A water-stable Cd-MOF and corresponding MOF@melamine foam composite for detection and removal of antibiotics, explosives, and anions

Design and preparation of a multi-responsive Cd-based fluorescent coordination polymer for smart sensing of nitrobenzene and ornidazole

The improper utilization of nitrobenzene (NB) and ornidazole (ORN) has resulted in irreversible effects on the environment. By combining experimental investigation, density functional theory (DFT) calculations, and machine learning, an effective green strategy for detecting NB and ORN in aqueous solutions can be developed. In this study, a one-dimensional Cd-based coordination polymer (Cd-HCIA-3) was designed and synthesized using 5-((4-carboxybenzyl)oxy)isophthalic acid and rigid 2,2'-bipyridine under solvothermal reaction conditions. Cd-HCIA-3 exhibits excellent fluorescence properties and stability in aqueous solutions. DFT calculations were performed to predict the fluorescence sensing performance of Cd-HCIA-3, revealing that photoinduced electron transfer is the key mechanism for inducing fluorescence quenching in the presence of NB and ORN, with weak molecular interactions promoting electron transfer. Fluorescence sensing experiments were conducted to verify the DFT results, showing that Cd-HCIA-3 can selectively detect NB and ORN in aqueous solutions with limits of detection of 7.22 × 10-8 and 1.31 × 10-7 mol/L, respectively. This study's findings provide valuable insights into the design and synthesis of fluorescent coordination polymers for target analytes.

Rationally design a novel Zn-MOF for fluorescent detection of nitrofuran antibiotics: The synthesis, structure and sensing applications

Nitrofuran antibiotics (NFAs) residues in waterare a persistent concern for the public due to the potential threats they pose to human health and the environment. Therefore, efficient probes that are capable of detecting trace amounts of antibiotics in real water environments have become a top priority. Herein, a novel fluorescent Zn-MOF probe (MOF-1) was revealed for the highly selective and sensitive sensing of NFAs. MOF-1 was rationally constructed with Zn(NO3)2·6H2O, 5,5'-(anthracene-9,10-diyl) diisophthalic acid (H4ADIP) and 1,3-bis(imidazol-1-ylmethyl)-benzene (mbib) by using the solvothermal method. Fluorescence sensing experiments demonstrate that MOF-1 can function as a fluorescent sensor for selective, sensitive, and rapid detection of NFAs among 15 antibiotics including ciprofloxacin (CPFX), chloramphenicol (CAP), sulfonamides and NFAs. Fluorescence titration experiments indicated that MOF-1 exhibited remarkably low detection limits of 0.19 μM, 0.26 μM, and 0.34 μM for furazolidone (FZD), furaltadone (FDH) and nitrofurazone (NFZ), respectively. Meanwhile, MOF-1 was successfully employed for NFAs detection in real samples with the recoveries of 98.7 % - 104.1 %, and a relative standard deviation below 5.1 %. Moreover, the sensing mechanism could be ascribed to the synergistic effect between the internal filtering effect and photoinduced electron transfer according to the experiment results and DFT calculations. Additionally, test strips were prepared based on MOF-1 for point of care testing of NFAs.

Detection methods for antibiotics in wastewater: a review

Antibiotics are widely used as fungicides because of their antibacterial and bactericidal effects. However, it is necessary to control their dosage. If the amount of antbiotics is too much, it cannot be completely metabolized and absorbed, will pollute the environment, and have a great impact on human health. Many antibiotics usually left in factory or aquaculture wastewater pollute the environment, so it is vital to detect the content of antibiotics in wastewater. This article summarizes several common methods of antibiotic detection and pretreatment steps. The detection methods of antibiotics in wastewater mainly include immunoassay, instrumental analysis method, and sensor. Studies have shown that immunoassay can detect deficient concentrations of antibiotics, but it is affected by external factors leading to errors. The detection speed of the instrumental analysis method is fast, but the repeatability is poor, the price is high, and the operation is complicated. The sensor is a method that is currently increasingly studied, including electrochemical sensors, optical sensors, biosensors, photoelectrochemical sensors, and surface plasmon resonance sensors. It has the advantages of fast detection speed, high accuracy, and strong sensitivity. However, the reproducibility and stability of the sensor are poor. At present, there is no method that can comprehensively integrate the advantages. This paper aims to review the enrichment and detection methods of antibiotics in wastewater from 2020 to the present. It also aims to provide some ideas for future research directions in this field.

