Selected Metal Ions Research Articles

Ultra-High Metal-Ion Selectivity Induced by Intramolecular Cation-π Interactions for the One-Pot Synthesis of Precise Heterometallic Architectures.

Heterometallic supramolecules, known for their unique synergistic effects, have shown broad applications in photochemistry, host-guest chemistry, and catalysis. However, there are great challenges to precisely construct heterometallic supramolecules rather than a statistical mixture, due to the limited metal-ion selectivity of coordination units. In particular, heterometallic architectures precisely encoded with different metal ions usually fail to form in a one-pot method when only one type of coordinated motif exists due to its poor metal-ion selectivity. Herein, we propose an effective intramolecular cation-π (ICπ) strategy and successfully constructed the heterometallic supramolecule Zn2Cu4L34 by the one-pot self-assembly of tritopic terpyridyl ligand L3 with Zn(II) and Cu(II), following a clear self-assembly mechanism in which only thermodynamic dimers ZnL12 and Cu2L22 were constructed with model ligands L1, L2, Zn(II) and Cu(II) with perfect self-sorting and an ultra-high metal-selectivity feature. The successful construction of the heterometallic supramolecule Zn2Cu4L34, in which the definite sequence of metal ions Zn(II) and Cu(II) is encoded in the one-pot method, will offer a novel approach to precisely construct heterometallic architectures.

Machine learning framework for selective and sensitive metal ion sensing with nitrogen-doped graphene quantum dots heterostructure

This study introduces a machine learning (ML) framework to optimize photodetector performance for sensor applications. Using the data from the fabricated photodetector with the heterostructure of nitrogen-doped graphene quantum dot and gold nanoparticles (Au@N-GQDs), various supervised ML models (more than 20 models) are trained and tested for the selection and refinement of the most effective algorithm for our work. Depending on the best-performed ML model, the optimized working wavelength of the photodetector is found for the detection of metal ions. Remarkably, the ML-based sensor shows a high level of selectivity and sensitivity in nM level towards Fe3+ ions in Brahmaputra river water. A strong alignment between model predictions and experimental outcomes validates the efficacy of the proposed ML-based framework. Moreover, data visualization techniques such as heatmaps, classification algorithms, and confusion matrices are introduced to identify the trends in the database. The mechanistic insight of the sensor performance towards Fe3+ ion sensing is further explained with heatmap analysis and experimental verification, which emphasizes the role of photo-induced charge transfer and Fe–O bond formation between metal ions and Au@N-GQDs due to the high electron affinity of Fe3+ ions.

Rational MOF Membrane Design for Gas Detection in Complex Environments.

Metal-organic frameworks (MOFs) hold significant promise in the realm of gas sensing. However, current understanding of their sensing mechanisms remains limited. Furthermore, the large-scale fabrication of MOFs is hampered by their inadequate mechanical properties. These two challenges contribute to the sluggish development of MOF-based gas-sensing materials. In this review, the selection of metal ions and organic ligands for designing MOFs is first presented, deepening the understanding of the interactions between different metal ions/organic ligands and target gases. Subsequently, the typical interfacial synthesis strategies (gas-solid, gas-liquid, solid-liquid interfaces) are provided, highlighting the potential for constructing MOF membranes on superhydrophobic and/or superhydrophilic substrates. Then, a multi-scale structure design strategies is proposed, including multi-dimensional membrane design and heterogeneous membrane design, to improve sensing performance through enhanced interfacial mass transfer and specific gas sieving. This strategy is anticipated to augment the task-specific capabilities of MOF-based materials in complex environments. Finally, several key future research directions are outlined with the aim not only to further investigate the underlying sensing principles of MOF membranes but also to achieve efficient detection of target gases amidst interfering gases and elevated moisture levels.

