A Pillar-Layered Zn-LMOF with Uncoordinated Carboxylic Acid Sites: High Performance for Luminescence Sensing Fe3+ and TNP

Novel Covalent Bonds and Hydrogen Bonds Linked Porous Organic Frameworks as Chemosensor for Detecting 2,4,6-Trinitrophenol in Water and Soil Samples

A novel and unconventional structural porous organic framework combined through the synergistic effect of covalent bonds and hydrogen bonds was prepared with the combination of 4,4',4″,4‴-(pyrene-1,3,6,8-tetrayl)tetraaniline (Py) and 5-hydroxyisophthalaldehyde (HP). It was the second example of CHOF until now and had been designated as Py-HP CHOF. The suspension of Py-HP CHOF in various solvents, such as ethanol, CH3CN, and methanol, exhibited a remarkably selective and sensitive "on-off" fluorescence response toward 2,4,6-trinitrophenol (TNP) compared with other explosives, with exceptionally low detection limits. The X-ray diffraction (XRD) spectra confirmed that the framework of Py-HP CHOF collapsed after interaction with TNP and acid, further indicating the existence of hydrogen bonds in the framework of Py-HP CHOF. The fluorescence quenching can be ascribed to the photoinduced electron transfer and the absorption competition quenching, as supported by XRD, X-ray photoelectron spectroscopy results, UV-vis absorption spectra, and density functional theory calculations. Fluorescence channels can be utilized by Py-HP CHOF to function as chemosensor, enabling the identification and detection of TNP in water and soil, and Py-HP CHOF is also the second CHOF example of sensing TNP reported to date. The application of this technique exhibits considerable potential in the analysis and detection of environmental pollutants, thereby presenting substantial practical implications.

Cellulose/amylose derivatives bearing bulky substituents as reversible fluorescent sensors for detection of Fe3

Two novel cellulose and amylose derivatives bearing bulky tris(2-benzothienylformate) pendants (Cel-3 and Amy-3) were expeditiously prepared by one-step esterification. The fluorescent sensing performance of six polysaccharide derivatives, including Cel-3/Amy-3, and other four previously prepared benzothienyl- or benzofuranyl-phenylcarbamates of cellulose and amylose (Cel-1/Amy-1, Cel-2/Amy-2), were carefully evaluated using eight metal ions, including Co2+, K+, Na+, Li+, Hg2+, Ni2+, Ca2+ and Fe3+. All six derivatives exhibited excellent fluorescence quenching property to Fe3+ ions with high sensitivity and selectivity. Especially, the limit of detection of Amy-2 with benzofuranylphenylcarbamates for Fe3+ was 3.0 μM, much lower than the maximum contaminant level for Fe3+ in the drinking water. Additionally, the six bulky derivatives displayed the interesting fluorescence "turn-off" and "turn-on" observation, indicating a desirable reversibility for Fe3+ detection. The high anti-interference ability was also observed for detection of Fe3+ on the benzothienyl/benzofuranyl derivatives of cellulose and amylose in the combined system containing Co2+, K+, Na+, Li+, Hg2+, Ni2+ and Ca2+. It suggested that the obtained polysaccharide derivatives with bulky chromophores possessed good potentials for detection of Fe3+ as high-efficient fluorescent sensors in diverse applications. The sensing mechanism for detection of Fe3+ was further proposed based on the Stern-Volmer plots and fluorescence titration analysis.

Post-Synthetic Modification of Zr-based Metal-Organic Frameworks with Imidazole: Variable Optical Behavior and Sensing

