A highly luminescent entangled metal-organic framework based on pyridine-substituted tetraphenylethene for efficient pesticide detection

A Zn-MOF-based mixed matrix membrane as an ultrastable luminescent sensor for selective and visual detection of antibiotics and pesticides in food samples

The detection of antibiotics and pesticides are of great significance since their residues threaten the health of human beings by accumulation. However, most traditional solid chemical sensors are suffer from the limitations of low sensitivity and economic practicability because of the aggregating nature and unstable of solid sensors. Herein, a new luminescent sensor 1@PMMA (1, [(ZnL)·H2O]n (H2L = 5-(4-(pyridin-4-yl)benzamido)benzene-1,3-dioic acid); PMMA = poly(methyl methacrylate)) was successfully prepared. Notably, the polymer matrix provided the chemical protection for MOF particles. The as fabricated 1@PMMA was stable in milk, honey and egg as well as exhibited strong blue emission under ultraviolet light irradiation, which can act as luminescent probe for detecting antibiotics and pesticides. More interestingly, 1@PMMA exhibited visual, real-time and recyclable detection of antibiotics ornidazole (ODZ) and pesticides 2,6-dichloro-4-nitrobenzenamine (DCN) in real food samples. This work shows that the luminescent MOF-based mixed matrix membranes could be applied as good candidates for sensing analytes in practical application.

Fluorescent bacterial cellulose@Zr-MOF via in-situ synthesis for efficient enrichment and sensitive detection of Cr(VI)

In this study, for the first time, a new Zr-metal-organic framework (MOF) with strong aggregation-induced emission was successfully grown on bacterial cellulose (BC) using an in situ synthesis method, yielding the fluorescent composite nanofiber BC@Zr-MOF. The BC with abundant hydroxyl groups, which can be uniformly wrapped in the interior of the MOF layer to form BC@Zr-MOF, was used as the growth template. The resulting composite nanofibers had a higher specific surface area (1, 116 m2/g), stronger fluorescence emission and better pH stability than MOF particles. In addition, BC@Zr-MOF exhibited selective recognition and enrichment of Cr2O72- in the aqueous phase and a high adsorption capacity of 90 mg/g. Moreover, because of the high aspect ratio and good tensile strength (6.73 N/mm2), BC@Zr-MOF nanofibers could be readily made into freestanding nanopapers via vacuum filtration, thus solving the molding and recycling problems of MOFs. The facilely prepared test paper could rapidly, sensitively and selectively detect Cr2O72- with the limit of detection (LOD) of 41.8 nM, which is nearly 500 times lower than that of the national drinking water standard. Moreover, the LOD of BC@Zr-MOF nanopapers, when used in combination with circulating filtration, decreases to 6.9 nM owing to the adsorption-enrichment effect.

Coordination-Induced Emissive Poly-NHC-Derived Metallacage for Pesticide Detection

Developing sensitive, rapid, and convenient methods for the detection of residual toxic pesticides is immensely important to prevent irreversible damage to the human body. Luminescent metal-organic cages and macrocycles have shown great applications, and designing highly emissive supramolecular systems in dilute solution using metal-ligand coordination-driven self-assembly is demanded. In this study, we have demonstrated the development of a silver-carbene bond directed tetranuclear silver(I)-octacarbene metallacage [Ag4(L)2](PF6)4 (1) based on an aggregation-induced emissive (AIE) cored 1,1',1″,1‴-((1,4-phenylenebis(ethene-2,1,1-triyl))tetrakis(benzene-4,1-diyl))tetrakis(3-methyl-1H-imidazol-3-ium) salt (L). A 36-fold enhanced emission was observed after metallacage (1) formation when compared with the ligand (L) in dilute solution due to the restriction of intramolecular motions imparted by metal-ligand coordination. Such an increase in fluorescence made 1 a potential candidate for the detection of a broad-spectrum pesticide, 2,6-dichloro-nitroaniline (DCN). 1 was able to detect DCN efficiently by the fluorescence quenching method with a significant detection limit (1.64 ppm). A combination of static and dynamic quenching was applicable depending on the analyte concentration. The use of silver-carbene bond directed self-assembly to exploit coordination-induced emission as an alternative to AIE in dilute solution and then apply this approach to solve health and safety concerns is noteworthy and carries a lot of potential for future developments.