Metal and metal oxide nanomaterials for heavy metal remediation: novel approaches for selective, regenerative, and scalable water treatment

Heavy metal contamination in water sources poses a significant threat to environmental and public health, necessitating effective remediation strategies. Nanomaterial-based approaches have emerged as promising solutions for heavy metal removal, offering enhanced selectivity, efficiency, and sustainability compared to traditional methods. This comprehensive review explores novel nanomaterial-based approaches for heavy metal remediation, focusing on factors such as selectivity, regeneration, scalability, and practical considerations. A systematic literature search was conducted using multiple academic databases, including PubMed, Web of Science, and Scopus, to identify relevant articles published between 2013 and 2024. The review identifies several promising nanomaterials, such as graphene oxide, carbon nanotubes, and metal-organic frameworks, which exhibit high surface areas, tunable surface chemistries, and excellent adsorption capacities. Surface functionalization with specific functional groups (e.g., carboxyl, amino, thiol) significantly enhances the selectivity for target heavy metal ions. Advances in regeneration strategies, including chemical desorption, electrochemical regeneration, and photocatalytic regeneration, have improved the reusability and cost-effectiveness of these materials. Scalability remains a critical challenge, but recent developments in synthesis methods, such as green synthesis and continuous-flow synthesis, offer promising solutions for large-scale production. The stability and longevity of nanomaterials have been improved through surface modification and the development of hybrid nanocomposites. Integrating nanomaterials with existing water treatment infrastructure and combining them with other remediation techniques, such as membrane filtration and electrochemical methods, can enhance overall treatment efficiency and feasibility. In conclusion, nanomaterial-based approaches hold immense promise for revolutionizing heavy metal remediation and advancing sustainable water management practices. As future research is geared towards retrofitting existing treatment plants, it is equally critical to mitigate unintended environmental and public health consequences associated with the widespread production and use of nanomaterials, such as their leachability into water systems and environmental persistence.

Design of Recyclable Adsorbent for Water Pollutants Based on Chitosan-Coated Carboxymethyl Cellulose-Calcium Alginate Wrapped Iron Oxide-Copper Oxide Composite Beads

ABSTRACT In this study, an efficient nanocomposite based on calcium alginate-carboxymethyl cellulose/iron oxide-copper oxide (CA-CMC/Fe2O3-CuO) is developed in beads form and utilized as nanoadsorbent and nanocatalyst. Further, the beads were coated with chitosan, resulting in Cs@CA-CMC/Fe2O3-CuO beads. The prepared beads exhibited exceptional adsorption capabilities for selected heavy metal ions. Notably, the Cs@CA-CMC/Fe2O3-CuO beads displayed remarkable adsorption among the other beads toward the three selected metal ions. Ag(I) was highly adsorbed by Cs@CA-CMC/Fe2O3-CuO beads, and the adsorption capacity of beads was 4.91 mgg−1, while 4.5 mgg−1 and 3.0 mgg−1 for Co(II) and Ni(II), respectively. Beads’ ability to adsorb Ag(I) varied depending on several factors. It was observed that the adsorption capacity of Ag(I) ions increased as the interaction time and metal concentration rose. However, increasing the beads dose led to a decrease in the Ag(I) ion adsorption. Further, the waste beads after Ag(I) adsorption were treated with reducing agent to form beads supported Ag nanoparticles (Ag/Cs@CA-CMC/Fe2O3-CuO) and used as effective catalyst for reducing 4-nitrophenol in the presence of NaBH4 as a reducing agent. Ag/Cs@CA-CMC/Fe2O3-CuO achieved reduction up to 93% for 4-NP within 30 min. The designed nanocomposite beads displayed several desirable attributes, including eco-friendliness and robust catalytic performance, making them highly promising for useful reduction of 4-NP.

Effectively Sieving Alkali Metal Ions Using Functionalized Graphene Oxide Membranes by Exploiting Water-Repellent Interactions.