UiO-66-NH2 -IM, a fluorescent metal-organic framework (MOF), was synthesized by post-synthetic modification of UiO-66-NH2 with 2-imidazole carboxaldehyde via a Schiff base reaction. It was examined using various characterization techniques (PXRD, FTIR, NMR, SEM, TGA, UV-Vis DRS, and photoluminescence spectroscopy). The emissive feature of UiO-66-NH2 -IM was utilized to detect volatile organic compounds (VOCs), metal ions, and anions, such as acetone, Fe3+ , and carbonate (CO3 2- ). Acetone turns off the high luminescence of UiO-66-NH2 -IM in DMSO, with the limit of detection (LOD) being 3.6 ppm. Similarly, Fe3+ in an aqueous medium is detected at LOD=0.67 μM (0.04 ppm) via quenching. On the contrary, CO3 2- in an aqueous medium significantly enhances the luminescence of UiO-66-NH2 -IM, which is detected with extremely high sensitivity (LOD=1.16 μM, i. e., 0.07 ppm). Large Stern-Volmer constant, Ksv , and low LOD values indicate excellent sensitivity of the post-synthetic MOF. Experimental data supported by density functional theory (DFT) calculations discern photo-induced electron transfer (PET), resonance energy transfer (RET), inner filter effect (IFE), or proton abstraction as putative sensing mechanisms. NMR and computational studies propose a proton abstraction mechanism for luminescence enhancement with CO3 2- . Moreover, the optical behavior of the post-synthetic material toward analytes is recyclable.

Supramolecular nanostructures of coil-rod-coil molecules containing a 9,10-distyrylanthracene group in aqueous solution and their optical properties of assemblies

A series of coil-rod-coil molecules containing a 9,10-distyrylanthracene (DSA) core was successfully synthesized. The flexible parts of these molecules are composed of different polyethylene oxide chains. These molecules with aggregation-induced luminescence properties can be assembled into micelles, spheres, and sheet-like nano-assemblies in aqueous solution and have a strong ability to form charge-transfer complexes with the electron-deficient small molecules 2,4,5,7-tetranitro-9-fluorenone and 2,4,6-trinitrophenol. Interestingly, under ultraviolet light irradiation, the DSA structure undergoes photolysis and induces the disappearance of the aggregation-induced luminescence phenomena, giving these molecules application potential as a photodegradable material. In addition, these molecules are suitable organic dyes for information encryption and anti-counterfeiting applications.

Ligand Modulation on the Various Structures of Three Zinc(II)-Based Coordination Polymers for Antibiotics Degradation

The efficient removal of organic contaminants from wastewater is, nowadays, a prominent area of study due to its biological as well as environmental significance. Antibiotics are now found in wastewater because of their high use, which has become a source of aquatic pollution. These antibiotics have dangerous implications for people’s health. Hence, effective pharmaceutical removal from wastewater and contaminated water bodies, especially the removal of antibiotics, is of major interest to global research organizations. This is why it is necessary to investigate this class of toxic material in wastewater discharge. We synthesized three different coordination polymers (CPs) in the presence of various assistant carboxylate linkers, namely, [Zn(Hbtc)(dip)]n (1), [Zn4(1,2-bdc)4(dip)4]n (2), and [Zn(1,4-bdc)(dip)]n (3) (3,5-di(1H-imidazol-1-yl)pyridine = dip, 1,3,5-benzenetricarboxylic acid = H3btc, 1,2-benzenedicarboxylic acid = 1,2-H2bdc, and 1,4-benzendicarboxylic acid = 1,4-bdc). These CPs were characterized by using different techniques, including single-crystal X-ray diffraction. The structural studies demonstrated that in 2, there are four Zn(II) centers and both centers are in different coordination environments (Zn2 has distorted tetrahedral geometry, whereas Zn1, Zn3, and Zn4 have square pyramidal geometry). Hirshfeld surfaces analysis revealed that different types of intermolecular interactions (C⋯C, H⋯C, H⋯H, O⋯C, N⋯H, and O⋯H) are present in the synthesized CPs. We examined the different antibiotics, such as metronidazole (MDZ), nitrofurazone (NFZ), dimetridazole (DTZ), sulfasalazine(SLA), and oxytetracycline (OXY), degradation behaviors of the synthesized CPs, which showed remarkable degradation efficiency. 1 showed photocatalytic behavior toward the NFZ antibiotic in an aqueous media. This study also showed that these catalysts are stable and reusable under mild conditions.

