Recent progress in the removal of mercury ions from water based MOFs materials

Efficient Hg(Ⅱ) removed by l-cysteine modified UiO-66 through chemical adsorption via a facile partial ligand replacement strategy

In this work, UiO-66-l-cys with enhanced adsorption capacity for Hg(Ⅱ) in water was synthesized through a facile two-step partial ligand replacement strategy. The presence of the functional groups significantly enhanced the capacity of the material for Hg(Ⅱ). According to the Langmuir model, the maximum theoretical adsorption capacity was calculated to be 1321.4 mg/g, which is 20 times that of the original UiO-66. Thermodynamic study revealed that the adsorption of Hg(II) onto UiO-66-l-cys is a spontaneous and endothermic process, thus exhibiting an elevated adsorption capacity at higher temperatures. XPS results confirmed that the sulfhydryl (SH) and amino (NH2) groups react with Hg(Ⅱ), enabling the material to adsorb a large quantity of Hg(Ⅱ). Through DFT theoretical calculation and simulation, it has been found that S atoms and N atoms exhibit significant attraction to Hg atoms. Moreover, the corrosion potential of UiO-66 in Hg solution becomes lower. It is demonstrated that it has a faster electron transfer rate, which is conducive to the adsorption process. Furthermore, UiO-66-l-cys exhibited an excellent cyclic stability, with only a 2.7 % decrease in adsorption capacity after five cycles. This method eliminates the necessity for the pre-synthesis of complex chemical ligands and intricate chemical reactions. It also streamlines the process, and lowers material costs. The UiO-66-l-cys exhibits considerable potential applications for the treatment of heavy metal pollution.

Hybrid Metal-Organic Frameworks (MOFs) for Various Catalysis Applications

Porous materials have been gaining popularity in catalysis applications, solving the current ecological challenges. Metal-organic frameworks (MOFs) are especially noteworthy for their high surface areas and customizable chemistry, giving them a wide range of potential applications in catalysis remediation. The review study delves into the various applications of MOFs in catalysis and provides a comprehensive summary. This review thoroughly explores MOF materials, specifically focusing on their diverse catalytic applications, including Lewis catalysis, oxidation, reduction, photocatalysis, and electrocatalysis. Also, this study emphasizes the significance of high-performance MOF materials, which possess adjustable properties and exceptional features, as a novel approach to tackling technological challenges across multiple sectors. MOFs make it an ideal candidate for catalytic reactions, as it enables efficient conversion rates and selectivity. Furthermore, the tunable properties of MOF make it possible to tailor its structure to suit specific catalytic requirements. This feature improves performance and reduces costs associated with traditional catalysts. In conclusion, MOF materials have revolutionized the field of catalysis and offer immense potential in solving various technological challenges across different industries.

Advances in the study of metal-organic frameworks and their biomolecule composites for osteoporosis therapeutic applications

With the population aging, osteoporosis (OP) is becoming more and more common, seriously affecting patients' quality of life and their families, and how to prevent and treat osteoporosis has become a hot topic. However, the current conventional method of treating OP is oral anti-osteoporosis medication, which has drawbacks such as first-pass elimination and gastrointestinal adverse effects. At the same time, osteoporosis can lead to microbial infections and the need to promote angiogenesis for bone healing, among other needs that often cannot be met with conventional treatments, and there is a risk of resistance to oral antibiotics for microbial infections. Metal-organic frameworks (MOFs) having a high specific surface area, high porosity, controlled degradation, and variable composition; they can not only be used as a carrier to control drug release, but can also play multiple roles in the treatment of OP and microbial infections by releasing metal ions, etc., so they have inherent advantages for OP, which is a disease that requires long-term treatment. Therefore, this paper reviews the research progress of MOFs and their biomacromolecular composites in therapeutic applications for osteoporosis, categorized by MOF type, and briefly describes the mechanism of osteoporosis, and different synthesis methods of MOFs and MOF-based composites, and finally presents the main existing problems and future perspectives, aiming to make MOFs more helpful for OP treatment.

Cysteamine-Anchored MOF through Post-Synthetic Modification Strategy for the Effective Removal of Mercury from Water

The introduction of cysteamine functionality, referred to as Q-ZIF-67-SH, was successfully achieved through postsynthetic modification while maintaining the structural and thermal stability of the quasi metal-organic framework Q-ZIF-67. By subjecting ZIF-67 to controlled partial deligandation at 310 °C under an air atmosphere, a substantial number of unsaturated cobalt sites were generated within the quasi ZIF-67 (Q-ZIF-67) structure. These unsaturated cobalt sites facilitated effective coordination with cysteamine, resulting in the development of the thiol-functionalized framework Q-ZIF-67-SH. The potential of these metal-organic frameworks (MOFs) for the adsorptive removal of hazardous Hg(II) was investigated. Various factors, such as the type of sorbent, pH, adsorbent dosage, initial concentration of Hg(II), and presence of coexisting ions, were thoroughly examined and comprehensively explained. Thiol-anchored MOF significantly enhanced the efficiency of Hg(II) removal, achieving an impressive removal rate of up to 99.2%. Furthermore, it demonstrated a maximum adsorption capacity of 994 mg g-1 and a distribution coefficient of 2.5 × 106 mL g-1. A good correspondence with pseudo-second-order kinetics and the Langmuir model was observed through the fitting of adsorption kinetics and the isotherm model. The thermodynamic data strongly indicate that the adsorptive removal of Hg(II) is characterized by endothermicity and spontaneity. This signifies that the process is energetically favorable and has potential for efficient Hg(II) removal. Therefore, the Q-ZIF-67-SH sorbent emerges as a promising and advantageous option for the removal of Hg(II) from water.

Captivating nano sensors for mercury detection: a promising approach for monitoring of toxic mercury in environmental samples

Mercury, a widespread highly toxic environmental pollutant, poses significant risks to both human health and ecosystems. It commonly infiltrates the food chain, particularly through fish, and water resources via multiple pathways, leading to adverse impacts on human health and the environment. To monitor and keep track of mercury ion levels various methods traditionally have been employed. However, conventional detection techniques are often hindered by limitations. In response to challenges, nano-sensors, capitalizing on the distinctive properties of nanomaterials, emerge as a promising solution. This comprehensive review provides insight into the extensive spectrum of nano-sensor development for mercury detection. It encompasses various types of nanomaterials such as silver, gold, silica, magnetic, quantum dot, carbon dot, and electrochemical variants, elucidating their sensing mechanisms and fabrication. The aim of this review is to offer an in-depth exploration to researchers, technologists, and the scientific community, and understanding of the evolving landscape in nano-sensor development for mercury sensing. Ultimately, this review aims to encourage innovation in the pursuit of efficient and reliable solutions for mercury detection, thereby contributing to advancements in environmental protection and public health.