A Benzothiadiazole-Based Zn(II) Metal-Organic Framework with Visual Turn-On Sensing for Anthrax Biomarker and Theoretical Calculation

2,6-pyridine dicarboxylic acid (DPA) is an exceptional biomarker of notorious anthrax spores. Therefore, the rapid, sensitive, and selective quantitative detection of DPA is extremely significant and urgent. This paper reports a Zn(II) metal-organic framework with the formula of {[Zn6(NDA)6(DPBT)3] 2H2O·3DMF}n (MOF-1), which consists of 2,6-naphthalenedicarboxylic acid (2,6-NDA), 4,7-di(4-pyridyl)-2,1,3-benzothiadiazole (DPBT), and Zn(II) ions. Structural analysis indicated that MOF-1 is a three-dimensional (3D) network which crystallized in the monoclinic system with the C2/c space group, revealing high pH, solvent, and thermal stability. Luminescence sensing studies demonstrated that MOF-1 had the potential to be a highly selective, sensitive, and recyclable fluorescence sensor for the identification of DPA. Furthermore, fluorescent test paper was made to detect DPA promptly with color changes. The enhancement mechanism was established by the hydrogen-bonding interaction and photoinduced electron transfer transition between MOF-1 and DPA molecules.

Applications of hollow nanostructures in water treatment considering organic, inorganic, and bacterial pollutants

One of the major issues of modern society is water contamination with different organic, inorganic, and contaminants bacteria. Finding cost-effective and efficient materials and methods for water treatment and environment remediation is among the scientists' most important considerations. Hollow-structured nanomaterials, including hollow fiber membranes, hollow spheres, hollow nanoboxes, etc., have shown an exciting capability for wastewater refinement approaches, including membrane technology, adsorption, and photocatalytic procedure due to their extremely high specific surface area, high porosity, unique morphology, and low density. Diverse hollow nanostructures could potentially eliminate organic contaminants, including dyes, antibiotics, oil/water emulsions, pesticides, and other phenolic compounds, inorganic pollutants, such as heavy metal ions, salts, phosphate, bromate, and other ions, and bacteria contaminations. Here, a comprehensive overview of hollow nanostructures' fabrication and modification, water contaminant classification, and recent studies in the water treatment field using hollow-structured nanomaterials with a comparative attitude have been provided, indicating the privilege abd detriments of this class of nanomaterials. Eventually, the future outlook of employing hollow nanomaterials in water refinery systems and the upcoming challenges arising in scaling up are also propounded.

Fluorescence-quenching mechanisms of novel isomorphic Zn/Cd coordination polymers for selective nitrobenzene detection

Nitroaromatic compounds in aqueous undermine environmental sustainability and affect human health. The development of a fluorescent sensor capable of efficiently and selectively detecting trace amounts of nitroaromatic compounds presents a considerable challenge. This study introduced Zn/Cd isomeric coordination polymers (Zn-H2CIA-1/Cd-H2CIA-2), which are synthesized using 5-((4-carboxybenzyl)oxy)isophthalic acid (5-H3CIA) and 1,10-phenanthroline (Phen). The polymers have zero-dimensional discrete crystal structure with a six-coordinated scissor-like shape. The two coordination polymers can be used as fluorescent sensors for detecting nitrobenzene (NB) and demonstrated favorable sensitivity, with detection limits of 1.95 × 10-8 and 4.66 × 10-7 mol/L, respectively. Zn-H2CIA-1 exhibited stronger fluorescence and a more sensitive response to NB compared with Cd-H2CIA-2. To elucidate their fluorescence-quenching mechanisms, we analyzed Zn-H2CIA-1 by performing DFT and TD-DFT calculations. The pore structure, density of states, excitation energy, hole-electron distribution, and orbital composition were analyzed. The suitable size of pores in Zn-H2CIA-1 is the main reason for its high NB selectivity. Moreover, intermolecular π-π stacking interactions result in an orbital overlap between Zn-H2CIA-1 and NB, enabling the transfer of electrons from Zn-H2CIA-1 to NB. This electron transfer is identified as the fundamental cause of fluorescence quenching in Zn-H2CIA-1.

Functionalization strategies of metal-organic frameworks for biomedical applications and treatment of emerging pollutants: A review

One of the representative coordination polymers, metal-organic frameworks (MOFs) material, is of hotspot interest in the multi field thanks to their unique structural characteristics and properties. As a novel hierarchical structural class, MOFs show diverse topologies, intrinsic behaviors, flexibility, etc. However, bare MOFs have less desirable biofunction, high humid sensitivity and instability in water, restraining their efficiencies in biomedical and environmental applications. Thus, a structural modification is required to address such drawbacks. Herein, we pinpoint new strategies in the synthesis and functionalization of MOFs to meet demanding requirements in in vitro tests, i.e., antibacterial face masks against corona virus infection and in wound healing and nanocarriers for drug delivery in anticancer. Regarding the treatment of wastewater containing emerging pollutants such as POPs, PFAS, and PPCPs, functionalized MOFs showed excellent performance with high efficiency and selectivity. Challenges in toxicity, vast database of clinical trials for biomedical tests and production cost can be still presented. MOFs-based composites can be, however, a bright candidate for reasonable replacement of traditional nanomaterials in biomedical and wastewater treatment applications.