Zn-MOFs composites loaded with silver nanoparticles are used for fluorescence sensing pesticides, Trp, EDA and photocatalytic degradation of organic dyes

The abuse of pesticides, antibiotics, organic solvents, etc., not only deteriorates the ecological environment, but even affects the normal development of organisms, posing a serious threat to global public health.Efficient and sensitive detection of pesticides, antibiotics, organic solvents and so on are very important, but also a challenge to scientists. By depositing Ag nanoparticles on the surface of Zn-MOF (1: {[Zn₂(bta)(bpy)(H₂O)₂]·2H₂O}_n), a new type of composite material (Ag@1) was successfully synthesized and analyzed by TEM, EDS, XPS, XRD, IR and other characterization methods. Ag@1 can serve as multi-response fluorescence sensor to detect pesticides (fluazinam (FLU) and emamectin benzoate (EMB)), Tryptophan (Trp) and Ethylenediamine (EDA). In particular, Ag@1 showed "turn-off" fluorescence sensing for FLU and EDA, and "turn-on" fluorescence sensing for EMB and Trp. It is worth mentioning that we further explored its analysis of FLU and Trp in real water samples and fetal bovine serum. The recoveries are satisfactory, 97.95 % - 102.39 % and 96.69 % - 101.85 %, respectively. In addition, the photocatalytic performance of Ag@1 was found to be excellent, the degradation rate of methylene blue (MB) reached 86 %, and its degradation mechanism was discussed.

Metal-Organic Framework Flowers as a Naked-Eye Colorimetric Indicator of Trace Water

Convenient and sensitive trace water indication is of great significance in various industrial processes. Here, a flower-like metal-organic framework Cu-FMM is assembled from ultrathin nanosheets that change its coordination structure reversibly with the capture and loss of water molecules, enabling sensitive trace water naked-eye colorimetric indication ability. A recognizable black/yellow color change can be observed when the dried Cu-FMM is exposed to the atmosphere or solvent with trace water as low as RH 3% and a water content of 0.25‰ (v/v) and further enables potential trace water imaging applications. The excellent accessibility of the multi-scale pore structure of Cu-FMM contributes to a fast response time of 3.8 s with good reversibility (>100 cycles), outperforming traditional coordination polymer humidity sensors. The present study provides new inspirations for the design of sensitive and applicable naked-eye water indicator materials that are applicable to in situ and continuous monitoring in industrial processes.

A "heat set" Zr-Diimide based Fibrous Metallogel: Multiresponsive Sensor, Column-based Dye Separation, and Iodine Sequestration

Sensing and monitoring hazardous contaminants in water and radioactive iodine sequestration is pivotal due to their detrimental impact on biological ecosystems. In this context, herein, a water stable zirconium-diimide based metallogel (Zr@MG) with fibrous columnar morphology is accomplished through the "heat set" method. The presence of diimide linkage with long aromatic chain manifests active luminescence properties in the linker as well as in the supramolecular framework structure. The as-synthesized Zr@MG xerogel can selectively detectCr₂O₇^2- (LOD = 0.52 ppm) and 2,4,6-trinitrophenol (TNP) (LOD = 80.2 ppb) in the aqueous medium. The Zr@MG paper strip-based detection for Cr₂O₇^2- and nitro explosive makes this metallogel reliable and an attractive luminescent sensor for practical use. Moreover, a column-based dye separation experiment was performed to show selective capture of positively charged methylene blue (MB) dye with 98 % separation efficiency from the mixture of two dyes. Also, the Zr@MG xerogel showed effective iodine sequestration from the vapor phase (232 wt%).

