A Bifunctional Luminescent Metal-Organic Framework for the Sensing of Paraquat and Fe3+ Ions in Water

A Series of Lanthanide Coordination Polymers as Luminescent Sensors for Selective Detection of Inorganic Ions and Nitrobenzene

Seven new lanthanide coordination polymers, namely [Ln(cpt)3H2O)]n(Ln = La (1), Pr (2), Sm (3), Eu (4), Gd (5), Dy (6), and Er (7)), which were synthesized under hydrothermal conditions using 4'-(4-(4-carboxyphenyloxy)phenyl)-4,2':6',4'-tripyridine (Hcpt) as the ligand. The crystal structures of these seven complexes were determined using single-crystal X-ray diffraction, and they were found to be isostructural, crystallizing in the triclinic P1- space group. The Ln(III) ions were nine-coordinated with tricapped trigonal prism coordination geometry. The Ln(III) cations were coordinated by carboxylic and pyridine groups from (cpt)- ligands, forming one-dimensional ring-chain structures. Furthermore, the luminescent properties of complexes 1-7 were investigated using fluorescent spectra in the solid state. The fluorescence sensing experiments demonstrated that complex 4 exhibits high selectivity and sensitivity for detecting Co2+, Cu2+ ions, and nitrobenzene. Moreover, complex 3 shows good capability for detecting Cu2+ ions and nitrobenzene. Additionally, the sensing mechanism was also thoroughly examined through theoretical calculations.

A fluorescent MOF and its synthesized MOF@cotton composite: Ratiometric sensing of vitamin B2 and antibiotic drug molecule

Here, we demonstrated the synthesis of a zinc based luminescent MOF, 1 (NDC = 2,6- naphthalenedicarboxylate) for the ratiometric detection of biomarker riboflavin (RBF; vitamin B2) in water dispersed medium. Further, this MOF detected two other antibiotic drug molecules, nitrofurantoin (NFT) and nitrofurazone (NZF). The detection of these analytes is very quick (∼seconds), and the limit of detection (LOD) for RBF, NZF and NFT are calculated as 16.58 ppm, 47.63 ppb and 56.96 ppb, respectively. The detection of these analytes was also comprehended by solid, solution, cost-effective paper strip method i.e., triphasic identification capabilities. The sensor is reusable without losing its detection efficacy. The sensor further showed the recognition abilities of these antibiotics in real field samples (river water, urine and tablet) and RBF in vitamin B2 pills and food samples (milk and cold drinks). The sensing merit of 1 urged us to fabricate of 1@cotton fabric composite, which exhibited the colorimetric detection of these analytes. In-depth experimental analysis suggested that the occurrence of photo-induced electron transfer (PET), fluorescence resonance energy transfer (FRET), and the inner filter effect (IFE) are the possible sensing mechanisms for the recognition of the antibiotics drug. The FRET mechanism is responsible for the recognition of RBF. The sensing mechanism is further supported by the theoretical analysis and the excited lifetime measurement.

Fluorescent MOF and Its Gel Composite for the Fluorescence Recovery "Turn-On" Detection of Al3+ Ions and "Turn-Off" Detection of Oxo-Anions

The exploration of smart sensors is of great significance for the selectivity, sensitivity, and ability to show the low detection limit for the target analyte. Here, we have used the linker H2L (5-((anthracen-9-ylmethyl)amino)isophthalic acid) for the construction of {[Cd(L)(DMF)(H2O)2]·H2O}n (1) which is in order with the chromophore anthracene moiety and the free -NH functionality as a guest interaction site. This framework showed the luminescence recovery "turn-on" detection of the Al3+ ion in an aqueous solution. An exhaustive mechanism study disclosed that the Lewis acid-base-type interaction between the Al3+ ion and the -NH functionality of the linker in the framework revealed that the absorbance caused an enhancement for the "turn-on" sensing event. Besides the "turn-on" sensing event, the "turn-off" sensing phenomenon of 1 is also noticed when it detects the hazardous oxo-anions (MnO4- and CrO42-) with limit of detection values of 17.08 and 19.91 ppb, respectively. The detection of these diverse analytes are very fast (10 s) and they can also be recognized through a colorimetric response. The sensing mechanisms for these analytes are established by photoinduced electron transfer, Forster resonance energy transfer, and inert filter effect along with theoretical investigation. Furthermore, to show the sensing application of 1 in a versatile podium, a MOF gel composite, 1@AA (AA = Agar-Agar), was developed from 1 with AA. Interestingly, 1@AA showed the colorimetric detection of these analytes under UV light. Therefore, sensor 1 behaves as a smart sensory material for the recognition of the above analytes through a simultaneous "turn-on" and "turn-off" effect.