A Europium Metal-Organic Framework and Its Polymer Composite Membrane as Switch-Off Fluorescence Sensors for Antibiotic Detection in Lake Water

The detection of antibiotic residues is of great significance in monitoring their overuse in healthcare, livestock and poultry farming, and agricultural production. Herein, EuCl3 and 4,4'-dicarboxyl-diphenoxyethene (H2DPOE) ionothermally reacted in 1-methyl-3-butylimidazolium chloride to give a europium metal-organic framework (Eu-DPOE). Eu-DPOE shows different fluorescence quenching rates for sensing eight antibiotics under different excitation wavelengths. Eu-DPOE displays a fast response, high selectivity, and sensitivity in antibiotic detection by fluorescence quenching. Eu-DPOE can sensitively detect TCs (tetracyclines), NOR (norfloxacin), NFT (furazolidone), ODZ (ornidazole), SDZ (sulfadiazine), and CHL (chloramphenicol) with limits of detection below 0.5 μmol/L. It provides a convenient and rapid tool for sensing antibiotics in aqueous solution. The detection mechanism is a competition absorption between DPOE2- and antibiotics with the supports from powder X-ray diffraction (PXRD), UV-vis spectra, and fluorescence lifetime. With a composite membrane of poly(vinylidene fluoride) (PVDF) matrix loading Eu-DPOE (Eu-DPOE@PVDF), Eu-DPOE@PVDF exhibits a visual fluorescence response to NOR under a 254 nm UV lamp and NFT and CTC under 365 nm. Eu-DPOE@PVDF is applied in the quantitative detection of CTC, NOR, and NFT in lake water with recovery rates ranging from 88.37 to 113.8%. Totally, fluorescence-quenched Eu-DPOE@PVDF exhibits a fast response, high selectivity, and sensitivity in sensing CTC, NOR, and NFT.

Metal-organic frameworks (MOFs) based luminescent and electrochemical sensors for food contaminant detection

With the increasing population, food toxicity has become a prevalent concern due to the growing contaminants of food products. Therefore, the need for new materials for toxicant detection and food quality monitoring will always be in demand. Metal-organic frameworks (MOFs) based on luminescence and electrochemical sensors with tunable porosity and active surface area are promising materials for food contaminants monitoring. This review summarizes and studies the most recent progress on MOF sensors for detecting food contaminants such as pesticides, antibiotics, toxins, biomolecules, and ionic species. First, with the introduction of MOFs, food contaminants and materials for toxicants detection are discussed. Then the insights into the MOFs as emerging materials for sensing applications with luminescent and electrochemical properties, signal changes, and sensing mechanisms are discussed. Next, recent advances in luminescent and electrochemical MOFs food sensors and their sensitivity, selectivity, and capacities for common food toxicants are summarized. Further, the challenges and outlooks are discussed for providing a new pathway for MOF food contaminant detection tools. Overall, a timely source of information on advanced MOF materials provides materials for next-generation food sensors.

A novel single-particle multiple-signal sensor array combined with multidimensional data mining for the detection of tricarboxylic acid cycle metabolites and discrimination of cells

Tricarboxylic acid (TCA) metabolites in cancer cells show a marked difference from those in normal cells. Herein, we report a single-particle multiple-signal lanthanide/europium-based metal-organic framework (Tb/Eu MOF) sensor array for the detection of TCA metabolites and discrimination of cancer cells. In the presence of TCA metabolite, 6 characteristic peaks of Tb/Eu MOF showed dramatic changes due to host-guest interactions, allowing sensor array-based qualitative and quantitative detection to be performed. In the qualitative detection ability test, 18 TCA metabolites at 4 concentrations (50 μM, 100 μM, 200 μM, 300 μM) were accurately discriminated by the sensor array via linear discriminant analysis (LDA). Significantly, these 4 concentrations include the clinical detection criteria for most TCA metabolites. In the quantitative detection ability test, a good linear relationship between Euclidean distances and the concentrations of L-valine (Val) could be obtained in the range of 50 to 500 μM (R² = 0.9755). On this basis, the provided method was successfully applied for the classification of 2 normal cells and 5 cancer cells via principal components analysis (PCA), LDA and a radial basis function neural network (RBFN). What's more, by verifying the weight coefficient of each point, detection and discrimination results are proved as a trustworthy balanced evaluation of multiple factors. Depending on precise data processing, the experimental operation was simplified on the premise of ensuring accuracy, so our method is a meaningful exploration for array design.