Porous Organic Frameworks Constructed by the Synergetic Effect of Covalent Bonds and Hydrogen Bonds for the Selective Identification and Detection of Explosives

Covalent organic frameworks (COFs) and hydrogen-bonded organic frameworks (HOFs) have emerged as novel platforms for material design and functional explorations. Here, we report an unconventional structural organic framework (named CHOF-1) combined with 1,3,5-tris(4-aminophenyl)benzene (TAPB) and 5-hydroxyisophthalaldehyde (HP) through the synergetic effect of covalent bonds and hydrogen bonds. CHOF-1 contains two different pores and is an eclipsed AA-stacking model with high thermal stability. It exhibits selective "turn-off" and red shift fluorescence responses toward 4-nitrophenol (4-NP) and 2,4,6-trinitrophenol (TNP) in ethanol, respectively, and the low detection limit was 8.78 μM for 4-NP and 11.1 μM for TNP. It has satisfactory recovery in the detection of 4-NP and TNP in practical water samples. The fluorescence quenching of CHOF-1 caused by 4-NP is attributed to the absorption competition quenching (ACQ) mechanism. In the structure of CHOF-1, the hydroxyl of TNP has strong acidity and can form strong hydrogen bonds with the unreacted NH2. Then, the crystalline structure of CHOF-1 decomposed and the electron structure of the photophore changed; thus, the fluorescence spectra red-shifted. This is a novel example of a covalent bond and hydrogen bonds combined organic framework (CHOF). This work not only demonstrates a synthesis strategy of the first novel structural organic framework through the synergetic effect of covalent bonds and hydrogen bonds but also provides a fluorescent sensing material for the detection of explosives 4-NP and TNP with high selectivity and sensitivity.

Hydrogen-Bond-Connected 2D Zn-LMOF with Fluorescent Sensing for Inorganic Pollutants and Nitro Aromatic Explosives in the Aqueous Phase

Herein, a novel luminescent Zn-LMOF, JLU-MOF109 ([Zn(PBBA)(H₂O)]·3DMF·2H₂O, PBBA = 4,4'-(2,6-pyrazinediyl)bis[benzoic acid], DMF = N,N-dimethylformamide), was successfully synthesized under solvothermal conditions. Zinc ions are connected by PBBA ligands to form two-dimensional (2D) layers, and the layers are further propped up through hydrogen-bonding interactions. JLU-MOF109 exhibits good sensitivity to inorganic pollutants, Fe³⁺ and Cr₂O₇^2-, as well as nitro aromatic explosives, 2,4,6-trinitrophenol and 2,4-dinitrophenol. JLU-MOF109 exhibits high K_sv (at 10⁴ M^-1 level) and low limit of detection values (∼10^-6 mol/L) for the abovementioned hazardous pollutants, which is better than a majority of previously reported MOF-based fluorescent sensors. With good stability in the aqueous phase, JLU-MOF109 can serve as a promising chemical sensor for pollutant detection in wastewater.

pH-Stable Luminescent Metal-Organic Frameworks for the Selective Detection of Aqueous-Phase FeIII and CrVI Ions

The development of chemically stable metal-organic framework (MOF)-based luminescent platforms for toxic ion detection in an aqueous medium is highly challenging because most of the classical MOFs are prone to water degradation, and that is the reason why most of the MOF-based luminescent sensors use a nonaqueous medium for sensing. In this contribution, we report two new water-stable luminescent MOFs (Zn-MOF-1 and Zn-MOF-2), assembled from a mixed-ligand synthesis approach. Because of the presence of a hydrophobic trifluoromethyl group to the backbone and stronger metal-N coordination, these MOFs exhibit excellent stability not only in water but also in acidic/alkaline aqueous solutions (pH = 3-10). Here, we report a green sensing approach by exploiting the significant reduction in photoluminescence of these MOFs in the presence of toxic ions. Fe³⁺ and CrO₄^2-/Cr₂O₇^2- ions could be traced with a detection limit (LOD) in the micromolar range (0.045 and 0.745/0.33 μM for Zn-MOF-1; 125.2 and 114.2/83.5 μM for Zn-MOF-2). The mechanistic study reveals that competitive absorption of the excitation energy coupled with fluorescent resonance energy transfer are responsible for the turn-off quenching. The anti-interference ability and recyclability along with the pH stability gave these MOFs high potential to be used as practical sensors toward Fe^III and Cr^VI ions in water as a greenest medium.