A Zn(II) coordination polymer as a dual sensor for ppb level detection of antibiotics and organo-toxins in a green solvent

Herein, we describe the synthesis of a new fluorescent d¹⁰ coordination polymer, [Zn₂(CFDA)₂(BPEP)]_n·nDMF (CP-1) under solvothermal reaction condition using zinc metal ion. In CP-1, Zn(II) ion along with CFDA and BPED ligand forms a 2-fold self-interpenetrated 3D coordination polymers. This CP-1 is characterized by the single crystal X-ray diffraction (SCXRD), powder X-ray diffraction (PXRD), infrared spectra, optical microscope image and thermogravimetric analysis and the framework is found to maintain its structural stability in different solvents. The framework (CP-1) detected antibiotics (NFT (nitrofurantoin) and NZF (nitrofurazone)) and organo-toxin trinitrophenol in aqueous dispersed medium. Apart from the fast responsive (10 s), the detection limit for them was found at ppb level. The detection of these organo-aromatics were also comprehended by the colorimetric response through solid, solution and low cost paper strip technique i.e., triple mode recognition capability. The probe is re-usable without changing in its sensing efficiency and in addition, it has been applied for the detection of these analytes in the real field specimens (soil, river water, human urine and commercial tablet). The sensing ability is established by in-depth experimental analysis and the life time measurement where mechanism such as photo induced electron transfer (PET), fluorescence resonance energy transfer (FRET), inner filter effect (IFE) was recognized. The presence of guest interaction sites on the linker backbone in CP-1 induces diverse supramolecular interaction with the targeted analytes results to bring them in proximity for the occurrence of these sensing mechanism. The Stern-Volmer quenching constant values of CP-1 for the targeted analytes are admirable and the low detection limit (LOD) values for NFT, NZF and TNP are found to be 34.54, 67.79 and 43.93 ppb respectively. Further, the DFT theory is carried out in details to justify the sensing mechanism.

Constructing functional metal-organic frameworks by ligand design for environmental applications

Metal-organic frameworks (MOFs) with unique physical and chemical properties are composed of metal ions/clusters and organic ligands, including high porosity, large specific surface area, tunable structure and functionality, which have been widely used in chemical sensing, environmental remediation, and other fields. Organic ligands have a significant impact on the performance of MOFs. Selecting appropriate types, quantities and properties of ligands can well improve the overall performance of MOFs, which is one of the critical issues in the synthesis of MOFs. This article provides a comprehensive review of ligand design strategies for functional MOFs from the number of different types of organic ligands. Single-, dual- and multi-ligand design strategies are systematically presented. The latest advances of these functional MOFs in environmental applications, including pollutant sensing, pollutant separation, and pollutant degradation are further expounded. Furthermore, an outlook section of providing some insights on the future research problems and prospects of functional MOFs is highlighted with the purpose of conquering current restrictions by exploring more innovative approaches.

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.

Recent Progress in Metal-Organic Framework Based Fluorescent Sensors for Hazardous Materials Detection

Population growth and industrial development have exacerbated environmental pollution of both land and aquatic environments with toxic and harmful materials. Luminescence-based chemical sensors crafted for specific hazardous substances operate on host-guest interactions, leading to the detection of target molecules down to the nanomolar range. Particularly, the luminescence-based sensors constructed on the basis of metal-organic frameworks (MOFs) are of increasing interest, as they can not only compensate for the shortcomings of traditional detection techniques, but also can provide more sensitive detection for analytes. Recent years have seen MOFs-based fluorescent sensors show outstanding advantages in the field of hazardous substance identification and detection. Here, we critically discuss the application of MOFs for the detection of a broad scope of hazardous substances, including hazardous gases, heavy metal ions, radioactive ions, antibiotics, pesticides, nitro-explosives, and some harmful solvents as well as luminous and sensing mechanisms of MOF-based fluorescent sensors. The outlook and several crucial issues of this area are also discussed, with the expectation that it may help arouse widespread attention on exploring fluorescent MOFs (LMOFs) in potential sensing applications.

Two porous three-dimensional (3D) metal–organic frameworks based on diverse metal clusters: selective sensing of Fe3+ and Cr2O72−

Using a rigid 3,5-di(2′,5′-dicarboxylphenyl)benzoic acid, two porous 3D MOFs have been synthesized and characterized, and the luminescent properties have been studied.

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.

