Highly Efficient Uptake of Cs+ by Robust Layered Metal-Organic Frameworks with a Distinctive Ion Exchange Mechanism

Cesium adsorption from an aqueous medium for environmental remediation: A comprehensive analysis of adsorbents, sources, factors, models, challenges, and opportunities

Considering the widespread and indispensable nature of nuclear energy for future power generation, there is a concurrent increase in the discharge of radioactive Cs into water streams. Recent studies have demonstrated that adsorption is crucial in removing Cs from wastewater for environmental remediation. However, the existing literature lacks comprehensive studies on various adsorption methods, the capacities or efficiencies of adsorbents, influencing factors, isotherm and kinetic models of the Cs adsorption process. A bibliometric and comprehensive analysis was conducted using 1179 publications from the Web of Science Core Collection spanning from 2014 to 2023. It reviews and summarizes current publication trends, active countries, adsorption methods, adsorption capacities or efficiencies of adsorbents, tested water sources, influencing factors, isotherm, and kinetic models of Cs adsorption. The selection of suitable adsorbents and operating parameters is identified as a crucial factor. Over the past decade, due to their notable capacity for Cs adsorption, considerable research has focused on novel adsorbents, such as Prussian blue, graphene oxide, hydrogel, and nanoadsorbents (NA). However, there remains a need for further development of application-oriented laboratory-scale experiments. Future research directions should encompass exploring adsorption mechanisms, developing new adsorbents or their combinations, practical applications of lab-scale studies, and recycling radioactive Cs from wastewater. Drawing upon this literature review, we present the most recent research patterns concerning adsorbents to remove Cs, outline potential avenues for future research, and delineate the obstacles hindering effective adsorption. This comprehensive bibliometric review provides valuable insights into prevalent research focal points and emerging trends, serving as a helpful resource for researchers and policymakers seeking to understand the dynamics of adsorbents for Cs removal from water.

Stable, porous, light-emitting post-modification covalent organic frameworks conjugated molecularly imprinted polymers for selective detection of pyrraline in salami products

Molecular imprinting is one of the most frequently occurring post-modification in the preparation of covalent organic frameworks (COFs) to enhance selectivity and specificity. In this study, we prepared a 2D layer structure of methoxy-conjugated COFs with the modification of azide (4-azido-L-phenylalanine), named [4-ALP]0.17-COFs, which exhibited a large specific surface area of 827.6 m2/g, good stability of water, polar solvents, chemistry, and thermodynamics. Fluorescent COF nanosheets ([4-ALP]0.17-CONs) obtained by liquid-assisted ultrasonic stripping have excellent blue luminescence properties and ultra-high absolute fluorescence quantum yield of 33.34 %. The modifiable functional groups in the surface of [4-ALP]0.17-CONs interacted with the targets and functional monomers of molecularly imprinted polymers (MIPs) through hydrogen bonding interactions, to form the 3D holes with recognition sites. The quantitative detection of pyrraline (PRL) could be achieved in the concentration range of 0.05-4 μg/L with the LOD was 34.81 ng/L. The spiked recovery of PRL in meat products was 88.01-106.00 %. The [4-ALP]0.17-CONs@MIPs sensing system showed excellent stability, reliability, reusability, and practicability, promising its potential for targeted monitoring of trace molecules in real matrices.

Selective detection of food contaminants using engineered gallium-organic frameworks with MD and metadynamics simulations

The exclusion mechanism of food contaminants such as bisphenol A (BPA), Flavonoids (FLA), and Goitrin (GOI) onto the novel gallium-metal organic framework (MOF) and functionalized MOF with oxalamide group (MOF-OX) is evaluated by utilizing molecular dynamics (MD) and Metadynamics simulations. The atoms in molecules (AIM) analysis detected different types of atomic interactions between contaminant molecules and substrates. To assess this procedure, a range of descriptors including interaction energies, root mean square displacement, radial distribution function (RDF), density, hydrogen bond count (HB), and contact numbers are examined across the simulation trajectories. The most important elements in the stability of the systems under examination are found to be stacking π-π and HB interactions. It was confirmed by a significant value of total interaction energy for BPA/MOF-OX (- 338.21 kJ mol-1) and BPA/MOF (- 389.95 kJ mol-1) complexes. Evaluation of interaction energies reveals that L-J interaction plays an essential role in the adsorption of food contaminants on the substrates. The free energy values for the stability systems of BPA/MOF and BPA/MOF-OX complexes at their global minima reached about BPA/MOF = - 254.29 kJ mol-1 and BPA/MOF-OX = - 187.62 kJ mol-1, respectively. Nevertheless, this work provides a new strategy for the preparation of a new hierarchical tree-dimensional of the Ga-MOF hybrid material for the adsorption and exclusion of food contaminates and their effect on human health.