Self-luminescent europium based metal organic frameworks nanorods as a novel electrochemiluminescence chromophore for sensitive ulinastatin detection in biological samples

In this work, we developed a novel electrochemiluminescence (ECL) biosensor for ulinastatin (UTI) detection based on self-luminescent metal-organic framework (L-MOF) nanomaterials. The L-MOFs could be simply prepared by one-pot methods using Eu³⁺ and 4,4',4″-s-triazine-1,3,5-triyltri-m-aminobenzoic acid (H₃TATAB) as the metallic center and organic ligand, respectively. The Eu-TATAB exhibited high efficiency and stable ECL performance when using K₂S₂O₈ as coreactant. For the established biosensor, Eu-TATAB was both used as the ECL chromophore and protein carrier due to its outstanding biocompatibility and large superficial area, which could load sufficient antibodies to link with antigen in the biosensor for subsequent detection. The established sandwich ECL biosensor showed a wide linear range of 0.1 ng mL^-1 - 10⁵ ng mL^-1 and a low limit of detection of 9.7 pg mL^-1 for UTI detection. In addition, the developed ECL biosensor could also be successfully applied to the real UTI sample determination in serum. The reported biosensor strategy could provide a guide for developing more other novel and promising high-performance ECL nanomaterials, and also be used as a potential method for ultrasensitive UTI detection in disease research.

A Dihydrotetrazine-Functionalized Metal-Organic Framework as a Highly Selective Luminescent Host-Guest Sensor for Detection of 2,4,6-Trinitrophenol

Pore decoration of metal-organic frameworks (MOFs) with functional groups is a useful strategy to attain high selectivity toward specific analytes, especially in the presence of interfering molecules with similar structures and energy levels, through selective host-guest interactions. In this work, we applied a dihydrotetrazine-decorated MOF, TMU-34, with the formula [Zn(OBA)(H₂DPT)_0.5]_n·DMF, where H₂OBA is 4,4'-oxybis(benzoic acid) and H₂DPT is 3,6-bis(pyridin-4-yl)-1,4-dihydro-1,2,4,5-tetrazine, for the highly selective detection of phenolic NACs, especially TNP (94% quenching efficiency, detection limit 8.1 × 10^-6 M, K_SV = 182663 mol L^-1), in the presence of other substituted NACs especially -NH₂-substituted NACs. Investigations reveal that the quenching mechanism is dominated by photoinduced MOF-to-TNP electron transfer through possible hydrogen-bonding interactions between the phenolic hydroxyl group of TNP and dihydrotetrazine functions of TMU-34. Despite extensive publications on the detection of TNP in the presence of other NACs, the significance of this work will be elucidated if attention is paid to the fact that TMU-34 is among the rare and highly selective MOF-based TNP sensors in the presence of -NH₂-substituted NACs as the serious interferers.

An anthracene-based microporous metal–organic framework for adsorbing CO2 and detecting TNP sensitivity

An anthracene-based microporous MOF of CUST-607 was synthesized by a solvothermal method. CUST-607 possesses a large surface area and shows strong adsorption toward CO2. In the fluorescence experiments, CUST-607 exhibits total quenching for TNP.

Three-fold interpenetrated metal–organic framework as a multifunctional fluorescent probe for detecting 2,4,6-trinitrophenol, levofloxacin, and l-cystine

A robust Zn(ii) MOF with good chemical and thermal stability, was prepared as an effective fluorescent probe for 2,4,6-trinitrophenol (TNP), levofloxacin (LVX) and l-cystine (l-Cys) with recyclability.

A series of isostructural lanthanide metal-organic frameworks: effective fluorescence sensing for Fe3+, 2,4-DNP and 4-NP

Because of the fluorescence properties, lanthanide metal-organic frameworks (Ln-MOFs) materials have potential application in the detections of metal ions and nitro-aromatic explosives. Herein, a series of isostructural Ln-MOFs [Ln2(PIA)3(DMF)3(CH3OH)] (JLU-MOF201-Ln,...