Sieving membranes capable of discerning different alkali metal ions are important for many technologies, such as energy, environment, and life science. Recently, two-dimensional (2D) materials have been extensively explored for the creation of sieving membranes with angstrom-scale channels. However, because of the same charge and similar hydrated sizes, mostly laminated membranes typically show low selectivity (<10). Herein, we report a facile and scalable method for functionalizing graphene oxide (GO) laminates by dually grafting cations and water-repellent dimethylsiloxane (DMDMS) molecules to achieve high selectivities of ∼50 and ∼20 toward the transport of Cs+/Li+ and K+/Li+ ion pairs, surpassing many of the state-of-the-art laminated membranes. The enhanced selectivity for alkali metal ions can be credited to a dual impact: (i) strong hydrophobic interactions between the incident cations' hydration shells and the water-repellent DMDMS; (ii) the efficient screening of electrostatic interactions that hamper selectivity.

Microwave-assisted supramolecular double crosslinked chitosan-based molecularly imprinted polymer for synergistic recognition and selective recovery of Cd(II) and As(V) from water: Performance and mechanistic insights

A novel model of the sustainable double crosslinked molecularly imprinted polymer (D-Crosslinked MIP) represented as a supramolecular imprinted polymer was synthesized via the bulk polymerization method. The primary crosslinking was fabricated using biomacromolecule chitosan as a functional monomer and glutaraldehyde as a crosslinker. The primary crosslinked was subjected to dynamic interactions in a secondary crosslinking by binding Al2O3-NPs and TiO2-NPs, forming the supramolecular D-Crosslinked-MIP. The dually crosslinked formed from combining three distinct crosslinkers in one system for the interaction with As(V) and Cd(II). A microwave was employed to evaluate the performance of the designed material in selectivity and extraction of metal ions from water. The FT-IR, XRD, TG/DTA, SEM-EDX, TEM, and XPS were used to verify the characteristics of (D-nano-Al2O3@Crosslinked Chitosan@D-nano-TiO2). The type of solvents, selectivity, interferences, microwave-contact time, pH, temperatures, concentrations, and regeneration were investigated. By using the D-Crosslinked-MIP, at 15 s, Cd(II) revealed a recovery capacity of 99.03 %, Qmax 862.07 mg/g, while As(V) demonstrated a recovery capacity of 99.06 %, Qmax 850.75 mg/g. The D-Crosslinked-MIP exhibited BETs of 69.01 m2/g with a pore volume of 0.2340 cm3/g owing to polymeric crosslinking by metal oxide NPs. The kinetics, isotherm models, and mechanisms of dually crosslinking and extraction of toxic metals were discussed.

PREPARATION AND CHARACTERIZATION OF POLYMER INCLUSION MEMBRANES BASED ON BIODEGRADABLE CELLULOSE/ALGERIAN CLAY FOR HEAVY METALS REMOVAL FROM WASTEWATER

Separation membranes have gained attention as promising options for water and wastewater treatment due to their financial sustainability, and eco-friendliness. However, practical challenges have limited their application in water separation. To overcome these limitations, inorganic-organic hybrid membranes have been developed in this study. The present work deals with two attractive aspects: (i) economical, through the valorization of a local clay (Algerian kaolin), and (ii) environmental, which is based on the membrane selectivity for metal ions. The principal objective of this work is the development of enhanced nanocomposite membranes. It is achieved with low costs, based on cellulose triacetate (CTA) as a polymeric matrix modified by the addition of a lamellar filler, i.e. yellow clay obtained from Jijel, located in the east of Algeria, and plasticized by dioctyl phthalate (DOP). A further objective of this paper was the treatment of wastewater polluted by lead (Pb2+) and cadmium (Cd2+). The prepared membranes were characterized by various characterization techniques, including scanning electron microscopy (SEM), Fourier-transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA). All synthetized membranes had an amorphous structure, with homogeneous pore morphology and distribution. Moreover, the presence of nanocomposite clay showed effective integration into the membrane matrix and led to a significant improvement in thermal resistance. These membranes were applied to treat a synthetic aqueous solution contaminated with heavy metals, namely Pb2+ and Cd2+. The results revealed a rejection rate higher than 50%, suggesting the potential effectiveness of a stable and environmentally sustainable polymer inclusion membrane system for water purification.