Terpyridine-Based 3D Metal-Organic-Frameworks: A Structure-Property Correlation

Design, synthesis, and applications of metal-organic frameworks (MOFs) are among the most salient fields of research in modern inorganic and materials chemistry. As the structure and physical properties of MOFs are mostly dependent on the organic linkers or ligands, the choice of ligand system is of utmost importance in the design of MOFs. One such crucial organic linker/ligand is terpyridine (tpy), which can adopt various coordination modes to generate an enormous number of metal-organic frameworks. These frameworks generally carry physicochemical characteristics induced by the π-electron-rich (basically N-electron-rich moiety) terpyridines. In this minireview, the construction of 3D MOFs associated with symmetrical terpyridines is discussed. These ligands can be easily derivatized at the lateral phenyl (4'-phenyl) position and incorporate additional organic functionalities. These functionalities lead to some different binding modes and form higher dimensional (3D) frameworks. Therefore, these 3D MOFs can carry multiple features along with the characteristics of terpyridines. Some properties of these MOFs, like photophysical, chemical selectivity, photocatalytic degradation, proton conductivity, and magnetism, etc. have also been discussed and correlated with their frameworks.

Assemblies of cucurbit[6]uril-based coordination complexes with disulfonate ligands: from discrete complexes to one- and two-dimensional polymers

Nine assemblies of Q[6]-based coordination complexes incorporating disulfonate ligands were obtained and two of them were found to have the ability to sense Fe³⁺via a fluorescence quenching effect.

Polyoxometalate-based metal–organic frameworks for heterogeneous catalysis

POM-based MOFs simultaneously possessing the virtues of POMs and MOFs exhibit excellent heterogeneous catalytic properties.

Recent advances in metal-organic frameworks for pesticide detection and adsorption

The large-scale use of pesticides such as organophosphate pesticides (OPPs) and organochlorine pesticides (OCPs) has led to serious environmental problems worldwide, and their high toxicity could cause serious damage to human health. It is crucial to remove and track them precisely in the environment and food resources. As novel nanomaterials, metal-organic frameworks (MOFs) have attracted significant attention in the fields of adsorption and luminescence sensing due to their rich topology, tunable pore size and shape, high surface area, and abundant active sites. Luminescent metal-organic frameworks (LMOFs) have sprung up as great potential chemical sensors to detect pesticides with fast response, high sensitivity, high selectivity and easy operation. Therefore, in this highlight, we focus on recent progress of MOFs in sensing and adsorbing pesticides, as well as in the possible mechanism of sensing, so as to attract more attention to pesticide detection and adsorption.

A dual-sensitized luminescent europium(iii) complex as a photoluminescent probe for selectively detecting Fe3

A new luminescent EuIII complex, namely [Eu2(BTFA)4(OMe)2(dpq)2] (1), in which BTFA = 3-benzoyl-1,1,1-trifluoroacetone and dpq = dipyrido [3,2-d:2',3'-f] quinoxaline, has been designed and synthesized by employing two different ligands as sensitizers. Crystal structure analysis reveals that complex 1 is composed of dinuclear EuIII units crystallized in the monoclinic P1̄ space group. Notably, 1 exhibits high thermal stability up to 270 °C and excellent water stability. The photoluminescence property of the complex is investigated. Further studies show 1 can recognize Fe3+ ions with high selectivity from mixed metal ions in aqueous solution through the luminescence quenching phenomenon. Furthermore, the recyclability and stability of 1 after sensing experiments are observed to be adequate. By virtue of the superior stability, detection efficiency, applicability and reusability, the as-prepared EuIII complex can be a promising fluorescent material for practical sensing.

Zn(ii)/Cd(ii) based mixed ligand coordination polymers as fluorosensors for aqueous phase detection of hazardous pollutants

The recent developments and prospects of fluorosensors with a handful of recent examples based on mixed ligand Zn(ii)/Cd(ii) coordination polymers for aqueous phase detection of organic as well as inorganic pollutants have been discussed.

Temperature-induced structural transformations accompanied by changes in magnetic properties of two copper coordination polymers

Two ferromagnetic copper compounds have been synthesized under different temperature, which represented the rare example of structural transformations resulting from the coordination modes of organic ligands supported by magnetic results.

First Ln-MOF as a trifunctional luminescent probe for the efficient sensing of aspartic acid, Fe3+ and DMSO

The first Ln-MOF (Tb-MOF) as a trifunctional luminescent probe for the efficient sensing of aspartic acid, Fe³⁺ and DMSO was demonstrated.

Luminescent metal–organic frameworks (LMOFs) as potential probes for the recognition of cationic water pollutants

This review aims to provide an overview regarding the development of luminescent metal–organic frameworks (LMOFs) based sensory materials for the detection of cationic inorganic and organic water pollutants.

A water-stable terbium metal–organic framework as a highly sensitive fluorescent sensor for nitrite

A terbium metal–organic framework was synthesized for highly sensitive nitrite detection. The mechanism of the quenching process was also studied in detail.