A hydrostable Zn2+ coordination polymer for multifunctional detection of inorganic and organic contaminants in water

From the perspective of human health and environmental safety, the development of hydrostable fluorescent sensors for the detection of heavy metal ions and nitroaromatics is an important but a challenging issue. To this end, a water-stable Zn²⁺ coordination polymer formulated as {[Zn(H₂L)]·2DMF·3H₂O}_n (ZnCP) was prepared elaborately by a solvothermal method using a multidentate ligand (H₄L) with 2,6-pyridine-dicarboxylic acid spaced by para-substituted benzene. Single-crystal analysis shows that the new ZnCP exhibits one-dimensional chain structural features, which further promoted to afford a wrinkled two-dimensional network structure via inter-chain hydrogen bonding. Powder X-ray diffraction and fluorescence measurements show that it can maintain crystallinity and structural integrity under harsh acidic and alkaline conditions with the pH ranging from 4 to 11. Notably, the bright blue-emissive ZnCP showed selective fluorescence quenching effects for Fe³⁺ and picric acid (PA), which makes it an excellent chemical sensor for Fe³⁺ and picric acid (PA) with low detection limits of 0.41 and 0.26 μM in water. The recognition mechanism of Fe³⁺ could be attributed to UV absorption competition and resonance energy transfer in the aid of weak electrostatic interactions, while the recognition mechanism of PA is considered to be a multi-quenching mechanism dominated by absorption competition and PET effects with the assistance of hydrogen bonding. In addition, poly(methyl methacrylate) (PMMA) films doped with ZnCP (ZnCP@PMMA) were developed to provide better sensing performance and portability for practical applications.

Construction of a Luminescent Cadmium-Based Metal-Organic Framework for Highly Selective Discrimination of Ferric Ions

Fluorescent metal–organic frameworks (MOFs) are ideal materials for sensors because of their adjustable pore size and functional groups, which provide them with favorable metal ion selective recognition. In this paper, a new cadmium-based MOF was synthesized using Cd(NO₃)₂·4H₂O and 3,3′,5,5′-biphenyltetracarboxylic acid by solvothermal method. CdBPTC owned three types of channels with dimensions of approximately 8.4 × 8.3 Å, 6.0 × 5.2 Å, 9.7 × 8.4 Å along a, b, and c axis, respectively. This MOF has high selectivity to ferric ions and shows excellent anti-inference ability toward many other cations. The results indicate that the fluorescence quenching efficiency of CdBPTC is close to 100% when the concentration of Fe³⁺ reaches 1.0 × 10⁻³ mol·L⁻¹. Moreover, the luminescent intensity at 427 nm presents a linear relationship at a concentration range of 2.0 × 10⁻⁴~7.0 × 10⁻⁴ mol·L⁻¹, which can be quantitatively expressed by the linear Stern–Volmer equation I₀/I = 8489 [Fe³⁺] − 0.1400, which is comparable to the previously reported better-performing materials. Competitive energy absorption and ion exchange may be responsible for the variation in fluorescence intensity of CdBPTC in different Fe³⁺ concentrations.

Structural Design of Low Toxicity Metal-Organic Frameworks for Multifunction Detection of Organic and Inorganic Contaminants from Water

Metal-organic frameworks (MOFs)-based sensors for monitoring toxic substances in wastewater have attracted great attention due to the efficient and reliable performance. Here, we has synthesized two novel zinc-based MOFs [Zn(ttb)₂(H₂O)₂]_n (Zn1-ttb) and {[Zn(ttb)₂]·0.5CH₃CN}_n (Zn2-ttb) through changing the polarity of reaction solvents and finally obtained target 2D MOF material [Zn(ttb)(bdc)_0.5]_n(Zn3-ttb-bdc) by successfully introducing an ancillary ligand H₂bdc (Httb = 1-(triazo-1-ly)-4-(tetrazol-5-ylmethyl)benzene, H₂bdc = 1,4-benzenedicarboxylic acid). As-prepared Zn3-ttb-bdc exhibits high water and chemical stability as well as excellent fluorescence property. Due to the -COOH binding sites from H₂bdc, Zn3-ttb-bdc shows high sensitivity and a rapid luminescent response to a representative organic micropollutant trinitrophenol (TNP) and inorganic pollutants (Fe³⁺ and Cr₂O₇^2-) in wastewater. The mechanisms of multifunctional detection abilities of Zn3-ttb-bdc toward different types of pollutants are further studied. This work presents the structural design in preparing MOF materials for multifunctional detection performance, thus opening new perspectives for emerging MOF-based sensors as environmental monitors.