A Recent Advancement in Food Quality Assessment: Using MOF-Based Sensors: Challenges and Future Aspects

Monitoring food safety is crucial and significantly impacts the ecosystem and human health. To adequately address food safety problems, a collaborative effort needed from government, industry, and consumers. Modern sensing technologies with outstanding performance are needed to meet the growing demands for quick and accurate food safety monitoring. Recently, emerging sensors for regulating food safety have been extensively explored. Along with the development in sensing technology, the metal-organic frameworks (MOF)-based sensors gained more attention due to their excellent sensing, catalytic, and adsorption properties. This review summarizes the current advancements and applications of MOFs-based sensors, including colorimetric, electrochemical, luminescent, surface-enhanced Raman scattering, and electrochemiluminescent sensors. and also focused on the applications of MOF-based sensors for the monitoring of toxins such as heavy metals, pesticide residues, mycotoxins, pathogens, and illegal food additives from food samples. Future trends, as well as current developments in MOF-based materials.

Fabrication of Two Luminescent Imidazolyl Cadmium-Organic Frameworks and Their Sensing Mechanism for 2,6-Dichloro-4-nitroaniline

2,6-Dichloro-4-nitroaniline, alias dicloran (DCN), is a broad-spectrum pesticide that can cause irreversible damage to the human body. Therefore, it is of great significance to develop a technology for the rapid and convenient detection of DCN. Luminescent metal organic frameworks have attracted extensive attention in the field of sensing and detection due to their excellent optical properties. In this study, two kinds of 2D Cd-MOFs (CdMOF-1 and CdMOF-2) were developed for the detection of residual DCN in the environment. Both CdMOFs exhibit excellent solvent and acid-base stability and can respond to DCN quickly and sensitively in a short time (30 s). CdMOFs not only have good selectivity and anti-interference toward DCN but also have good reusability. Under the conditions of DCN concentrations of 1-15 and 0.3-30 μM, the change in fluorescence intensity of CdMOF-1 and CdMOF-2 showed a good linear relationship with DCN concentration (R² = 0.999/0.991), and the detection limits were 0.36 and 0.12 μM, respectively. Through ultraviolet-visible absorption spectroscopy (UV-Vis), X-ray photoelectron spectroscopy, fluorescence lifetime, and density functional theory calculations, it is revealed that the fluorescence quenching mechanisms of DCN for two kinds of Cd-MOFs are competitive absorption and photoinduced electron transfer, and there may be a weak π-π interaction. Finally, it is demonstrated that by using two types of fluorescent CdMOFs to make the fluorescent test paper and detect actual soil, these can be applied to the actual scene and achieve onsite real-time detection.

Metal-organic frameworks for food contaminant adsorption and detection

Metal-organic framework materials (MOFs) have been widely used in food contamination adsorption and detection due to their large specific surface area, specific pore structure and flexible post-modification. MOFs with specific pore size can be targeted for selective adsorption of some contaminants and can be used as pretreatment and pre-concentration steps to purify samples and enrich target analytes for food contamination detection to improve the detection efficiency. In addition, MOFs, as a new functional material, play an important role in developing new rapid detection methods that are simple, portable, inexpensive and with high sensitivity and accuracy. The aim of this paper is to summarize the latest and insightful research results on MOFs for the adsorption and detection of food contaminants. By summarizing Zn-based, Cu-based and Zr-based MOFs with low cost, easily available raw materials and convenient synthesis conditions, we describe their principles and discuss their applications in chemical and biological contaminant adsorption and sensing detection in terms of stability, adsorption capacity and sensitivity. Finally, we present the limitations and challenges of MOFs in food detection, hoping to provide some ideas for future development.

Ultrathin 2D Eu3+@Zn-MOF Nanosheets: A Functional Nanoplatform for Highly Selective, Sensitive, and Visualized Detection of Organochlorine Pesticides in a Water Environment

Facile and rapid detection of residual organic pesticides on the fruits and vegetables has recently drawn increased attention in the food safety field. Herein, a surfactant-assisted solvothermal route with subsequent post-modification was designed for the preparation of Eu³⁺-functionated Zn-BDC ultrathin nanosheets (labeled as Eu³⁺@Zn-MOF-NS, BDC: 1,4-benzenedicarboxylate) with the thickness of 5 nm. The as-obtained Eu³⁺@Zn-MOF-NS could be homogeneously dispersed in aqueous systems to form a highly-stable collosol. Under the UV excitation of 325 nm, the as-obtained Eu³⁺@Zn-MOF-NS displayed red photoluminescence emission of Eu³⁺ ions, which could be notably quenched by an organochlorine pesticide, 2,6-dichloro-4-nitroaniline (DCNA), without interferences from ions, organic small molecules, and other pesticides. The detection limit and K_sv were 0.17 μM (35 ppb) and 3.2 × 10⁵ M^-1 in the water system, respectively. Moreover, the present 2D Eu³⁺@Zn-MOF sensor was also employed for the detection of DCNA in Chaohu Lake water and tap water and in apple, cabbage, and pakchoi samples with the relative standard deviation (RSD) ranging from 4.74 to 9.77%. Further investigations revealed that the competitive absorption between DCNA and the as-obtained Eu³⁺@Zn-MOF-NS resulted in the fluorescence quenching of the probe.

