adsorbents are considered ideal materials for large-scale uranium extraction from seawater due to their ease of collection and reuse. This review discusses different types of membrane-based adsorbent materials, including modified non-woven membranes, phase conversion membranes, and other types of membrane materials. In addition, this review summarizes recent studies on the use of membrane-based adsorbents for extracting uranium from seawater and the prospects for their development. With the rapid development of membrane-based adsorbents for uranium extraction from seawater, this review also discusses the challenges and future prospects of this frontier field.

Efficient capture of 99TcO4-/ReO4- via node and linker bifunctional anion exchange covalent organic frameworks

In nuclear wastewater treatment, ion-scavenging materials designed to trap 99TcO4- is urgently needed. However, strong acid/base, high radiation and high salt concentration of nuclear wastewater usually result in inadequate stability and adsorption capacity of the adsorbent. Herein, we report a new class of bifunctional anion-exchange olefin-linked COF (BPDC-MTMP) prepared via Knoevenagel condensation reactions, the first example exploring the synergistic integration of positively charged fragments at both nodes and linkers. Surprisingly, BPDC-MTMP exhibits a record ReO4- (a non-radioactive surrogate of 99TcO4-) adsorption capacity up to 1593.21 mg g-1, its outstanding adsorption capacity can be attributed to the synergistic enhancement of the positively charged fragments of the nodes and linkers leading to a significant increase in the positive charge density and the number of anion exchange sites. BPDC-MTMP's hydrophobicity is enhanced by the highly conjugated bulky alkyl skeleton, the affinity toward ReO4- and chemical stability are therefore significantly improved, ReO4- can be selectively and reversibly extracted even under strong acid/base and high salt concentration solutions. This study illustrates that the node and linker bifunctional anion exchange COF is of great potential for ReO4-/99TcO4- trapping, which provides a new method to design high-performance adsorbents for the treatment of nuclear wastewater.

Construction of carbazole-conjugated dual-emission fluorescent covalent organic framework for distinguishing p-nitroaniline/p-nitrophenol and adsorbing nitroanilines/nitrophenols

Nitroanilines (NAs) and nitrophenols (NPs), crucial industrial raw materials, are extensively utilized across various sectors. However, the environmental pollution and health hazards stemming from their usage are significant, necessitating urgent monitoring and removal to address environmental and safety concerns. The challenge is further compounded by the presence of NAs/NPs isomers, making the selective analysis of specific isomers crucial. In response, a new post-modified fluorescent covalent organic framework (COF) termed COF@CB, exhibiting dual-emission fluorescence, was synthesized. This synthesis involved coupling a high-crystallinity fluorescent COF (COF-TTDB) with carbazole-9-ethanol (CB) via a "Williamson" reaction. COF@CB featured exceptional dual-emission fluorescence, a high specific surface area (919.4 m2·g-1), superior thermal stability, and abundant active sites. These attributes enabled COF@CB to function as a ratiometric fluorescence sensor capable of simultaneous detection and adsorption. The distinct number and arrangement of hydrogen bond sites in NAs/NPs isomers influenced the intramolecular charge transfer (ICT) effects on COF@CB, thereby enabling the COF@CB-ratiometric fluorescence sensor to distinguish and selectively detect p-NA/p-NP from isomers. Analysis of actual water samples further underscored the sensor's effectiveness in detecting p-NA/p-NP. Furthermore, the presence of multiple active sites on the COF@CB-ratiometric fluorescence sensor facilitated the adsorption of NAs/NPs, promoting the removal of them from actual samples.

Hydrazone-linked covalent organic frameworks for fluorescence detection of Hg2

A hydrazone-linked COF (DvDf-C3XJ-COF) with hydrogen-bond reinforcement and abundant coordination sites was synthesized, exhibiting strong fluorescence and high sensitivity/selectivity for Hg2+ detection, with a detection limit of 1.65 × 10-6 M. The fluorescence quenching for Hg2+ is attributed to coordination interactions, which occur through a dynamic quenching process.

Carbazole and Triazine-Based D-A Covalent Organic Framework for Visible Light-Mediated Photocatalytic C-H Activation of Imidazopyridine and Indole

Two-dimensional donor-acceptor covalent organic frameworks (COFs) show considerable promise for metal-free and heterogeneous photocatalysis due to their efficient charge carrier separation and exciton transport upon photoexcitation. To date, numerous photocatalysts have been developed. However, they encounter several challenges, such as inadequate sunlight harvesting ability, poor photostability, and nonreusability. Fortunately, the emergence of COFs presents a promising solution to these problems. Herein, we report an imine-linked CzTA-TAPT COF featuring carbazole as the electron donor and triazine as the electron acceptor. Compared to the previously reported C2-linker-derived CzDA-TAPT COF, this C3-linked COF exhibits good charge separation and charge carrier transport. As a consequence, it demonstrates excellent photocatalytic applicability in the C-3 thiocyanation of imidazo[1,2-a]pyridine and indole under ambient conditions under visible light. Moreover, its broad substrate compatibility and high recyclability provide a green and sustainable approach for the thiocyanation of imidazopyridine and indole. To the best of our knowledge, this is the first heterogeneous catalyst demonstrated for the thiocyanation of imidazo[1,2-a]pyridine. These findings will inspire further research in the development of high-performance D-A COFs as photocatalysts for organic transformations.