Chemical, electrochemical, and quantum investigation into the use of an organophosphorus derivative to inhibit copper corrosion in acidic environments

In order to protect the copper against corrosion, a novel corrosion inhibitor known as diphenyl ((2-aminoethyl) amino) (4-methoxyphenyl) methyl) phosphonate (DAMP) was developed. Acid solutions of HCl and H2SO4 were the aggressive solutions employed in this study. Analysis using the FT-IR, 1H-NMR, 31P-NMR, 13C-NMR and BET confirmed that the DAMP was successfully synthesized. The anti-corrosion capabilities of DAMP are evaluated using a combination of chemical, electrochemical and quantum studies. The DAMP has been found to be crucial in preventing the corrosion of copper in both HCl and H2SO4 acid. This was obviously implied by the observation that the corrosion rate of copper in acid solutions decreased when DAMP was added. It is significant to note that 180 ppm produced the highest levels of inhibiting efficiency (96.6% for HCl and 95.2% for H2SO4). The tendency of DAMP to adsorb on the surface of copper through its hetero-atoms (O, N, and P) is the main factor for the anti-corrosion capabilities of DAMP. Results from SEM/EDX tests supported this. The actual adsorption takes place via various active centers, physical and chemical mechanisms that are coordinated with the estimated quantum parameters. Additionally, the adsorption of DAMP adheres to the Langmuir isotherm.

Highly efficient capture of mercury from complex water matrices by AlZn alloy reduction-amalgamation and in situ layered double hydroxide

Mercury pollution is a critical, worldwide problem and the efficient, cost-effective removal of mercury from complex, contaminated water matrices in a wide pH range from strongly acidic to alkaline has been a challenge. Here, AlZn and AlFe alloys are investigated and a new process of synergistic reduction-amalgamation and in situ layered double hydroxide (SRA-iLDH) for highly efficient capture of aqueous Hg(II) is developed using AlZn alloys. The parameters include the pH values of 1-12, the Hg(II) concentrations of 10-1000 mg L-1, and the alloy's Zn concentrations of 20%, 50% and 70% and Fe concentrations of 10%, 20% and 50%. The initial rate of Hg(II) uptake by AlZn alloys decreases with increasing Zn concentration while the overall rate is not affected. Specifically, AlZn50 alloy removes >99.5% Hg(II) from 10 mg L-1 solutions at pH 1-12 in 5 min at a rate constant of 0.055 g mg-1 min-1 and achieves a capacity of 5000 mg g-1, being the highest value reported so far. The super-performance of AlZn alloy is attributed to multiple functions of chemical reduction, dual amalgamation, in situ LDH's surface complexation and adsorption, isomorphous substitution and intercalation. This study provides a simple and highly efficient approach for removing Hg(II) from complex water matrices.

Highly selective detection and removal of mercury ions in the aquatic environment based on magnetic ZIF-71 multifunctional composites with sufficient chlorine functional groups

The development of both detection and removal technologies for heavy metal ions is of great importance. Most of the existing adsorbents that contain oxygen, nitrogen or sulfur functional groups can remove heavy metals, but achieving both selective detection and removal of a single metal ion is difficult because they bind to a wide range of heavy metal ions. Herein, we selected zeolite imidazolium hydrochloride framework-71 (ZIF-71) with sufficient chlorine functional groups to fabricate magnetic ZIF-71 multifunctional composites (M-ZIF-71). M-ZIF-71 had a large specific surface area, excellent water stability, and good magnetic properties, which made M-ZIF-71 conducive to the separation and recovery of adsorbents and the assembly of electrodes. M-ZIF-71 exhibited high selectivity, wide linear range (1-500 μg/L), and low detection limit (0.32 μg/L) for electrochemical detection of mercury ions (Hg2+). Meanwhile, M-ZIF-71 demonstrated rapid Hg2+ adsorption with a high capacity of 571.2 mg/g and excellent recyclability. The high selectivity for Hg2+ was attributed to the powerful affinity of highly electronegative chlorine and Hg2+. Moreover, XPS spectra demonstrated the interaction between chlorine and Hg2+. This work provides a new inspiration for applications in the targeted monitoring and removal of heavy metal pollution.

Determination of diethylstilbestrol in environmental water based on electrochemical senser modified with vanadium based metal organic framework material composite

In this research, the MIL-47/ACET/Nafion/GCE electrochemical senser for the determination of diethylstilbestrol (DES) was prepared with vanadyl sulfate (VOSO4·nH2O) and terephthalic acid (H2BDC) as the main raw materials, compounded with acetylene black (ACET) and perfluorosulfonic acid polymer (Nafion). The compound DES belongs to the category of estrogens, and prolonged exposure to the environment can have detrimental effects on the physiological functioning of both humans and animals. Due to the strong DES enrichment performance of MIL-47(V-MOFs) with large specific surface area, in addition to the excellent conductivity and electrocatalysis of composite materials, this modified senser had good electrochemical response to DES. With differential pulse voltammetry, in optimum condition of 0.1 M NaH2PO4-Na2HPO4at pH = 7.0, potential interval of -1.0 to 1.0 V, enrichment time of 120 s and enrichment potential of 0.2 V, there was a good linear relationship between peak current and the concentration of DES over the range of 0.1 and 50μM, and the limit of detection was 0.008μM. The sensor accurately detected DES in actual water samples, with recovery rates ranging from 89.21% to 105.3%. The electrochemical sensor was simple to prepare and had practical significance for the detection of DES in water. The research results of the sensor provide another alternative analytical means for the sensitive detection of DES in the environment, which is important for maintaining public health.

Well-defined Fe3O4@MIL-100(Fe) hollow nanoflower heterostructures for selective dection and monitoring of benzoylurea insecticides from food and water

Developing a platform for the selective detection and effective monitor of toxic contaminants is a major challenge to address organic contaminants contamination in environmental science. Here, for the first time, the thickness-controllable Fe3O4@MIL-100(Fe) heterogeneous materials with special hollow nanoflower (HFs) morphology had been synthesized. The morphology and shell thickness of the nano-petal could be tuned by changing the reaction time. The resultant Fe3O4@MIL-100(Fe) HFs exhibited the hollow nanoflower shapes and exposed abundant accessible active sites. The enrichment performance of Fe3O4@MIL-100(Fe) HFs was approximately 1.4-1.7 times that of spherical Fe3O4@MIL-100(Fe) composite for benzoylurea insecticides (BUs). Furthermore, the optimal sample achieved the wide linearity (0.05-500 ng mL-1) and low limits of detection, (0.003-0.01 ng mL-1) for BUs. The research provides a new strategy for highly sensitive detection and monitoring of harmful pollutant levels in the environment.