Formaldehyde recognition through aminal formation in a luminescent metal-organic framework

Two isostructural pillar-layer MOFs (JNU-105 and JNU-105-(NH2)2) have been successfully synthesized. JNU-105-(NH2)2 exhibits a red-shifted luminescence "turn on" for formaldehyde without the interference from other VOCs and a detection limit of 1.87 ppb. In situ single-crystal transformation studies confirm the aminal formation on the pillar linker, which was attributed to the exclusive luminescence response toward formaldehyde.

Construction of an ECL Detection Platform for Sensitive Detection of Carbaryl Based on an Eu3+-Functionalized Metal–Organic Framework Encapsulated with Nanogold

In this work, an Eu3+-MOF-253@Au electrochemiluminescence sensor was successfully constructed for the first time by encapsulating nanogold in the metal–organic frameworks (MOFs) backbone and pore channels, and assembling Eu3+ on the MOF backbone. Firstly, the introduction of nanogold overcomes the weakness of MOFs, which was difficult to achieve, and enhances its catalytic performance, followed by the modification of Eu3+ to confer the electrochemiluminescence performance and the function of target detection on the sensor. Moreover, carbaryl was placed in an alkaline working solution to enhance the intensity of electrochemiluminescence signal, as well as to promote the hydrolysis of carbaryl into 1-naphthol, which caused the burst of Eu3+-MOF-253@Au electrochemiluminescence sensor, thereby achieving the sensitive detection of carbaryl. On this basis, the electrochemiluminescence detection conditions were optimized, the performance was analyzed, and finally it was successfully used for the detection of carbaryl with good linearity in the range of 0.2–200 μg L−1 and a low detection limit (0.14 μg L−1).

Smart MOF-on-MOF Hydrogel as a Simple Rod-shaped Core for Visual Detection and Effective Removal of Pesticides

The immoderate use of pesticides in the modern agricultural industry has led to the pollution of water resources and ultimately threatens the human body. Herein, two metal-organic frameworks (MOFs), namely {[Zn(tpt)₂ ·2H₂ O]}_n (Zn1) and {[Zn₂ (tpt)₂ (bdc)]}_n (Zn2), (Htpt = 5-[4(1H-1,2,4-triazol-1-yl)]phenyl-2H-tetrazole), respectively, are constructed as smart materials for visual and on-site detection of pesticides and their removal from water. The exposed nitrogen-rich sites and high chemical stability make Zn2 a self-assembly core to further fabricate MOF-on-MOF-sodium alginate (ZIF-8-on-Zn2@SA) composite by wrapping ZIF-8 on the outside surface. Inheriting the excellent fluorescent emission of Zn2, the rod-like ZIF-8-on-Zn2@SA module exhibits naked-eye detection of thiophanate-methyl (TM) in real fruits and vegetables with a broad linear range (10-100 × 10^-6  m), a low limit of detection (LOD = 0.14 × 10^-6  m), and satisfactory recoveries (98.30-102.70%). In addition, carbendazim (CBZ), the metabolite of TM after usage in crops, can be efficiently removed from water by the ZIF-8-on-Zn2@SA (q_max  = 161.8 mg g^-1 ) with a high correlation coefficient (R²  > 0.99). Therefore, the portable ZIF-8-on-Zn2@SA sensing platform presents a promising candidate for monitoring and removal of pesticides, especially suitable for regions with serious pesticide environmental pollution.