Evaluation of an Extraction Chromatographic Resin Based on the DOODA Extractant: Characterization, Comparison to DGA, and Potential Applications

ABSTRACT The extraction of selected metal ions by an extraction chromatographic (EXC) resin containing N,N,N’,N’-tetraoctyl-3,6-dioxaoctane diamide (DOODA) on a porous methacrylate support was measured from nitric acid and hydrochloric acid. Metal ion extraction with the DOODA resin was compared to structurally similar diglycolamide (DGA) resins containing the extractants N,N,N’,N’-tetraoctyl-diglycolamide (TODGA; DGA, Normal resin) and N,N,N’,N’-tetra(2-ethyl-1-hexyl)-diglycolamide (TEHDGA; DGA, Branched resin). The EXC resins were studied via batch uptake, column elution, extraction capacity, and column stability experiments focusing on potential applications in analytical radiochemistry and nuclear medicine isotope production and purification. The DOODA resin exhibited similar extraction trends to the DGA resins for many metal ions, however, the capacity factors (k’) were reduced, typically following the trend of DGA, normal > DGA, branched > DOODA. The selectivity of DOODA resin towards rare earth elements, trivalent actinides, and some transition metal ions, particularly Cd, Ca, and Ac, is quite different from the existing DGA resins, but follows trends previously identified in solvent extraction experiments. The capacity for extraction of Ca(II) and Eu(III) from nitric acid was higher for the DOODA resin than either DGA resin, while all resins exhibited little extractant loss to the mobile phase over >18,000 bed volumes of elution.

Zinc Oxide/Moringa Oleifera Gum-Grafted L-Methionine-Functionalized Polyaniline Bionanocomposites for Water Purification

This study evaluates the preparation of novel ternary functional adsorbents based on polyaniline, zinc oxide nanoparticles, and moringa oleifera gum to produce zinc oxide/Moringa oleifera gum-grafted L-methionine-functionalized polyaniline bionanocomposites (ZM-g-Pani) and employed to sequestrate divalent metal ions (Cd2+, Hg2+ and Pb2+) from wastewater samples. The morphological and structural properties of ZM-g-Pani were exploited using FT-IR, FE-SEM/EDS, TEM, and XRD. FT-IR and FE-SEM studies show that the as prepared nanocomposite has an abundant number of reactive groups and a porous structure, thus demonstrating outstanding divalent metal cation removal. FT-IR study confirms that the attachment of L-methionine to polyaniline is facilitated by the C-S linkage. Both TEM and FE-SEM techniques confirmed the clustered granules of ZnO over the surface of polyaniline, which ultimately provided more surface area to adsorb metal ions. The study demonstrated that Cd2+, Hg2+ and Pb2+ ions could undergo physical sorption and chemisorption simultaneously during the adsorption process. The maximum adsorption capacity was 840.33, 497.51, and 497.51 mg/g for Cd2+, Hg2+, and Pb2+, respectively. The impact of co-existing ions, including NO3−, PO43−, SO42−, Cl−, Na+, Cu2+, and Al3+, showed that there were no notable alterations in the adsorption of the selected metal ions with ZM-g-Pani. ZM-g-Pani showed eight successive regeneration cycles for Cd2+, Hg2+, and Pb2+ with more than 85% removal efficiency.

Thermodynamics-based sealing method for anodized aluminum used in semiconductor processing apparatuses

A principle was proposed for designing a method to seal anodized aluminum used in semiconductor processing apparatuses. Thermodynamic calculations and Fick's second law were used to reveal trends in the metal ion deposition, deposition product stability, vapor pressures of halides for selected metal ions, the holding temperature, and time. Interactions between ion concentrations and the sealing temperature were also revealed. According to the design principles, anodized aluminum dipped in 1 mM Cr3+ ion solution and steam-sealed for 18 h exhibited the highest corrosion resistance when exposed to 5 wt.% HCl solution and HCl gas, verifying the designed results.