Biochar as Alternative Material for Heavy Metal Adsorption from Groundwaters: Lab-Scale (Column) Experiment Review

The purpose of this manuscript is to present a review of laboratory experiments (including methodology and results) that use biochar, a specific carbon obtained by a pyrolysis process from different feedstocks, as an alternative material for heavy metal adsorption from groundwater. In recent years, many studies have been conducted regarding the application of innovative materials to water decontamination to develop a more sustainable approach to remediation processes. The use of biochar for groundwater remediation has particularly attracted the interest of researchers because it permits the reuse of materials that would be otherwise disposed of, in accordance with circular economy, and reduces the generation of greenhouse gases if compared to the use of virgin materials. A review of the different approaches and results reported in the current literature could be useful because when applying remediation technologies at the field scale, a preliminary phase in which the suitability of the adsorbent is evaluated at the lab scale is often necessary. This paper is therefore organised with a short description of the involved metals and of the biochar production and composition. A comprehensive analysis of the current knowledge related to the use of biochar in groundwater remediation at the laboratory scale to obtain the characteristic parameters of the process that are necessary for the upscaling of the technology at the field scale is also presented. An overview of the results achieved using different experimental conditions, such as the chemical properties and dosage of biochar as well as heavy metal concentrations with their different values of pH, is reported. At the end, numerical studies useful for the interpretation of the experiment results are introduced.

In Situ Synthesis of NH2-MIL-53-Al/PAN Nanofibers for Removal Co(II) through an Electrospinning Process

In this study, researchers developed a novel composite material called NH2-MIL-53-Al/PAN, which consists of metal-organic frameworks (MOFs) grown on electrospun PAN nanofibers (NFs). The successful formation of the composite was confirmed by X-ray diffraction (XRD) and Fourier transform infrared (FTIR), and the hydrophilicity of NH2-MIL-53-Al/PAN was demonstrated by the water contact angle (WCA). Batch experiments were conducted to investigate the adsorption performance of Co(II) under different conditions. The maximum adsorption capacity reached 58.72 mg/g, and almost 95% of the adsorption was achieved within the first 6 h. The adsorption process was found to be spontaneous and endothermic and followed the pseudo-second-order kinetics and Langmuir models. Chemisorption and molecular layer adsorption are the main mechanisms of adsorption, and X-ray photoelectron spectroscopy (XPS) analysis further reveals that the interaction between the adsorbent and cobalt is a coordination interaction. In this study, NH2-MIL-53-Al was grown in situ on PAN to ensure effective loading of MOFs and prevent agglomeration during the NF mixing process. This approach successfully addressed the challenge of exposing active sites within the embedded MOF crystals. Additionally, it overcame the difficulty of recycling traditional MOF adsorbents. As a result, the exceptional performance of MOF NFs offers a promising solution for the efficient removal of cobalt-containing wastewater.

Isolation of Sensing Units and Adsorption Groups Based on MOF-on-MOF Hierarchical Structure for Both Highly Sensitive Detection and Removal of Hg2

Bifunctional materials have attracted ongoing interest in the field of detection and removal of contaminants because of their integration of two functions, but they exhibit commonly exceptional performance in only one of these two aspects. The interaction between the two functional units of the bifunctional materials may compromise their sensing and adsorption abilities. Guided by the concept of domain building blocks (DBBs), a hierarchical metal-organic framework (MOF)-on-MOF hybrid was designed by growing gold nanoclusters (AuNCs)-embedded zeolitic imidazolate framework 8 (AuNCs/ZIF-8) on the surface of Zr-MOF (UiO-66-NH2) for the simultaneous detection and removal of Hg2+. In the hybrid, the amino groups (-NH2) and AuNCs─which were the adsorption groups and sensing units, respectively, were isolated from each other. Specifically, the adsorption groups (-NH2) were assembled in the inner UiO-66-NH2 layer, while the sensing units (AuNCs) were confined in the outer ZIF-8 layer. This hierarchical structure not only spatially hindered the electron transfer between these two units but also triggered the aggregation-induced emission of AuNCs because of the confinement of ZIF-8 on the AuNCs, thus changing the fluorescence of AuNCs from quenching to enhancement. The newly prepared UiO-66-NH2@AuNCs/ZIF-8 hybrid, as expected, showed an ultralow detection limit (0.42 ppb) and a high adsorption capacity (129.9 mg·g-1) for Hg2+. Overall, this work provides a feasible approach to improve the integrated performance of MOF-based composites based on DBBs.

Zeolite imidazolate framework-8 in bone regeneration: A systematic review

Zeolite imidazolate framework-8 (ZIF-8) is a biomaterial that has been increasingly studied in recent years. It has several applications such as bone regeneration, promotion of angiogenesis, drug loading, and antibacterial activity, and exerts multiple effects to deal with various problems in the process of bone regeneration. This systematic review aims to provide an overview of the applications and effectiveness of ZIF-8 in bone regeneration. A search of papers published in the PubMed, Web of Science, Embase, and Cochrane Library databases revealed 532 relevant studies. Title, abstract, and full-text screening resulted in 39 papers being included in the review, including 39 in vitro and 22 animal studies. Appropriate concentrations of nano ZIF-8 can promote cell proliferation and osteogenic differentiation by releasing Zn2+ and entering the cell, whereas high doses of ZIF-8 are cytotoxic and inhibit osteogenic differentiation. In addition, five studies confirmed that ZIF-8 exhibits good vasogenic activity. In all in vivo experiments, nano ZIF-8 promoted bone formation. These results indicate that, at appropriate concentrations, materials containing ZIF-8 promote bone regeneration more than materials without ZIF-8, and with characteristics such as promoting angiogenesis, drug loading, and antibacterial activity, it is expected to show promising applications in the field of bone regeneration. STATEMENT OF SIGNIFICANCE: This manuscript reviewed the use of ZIF-8 in bone regeneration, clarified the biocompatibility and effectiveness in promoting bone regeneration of ZIF-8 materials, and discussed the possible mechanisms and factors affecting its promotion of bone regeneration. Overall, this study provides a better understanding of the latest advances in the field of bone regeneration of ZIF-8, serves as a design guide, and contributes to the design of future experimental studies.