Water stable MOFs as emerging class of porous materials for potential environmental applications

Metal-organic frameworks (MOFs) are extensively recognized for their wide applications in a variety of fields such as water purification, adsorption, sensing, catalysis and drug delivery. The fundamental characteristics of the majority of MOFs, such as their structure and shape, are known to be sensitively impacted by water or moisture. As a result, a thorough evaluation of the stability of MOFs in respect to factors linked to these property changes is required. It is quite rare for MOFs in their early stages to have strong water-stability, which is necessary for the commercialization and development of wider applications of this interesting material. Also, numerous applications in presence of water have progressed considerably as a "proof of concept" stage in the past and a growing number of water-stable MOFs (WSMOFs) have been discovered in recent years. This review discusses the variables and processes that affect the aqueous stability of several MOFs, including imidazolate and carboxylate frameworks. Accordingly, this article will assist researchers in accurately evaluating how water affects the stability of MOFs so that effective techniques can be identified for the advancement of water-stable metal-organic frameworks (WSMOFs) and for their effective applications toward a variety of fields.

Metal-organic framework-based materials for the abatement of air pollution and decontamination of wastewater

Developing new and efficient technologies for environmental remediation is becoming significant due to the increase in global concerns such as climate change, severe epidemics, and energy crises. Air pollution, primarily due to increased levels of H₂S, SO_x, NH₃, NO_x, CO, volatile organic compounds (VOC), and particulate matter (PM) in the atmosphere, has a significant impact on public health, and exhaust gases harm the natural sulfur, nitrogen, and carbon cycles. Similarly, wastewater discharged to the environment with metal ions, herbicides, pharmaceuticals, personal care products, dyes, and aromatics/organic compounds is a risk for health since it may lead to an outbreak of waterborne pathogens and increase the exposure to endocrine-disrupting agents. Therefore, developing new and efficient air and water quality management systems is critical. Metal-organic frameworks (MOFs) are novel materials for which the main application areas include gas storage and separation, water harvesting from the atmosphere, chemical sensing, power storage, drug delivery, and food preservation. Due to their versatile structural motifs that can be modified during synthesis, MOFs also have a great promise for green applications including air and water pollution remediation. The motivation to use MOFs for environmental applications prompted the modification of their structures via the addition of metal and functional groups, as well as the creation of heterostructures by mixing MOFs with other nanomaterials, to effectively remove hazardous contaminants from wastewater and the atmosphere. In this review, we focus on the state-of-the-art environmental applications of MOFs, particularly for water treatment and air pollution, by highlighting the groundbreaking studies in which MOFs have been used as adsorbents, membranes, and photocatalysts for the abatement of air and water pollution. We finally address the opportunities and challenges for the environmental applications of MOFs.

Preparation of Three-Dimensional MF/Ti3C2Tx/PmPD by Interfacial Polymerization for Efficient Hexavalent Chromium Removal

Heavy metal pollution is a serious threat to human health and the ecological environment, but adsorption technology based on nano adsorbents can effectively treat the crisis. However, due to the nanoscale effect, nano adsorbents have some crucial shortcomings, such as recycling difficulty and the loss of nanoparticles, which seriously limit their application. The feasible assembly of nano adsorbents is an accessible technology in urgent need of a breakthrough. In this study, three-dimensional (3D) adsorbent (MF/Ti₃C₂T_x/PmPD) with excellent performance and favorable recyclability was prepared by interfacial polymerization with melamine foam (MF) as the framework, two-dimensional (2D) titanium carbide (Ti₃C₂T_x) as the bridge and Poly (m-Phenylenediamine) (PmPD) as the active nano component. The morphology, structure, mechanical property of MF/Ti₃C₂T_x/PmPD and reference MF/PmPD were investigated through a scanning electron microscope (SEM), Fourier transformed infrared spectra (FT-IR), Raman scattering spectra and a pressure-stress test, respectively. Owning to the regulation of Ti₃C₂T_x on the morphology and structure of PmPD, MF/Ti₃C₂T_x/PmPD showed excellent adsorption capacity (352.15 mg/g) and favorable cycling performance. R-P and pseudo-second-order kinetics models could well describe the adsorption phenomenon, indicating that the adsorption process involved a composite process of single-layer and multi-layer adsorption and was dominated by chemical adsorption. In this research, the preparation mechanism of MF/Ti₃C₂T_x/PmPD and the adsorption process of Cr(VI) were systematically investigated, which provided a feasible approach for the feasible assembly and application of nano adsorbents in the environmental field.