A New Compound for Sequential Sensing of Picric Acid and Aliphatic Amines: Physicochemical Details and Construction of Molecular Logic Gates

Picric acid (PA) at low concentration is a serious water pollutant. Alongside, aliphatic amines (AAs) add to the queue to pollute surface water. Plenty of reports are available to sense PA with an ultralow limit of detection (LOD). However, only a handful of works are testified to detect AAs. A new fluorescent donor-acceptor compound has been synthesized with inherent intramolecular charge transfer (ICT) character that enables selective and sensitive colorimetric quantitative detection of PA and AAs with low LODs in non-aqueous as well as aqueous solutions. The synthesized compound is based on a hemicyanine skeleton containing two pyridenylmethylamino groups at the donor and a benzothiazole moiety at the acceptor ends. The detailed mechanisms and reaction dynamics are explained spectroscopically along with computational support. The fluorescence property of the detecting compound changes due to protonation of its pyridinyl centers by PA leading to quenching of fluorescence and subsequently de-protonation by AAs to revive the signal. We have further designed logic circuits from the acquired optical responses by sequential interactions.

Construction of a Stable Lanthanide Metal-Organic Framework as a Luminescent Probe for Rapid Naked-Eye Recognition of Fe3+ and Acetone

Four lanthanide metal-organic frameworks (Ln-MOFs), namely {[Me2NH2][LnL]·2H2O}n (Ln = Eu 1, Tb 2, Dy 3, Gd 4), have been constructed from a new tetradentate ligand 1-(3,5-dicarboxylatobenzyl)-3,5-pyrazole dicarboxylic acid (H4L). These isostructural Ln-MOFs, crystallizing in the monoclinic P21/c space group, feature a 3D structure with 7.5 Å × 9.8 Å channels along the b axis and the point symbol of {410.614.84} {45.6}2. The framework shows high air and hydrolytic stability, which can keep stable after exposed to humid air for 30 days or immersed in water for seven days. Four MOFs with different lanthanide ions (Eu3+, Tb3+, Dy3+, and Gd3+) ions exhibit red, green, yellow, and blue emissions, respectively. The Tb-MOF emitting bright green luminescence can selectively and rapidly (<40 s) detect Fe3+ in aqueous media via a fluorescence quenching effect. The detection shows excellent anti-inference ability toward many other cations and can be easily recognized by naked eyes. In addition, it can also be utilized as a rapid fluorescent sensor to detect acetone solvent as well as acetone vapor. Similar results of sensing experiments were observed from Eu-MOF. The sensing mechanism are further discussed.

A Cd-MOF fluorescence sensor with dual functional sites for efficient detection of metal ions in multifarious water environments

A 2D MOF displays high performance luminescence quenching for detecting Fe3+ and Cu2+ in pure water, actual river water and simulated HEPES with superior low LODs. Multiple experiments and DFT calculations co-verify a weak interaction quenching mechanism.

Synthesis, structure, and fluorescence properties of coordination polymers of 3,5-bis(1′,2′,4′-triazol-1′-yl) pyridine

Four coordination polymers based on 3,5-bis(1′,2′,4′-triazol-1′-yl) pyridine were synthesized. Compounds [Cd₃(btc)₂(btap)(H₂O)₆] and [Cd(oa)(btap)] exhibited high sensitivity luminescence response towards Fe³⁺, Ce³⁺, Cr₂O₇²⁻ and MnO₄⁻ in aqueous solution.