MOF-Based Photocatalytic Membrane for Water Purification: A Review

Photocatalytic membranes can effectively integrate membrane separation and photocatalytic degradation processes to provide an eco-friendly solution for efficient water purification. It is of great significance to develop highly efficient photocatalytic membranes driven by visible light to ensure the long-term stability of membrane separation systems and the maximum utilization of solar energy. Metal-organic framework (MOF) is an emerging photocatalyst with a well-defined structure and tunable chemical properties, showing a broad application prospect in the construction of high-performance photocatalytic membranes. Herein, this work provides a comprehensive review of recent advancements in MOF-based photocatalytic membranes. Initially, this work outlines the main tailoring strategies that facilitate the enhancement of the photocatalytic activity of MOF-based photocatalysts. Next, this work introduces commonly used methods for fabricating MOF-based photocatalytic membranes. Subsequently, this work discusses the application and mechanisms of MOF-based photocatalytic membranes toward organic pollutant degradation, metal ion removal, and membrane fouling mitigation. Finally, challenges in developing MOF-based photocatalytic membranes and their practical applications are presented, while also pointing out future research directions toward overcoming these existing limitations.

Thiol and thioether-based metal-organic frameworks: synthesis, structure, and multifaceted applications

Metal-organic frameworks (MOFs) are unique hybrid porous materials formed by combining metal ions or clusters with organic ligands. Thiol and thioether-based MOFs belong to a specific category of MOFs where one or many thiols or thioether groups are present in organic linkers. Depending on the linkers, thiol-thioether MOFs can be divided into three categories: (i) MOFs where both thiol or thioether groups are part of the carboxylic acid ligands, (ii) MOFs where only thiol or thioether groups are present in the organic linker, and (iii) MOFs where both thiol or thioether groups are part of azolate-containing linkers. MOFs containing thiol-thioether-based acid ligands are synthesized through two primary approaches; one is by utilizing thiol and thioether-based carboxylic acid ligands where the bonding pattern of ligands with metal ions plays a vital role in MOF formation (HSAB principle). MOFs synthesized by this approach can be structurally differentiated into two categories: structures without common structural motifs and structures with common structural motifs (related to UiO-66, UiO-67, UiO-68, MIL-53, NU-1100, etc.). The second approach to synthesize thiol and thioether-based MOFs is indirect methods, where thiol or thioether functionality is introduced in MOFs by techniques like post-synthetic modifications (PSM), post-synthetic exchange (PSE) and by forming composite materials. Generally, MOFs containing only thiol-thioether-based ligands are synthesized by interfacial assisted synthesis, forming two-dimensional sheet frameworks, and show significantly high conductivity. A limited study has been done on MOFs containing thiol-thioether-based azolate ligands where both nitrogen- and sulfur-containing functionality are present in the MOF frameworks. These materials exhibit intriguing properties stemming from the interplay between metal centres, organic ligands, and sulfur functionality. As a result, they offer great potential for multifaceted applications, ranging from catalysis, sensing, and conductivity, to adsorption. This perspective is organised through an introduction, schematic representations, and tabular data of the reported thiol and thioether MOFs and concluded with future directions.

Green Nanocellulose/PEI-Grafted Magnetic Nanoparticles for Effective Removal of Heavy Metal Ions

In response to the pressing issue of water pollution caused by heavy metal ions, there is a growing demand for green adsorbents that can effectively remove these contaminants while being easy to separate and regenerate. A novel magnetic composite was synthesized by bonding amino-functionalized Fe3 O4 -SiO2 magnetic particles (MNP-NH2 ) to polyethyleneimine (PEI)-grafted cellulose nanofibers (CNF). The modification of CNF with PEI through a peptidic coupling reaction resulted in the uniform dispersion and strong attachment of MNP-NH2 particles (286.7 nm) onto the PEI-CNF surface. This composite exhibited exceptional adsorption capabilities for heavy metals, achieving 16.73 mg/g for Pb, 16.12 mg/g for Cu, and 12.53 mg/g for Co. These remarkable adsorption capacities are attributed to the complex interactions between the metal ions and the amino, carboxyl, and hydroxyl groups on the surface of PEI-CNF-MNP. The introduction of PEI significantly enhanced the adsorption capacities, and the adsorption sequence (Pb(II)>Cu(II)>Co(II)) can be explained by differences in ionic radius and surface complexation strength. Langmuir isotherm and pseudo-second-order kinetic models described the adsorption process, while Na2 EDTA was proved effective for desorption with high recovery rates. This magnetic composite holds promise for treating heavy metal-contaminated wastewater due to its impressive performance.

Advances in green materials derived from wood for detecting and removing mercury ions in water

The issue of mercury pollution in environmental remediation has garnered significant attention due to its severe health hazards to humans. Various strategies have been devised to mitigate the impact of toxic mercury ions, including coagulation, ion exchange, adsorption, membrane technology, and electrochemical treatment. Among these approaches, adsorption has emerged as an efficient and widely employed method for the uptake of low concentrations of mercury ions. It offers convenient operation, high removal efficiency, and facile regeneration of the adsorbent. Wood, being the most abundant renewable and sustainable bioresource, has garnered attention as a promising material for treating heavy metal wastewater. This is attributed to its unique physical and chemical characteristics, encompassing hierarchical pores, aligned channels, active functional groups, biodegradability, and cost-effectiveness. However, a comprehensive examination of the cutting-edge applications of wood and wood-derived biopolymers in the detection and removal of mercury ions from wastewater has yet to be undertaken. Consequently, this article presents a chronological overview of recent advancements in materials and structures derived from bulk wood and its constituents, including cellulose, lignin, hemicellulose, and tannin, with a specific focus on their utility in detecting and eliminating mercury from water sources. Subsequently, the most promising techniques and strategies involving wood and wood-derived biopolymers in addressing the predicament of mercury pollution are explored. Furthermore, this piece offers insights into the existing challenges and future prospects concerning environmentally friendly materials derived from wood, aiming to foster the development of cost-effective mercury adsorbents and detection devices.

One-step synthesis of thiol-functionalized metal coordination polymers: effective and superfast removal of Hg (II) in the different matrices to ppb level

The mercury in water bodies has posed a great threat to the environment and humans, and removing mercury and purifying wastewater has become a global environmental issue. Adopting Zn(II) coordination polymers (Zn-CPs) emerged as a new approach, however, the kind of Zn-CPs, which solely consisted of amino groups, exhibited unsatisfactory performance in capturing Hg(II) at a low level and causing the subsequent leaching of Zn(II) after adsorption. In this study, we fabricated the thiol-modified Zn-based coordination polymers (Zn-CPs-SH) through a one-step solvothermal reaction to efficiently capture Hg(II) from wastewater. Its preeminent adsorption performance could be maintained across a broad range of pH (2-7), ion strength (Cl-, SO42-, and NO3- at 0-10,000 mg/L), and dissolved organic matter (0-100 mg/L). The impressive properties, including fast kinetics (k2∼1.01 × 10-4 L/min), outstanding adsorption capacity (1278.72 mg/g, 298 K), superior selectivity (Kd∼2.3 × 104 mL/g), and excellent regeneration capability (Re = 93.54% after 5 cycles), were attributed to the ultra-abundance of adsorption sites donating from thiol groups, which was revealed by XPS analysis, DFT calculations, and molecular orbital theory. Noteworthy, the high practical application potential of Zn-CPs-SH was demonstrated by its outstanding Hg(II) removal efficiency (Re ≥ 99.10%) in various Hg(II)-spiked water matrices, e.g., tap water, river water, and industrial wastewater. Importantly, the residual Hg(II) in the treated water declined to the ppb level without any Zn(II) leaching. Overall, it is highly anticipated that the incorporation of Zn-CPs-SH would facilitate the practical implementation of highly efficient Hg(II) removal in wastewater treatment owing to its exhibiting high selective affinity, superior adsorption capacity, and enhanced efficiency.

