On site portable detection of gaseous I using green and pollution-free electrochemical methods.

A poly(ionic liquid) probe material was prepared that is conductive, uniformly film-forming, and rich in I interaction sites by structural design. Green and pollution-free electrochemical detection of gaseous I was achieved based on the variation of redox peak currents, and the limit of detection was 1.44 nM.

Mild and Subtle Synthesis of β-Ketoenamine COFs with High Crystallinity and Controllable Solubility Guided by a Monomer Preassembly Strategy.

The stability of covalent organic frameworks (COFs) is crucial for their applications in demanding environments. However, increasing the stability of COFs often comes with challenges such as higher synthesis difficulty, lower crystal quality, and reduced controllability during synthesis, making it difficult to regulate dimensions and morphology, thereby impacting the processing and shaping of stable COFs. Herein, the study presents a novel confined polymerization approach guided by hydrogen bonding preassembly to synthesize a soluble and stable COF featuring β-ketoenamine linkage.

Synthesis of Carboxyl-Functionalized COFs with Alternate Stable β-Ketoenamine and Benzimidazole Linkages: Unraveling Exceptional Solvent Effects for Efficient Uranium Separation.

The prevalent π-π interactions in 2D covalent organic frameworks (COFs) impart a certain flexibility to the structures, making the stacking of COF layers susceptible to external stimuli and introducing some structural disorder. Recent research indicates that the flexibility between COF layers and the associated disorder significantly influence their selective adsorption performance toward gas molecules. However, the adsorption process in a solution environment is more complex compared to gas-phase adsorption, involving interactions between adsorbents and adsorbates, as well as the solvation effects of flexible 2D COFs.

Dynamic Cleavage-Remodeling of Covalent Organic Networks into Multidimensional Superstructures.

Superstructures with complex hierarchical spatial configurations exhibit broader structural depth than single hierarchical structures and the associated broader application prospects. However, current preparation methods are greatly constrained by cumbersome steps and harsh conditions. Here, for the first time, a concise and efficient thermally responsive dynamic synthesis strategy for the preparation of multidimensional complex superstructures within soluble covalent organic networks (SCONs) with tunable morphology from 0D hollow supraparticles to 2D films is presented.

Constructing ordered and tunable extrinsic porosity in covalent organic frameworks via water-mediated soft-template strategy.

As one of the most attractive methods for the synthesis of ordered hierarchically porous crystalline materials, the soft-template method has not appeared in covalent organic frameworks (COFs) due to the incompatibility of surfactant self-assembly and guided crystallization process of COF precursors in the organic phase. Herein, we connect the soft templates to the COF backbone through ionic bonds, avoiding their crystallization incompatibilities, thus introducing an additional ordered arrangement of soft templates into the anionic microporous COFs. The ion exchange method is used to remove the templates while maintaining the high crystallinity of COFs, resulting in the construction of COFs with ordered hierarchically micropores/mesopores, herein named OHMMCOFs (OHMMCOF-1 and OHMMCOF-2).

Branched-Chain-Induced Host-Guest Assembly in Covalent-Organic Frameworks for Efficient Separation of No-Carrier-Added Lu.

No-carrier-added (NCA) Lu is one of the most interesting nuclides for endoradiotherapy. With the dramatically rapid development of radiopharmaceutical and nuclear medicine, there is a sharp increase in the radionuclide supply of NCA Lu, which has formed a great challenge to current radiochemical separation constituted on classical materials. Hence, it is of vital importance to design and prepare new functional materials able of recovering Lu from an irradiated target with excellent efficacy.

On-site portable detection of gaseous methyl iodide using an electrochemical method.

We report an electrochemical device for portable on-site detection of gaseous CHI based on PVIm-F for the first time. The device achieves detection of gaseous CHI with a significant selectivity and a low detection limit (0.474 ppb) in 20 min at 50 °C and 50% relative humidity, which is of great significance for achieving real-time on-site monitoring of radioactive hazardous environments.

Hydrogen-bonding and π-π interaction promoted solution-processable covalent organic frameworks.

Covalent organic frameworks show great potential in gas adsorption/separation, biomedicine, device, sensing, and printing arenas. However, covalent organic frameworks are generally not dispersible in common solvents resulting in the poor processability, which severely obstruct their application in practice. In this study, we develop a convenient top-down process for fabricating solution-processable covalent organic frameworks by introducing intermolecular hydrogen bonding and π-π interactions from ionic liquids.