Metal-Organic Frameworks in Agriculture

Agrochemicals, which are crucial to meet the world food qualitative and quantitative demand, are compounds used to kill pests (insects, fungi, rodents, or unwanted plants). Regrettably, there are some important issues associated with their widespread and extensive use (e.g., contamination, bioaccumulation, and development of pest resistance); thus, a reduced and more controlled use of agrochemicals and thorough detection in food, water, soil, and fields are necessary. In this regard, the development of new functional materials for the efficient application, detection, and removal of agrochemicals is a priority. Metal-organic frameworks (MOFs) with exceptional sorptive, recognition capabilities, and catalytical properties have very recently shown their potential in agriculture. This Review emphasizes the recent advances in the use of MOFs in agriculture through three main views: environmental remediation, controlled agrochemical release, and detection of agrochemicals.

Micro-/Mesoporous Fluorescent Polymers and Devices for Visual Pesticide Detection with Portability, High Sensitivity, and Ultrafast Response

The residue of pesticides in crops, soil, and water continues to be a widespread concern due to the threat to human health and food safety. With the aim to develop highly sensitive sensing materials and portable detection devices, two dicarbazole-based fluorescent micro-/mesoporous polymers (JYs) with a larger specific surface area and pore sizes ranging from 1.1 to 34.2 nm are synthesized. The Stern-Volmer constants of JY fluorescence quenching for imidacloprid (50,063 M^-1) exceed 23-51 times those of the reported porous organic polymers (980-2173 M^-1). Of particular interest is the observation that JYs show rapid fluorescence response (2 s) and ultralow detection limit (30 ppb) for imidacloprid in water medium. The pronounced chemsensing property is attributed to the synergistic role of the hierarchical pore structure, large π-conjugation of chromophore groups, and strong inner filter effect between the polymer and imidacloprid molecule. Moreover, the pesticide detection of JYs exhibits good interference resistance in complicated service environments such as the extract liquids of the apple peel and field soil as well as aqueous solutions of various cations and anions. Because of the portability, excellent reusability, and sensitive fluorescence response, the prepared JYs and detection devices have promising applications in the on-site monitoring and early warning of the pesticide residues.

Visual Hg(II) sensing in aqueous solution via a new 2,5-Bis(4-pyridyl)thiazolo[5,4-d]thiazole-based fluorescence coordination polymer

A new fluorescence coordination polymer [Zn(Py₂TTz)(5-OH-IPA)]_n (1) (Py₂TTz = 2,5-bis(4-pyridyl)thiazolo[5,4-d]thiazole, 5-OH-IPA = 5-hydroxyisophthalic acid dianion) was synthesized, which exhibited the characteristics of fluorescence quenching and bathochromic shift toward Hg(II) in aqueous solution at pH 7.00. Mechanism study showed that the interactions between Hg(II) ions and Py₂TTz ligands in 1 were responsible for the fluorescence emission change. Thanks to the specific interactions between 1 and Hg(II), excellent selectivity was achieved both in aqueous solution and in solid test paper. The detection limit of 1 for Hg(II) sensing was 125.76 nmol L^-1 and a linear rang was 1.00-10.00 μmol L^-1. More importantly, satisfactory recovery and accuracy of 1 for Hg(II) sensing were also obtained in buffer-free real water samples.

Non-biological fluorescent chemosensors for pesticides detection

The ongoing poisoning of agricultural products has pushed the security problem to become an important issue. Among them, exceeding the standard rate of pesticide residues is the main factor influencing the quality and security of agricultural products. Moreover, the abuse of pesticides has introduced a large amount of residues in soil and drinking water, which will enter the food chain to the human body, leading to neurological disorders and cancer. Therefore, great efforts have been devoted to developing fluorescent sensors for detecting pesticide in a facile, quickly, sensitive, selective, accurate manner, which exhibit greater advantages than some traditional methods. In this review, we mainly focus on summarizing the non-biological fluorescent probes for organic pesticides detection with the detection limit of micromole to nanomole, including organic functional small molecules, calixarenes and pillararenes, metal organic framework systems, and nanomaterials. Meanwhile, we described the different sensing mechanisms for pesticides detection of these mentioned fluorescent sensors, the detection limit of each pesticide, the application in detecting actual samples, as well as their respective advantages and development prospects associated with present non-biological fluorescent sensors.