Emulsion liquid membrane technique for optimal separation of Ni (II) and Sm (III) using response surface methodology and Box–Behnken experimental setup

ABSTRACT This study evaluated the reliability of the emulsified liquid membrane (ELM) extraction technique for recovering and separating metals, focusing on Nickel (Ni(II)) and Samarium (Sm(III)), both used in electrochemical devices. Key contributions include determining optimal conditions for creating a stable water-in-oil (W/O) emulsion. The optimal conditions were found to be a 5-minute emulsification time, 4 wt.% Span 80 surfactant concentration, a 1.6 volume ratio of the internal phase to the organic phase, 1 M H2SO4 concentration for the internal phase, a 40/160 volume ratio of the emulsion to the external phase, and kerosene as the diluent. Factors affecting the separation of Ni(II) and Sm(III) included the concentrations of the internal aqueous phase, surfactant, and extractant. Under these conditions, an equimolar mixture of Ni(II) and Sm(III) was extracted within 15 min. The study emphasized the importance of phase volume ratio and surfactant concentration for emulsion stability and extraction efficiency. The response surface method (RSM) and Box–Behnken design were used to optimize influential factors, with a modified quadratic model predicting extraction yields of 83.81% for Sm(III) and 15% for Ni(II). The study demonstrates that effective separation of Ni(II) and Sm(III) ions is achievable using this technique, providing valuable insights into efficient and selective metal ion extraction, contributing to the broader field of metal recovery and recycling technologies.

Molecular Origins of Near-Infrared Luminescence in Molybdenum and Tungsten Oxyhalide Perovskites.

Materials with near-infrared (near-IR) luminescence are desirable for applications in communications and sensing, as well as biomedical diagnostics and imaging. The most used inorganic near-IR emitters rely on precise doping of host crystal structures with select rare-earth or transition metal ions. Recently, another class of materials with intrinsic near-IR emission has been reported. The compositions of these materials were initially described as vacancy-ordered halide double perovskites Cs2MoCl6 and Cs2WCl6, but further investigation by some of us on the compound reported as Cs2WCl6 revealed an oxyhalide instead, with a composition Cs2WO x Cl6-x , where 1 < x < 2. Here we demonstrate that the Mo compounds similarly possess the composition Cs2MoO x Cl6-x or Cs2MoO x Br6-x where 1 < x < 2. Preparing the pure halide appears harder for Mo than for W, and we have not succeeded in doing so. The distinctly different composition requires the coordination environment and oxidation state for the Mo and W centers to be reconsidered from what was assumed for the pure halides. In this work, we examine the mechanism for near-IR emission in these materials given their true structures and compositions. We demonstrate that the luminescence is due to the specific d-orbital splitting caused by the presence of oxygen in the distorted [MOX5]2- octahedra (X is Cl or Br). The fine structure in the emission spectra at low temperatures has been resolved and is attributed to vibronic coupling to the Mo-O and W-O bond stretches. Understanding the true structure and composition of these interesting materials, besides explaining the near-IR luminescence, suggests how this desirable emission can be realized and manipulated.

Metal ions guide the production of silkworm silk fibers

Silk fibers’ unique mechanical properties have made them desirable materials, yet their formation mechanism remains poorly understood. While ions are known to support silk fiber production, their exact role has thus far eluded discovery. Here, we use cryo-electron microscopy coupled with elemental analysis to elucidate the changes in the composition and spatial localization of metal ions during silk evolution inside the silk gland. During the initial protein secretion and storage stages, ions are homogeneously dispersed in the silk gland. Once the fibers are spun, the ions delocalize from the fibroin core to the sericin-coating layer, a process accompanied by protein chain alignment and increased feedstock viscosity. This change makes the protein more shear-sensitive and initiates the liquid-to-solid transition. Selective metal ion doping modifies silk fibers’ mechanical performance. These findings enhance our understanding of the silk fiber formation mechanism, laying the foundations for developing new concepts in biomaterial design.