Study of the Adsorption and Separation Behavior of Scandium and Zirconium by Trialkyl Phosphine Oxide-Modified Resins in Sulfuric and Hydrochloric Acid Media

Zirconium is recognized as one of the main impurities of the rare earth element scandium during purification. It presents significant challenges due to its similar chemical properties, making separating it difficult. This study used trialkyl phosphine oxide (TRPO) as a functional ligand, and the effects of carrier type and acidity on adsorption performance were first investigated. Among these, the novel extraction resin SiO2-P as a carrier for TRPO demonstrated more prominent separation performance in 0.2 M H2SO4 and 5 M HCl solutions. The kinetic and isotherm data were consistent with the pseudo-secondary kinetics and Langmuir model, respectively, and the adsorption process could be regarded as homogeneous monolayer adsorption subject to the dual effects of chemisorption and internal diffusion. In addition, thermodynamic analysis showed that the adsorption process of zirconium under the experimental conditions was a spontaneous endothermic process. Combined with the results of SEM-EDS, FT-IR, and XPS analyses, scandium and zirconium were successfully adsorbed by the resin and uniformly distributed on its surface, and the greater affinity of the P=O groups on the resin for zirconium was the critical factor contributing to the separation of scandium and zirconium. Finally, scandium and zirconium in sulfuric acid and hydrochloric acid media were extracted and separated by column experiments, and the purity of scandium could reach 99.8% and 99.99%, respectively.

Introducing a Pyrazinoquinoxaline Derivative into a Metal-Organic Framework: Achieving Fluorescence-Enhanced Detection for Cs+ and Enhancing Photocatalytic Activity

Conventional photoresponsive materials have low photon utilization due to irregular distribution of photoactive groups, which severely limits the related real applications. Metal-organic frameworks (MOFs) can modulate the regular arrangement of functional groups to improve the electron transport paths and enhance the photon utilization, which provides strong support for the development of photoactive materials with excellent performance. In this work, one effective strategy for constructing a photoactive MOF had been developed via the utilization of Cd2+ and pyrazinoquinoxaline tetracarboxylic acid. The structural advantages of the Cd-MOF, such as a porous structure, abundant subject-object interaction sites, and a stable framework, ensure the prerequisite for various applications, while the better synergistic effect of Cd3 clusters and the pyrazinoquinoxaline derivative ensures efficient electron transfer efficiency. Therefore, by virtue of these structural advantages, the Cd-MOF can achieve fluorescence quenching detection for a variety of substrates, such as Fe3+, Cr2O72-, MnO4-, nitrofuran antibiotics, and TNP explosives, while fluorescence enhancement detection can be achieved for halogen ions, Cs+, Pb2+, and NO2-. In addition, the Cd-MOF can be used as a photocatalyst to successfully achieve the photocatalytic conversion of benzylamine to N-benzylbenzimidate under mild conditions. Thus, the Cd-MOF as a whole shows the possibility of application as a diverse fluorescence detection and photocatalyst and also illustrates the feasibility of preparing high-performance photoactive materials using the pyrazinoquinoxaline derivative.

Reduction-Induced Uptake of Cs+ in Metal-Organic Frameworks Loaded with Polyoxometalates

Materials for Cs+ adsorption continue to be important for the treatment of various solutions. Metal-organic frameworks (MOFs) with large specific surface areas promise adsorption properties for various gases, vapors, and ions. However, the utilization of MOFs for alkali ion capture, specifically, Cs+ capture is still in its infancy. Herein, MOFs are hybridized with polyoxometalates (POMs) to study the effect of i) MOF type, ii) POM type, and iii) POM loading amounts on Cs+ capture. In particular, the composite of ZIF-8 and [α-PMo12 O40 ]3- (PMo12 /ZIF-8) adsorbed Cs+ ions effectively when compared to pristine ZIF-8. In addition, the reduction of Mo within the POM from MoVI to MoV by ascorbic acid during the Cs+ uptake process doubled the Cs+ uptake capacity of PMo12 /ZIF-8. This observation can be attributed to the increased overall negative charge of the POM facilitating Cs+ uptake to compensate for the charge imbalance. Hybridization with other MOFs (MIL-101 and UiO-66) largely suppresses the Cs+ uptake, highlighting the importance of hydrophobicity in Cs+ capture. Furthermore, PMo12 /ZIF-8 led to an outstanding Cs+ uptake (291.5 mg g-1 ) with high selectivity (79.6%) from quinary mixtures of alkali metal cations even among other representative porous materials (Prussian blue and zeolites).