Simple and Efficient Hydrogen Bond-Assisted Unit Exchange for Constructing Highly Soluble Covalent Organic Frameworks.

The majority of COFs synthesized using current methods exist as insoluble powders, which is unfavorable for processing and molding and greatly limits their practical applications. The syntheses of solution-processable or soluble COFs are challenging but hold immense promise and potential. Herein, for the first time, we have developed a simple and high-efficiency solvothermal-treated unit exchange approach to convert insoluble COF powders into smaller, highly soluble COFs via a hydrogen bond-assisted strategy.

Regioselective One-Step Cyclization and Aromatization towards Directly Amino-Functionalized Covalent Organic Framework with Stable Benzodiimidazole Linkage.

The compatibility of crystallinity, stability, and functionality in covalent organic frameworks (COFs) is challenging but significant in reticular chemistry and materials science. Herein, it is presented for the first time a strategy to synthesize directly amino-functionalized COF with stable benzodiimidazole linkage by regioselective one-step cyclization and aromatization. Bandrowski's base with two types of amino groups is used as a unique monomer, providing not only construction sites for the material framework through specific region-selective reaction, but also amino active sites for functionality, which is usually difficult to achieve directly in COF synthesis because amino groups are the participants in COF bonding.

Monomer Symmetry-Regulated Defect Engineering: In Situ Preparation of Functionalized Covalent Organic Frameworks for Highly Efficient Capture and Separation of Carbon Dioxide.

Developing crystalline porous materials with highly efficient CO selective adsorption capacity is one of the key challenges to carbon capture and storage (CCS). In current studies, much more attention has been paid to the crystalline and porous properties of crystalline porous materials for CCS, while the defects, which are unavoidable and ubiquitous, are relatively neglected. Herein, for the first time, we propose a monomer-symmetry regulation strategy for directional defect release to achieve in situ functionalization of COFs while exposing uniformly distributed defect-aldehyde groups as functionalization sites for selective CO capture.

Solvent-Responsive Reversible and Controllable Conversion between a Polyimine Membrane and an Organic Molecule Cage.

Adaptive bionic self-correcting behavior offers an attractive property for chemical systems. Here, based on the dynamic feature of imine formation, we propose a solvent-responsive strategy for smart switching between an amorphous ionic polyimine membrane and a crystalline organic molecule cage without the addition of other building blocks. To adapt to solvent environmental constraints, the aldehyde and amine components undergo self-correction to form a polymer network or a molecular cage.

Construction of Flexible Amine-linked Covalent Organic Frameworks by Catalysis and Reduction of Formic Acid via the Eschweiler-Clarke Reaction.

Compared to the current mainstream rigid covalent organic frameworks (COFs) linked by imine bonds, flexible COFs have certain advantages of elasticity and self-adaptability, but their construction and application are greatly limited by the complexity in synthesis and difficulty in obtaining regular structure. Herein, we reported for the first time a series of flexible amine-linked COFs with high crystallinity synthesized by formic acid with unique catalytic and reductive bifunctional properties, rather than acetic acid, the most common catalyst for COF synthesis. The reaction mechanism was demonstrated to be a synchronous in situ reduction during the formation of imine bond.

Pore Size Control Multiple-Site Alkylation to Homogenize Sub-Nanoporous Covalent Organic Frameworks for Efficient Sieving of Xenon/Krypton.

Among various fission products generated in nuclear reactors, xenon and krypton are two important fission gases with high flow, diffusivity, and radioactivity. Moreover, xenon isolated from these products is an expensive industrial resource with wide applications in medicine and lighting, which makes the development of efficient methods for separation of xenon/krypton significant. However, it is usually difficult for xenon/krypton to be adsorbed by chemical adsorbents due to their inert gas properties, and sub-nanoporous adsorbents proven to be workable for the separation of xenon/krypton are still hard to prepare and regulate the pore size.

Construction of covalent organic framework with unique double-ring pore for size-matching adsorption of uranium.

The separation and recovery of key nuclides such as uranium and plutonium from effluents related to nuclear industry is of great significance for alleviating the shortage of nuclear energy resources and protecting the environment and human health. However, the high temperature, strong acidity and radioactivity of the nuclear effluents pose a severe challenge to the separation materials used in such conditions. The diversity of structure, flexibility of design, and excellent physicochemical stability of covalent organic framework materials (COFs) provide the possibility for the directional design and preparation of adsorbents for use under harsh conditions.