A green and facile one-step hydration method based on ZIF-8-PDA to prepare melamine composite sponges with excellent hydrophobicity for oil-water separation

Frequent crude oil spills and illegal discharges of industrial organic pollutants cause serious damage to the ecological environment and considerable loss of valuable resources. Therefore, there is an urgent need to develop efficient strategies to separate and recover oils or reagents from sewage. Herein, a green, facile and rapid one-step hydration method was applied to obtain the composite sponge (ZIF-8-PDA@MS) that monodispersed zeolitic imidazolate framework-8 nanoparticles with high porosity and large specific surface area were firmly loaded onto the melamine sponge by ligand exchange and the self-assembly of dopamine. The water contact angle of ZIF-8-PDA@MS with multiscale hierarchical porous structure could reach 162°, which remained stable over a long period of time and a wide pH range. ZIF-8-PDA@MS displayed excellent adsorption capacities (up to 85.45-168.95 g⋅g^-1), and could be reused at least 40 times. Besides, ZIF-8-PDA@MS exhibited remarkable photothermal effect. Simultaneously, Silver nanoparticle-immobilized composite sponges were also prepared via in-situ reduction of silver ions to inhibit bacterial contamination. The composite sponge developed in this work can be used not only for the treatment of industrial sewage, but also for the emergency response of large-scale marine oil spill accidents, which has inestimable practical value for water decontamination.

An in-situ strategy to construct uracil-conjugated covalent organic frameworks with tunable fluorescence/recognition characteristics for sensitive and selective Mercury(II) detection

Previous researches of covalent organic frameworks (COFs) have shown their potential as fluorescent probes, but the regulation of their optical properties and recognition characteristics still remains a challenge, and most of reports required complicated post-decoration to improve the sensing performance. In this context, we propose a novel in-situ strategy to construct uracil-conjugated COFs and modulate their fluorescence properties for sensitive and selective mercury(II) detection. By using 1,3,6,8-tetrakis(4-formylphenyl)pyrene (TFPPy) and 1,3,6,8-tetrakis(4-aminophenyl)pyrene (TAPPy) as fundamental blocks and 5-aminouraci (5-AU) as the functional monomer, a series of COFs (Py-COFs and Py-U-COFs-1 to Py-U-COFs-5) with tunable fluorescence were solvothermally synthesized through an in-situ Schiff base reaction. The π-conjugated framework serves as a signal reporter, the evenly and densely distributed uracil acts as a mercury(II) receptor, and the regular pores (channels) make the rapid and sensitive detection of the mercury(II) possible. In this research, we manage to regulate the crystalline structure, the fluorescence properties, and the sensing performance of COFs by simply changing the molar ratio of precursors. We expect this research to open up a new strategy for effective and controllable construction of functionalized COFs for environmental analysis.

Mercury Clathration-Driven Phase Transition in a Luminescent Bipyrazolate Metal-Organic Framework: A Multitechnique Investigation

Mercury is one of the most toxic heavy metals. By virtue of its triple bond, the novel ligand 1,2-bis(1H-pyrazol-4-yl)ethyne (H₂BPE) was expressly designed and synthesized to devise metal-organic frameworks (MOFs) exhibiting high chemical affinity for mercury. Two MOFs, Zn(BPE) and Zn(BPE)·nDMF [interpenetrated i-Zn and noninterpenetrated ni-Zn·S, respectively; DMF = dimethylformamide], were isolated as microcrystalline powders. While i-Zn is stable in water for at least 15 days, its suspension in HgCl₂ aqueous solutions prompts its conversion into HgCl₂@ni-Zn. A multitechnique approach allowed us to shed light onto the observed HgCl₂-triggered i-Zn-to-HgCl₂@ni-Zn transformation at the molecular level. Density functional theory calculations on model systems suggested that HgCl₂ interacts via the mercury atom with the carbon-carbon triple bond exclusively in ni-Zn. Powder X-ray diffraction enabled us to quantify the extent of the i-Zn-to-HgCl₂@ni-Zn transition in 100-5000 ppm HgCl_2 (aq) solutions, while X-ray fluorescence and inductively coupled plasma-mass spectrometry allowed us to demonstrate that HgCl₂ is quantitatively sequestered from the aqueous phase. Irradiating at 365 nm, an intense fluorescence is observed at 470 nm for ni-Zn·S, which is partially quenched for i-Zn. This spectral benchmark was exploited to monitor in real time the i-Zn-to-HgCl₂@ni-Zn conversion kinetics at different HgCl_2 (aq) concentrations. A sizeable fluorescence increase was observed, within a 1 h time lapse, even at a concentration of 5 ppb. Overall, this comprehensive investigation unraveled an intriguing molecular mechanism, featuring the disaggregation of a water-stable MOF in the presence of HgCl₂ and the self-assembly of a different crystalline phase around the pollutant, which is sequestered and simultaneously quantified by means of a luminescence change. Such a case study might open the way to new-conception strategies to achieve real-time sensing of mercury-containing pollutants in wastewaters and, eventually, pursue their straightforward and cost-effective purification.

Post-synthetic thiol modification of covalent organic frameworks for mercury(II) removal from water

Various materials have been developed for environmental remediation of mercury ion pollution. Among these materials, covalent organic frameworks (COFs) can efficiently adsorb Hg(II) from water. Herein, two thiol-modified COFs (COF-S-SH and COF-OH-SH) were prepared, through the reaction between 2,5-divinylterephthalaldehyde and 1,3,5-tris-(4-aminophenyl)benzene, followed by post-synthetic modification using bis(2-mercaptoethyl) sulfide and dithiothreitol, respectively. The modified COFs showed excellent Hg(II) adsorption abilities with maximum adsorption capacities of 586.3 and 535.5 mg g^-1 for COF-S-SH and COF-OH-SH, respectively. The prepared materials showed excellent selective absorbability for Hg(II) against multiple cationic metals in water. Unexpectedly, the experimental data showed that both co-existing toxic anionic diclofenac sodium (DCF) and Hg(II) performed positive effect for capturing another pollutant by these two modified COFs. Thus, a synergistic adsorption mechanism between Hg(II) and DCF on COFs was proposed. Moreover, density functional theory calculations revealed that synergistic adsorption occurred between Hg(II) and DCF, which resulted in a significant reduction in the adsorption system's energy. This work highlights a new direction for application of COFs to simultaneous removal of heavy metals and co-existing organic pollutants from water.