Latest advances in layered covalent organic frameworks for water and wastewater treatment

This review provides an overview of recent progress in the development of layered covalent organic frameworks (LCOFs) for the adsorption and degradation of pollutants in water and wastewater treatment. LCOFs have unique properties such as high surface area, porosity, and tunability, which make them attractive adsorbents and catalysts for water and wastewater treatment. The review covers the different synthesis methods for LCOFs, including self-assembly, co-crystallization, template-directed synthesis, covalent organic polymerization (COP), and solvothermal synthesis. It also covers the structural and chemical characteristics of LCOFs, their adsorption and degradation capacity for different pollutants, and their comparison with other adsorbents and catalysts. Additionally, it discussed the mechanism of adsorption and degradation by LCOFs, the potential applications of LCOFs in water and wastewater treatment, case studies and pilot-scale experiments, challenges, and limitations of using LCOFs, and future research directions. The current state of research on LCOFs for water and wastewater treatment is promising, however, more research is needed to improve their performance and practicality. The review highlights that LCOFs have the potential to significantly improve the efficiency and effectiveness of current water and wastewater treatment methods and can also have implications for policy and practice.

Ion-Selective Assembly of Supertetrahedral Selenido Germanate Clusters for Alkali Metal Ion Capture and Separation

Supertetrahedral chalcogenido (semi)metalate cluster-based frameworks possess high selectivity for alkali metal cations, matching the specific charge density of their inner surfaces, which enables their use as ion-exchange materials. Aggregates of the supertetrahedral chalcogenido metalate cluster offer even new perspectives for metal ion capture and separation. Herein, we report on ionothermal preparation of two corresponding model compounds, (C₂C₁Im)₇[Cs@Ge^II₄(Ge^IV₄Se₁₀)₄] (1) and (C₂C₁Im)₁₀[Na₅(CN)₆@Cu₆(Ge₄Se₁₀)₄(Cu)] (2). Their formation is reliant on one specific cation type each, Cs⁺ for 1 and Na⁺ for 2, thus providing promising separation potential during crystallization. Compound 1 is based on the largest discrete binary selenido germanate cluster reported to date and the first mixed-valent chalcogenido germanate(II/IV) supertetrahedron. Moreover, it adds to the few examples of chalcogenides capable of capturing Cs⁺ ions. Its high selectivity for Cs⁺ compared to that of Li⁺, Na⁺, K⁺, and Rb⁺ was confirmed by single-crystal X-ray diffraction, energy-dispersive X-ray spectroscopy, and electrospray ionization mass spectrometry. Quantum chemical studies indicate that smaller ions, K⁺ and Rb⁺, could also be embedded in an isolated cluster assembly, but as the cluster aggregate slightly distorts for crystallization, the selectivity for Cs⁺ becomes exclusive in the salt. The anionic substructure of compound 2 is based on a two-dimensional network of supramolecular assemblies and exhibits an exclusive preference for Na⁺. This work thus provides the first comprehensive insight into the selective incorporation of specific alkali metal ions into supramolecular aggregates of supertetrahedral chalcogenide clusters, as a promising basis for new ion trapping techniques─especially for heavy alkali metal ions that pose environmental challenges.

Ferric ion substitution renders cadmium metal-organic framework derivatives for modulated Li storage based on local oxidation active centers

In this work, a novel anionic Cd-MOF ([(CH₃)₂NH₂]_n[Cd(HL)DMF]_n·2nH₂O·nDMF, H₄L = 1,2,4,5-tetrakis[(4-carboxy)phenoxymethyl]benzene) was synthesized for the first time. As a precursor, it was utilized to obtain Fe@Cd-MOF crystals via the substitution of Fe³⁺ ions due to a negatively charged framework and free-coordinated carboxyl group. Fe₃O₄/Fe-embedded carbon-based materials (Fe@Cd-MOFD) were further constructed by deriving Fe@Cd-MOF at high temperatures. The derived Fe@Cd-MOFD showed a structure resembling a central city with metal redox centers embedded into a carbon matrix. The introduced Fe³⁺ ions formed a local nano-sized metal oxide upon annealing, and these derived carbon materials offered high electronic conductivity. These pushed Fe@Cd-MOFD to remarkable electrochemical performance with an initial discharge capacity of 1703.8 mA h g^-1. This work offers new insights into the fabrication of novel MOF-derived iron oxide hybrids for lithium storage.