Luminescent binuclear Zinc(II) organic framework as bifunctional water-stable chemosensor for efficient detection of antibiotics and Cr(VI) anions in water

To achieve the ultrastable LMOFs with predominant luminescent sensing performances, the aromatic π-electron mixed ligands strategy was introduced, and the ternary LMOF of {[Zn₂(HDDB)(bib)_1.5]·3H₂O}_n (1), was fabricated based on 3,5-di(2',4'-dicarboxylphenyl)benozoic acid (H₅DDB) and the N-donor of meta-bis(imidazol-1-yl)benzene (bib) under mixed solvothermal condition. LMOF 1 features the first reported 3D 3,4,4-c {6².8³.10}{6².8}₂{6³.8².10}₂ framework with 21.2 % porosity as well as high thermal and chemical stability. Further luminescent sensing showed that LMOF 1 as a bifunctional chemosensor possessing predominant detectability for sensitive detect the hexavalent chromates and nitroimidazoles/nitrofurans antibiotics in water through strong luminescent quenching effects, with excellent reusability as well as trace detection limits. Moreover, luminescent quenching mechanisms were further investigated from electron transfer and energy transfer viewpoints.

A water-stable Zn4O-based MOF decorated with carbazolyl chromophores for multi-responsive fluorescence sensing of Fe3+, Cr2O72− and nitro-compounds

A MOF with strong deep blue light emission and high quantum efficiency has high selectivity and sensitivity for detecting 2,6-dichloro-4-nitroaniline.

Rapid and reliable triple-emissive detection of 2,6-dichloro-4-nitroaniline as a pesticide based on a high-nuclear Cd(ii)–Sm(iii) nanocluster

A 56-metal Cd(ii)–Sm(iii) nanocluster (molecular sizes: 4.5 × 2.7 × 2.7 nm) was constructed for the rapid and reliable triple-emissive detection of 2,6-dichloro-4-nitroaniline (DCN) as a pesticide.

Naphthalene-tagged highly stable and reusable luminescent metal-organic probes for selective and fast detection of 4-nitroaniline in water

In this paper we report the synthesis, characterization, properties and application of four new Zn(II) and Cd(II) based luminescent metal-organic probes, {[Zn(mbhna)(bpea)]}n (1), {[Cd(mbhna)(bpea)]}n (2), {[Zn(mbhna)(bpba)].CH3OH.H2O}n (3) and {[Cd(mbhna)(bpba)]}n (4),...

Temperature- and solvent-induced reversible single-crystal-to-single-crystal transformations of TbIII-based MOFs with excellent stabilities and fluorescence sensing properties toward drug molecules

Recently, single-crystal-to-single-crystal conversion has been a hot topic in the field of metal-organic framework (MOF) materials, which could improve the stability and properties due to the structural change. A new...

The modulation effect of an electron-rich guest on the luminescence of naphthalene diimide-based metal–organic frameworks

A series of host–guest MOF materials were successfully fabricated by virtue of donor–acceptor interactions, which exhibit color-tunable emissions in a wide wavelength range by rational selection of guest molecules.

Zn(ii) and Co(ii) coordination polymers based on semi-rigid bis-pyridyl-bis-amide and angular dicarboxylate ligands: synthesis, structures and properties

Hydro(solvo)thermal reactions of N,N′-di(3-methylpyridyl)oxalamide (L1) and N,N′-di(4-methylpyridyl)oxalamide (L2) with angular dicarboxylic acids and metal salts afforded six new coordination polymers showing interesting properties.

Dramatic Emission Enhancement of Aggregation-Induced Emission Luminogens by Dynamic Metal Coordination Bonds and Anti-Heavy-Atom Effect

Restriction of intramolecular motions of AIEgens is greatly intensified by introducing dynamic metal coordination bonds to achieve dramatic fluorescence enhancement, which provides a simple and effective way to dramatically improve...

Pyrene-Based Fluorescent Porous Organic Polymers for Recognition and Detection of Pesticides

Eating vegetables with pesticide residues over a long period of time causes serious adverse effects on the human body, such as acute poisoning, chronic poisoning, and endocrine system interference. To achieve the goal of a healthy society, it is an urgent issue to find a simple and effective method to detect organic pesticides. In this work, two fluorescent porous organic polymers, LNU-45 and LNU-47 (abbreviation for Liaoning University), were prepared using π-conjugated dibromopyrene monomer and boronic acid compounds as building units through a Suzuki coupling reaction. Due to the large π-electron delocalization effect, the resulting polymers revealed enhanced fluorescence performance. Significantly, in sharp contrast with the planar π-conjugated polymer framework (LNU-47), the distorted conjugated structure (LNU-45) shows a higher specific surface area and provides a broad interface for analyte interaction, which is helpful to achieve rapid response and detection sensitivity. LNU-45 exhibits strong fluorescence emission at 469 nm after excitation at 365 nm in THF solution, providing strong evidence for its suitability as a luminescent chemosensor for organic pesticides. The fluorescence quenching coefficients of LNU-45 for trifluralin and dicloran were 5710 and 12,000 (LNU-47 sample by ca. 1.98 and 3.38 times), respectively. Therefore, LNU-45 serves as an effective "real-time" sensor for the detection of trifluralin and dicloran with high sensitivity and selectivity.