Preparation of cellulose-based porous adsorption materials derived from corn straw for wastewater purification

Various methods have been used to cope with heavy metal ion contamination in wastewater, which caused serious hazards to ecological and human health. Adsorption is one of the most frequent, economical and effective methods for removing these contaminants. Herein, a porous and amino-rich cellulose-based composite adsorbent (PEI-PCS) with anisotropic property was successfully prepared by covalently cross-linking polyethyleneimine on delignified corn straw. Combined with the porosity of straw substrate and the chelating ability of amino group to metal ions, the as-prepared PEI-PCS exhibited universality (various metal ions), rapid adsorption behavior (within 180 min achieve adsorption equilibrium), high adsorption capacity (85.47 mg g^-1 for Cu(II)), and good durability (70 % of adsorption efficiency after 5 cycles). In addition, the adsorption process was conformed to pseudo-second-order dynamics and the Langmuir isotherm models. Lastly, the adsorption mechanism was also elucidated. This study provides a sustainable pathway for the manufacture of efficient biomass-based adsorbents and confirms that functionalized corn straw is a promising material for the treatment of heavy metal ions.

Recent advances in adsorption of environmental pollutants using metal-organic frameworks-based hydrogels

Water pollution is increasing significantly owing to industrialization and population growth that lead to serious environmental and health issues. Therefore, the design and development of more effective wastewater treatment approaches are necessary due to a significant upsurge in demand for freshwater. More recently, metal-organic frameworks (MOFs) have attracted attention in environmental science owing to their tunable porosity, unique structure, flexibility, and various composition. Despite these attractive advantages, some drawbacks, including intrinsic fragility, unsatisfied processability, dust formation, and poor reusability, have greatly limited their applications. Therefore, MOFs are often designed as supported-based MOFs (e.g., MOFs-coated composites) or 3D structured composites, such as MOFs-based hydrogels. MOFs-based hydrogels are excellent candidates in the sorption process because of their appropriate adsorption capacity, porous structure, good mechanical properties, durability as well as biodegradable features. In this review, the removal of different pollutants (e.g., synthetic dyes, phosphates, heavy metals, antibiotics, and some organic compounds) from aqueous media has been studied by the adsorption process using MOFs-based hydrogels. The important advancements in the fabrication of MOFs-based hydrogels and their capacities in the adsorption of pollutants under experimental conditions have been discussed. Finally, problems and future perspectives on the adsorption process using MOFs-based hydrogels have been investigated.

Porous Materials for Water Purification

Water pollution is a growing threat to humanity due to the pervasiveness of contaminants in water bodies. Significant efforts have been made to separate these hazardous components to purify polluted water through various methods. However, conventional remediation methods suffer from limitations such as low uptake capacity or selectivity, and current water quality standards cannot be met. Recently, advanced porous materials (APMs) have shown promise in improved segregation of contaminants compared to traditional porous materials in uptake capacity and selectivity. These materials feature merits of high surface area and versatile functionality, rendering them ideal platforms for the design of novel adsorbents. This Review summarizes the development and employment of APMs in a variety of water treatments accompanied by assessments of task-specific adsorption performance. Finally, we discuss our perspectives on future opportunities for APMs in water purification.

Thiol-decorated defective metal-organic framework for effective removal of mercury(II) ion

Removal of mercury (Hg) ion from water is important while still faces challenges in capacity and adsorption speed. Herein, using thiol-containing mercaptoacetic acid (MA) as the template, we constructed a novel metal-organic framework (MOF) adsorbent, Zr-MSA-MA (MSA, mercaptosuccinic acid). Unlike other monodentate acids such as acetic acid and formic acid, MA benefits to maintain high-content binding sites, in the meantime of defect formation. On the basis, Zr-MSA-MA exhibits a high adsorption capacity of 714.8 mg g^-1 for Hg²⁺ and fast adsorption kinetics, superior to other MOF-based adsorbents. Co-existing metal ions and pH have only slight interference for the adsorption behavior. Besides, the adsorption is proved to an endothermic reaction and the adsorbent can be regenerated based on a simple elution. Further analysis indicates the strong chemical bonding of Hg²⁺ and -SH is the main adsorption mechanism. Thus, our work demonstrates the Zr-MSA-MA can serve as a potential adsorbent for Hg²⁺, and provides a novel strategy to construct defective adsorbent via using active group-containing template.

Highly Fluorescent Magnetic ATT-AuNCs@ZIF-8 for All-in-One Detection and Removal of Hg2+: An Ultrasensitive Probe to Evaluate Its Removal Efficiency

The development of multifunctional materials for the synchronous detection and removal of mercury ions (Hg²⁺) is in high demand. Although a few multifunctional materials as a fluorescent indicator and adsorbent have achieved this aim, the feedback of their removal efficiency still depends on other methods. Herein, magnetic Fe₃O₄ nanoparticles (MNPs) and 6-aza-2-thiothymine-protected gold nanoclusters (ATT-AuNCs) were rationally assembled into a zeolitic imidazolate framework 8 (ZIF-8) structure via a one-pot method. The coordination assembly of ATT-AuNCs and ZIF-8 not only strengthened the aurophilic interactions of adjacent ATT-AuNCs but also induced the restriction of intramolecular motion of ATT with a six-membered heterocyclic structure. As a consequence, the fluorescence (FL) quantum yield of MNPs/ATT-AuNCs@ZIF-8 was 12.5-fold higher than that of pristine ATT-AuNCs. Benefiting from the enhanced FL emission, MNPs/ATT-AuNCs@ZIF-8 showed improved sensitivity for Hg²⁺ detection and therefore could evaluate the removal efficiency via FL detection, without relying on another detection method. Additionally, the nanocomposite also displayed a satisfactory removal capability for Hg²⁺, including a short capture time (20 min), a high removal efficiency (>96.9%), and excellent reusability (10 cycles). This work provides an approach for customizing functional nanocomposites to concurrently detect and remove Hg²⁺ with superior performance, especially for high detection sensitivity.