Adsorption of Cu(II) and Zn(II) onto ZrO2–SiO2 composite: Characteristics, mechanism and application in wastewater treatment

The presented paper describes a perspective methodology of hazardous post-production wastewater treatment focused on recovering selected metal ions species, mainly copper, zinc, and arsenic. The idea included the design of multifunctional adsorbents composed of zirconia and silica, their physicochemical evaluations, and verification tests in the adsorption process performed using model wastewaters. The proposed synthesis protocol allowed to obtain the materials with unique structural and physicochemical properties, including well-developed surface area (ABET = 398 m2∙g−1), as well as specific surface nature. It was confirmed by the results of energy dispersive X-ray, X-ray fluorescence and Fourier transform infrared spectroscopy analyses. Furthermore, by analysing the batch experiments, optimal process parameters for recovering the analyzed metal ions were established as follows: T = 313 K, pH = 5, S:L ratio = 6.67 mg:cm3, and t = 120 min. It was found that the performed removal of selected metal ion species followed pseudo-second-order kinetic and Langmuir isotherm models, and the estimated sorption capacity of the designed material was 23.5 mg∙g−1 and 12.4 mg∙g−1 for Cu(II) and Zn(II) ions, respectively. The results indicate that it is possible to separate arsenic compounds from copper and zinc ions with efficiencies of 98.9 % and 99.5 % respectively.

Developing a novel radiosensitive metal ion-loaded PVA/NBT film as medical low-dose X-ray dosimeter

The hazards associated with ionizing radiation exposure has spurred the advancement of reliable and precise dosimetry techniques. Currently, there still lacks a viable and efficient dosimetry methods for measuring radiation expo-sure within low dosage ranges. This raises a concern in certain domains, such as radiodiagnostics and practitioners that employ low-dose X-ray radiation. Hence, this study aims to produce PVA/NBT film dosimeters that are capable in effectively detecting low dosages of X-ray radiation. Moreover, PVA/NBT films loaded by various metal ions will also be studied. The films were synthesized by the solvent casting method. The films were subjected to X-ray irradiation with a dosage ranging from 0 to 2.626 mGy. The films were further examined through EDX analysis, UV–Vis spectroscopy, optical density measurement, FTIR spectroscopy, and SEM analysis. It was observed that X-ray radiation exposure caused a broadening in the UV–Vis absorbance spectrum, which enhances its light absorption capability and making it more opaque. Furthermore, the careful selection of metal ion enhanced the film's ability in detecting X-ray radiation. Silver-loaded films were proven to significantly enhance the linearity and sensitivity of the PVA/NBT dosimeter film. These findings showed that silver-loaded PVA/NBT films exhibit a promising prospect for further applications in the domain of medical radiation.

Metal–organic frameworks for nonlinear optics and lasing

AbstractNonlinear optics (NLO) is a crucial branch of photonics that greatly facilitates the transmission, processing, and storage of photonic signals. It meets the needs of the rapidly growing information demands of modern society. Materials with NLO properties and laser capabilities have a wide range of applications in fields such as optical communication, optical information storage, biomedical imaging, laser technology, and quantum information technology. Metal–organic frameworks (MOFs) have emerged as particularly exciting hybrid inorganic–organic porous materials that can be easily self‐assembled from corresponding inorganic metal ions/clusters and organic linkers. The structural diversity and flexibility of MOFs offer ample opportunities for the orderly organization of highly hyperpolarizable chromophore molecules within confined spaces. This makes it ideal for NLO signal and laser emissions. In this review, we provide a comprehensive overview of strategies to construct MOFs with NLO and laser properties, as well as recent research developments for enhancing and adjusting these properties. Through analysis of chromophore arrangement and various interactions within the framework, we aim to gain insight into the correlation between MOF structures and optical properties. This will facilitate the design and synthesis of MOFs with excellent NLO and laser capabilities through the judicious selection of metal ions and organic linkers. Finally, we outline the future challenges and potential research directions for MOFs in NLO and laser fields.