ESIPT Active Assemblies for 'On-On' Detection, Cell Imaging and Hampering Cellular Activity of 2, 6-dichloro-4-nitroaniline

NIR-emissive ESIPT active PBI-keto/enol assemblies have been developed for the detection of 2, 6-dichloro-4-nitroaniline (DCN). These assemblies show 'on-on' optical response towards DCN due to combined ESIPT-AIEE phenomenon with a detection limit of 1.65 nM. The potential of PBI-keto/enol assemblies to detect DCN has also been explored in grapes juice/grape residue, and soil for six consecutive days. Further, the biological applications of PBI-keto/enol assemblies to detect DCN in blood serum and to image DCN in live cells and to restrict the DCN induced cell death has been demonstrated in MG-63 cell lines.

Fabrication of a 2D metal-organic framework (MOF) nanosheet colloidal system and investigation of its fluorescence response to pesticide molecules

Pesticides, as a type of toxic chemicals widely used for a long time, not only pollute the environment but also affect people's health and cause serious harm to the human body, soil and environment. Therefore, it is very necessary to exploit a portable and environmentally friendly method to detect pesticides with high sensitivity. Herein, a new luminescent metal-organic framework ([Zn(TPYBDC)·H₂O]_n, TPYBDC^2- = 4'-(pyridin-4-yl)-[2,2':6',2''-terpyridine]-4,4''-dicarboxylate) with 2D coordination layers has been designed and assembled using 4'-(pyridin-4-yl)-[2,2':6',2''-terpyridine]-4,4''-dicarboxylic acid as the ligand. The as-synthesized Zn-LMOF was exfoliated to ultrathin 2D nanosheets (4-5 nm) to form a luminescence colloidal sensor by destroying the weak interaction between the coordination layers such as H-bonding between the matrix H₂O and the coordination carboxyl oxygen, and the π-π interactions among the interlayer conjugated aromatic rings. Investigation of its recognition and detection ability towards chemical pesticides shows that it can sensitively detect pesticides such as imidacloprid, nitenpyram and dinotefuran via fluorescence quenching effect with very low detection limit (LOD). Using imidacloprid as a typical case, a LOD value of 0.562 μM and recoveries for the simulated agricultural environmental samples in the range of 94-115% suggests that the as-fabricated 2D Zn-MOF nanosheet colloidal sensor (Zn-LMOF probe) is a most promising candidate for sensing chemical pesticides.

Tetraphenylethene Functionalized Polyhedral Oligomeric Silsesquioxane Fluorescent Probe for Rapid and Selective Trifluralin Sensing in Vegetables and Fruits

A novel fluorescent probe was designed and synthesized from tetraphenylethene (TPE) and polyhedral oligomeric silsesquioxanes (POSS) via Heck-palladium catalyzed cross-coupling reaction. The as-synthesized TPE functionalized probe performed good solvent stability and selectively preconcentration capability towards target analyte due to its stable structure and the adsorption property. The morphology as well as the physical and chemical properties of the POSS@TPE were carefully characterized. The POSS@TPE was employed to develop an effective fluorescent probe for trifluralin, with a response range of 0.1-80 mg/kg and a detection limit of 0.102 mg/kg. The mixed mechanisms of inner-filter effect (IFE) and photoinduced electron transfer (PET) explain the selectivity of POSS@TPE. Rapid detection for trifluralin in tomato and celery has been achieved with recoveries between 99.4-120.7% (RSD≤3.4%), and the results were verified compared with GC-MS method.

Efficient artificial light-harvesting systems based on aggregation-induced emission in supramolecular gels

Based on a new designed acyl hydrazone gelator (G2), we developed a supramolecular organogel in glycol with two different hydrophobic fluorescent dyes, namely rhodamine B (RhB) and acridine red, as acceptors. Both the G2@gel-RhB and G2@gel-acridine red systems showed high levels of energy-transfer efficiency and high fluorescence quantum yields.