Selective mercury adsorption and enrichment enabled by phenylic carboxyl functionalized poly(pyrrole methane)s chelating polymers

Mercury decontamination from water requires highly effective and efficient methods for maintaining public health and environmental protection. Herein, based on the coordination theory between functional groups and metal ions, we proposed phenylic carboxyl group-based poly(pyrrole methane)s (PPDCBAs) as highly efficient mercury removal materials for environmental remediation applications. It was found that PPDCBAs can efficiently adsorb and remove mercury(II) from aqueous solutions by functionalizing the molecular structure with phenylic carboxyl groups. Among the as-prepared PPDCBAs, poly[pyrrole-2, 5-diyl (4-carboxybenzylidane)] (PPD4CBA) with the carboxyl group at the para position can not only adsorb mercury over 1400 mg⋅g^-1 but also achieve a 92.5 % mercury(II) uptake within 100 min by a very low dosage of 0.1 g⋅L^-1. In addition, PPDCBAs exhibited excellent adsorption selectivity for mercury(II) compared with copper(II), cadmium(II), zinc(II) and lead(II). Furthermore, as determined by Fourier transform infrared (FT-IR) spectra, X-ray photoelectron spectroscopy (XPS) and the density functional theory (DFT) calculation, the mercury removal was found to be mainly dependent on the high density of chelating sites, the phenylic carboxyl moieties, which helped us to realize an ultra-trace amount mercury removal (from 10.8 μg⋅L^-1 to 0.6-0.8 μg⋅L^-1) for meeting drinking water standard requirements (1.0 μg⋅L^-1).

Covalently Functionalized Cellulose Nanoparticles for Simultaneous Enrichment of Pb(II), Cd(II) and Cu(II) Ions

Cellulose nanoparticles are sustainable natural polymers with excellent application in environmental remediation technology. In this work, we synthesized cellulose nanoparticles and covalently functionalized them with a multi-functional group possessing ligands. The hybrid material shows excellent adsorption properties for the simultaneous extraction of multiple metal ions in the sample preparation technique. The sorbent shows excellent sorption capacity in the range of 1.8-2.2 mmol/g of material. The developed method was successfully employed for the simultaneous extraction of Pb(II), Cd(II) and Cu(II) from real-world samples (industrial effluent, river water, tap and groundwater) and subsequently determined by inductively coupled plasma optical emission spectroscopy (ICP-OES). The method shows a preconcentration limit of 0.7 ppb attributes to analyze the trace concentration of studied metal ions. The detection limit obtained for Pb(II), Cd(II) and Cu(II) is found to be 0.4 ppb.

MOF-Based Sorbents Used for the Removal of Hg2+ from Aqueous Solutions via a Sorption-Assisted Microfiltration

Mercury is considered to be one of the most important chemicals of public health concern. Therefore, it is necessary to develop an effective method of removing mercury ions from aqueous solutions to protect people from exposure to this element. This paper presents research on the application of a sorption-assisted microfiltration (SAMF) hybrid process for the removal of Hg²⁺ from aqueous solutions. As adsorbents used in the process, the metal-organic-framework-UiO-66-type materials have been considered. The methods of synthesis of two types of metal-organic-framework (MOF) sorbents were developed: UiO-66_MAA modified with mercaptoacetic acid (MAA) and a composite of UiO-66 with cellulose. The results of the experiments performed proved that the separation of Hg²⁺ from water solutions conducted in such a system was effective; however, a relatively long initial contact time of reagents before filtration was required. The experimental results can be used to optimize the parameters of the SAMF process in order to obtain an effective method of Hg²⁺ removal from aqueous solutions.

Exceptional removal and immobilization of selenium species by bimetal-organic frameworks

Binary metallic organic frameworks can always play excellent functions for pollutants removal. One binary MOFs, UiO-66(Fe/Zr)), was newly synthesized and applied to remove aquatic selenite (SeIV) and selenate (SeVI). The adsorption behaviors and mechanisms were investigated using batch experiments, spectroscopic analyses, and theoretical calculations (DFT). The characterization results showed that the material inherited the topological structure of UiO-66 and excellent thermal stability. The large specific surface area (467.52 m²/g) and uniform mesoporous structures of the synthesized MOFs resulted in fast adsorption efficiency and high adsorption capacity for selenium species. The adsorbent kept high adsorption efficiency in a wide pH range from 2 to 11 with good anti-interference ability. The maximum adsorption capacity for Se(IV) and Se(VI) reached as high as 196 mg/g at pH 3 and 258 mg/g at pH 5, respectively. The process was conformed to fit pseudo-second-order kinetics and Langmuir isotherm, and could be explained by the formation of Fe/Zr-O-Se bond on the material surface, which was interpreted by the results of XPS, FTIR and DFT calculation. The regeneration and TCLP experiments demonstrated that UiO-66(Fe/Zr) could be regenerated for five cycles without obvious decrease of efficiencies, and the leaching rate of the adsorbed Se(IV) and Se(VI) in the spent adsorbent were only 4.8% and 2.3%. More than 99% of original Se(IV) and Se(VI) in the lake and tap water samples (1.0 mg/L of Se) could be removed in 2.0 h.

Mercury removal efficiency of disulfide- and thiol-functionalized lanthanide coordination polymers

To compare efficiency of disulfide and thiol groups in removing mercury from aqueous medium without noteworthy influence from structural differences, a series of new [Ln^III(dtba)_1.5(H₂O)₂] (Ln^III = Eu^III (I), Gd^III (II) and Tb^III (III), H₂dtba = 4,4'-dithiobenzoic acid) were synthesized and characterized. The single crystal structure of I was elucidated and is described. Reaction of II with hydrazine gave II^SH containing disulfide and thiol groups. Experimental data confirmed the preserved framework structure and the co-existing of disulfide and thiol groups in II^SH. Robustness of II and II^SH over a wide range of pH (2-10) was confirmed and their mercury removal performances at different pH were evaluated in terms of removal efficiencies (%R), equilibrium uptake capacities (q_e) and distribution constant (K_d). The dependence of these parameters on pH is reported. The best values of %R, q_e and K_d could be achieved at pH 10 at which surfaces of the adsorbents were negatively charged; 86%R, 429 mg g^-1, and 6.04 × 10³ mL g^-1 (II), and 98%R, 490 mg g^-1 and 5.08 × 10⁴ mL g^-1 (II^SH). At pH 7, influences of the initial concentration of mercury on performances of the adsorbents as well as the adsorption isotherms and kinetics were examined from which the better performance of II^SH has been concluded. The characterization of the adsorptions by the Langmuir model and the pseudo-second-order kinetic as well as their excellent consistency with the experimental data are included. At neutral pH, selectivity to the adsorption of mercury and tolerance to common anions were illustrated. The better affinity between mercury and thiol group and therefore its contribution to the better performance of II^SH was then ascertained by a computational study.