Cu(II) and Zn(II) frameworks constructed by directional tuning of diverse substituted groups on a triazine skeleton and supermassive adsorption behavior for iodine and dyes

The controllable design, synthesis and functional properties of a series of triazine tetratopic carboxylic MOFs have always been hotspots and challenges for research. Based on the characterization of the C-Cl bond on the triazine skeleton being easily substituted by some functional groups, we designed and synthesized a series of triazine tetratopic carboxylic Cu(II) and Zn(II) MOFs via the reaction of Cu(NO₃)₂·2.5H₂O and ZnSO₄·7H₂O, as well as triazine tetratopic carboxylic H₄TDBA-Cl (H₄TBDA-Cl = 5,5'-((6-chloro-1,3,5-triazine-2,4-diyl)bis(azanediyl))diisophthalic acid) under hydrothermal conditions. During the process of synthesizing, the C-Cl bond on the triazine skeleton of the ligand was substituted with different groups, which formed the complexes ([Cu₂(TBDA-Cl)(H₂O)·10DMF·30H₂O]_n) (DMF = N,N-dimethylformamide) (1), N(Me)₂ -[(CH₃)₂NH₂]₄·[Zn₃(HTBDA-N)₂(SO₄)₂]_n (2) and H ([Cu₂(TBDA-H)(H₂O)]_n) (3), respectively. It is worth noting that the in situ substitution reaction occurred for complexes 2 and 3 during the process of synthesis. Also, the structural analysis showed that the molecules in complexes 1-3 were connected with different building blocks to form different three-dimensional structures. We performed iodine adsorption experiments on the three complexes and found that there was a significant relationship between the structural configuration and adsorption behaviour. The results showed that the complex 1 with the Cl atom on the triazine skeleton could have a boosting effect on adsorption with iodine. It displayed a remarkable adsorption effect for iodine (in the solution of water: 7.6 g g^-1 and in the solution of cyclohexane: 548.2 mg g^-1). In addition, it also displayed the adsorption effect for JGB dye (204.9 mg g^-1). For complex 2, it displayed an uptake effect for iodine in the solution of cyclohexane (529 mg g^-1). The possible adsorption mechanism was also investigated. By comparison, we found that chlorine atoms could play an important role in the adsorption processes. The adsorption capacity of complex 1 (containing the chlorine atom in the structure) was much higher than that for complex 3.

Metal–organic frameworks (MOFs) as fluorescence sensors: principles, development and prospects

This review classifies the latest developments of MOF-based fluorescence sensors according to the analytes, and discusses the challenges faced by MOF-based fluorescence sensors and promotes some directions for future research.

A Eu(iii) metal–organic framework based on anthracenyl and alkynyl conjugation as a fluorescence probe for the selective monitoring of Fe3+ and TNP

In this work, a luminescent metal–organic framework (Eu-MOF {[Eu₆L₆(μ₃-OH)₈(H₂O)₃]₈·H₂O}_n) was constructed by a solvothermal method with a linear organic ligand L (10-[(2-amino-4-carboxyl-phenyl)ethynyl]anthracene-9-carboxylic acid) based on anthracene and alkyne groups and using Eu³⁺ as the metal center. The MOF exhibits a stable UiO-66 crystal structure, and a six-core cluster twelve-linked secondary structural unit was successfully synthesized using 2-fluorobenzoic acid as a modulator, forming a classical fcu topology. Moreover, it exhibits good chemical stability. Interestingly, Eu-MOF exhibited high selectivity and sensitive fluorescence burst properties towards Fe³⁺ ions and 2,4,6-trinitrophenol (TNP) in DMF solution. For Fe³⁺, the K_SV value is 5.06 × 10⁵ M⁻¹ and the LOD value is 5.1 × 10⁻⁷ M. For TNP, the K_SV value is 1.92 × 10⁴ M⁻¹ and the LOD value is 1.93 × 10⁻⁶ M. In addition, Eu-MOF showed good anti-interference ability and fast response. This work provides an excellent fluorescent sensor for the detection of Fe³⁺ and 2,4,6-trinitrophenol (TNP) residues in contaminants.

In this work, Eu-MOF has been synthesized and has excellent luminescence recognition ability for Fe³⁺ and TNP with good selectivity and high sensitivity via luminescence quenching.