Fabricating Porous Alkali-Resistant Resin for Segregation of Perrhenate/Pertechnetate Anions from Wastewater

The elimination of the β-emitting pertechnetate ion (99TcO4-) from highly alkaline tank waste poses a daunting challenge that is of great significance for nuclear safety and environmental protection. Herein, we report a strategy to fabricate an alkaline-stable porous resin (PANPEI-MeCl) that features hyperbranched quaternary amine groups grafted on the surface and confined within the pores of a superhydrophobic polymer matrix synthesized by a one-pot method, exhibiting a clear superiority both in adsorption kinetics and efficiency compared with available commercial anion-exchange resins applying to 99TcO4- capture. Notably, the alkaline stability of the resin can be improved by manipulating the length of side chain alkyl groups, and it shows ultrahigh structural integrity and prominent performance toward acid/alkaline soaking, high-temperature calcination procedures, and high doses of ionizing radiation. Encouraged by its excellent peculiarity, PANPEI-MeCl can continuously capture most of the ReO4- from the simulated radioactive waste by using a sequential injection automatic separation system.

A robust amphiphilic ionic covalent organic framework intercalated into functionalized graphene oxide hybrid membranes for ultrafast extraction uranium from wastewater

The efficient capture of uranium from wastewater is crucial for environmental remediation and the sustainable development of nuclear energy, yet it poses considerable challenges. In this study, amphiphilic ionic covalent organic framework intercalated into graphene oxide (GO) nanosheets functionalized with polyethyleneimine (PEI) were used to construct hybrid membranes with ultrafast uranium adsorption. These hybrid membranes achieved equilibrium in just 10 min and the adsorption capacity was as high as 358.8 mg g-1 at pH = 6. X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) analyses revealed that the strong interaction between sulfonic acid groups and uranyl ions was the primary reason for the high adsorption capacity and selectivity. The extended transition state and natural orbitals for chemical valence (ETS-NOCV) analysis revealed that the interaction between the 7 s and 5f orbitals of uranyl and the 2p orbitals of S and O in the sulfonate was the primary reason for the strong interaction between the sulfonate and the uranyl ion. This research presents an effective method for the rapid extraction of uranium from wastewater.

DGA-grafting pyridine for ultra-selective and prior extraction of 99TcO4- from simulated spent nuclear fuel

Selective and prior extraction of 99TcO4- ahead of uranium and plutonium separation is a beneficial strategy for the modern nuclear fuel cycle. Herein, a novel DGA-grafting pyridine ligand BisDODGA-DAPy (L1) was tailored for the efficient separation of TcO4- from simulated spent nuclear fuel based on the selectivity of pyridine and synergistic effect of diglycolamide (DGA) group. Compared to the ligands BisDOSCA-DAPy (L2) and BisDODGA-MPDA (L3) with similar structure, BisDODGA-DAPy (L1) demonstrated the better separation performance including good extraction efficiency, reusability, and high loading capacity for TcO4- under high acidic medium. The interactions of the ligands with Tc(VII)/Re(VII) have been investigated in detail using FT-IR, 1H NMR titration, UV-Vis spectrophotometric titration, ESI-HRMS and DFT simulations. The extraction mechanism affected by the protonation of ligand was elucidated under different acidity. BisDODGA-DAPy (L1) demonstrated the ultra-selective extraction ability for TcO4- from simulated spent nuclear fuel. The maximum SFTc/U and SFTc/Pu values were up to 1.29 × 104 and 5.08 × 103, respectively. In the presence of 9 × 104-fold excess of NO3-, the extraction of TcO4- was almost unaffected. Moreover, the good radiolytic stability further highlights the promising potential of this ligand for 99Tc separation. DFT calculation revealed the dominant role of DAPy and DODGA in TcO4- extraction, providing the theoretical evidence for BisDODGA-DAPy (L1) to selectively bind TcO4- over NO3-.

Synthesis and performance of guanidinium-based cationic organic polymer for the efficient removal of TcO4-/ReO4. JOURNAL OF HAZARDOUS MATERIALS 2024;466:133602. [PMID: 38286051 DOI: 10.1016/j.jhazmat.2024.133602] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Cationic organic polymers have found relatively extensive utility for TcO4-/ReO4- removal, but the harsh preparation conditions constrain their practical application. The bifunctional guanidinium-based cationic organic polymer (GBCOP) was successfully and facilely synthesized in benign conditions within 1 h. Batch experiments showed that GBCOP exhibited rapid removal kinetics (1 min, >98.0%) and a substantial removal capacity of 536.8 mg/g for ReO4-. Even in 1000-fold co-existing NO3- anions, the removal efficiency of GBCOP for ReO4- was 74.0%, indicating its good selectivity. Moreover, GBCOP had high removal efficiencies for ReO4- across a wide pH (3.0-10.0) range and presented remarkable stability under the conditions of strong acid and base. GBCOP could be reused four times while removing 80.8% ReO4- from simulated Hanford wastewater. SEM and XPS results revealed that the mechanism of ReO4- removal involved Cl- ion exchange within the channels of GBCOP. Theoretical calculation results supported that existing the strong electrostatic interaction between guanidinium and ReO4-. This dual-function GBCOP material is cost-effective and holds significant potential for large-scale preparation, making it a promising solution for TcO4- removal from nuclear wastewater.