Mechanistic study of Hg(II) interaction with three different α-aminophosphonate adsorbents: Insights from batch experiments and theoretical calculations

Herein, efficient and potential chelating α-aminophosphonate based sorbents (AP-) derived from three different amine origins (aniline/anthranilic acid/O-phenylenediamine) to form AP-H, carboxylated and aminated enhanced aminophosphonate as AP-H, AP-COOH, and AP-NH₂ were synthesized via a facile method. The structure of the synthesized sorbents was elucidated using different techniques; elemental analysis (CHNP/O), FT-IR, NMR (¹H-, ¹³C and ³¹P NMR), TGA and BET. The fabricated sorbents were exploited for Hg(II) removal from aqueous solution via sorption properties. Isotherm fitted by Langmuir equation: the maximum sorption capacities at optimum pH 5.5, and T:25 ± 1 °C, were found to be 1.33, 1.23, and 1.15 mmol Hg g^-1 for AP-COOH, AP-NH₂, AP-H, respectively, which is roughly correlated with the active sites density and the hard/soft characteristics of adsorbents' reactive groups. Metal-ligand binding affinities are qualitatively rationalized in terms of hard and soft acids and bases (HSAB) theory. The interaction of Hg(II) (soft) has a stronger affinity to AP-COOH can be considered a softer base compared with reference material (AP-H) over than AP-NH₂ (hard). This sequence result showed opposite trends consistent with their reciprocal properties according to the steric effect modulates and the specific surface area. Thermodynamics analysis for absolute values of ΔH°, ΔS° and ΔG° afford the selectivity towards Hg(II) sorption with the following order: AP-COOH > AP-NH₂ >AP-H. Elution and regeneration was carried out by HCl solution and recycled for a minimum of five cycles, the sorption and desorption efficiencies are greater than 91%. Such sorbents exhibit good durability, stability and promising potential for Hg(II) removal. Finally, a new modelling technique for quantitative non-linear description and comparison of equivalent geographical positions in 3D space of extended relationships. Exothermic and spontaneous behavior were observed using a proposed Floatotherm that included the Van't Hoff parameters model.

Resource utilization of pig hair to prepare low-cost adsorbents with high density of sulfhydryl for enhanced and trace level removal of aqueous Hg(II)

Pig hair (PH), a keratinous waste, was modified by ammonium thioglycolate in a ball milling to promote its performance of Hg(II) sequestration. The ball milling broke the hydrophobic cuticle sheath and enhanced the reduction of disulfide bond, which increased the sulfydryl content of the modified PH (BTPH) from 0.07 to 11.05 μmol/g. BTPH exhibited a significantly higher capture capacity of Hg(II) (415.4 mg/g) than PH (3.1 mg/g), as well as the commercial activated carbon (219.7 mg/g), and persisted its performance over a wide range of solution pH. Meanwhile, BTPH with a distribution coefficient of 5.703 × 10⁵ mL/g could selectively capture Hg(II) from the water with the coexisting metal ions such as Mg(II), Cd(II) and Pb(II). Moreover, the low-cost BTPH could reduce the Hg(II) from 1.0 mg/L to well below the limit of drinkable water (2 μg/L) in real-world samples. Density functional theory (DFT) calculations and state-of-the-art characterizations illustrated that the binding of Hg(II) to sulfydryl groups was the main adsorption mechanism. Notably, BTPH decreased the mercury content of water spinaches from 24.1 to 0.50 mg/kg and thereby significantly reduced the phytotoxicity of Hg(II). This work therefore provides a sustainable way to utilize keratinous wastes for the remediation of aqueous Hg(II).

Bis-Pyridine-Based Organogel with AIE Effect and Sensing Performance towards Hg2

A novel gelator (1) based on a bis-pyridine derivative was designed and synthesized, which could form stable gels in methanol, ethanol, acetonitrile, ethyl acetate, DMF/H₂O (4/1, v/v) and DMSO/H₂O (4/1, v/v). The self-assembly process of gelator 1 was studied by field emission scanning electron microscopy (FESEM), UV–vis absorption spectroscopy, fluorescence emission spectroscopy, Fourier transform infrared spectroscopy (FT-IR), X-ray powder diffraction and a water contact angle experiment. Gelator 1 exhibited obvious AIE behavior. On the base of its AIE, the gel of 1 could detect Hg²⁺, which resulted in fluorescence quenching and a gel–sol transition. ¹H NMR titration experiments with Hg²⁺ revealed that the metal coordination interaction induced the fluorescence quenching and the breakdown of the noncovalent interaction in the gel system. This research provides a new molecular mode for designing a functional self-assembly gel system.

Mercury-instructed assembly (MiA): architecting clathrin triskelion-inspired highly functional C3-symmetric triskelion nanotorus functional structures into microtorus structures

To detect heavy metal toxicity using self-assembled nanostructures, a clathrin triskelion-inspired highly functional C₃-symmetric trimerized biotinylated di-tryptophan peptide was used. This triskelion peptide is known to self-assemble into nanotorus-like structures and can therefore act as a nanocage for various analytes. In this work, in addition to spectroscopy, force and electron microscopy were successfully used to detect the effect of toxic metal ions such as zinc, cadmium, and mercury by exploiting the change in the nanotorus morphology. Different concentrations of mercury led to the expansion of nanotorus structures into microtori. Therefore, we provide a unique application of heavy metal toxicity by utilizing "material nanoarchitectonics" to architect nanotorus structures into higher-order microtorus structures, as instructed by mercury. Such a strategy can make heavy metal sensing easier for materials scientists and open new avenues for biomedical/environmental science applications.

Recent Advances in the Application and Mechanism of Carbon Dots/Metal-Organic Frameworks Hybrids in Photocatalysis and the Detection of Environmental Pollutants

Metal-organic frameworks (MOFs) are a class of crystalline porous materials with simple synthesis conditions, large specific surface area, structural diversity, and a wide range of interesting properties. The integration of MOFs with other materials can provide new multifunctional composites that exhibit both component properties and new characteristics. In recent years, the integration of carbon dots (CDs) into MOFs to form composites has shown improved optical properties and fascinating new characteristics. This review focuses on the design and synthesis strategies of CDs@MOFs composites (including pore-confined synthesis, in situ encapsulation, post-synthesis modification and impregnation method) and their recent research progress in photocatalysis and detection of environmental pollutants. Both the achievements and problems are evaluated and proposed, and the opportunities and challenges of CDs@MOF composite are discussed.