Organic-Molecule-Based Fluorescent Chemosensor for Nerve Agents and Organophosphorus Pesticides

Organophosphorus (OP) compounds are typically a broad class of compounds that possess various uses such as insecticides, pesticides, etc. One of the most evil utilizations of these compounds is as chemical warfare agents, which pose a greater threat than biological weapons because of their ease of access. OP compounds are highly toxic compounds that cause irreversible inhibition of enzyme acetylcholinesterase, which is essential for hydrolysis of neurotransmitter acetylcholine, leading to series of neurological disorders and even death. Due to the extensive use of these organophosphorus compounds in agriculture, there is an increase in the environmental burden of these toxic chemicals, with severe environmental consequences. Hence, the rapid and sensitive, selective, real-time detection of OP compounds is very much required in terms of environmental protection, health, and survival. Several techniques have been developed over a few decades to easily detect them, but still, numerous challenges and problems remain to be solved. Major advancement has been observed in the development of sensors using the spectroscopic technique over recent years because of the advantages offered over other techniques, which we focus on in the presented review.

Efficient Gas and VOC Separation and Pesticide Detection in a Highly Stable Interpenetrated Indium-Organic Framework

The new indium-based organic framework {(Me₂NH₂)[In(BDPO)]·DMF·2H₂O}_n (1) was successfully constructed by using the oxalamide group modified ligand N,N'-bis(isophthalic acid)oxalamide (H₄BDPO). This framework presents a 2-fold interpenetrating structural characteristic, and the unique polar pore environment leads to a high capture ability for CO₂, C₂H_n and CH₃OH and good separation ability for CO₂ and C₂H_n over CH₄ as well as for CH₃OH over C₂H₅OH, which was further verified by an ideal adsorbed solution theory (IAST) calculation. Theoretical simulations pointed out the possible adsorption sites of different adsorbed gases in 1. In addition, the excellent chemical stability and strong luminescence of 1 give it an effective selective detection ability for 2,6-dichloro-4-nitroaniline (DCN) in water with a low detection limit of 3.85 ppm, and the detection mechanism is discussed in detail.

A water stable Eu(III)-organic framework as a recyclable multi-responsive luminescent sensor for efficient detection of p-aminophenol in simulated urine, and MnVII and CrVI anions in aqueous solutions

A novel 3D Eu(iii) metal-organic framework (Eu-MOF-1) formulated as [Eu(L)(H2O)(DMA)] (L = 2-(2-nitro-4-carboxylphenyl)terephthalic acid) has been successfully synthesized under solvothermal conditions and characterized by structural analyses. Eu-MOF-1 displays a new 3D framework containing EuIII ions, ligand L, and coordinated DMA molecules and water molecules. The fluorescence investigations indicate that Eu-MOF-1 emits bright red luminescence, and shows relatively high water stability and outstanding chemical stability under a relatively wide range of pH conditions. It is noteworthy that Eu-MOF-1 can quantitatively detect p-aminophenol (PAP) which is a metabolite of phenylamine in human urine. More significantly, Eu-MOF-1 is the first reported multi-responsive luminescent sensor for detecting the biomarker PAP, and MnVII and CrVI anions with high selectivity, sensitivity, recyclability and relatively low detection limits in aqueous solutions. Furthermore, the possible sensing mechanisms of Eu-MOF-1 for selective sensing have also been explored in detail. Eu-MOF-1 could be an ideal candidate as a multi-responsive luminescent sensor in biological and environmental areas.

Efficient chemosensors for toxic pollutants based on photoluminescent Zn(ii) and Cd(ii) metal-organic networks

Optical sensors with high sensitivity and selectivity, as important analytical tools for chemical and environmental research, can be realized by straightforward synthesis of luminescent one-, two- and three-dimensional Zn(ii) and Cd(ii) crystalline coordination arrays (CPs and MOFs). In these materials with emission centers typically based on charge transfer and intraligand emissions, the quantitative detection of specific analytes, as pesticides or anions, is probed by monitoring real-time changes in their photoluminescence and color emission properties. Pesticides/herbicides have extensive uses in agriculture and household applications. Also, a large amount of metal salts of cyanide is widely used in several industrial processes such as mining and plastic manufacturing. Acute or chronic exposure to these compounds can produce high levels of toxicity in humans, animals and plants. Due to environmental concerns associated with the accumulation of these noxious species in food products and water supplies, there is an urgent and growing need to develop direct, fast, accurate and low-cost sensing methodologies. In this critical frontier, we discuss the effective strategies, chemical stability, luminescence properties, sensitivity and selectivity of recently developed hybrid Zn(ii)/Cd(ii)-organic materials with analytical applications in the direct sensing of pesticides, herbicides and cyanide ions in the aqueous phase and organic solvents.