Eco-friendly Fluorescent Sensor for Sensitive and Selective Detection of Zn2+ and Fe3+ Ions: Applications in Human Hair Samples.

A new eco-friendly sensor, 3-((6-((4-chlorobenzylidene)amino)pyridin-2-yl)imino)indolin-2-one (CBAPI) was synthesized and well characterized. The CBAPI sensor was employed for detecting Zn2+ and Fe3+ ions. It exhibited a low limit of detection at pH 6.0, with values of 2.90, for Zn2+ and 3.59nmol L-1 for Fe3+ ions. The sensor demonstrated high selectivity over other interfering cations. Additionally, the high binding constants reflect the great affinity of sensor towards Zn2+ and Fe3+ ions. To further validate its quantification ability for Zn2+ ions, the synthesized CBAPI sensor was used to determine Zn levels in human hair samples, and the results were confirmed using atomic absorption spectroscopy (AAS). The AGREE metric tool was used to assess the method's environmental impact and practical applicability. These positive outcomes indicated that the new method for detecting Zn2+ and Fe3+ ions is environmentally friendly and safe for humans. The developed CBAPI sensor represents a potential development in metal ion detection, combining sensitivity, selectivity, and rapidity.

TRASUTA: The Effect of the Structural Rigidity of a Mesocyclic AAZTA-like Chelating Agent on the Thermodynamic, Kinetic, and Structural Properties of Some Divalent Metal and Ga3+ Complexes.

Mesocyclic chelating agents such as AAZTA and its derivatives have been recently reported to overcome the relatively low thermodynamic stability of metal complexes of acyclic chelating agents and the slow complexation kinetics of macrocyclic chelating agents. This work reports the preparation of a spirobicyclic hexadentate AAZTA-like chelating agent (TRASUTA) and the investigation of the thermodynamic, kinetic, and structural properties of the corresponding chelates with the PET-relevant Ga3+ and selected metal ions. A combination of analytical techniques allowed identification of a coordination isomerization process, involving the coordinating side arms and the inversion of a nitrogen atom and leading to lower thermodynamic and kinetic inertness with respect to mononuclear mesocyclic analogues. The bicyclic system of TRASUTA retains significant dynamics despite the conformational constraint imposed by the spiro-fusion, resulting in a lower stability of the corresponding metal chelates.

A novel COP adsorbent built up by thiophene group: Rapid and selective adsorption toward trace hazardous Hg(II)

Mercury is one of the most toxic heavy metals to humans. Developing highly efficient adsorbent for removing mercury is of great significance. Herein, two thiophene-based COPs were synthesized through Schiff base reaction by rationally selecting thiophene group as COP building block and functional component simultaneously, avoiding the drawbacks of functionalization strategy such as sacrificing the porous structure and blocking the active sites. The high S/N content in the COPs structure enables robust adsorption towards Hg(II), with maximum adsorption capacity up to 468.8 mg g−1. Notably, even in the presence of 12 interfering ions, the resulting COP-BTTS effectively reduced trace Hg(II) at 1000 μg L−1 to 33 μg L−1 within 30 s, achieving a removal rate up to 97 %, and below the regulatory discharge limit of 10 μg L−1 for wastewater in 15 min. Moreover, the temperature of COP-BTTS can rise to 140 °C-150 °C under xenon light due to its exceptional photothermal property, which can facilitate the efficient desorption of Hg2+. And the COP-BTTS maintains its exceptional recoverability after the successive repeated 5 cycles. This work sheds light on the feasible strategy for designing and synthesizing COP adsorbent with high adsorption capacity, selectivity, and irradiation-assisted desorption of metal ions.