A fully conjugated organic polymer via Knoevenagel condensation for fast separation of uranium.

Design and preparation of a kind of pore-free adsorbent with abundant active sites is favorable for fast separation of uranium. Here, a two-dimensional olefin-linked conjugated organic polymer was prepared via the Knoevenagel condensation reaction. The product owns good stability and excellent fluorescence property due to the fully conjugated skeleton.

Colyliform Crystalline 2D Covalent Organic Frameworks (COFs) with Quasi-3D Topologies for Rapid I Adsorption.

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.

Laminated self-standing covalent organic framework membrane with uniformly distributed subnanopores for ionic and molecular sieving.

The preparation of subnanoporous covalent-organic-framework (COF) membranes with high performance for ion/molecule sieving still remains a great challenge. In addition to the difficulties in fabricating large-area COF membranes, the main reason is that the pore size of 2D COFs is much larger than that of most gas molecules and/or ions. It is urgently required to further narrow their pore sizes to meet different separation demands.

Redox-Active Two-Dimensional Covalent Organic Frameworks (COFs) for Selective Reductive Separation of Valence-Variable, Redox-Sensitive and Long-Lived Radionuclides.

We report the first example of 2D covalent organic framework nanosheets (Redox-COF1) for the selective reduction and in situ loading of valence-variable, redox-sensitive and long-lived radionuclides (abbreviated as VRL nuclides). Compared with sorbents based on chemical adsorption and physical adsorption, the redox adsorption mechanism of Redox-COF1 can effectively reduce the impact of functional group protonation under the usual high-acidity conditions in chemisorption, and raise the adsorption efficiency from the monotonous capture by pores in physisorption. The adsorption selectivity for UO reaches up to unprecedented ca.

Crystalline quantum dots of covalent organic frameworks for fast and sensitive detection of uranium.

A crystalline quantum dot of a COF was prepared for the first time by the original BRB method and a novel pathway for online monitoring of the COF reaction rate was proposed. The quantum dot can respond to uranyl ion quickly and sensitively and is of great potential in uranium detection.

Synthesis of Microporous Covalent Phosphazene-Based Frameworks for Selective Separation of Uranium in Highly Acidic Media Based on Size-Matching Effect.

On the basis of high stability of phosphorus-oxygen linkage, we constructed two microporous covalent phosphazene-based frameworks (CPFs), for the first time, by choosing hexachlorocyclotriphosphazene as a core unit and polyhydroxy aromatic compounds (hydroquinone or phloroglucinol) as monomers, named CPF-D and CPF-T, respectively. Characterization studies by using Fourier transform infrared, nuclear magnetic resonance, thermal gravimetric analysis, Co γ-ray irradiation, and so forth, demonstrated that both of the CPF materials have excellent acid and radiation stability and relatively higher thermal stability. The results of batch adsorption experiments show that CPF-T is significantly more capable of sorbing uranium than CPF-D.

Graphene-synergized 2D covalent organic framework for adsorption: A mutual promotion strategy to achieve stabilization and functionalization simultaneously.

Most of current absorbents are difficult to hold favorable stability and functionality simultaneously when used in condition of high acidity and strong radiation existing in nuclear industry. Herein, a new graphene-synergized 2D covalent organic framework (GS-COF) was obtained via an in-situ loading of a covalent organic framework (TDCOF) on graphene sheets based on a mutual promotion strategy proposed in this work. The corresponding oximation products, o-GS-COF, and also o-TDCOF as a reference object, were respectively prepared subsequently.

Growth of high-quality covalent organic framework nanosheets at the interface of two miscible organic solvents.

Stronger covalent bonds between monomers, relatively more complex growth processes (polymerization, crystallization, assembly, etc.) and π-π stacking interactions between adjacent layers make it extremely difficult to obtain highly ordered crystalline 2D covalent organic framework (COF) nanosheets. So more effective solutions have to be developed to push the methods reported so far beyond their inherent limitations.

Interaction between U and Th on their uptake, distribution, and toxicity in V S. alfredii based on the phytoremediation of U and Th.

Variant Sedum alfredii Hance (V S. alfredii) could simultaneously take up U and Th from water with the highest concentrations recorded as 1.84 × 10 and 6.