Confinement-guided photophysics in MOFs, COFs, and cages

In this review, the dependence of the photophysical response of chromophores in the confined environments associated with crystalline scaffolds, such as metal-organic frameworks (MOFs), covalent-organic frameworks (COFs), and molecular cages, has been carefully evaluated. Tunability of the framework aperture, cavity microenvironment, and scaffold topology significantly affects emission profiles, quantum yields, or fluorescence lifetimes of confined chromophores. In addition to the role of the host and its effect on the guest, the methods for integration of a chromophore (e.g., as a framework backbone, capping linker, ligand side group, or guest) are discussed. The overall potential of chromophore-integrated frameworks for a wide-range of applications, including artificial biomimetic systems, white-light emitting diodes, photoresponsive devices, and fluorescent sensors with unparalleled spatial resolution are highlighted throughout the review.

New frontiers and prospects of metal-organic frameworks for removal, determination, and sensing of pesticides

Pesticides have been widely used in agriculture to control, reduce, and kill insects. Humans are also being using pesticides to control insidious animals in daily life. By these practices, a huge volume of pesticides is introduced to the environment. Despite broad-spectrum applicability, pesticides also have hazardous effects on both humans and animals at high and low concentrations. Long-term exposure to pesticides can cause different diseases, like leukemia, lymphoma, and cancers of the brain, breasts, prostate, testis, and ovaries. Reproductive disorders from pesticides include birth defects, stillbirth, spontaneous abortion, sterility, and infertility. Therefore, the application of determination and treatment methods for pre-concentration and removal of these toxic materials from the environment appears a vital concern. To date, different materials and approaches have been employed for these purposes. Among these approaches, multifunctional metal-organic frameworks (MOFs)-assisted adsorption and determination processes have always been in the spotlight. These facts are due to exclusive properties of MOFs in terms of the crystallinity, large surface area, high chemical, and physical stability, and controllable structure as well as unique features of adsorption and determination process in terms of simple, easy, cheap, available method and ability to use in large and industrial scales. In the present work, we illustrate the exceptional features of MOFs as well as the possible mechanism for the adsorption of pesticides by MOFs. The use of these fantastic materials for pre-concentration and removal of pesticides are extensively explored. In addition, the performance of MOFs was compared with other adsorbents. Finally, the new frontiers and prospects of MOFs for the determination, sensing, and removal of pesticides are presented.

Nitrogen-Rich Tetraphenylethene-Based Luminescent Metal-Organic Framework for Efficient Detection of Carcinogens

The introduction of nitrogen-rich functional groups into a luminescent metal-organic framework (LMOF) can enhance its fluorescent sensing ability. In this work, we designed and synthesized a triazole-containing tetracarboxyl-substituted tetraphenylethene (TPE) ligand, tetrakis[4-(4-carboxyphenyl)(1H-1,2,3-triazol-4,1-diyl)phenyl]ethene (H₄TCPTAPE), featuring a prominent aggregation-induced emission (AIE). A highly porous TPE-based LMOF [Zn₃(TCPTAPE)(H₂O)₂(OH)₂] (1) with large pores was successfully obtained via solvothermal assembly of the H₄TCPTAPE ligand and Zn(II) ions, which showed a high fluorescence quantum yield of 54%. The activated 1 could selectively and sensitively detect aristolochic acid I with a high fluorescence quenching efficiency of 96% and a low detection limit of 1.02 μM, indicating that it has a potential application as a luminescence-based chemical sensor for carcinogens.

Coordination-Induced Emission from Tetraphenylethylene Units and Their Applications

Thanks to the potential of aggregation-induced emission (AIE) phenomena, improved stabilities, and the good selectivity and sensitivity of the chemical responses exhibited by the products, coordination-driven self-assembly with tetraphenylethylene (TPE) units has recently received much attention and has been widely investigated for application in chemical sensors, cell imaging agents, light-harvesting systems, and others. Several reviews have emerged on the topics of AIE chemistry and aggregation-induced emission luminogen (AIEgen)-based supramolecular assembles, however, there is still a distinct lack of full overviews of emission enhancement from the viewpoint of metal-coordination effects. Thus, this minireview offers recent advances that have been made in the design and application of TPE-based metallacycles, metallacages, metal-organic frameworks (MOFs) and coordination polymers (CPs).