Hazardous 2,4,6-Trinitrophenol (TNP) Detection in Water by Amine and Azine Functionalized Metal-Organic Framework.

A Zn(II)-based metal-organic framework (MOF) decorated with amine and azine functionalities, TMU-17-NH2 (formulated as [Zn(H2ata)(L)].2DMF; L = 1,4-bis(4-pyridyl)-2,3-diaza-2,3-butadiene and H2ata = 2-aminoterephthalic acid) has been successfully synthesized via a solvothermal method. According to crystallographic studies, the synthesized TMU-17-NH2 has three dimensional cuboidal structure with the pore surface decorated with free amine (-NH2) and azine (= N-N =) functional groups. The photoluminescence investigations proved that the synthesized MOF can be effectively utilized for selective detection of 2,4,6-trinitrophenol (TNP) in water with an apparent turn-off quenching response. Its limits of detection (LOD) for TNP was 9.4 ppb and competitive nitro explosive testing confirmed its higher selectivity towards TNP (over other nitro explosives). Calculations based on density functional theory (DFT) and spectrum overlap were utilized to evaluate the sensing mechanisms. This MOF-based fluorescence sensing technique for TNP had a high sensitivity (Ksv = 3.26 × 104 M-1).

Porphyrin Metal-organic Framework Sensors for Chemical and Biological Sensing.

Porphyrins and porphyrin derivatives have been intensively explored for a number of applications such as sensing, catalysis, adsorption, and photocatalysis due to their outstanding photophysical properties. Their usage in sensing applications, however, is limited by intrinsic defects such as physiological instability and self-quenching. To reduce self-quenching susceptibility, researchers have developed porphyrin metal-organic frameworks (MOFs). Metal-organic frameworks (MOFs), a unique type of hybrid porous coordination polymers comprised of metal ions linked by organic linkers, are gaining popularity. Porphyrin molecules can be integrated into MOFs or employed as organic linkers in the production of MOFs. Porphyrin-based MOFs are a separate branch of the huge MOF family that combines the distinguishing qualities of porphyrins (e.g., fluorescent nature) and MOFs (e.g., high surface area, high porosity) to enable sensing applications with higher sensitivity, specificity, and extended target range. The key synthesis techniques for porphyrin-based MOFs, such as porphyrin@MOFs, porphyrinic MOFs, and composite porphyrinic MOFs, are outlined in this review article. This review article focuses on current advances and breakthroughs in the field of porphyrin-based MOFs for detecting a variety of targets (for example, metal ions, anions, explosives, biomolecules, pH, and toxins). Finally, the issues and potential future uses of this class of emerging materials for sensing applications are reviewed.

Facile Layer Diffusion Technique for Synthesis of Terbium-Based Metal Organic Framework for Fluorometric Sensing of Hydroquinone.

A photoluminescent terbium (III)-based Metal Organic Framework (MOF) was synthesized at room temperature by layer diffusion method utilizing mixed carboxylate linkers (4,4'-oxybis(benzoic acid) and benzene-1,3,5 tricarboxylic acid). Synthesized MOF has crystalline nature and rod-shaped morphology and is thermally stable up to 455 °C. The fluorescence emission spectra and theoretical results revealed that carboxylate linkers functioned as sensitizers for Tb(III) photoluminescence which resulted in four distinct emission peaks at 495, 547, 584, and 621 nm corresponding to the transitions 5D4 → 7F6, 5D4 → 7F5, 5D4 → 7F4, and 5D4 → 7F3. Using synthesized MOF as fluorescent probe, hydroquinone was detected in aqueous medium with a detection limit of 0.048 µM, remarkable recovery (95.6-101.1%), and relative standard deviation less than 2.25%. The quenching phenomenon may be ascribed to electron transfer from synthesized probe to oxidized hydroquinone via carboxylic groups on the surface of MOF, which is further supported by photo-induced electron transfer mechanism. This study introduces a cheaper, faster, and more accurate method for hydroquinone detection.

Pure and Antimony-doped Tin Oxide Nanoparticles for Fluorescence Sensing and Dye Degradation Applications.

Luminescent antimony doped tin oxide nanoparticles have drawn tremendous attention from researchers due to its low cost, chemical inertness and stability. Herein, a quick, facile and economic hydrothermal/solvothermal method was utilized for the preparation of antimony doped (1%, 3%, 5%, 7% and 10%) tin oxide nanoparticles. The antimony doping in a reasonable range can change the properties of SnO2. As such, a lattice distortion increases with increase in doping, which is evidenced through crystallographic studies. It was found that the highest photocatalytic degradation efficiency of malachite green (MG) dye of about 80.86% was achieved with 10% Sb-doped SnO2 in aqueous media due to small particle size. Moreover, 10% Sb-doped SnO2 also showed the highest fluorescence quenching efficiency of about 27% for Cd2+ of concentration 0.11 µg/ml in the drinking water. The limit of detection (LOD) comes out as 0.0152 µg/ml. This sample selectively detected the cadmium ion even in the presence of other heavy metal ions. Notably, 10% Sb-doped SnO2 could appeared as a promising sensor for fast analysis of Cd2+ ions in real samples.

Schiff Base-functionalized Metal-organic Frameworks for Selective Sensing of Chromate and Dichromate in Water.

In this research, Zn- or Cd-based metal-organic frameworks (coded ZnMOF-1 and CdMOF-1) containing benzene-1,4-dicarboxylic acid (H2bdc) and pyridyl-based Schiff base (4-pyridylcarboxaldehydeisonicotinoylhydrazone (L)) dual ligands were successfully assembled via a conventional solvothermal method. The photoluminescence quenching response of ZnMOF-1 and CdMOF-1 and their sensing sensitivity and selectivity towards various inorganic anions were evaluated in aqueous media. Crystallographic and thermogravimetric studies confirm the formation of both MOFs with good crystallinity and thermal stability. Photoluminescence studies also verify the selectivity of ZnMOF-1 and CdMOF-1 for efficient sensing of inorganic oxyanions (like chromate/dichromate: CrO42- and Cr2O72-). Further, it was noted that only chromate/dichromate (CrO42-/Cr2O72-) anions showed a significant turn-off quenching effect while other anions (like F-, Br-, I-, Cl-, ClO4-, SCN-, SO42-, NO3-, and NO2-) have a low/negligible effect on the photoluminescence intensity of both MOFs. The limit of detection (LOD) of chromate/dichromate by ZnMOF-1 and CdMOF-1 was 9.79/10.94 µM and 2.68/1.48 µM, respectively. A probable mechanism for turn-off quenching response towards chromate and dichromate anions could be attributed to the spectral overlap of both excitation and emission spectra of ZnMOF-1/CdMOF-1 with the absorption spectra of chromate/dichromate anions. As a result, the energy transfer from ZnMOF-1 or CdMOF-1 to the target chromate and dichromate anions decreased fluorescence intensity (i.e., fluorescence quenching effect).

Pyrazoline-Based Fluorescent Probe: Synthesis, Characterization, Theoretical Simulation, and Detection of Picric Acid.

2-Pyrazoline containing benzothiazole ring 2-[1-(1,3-benzothiazol-2-yl)-5-(4-methoxyphenyl)-4,5-dihydro-1H-pyrazol-3-yl]phenol (BP) have been synthesized for the effective identification of picric acid over other competing nitro compounds using fluorescence technique. The pyrazoline BP showed quenching efficiency as high as 82% comparative to other nitro aromatics. The limit of detection and limit of quantification were found to be 1.1 µM and 3.3 µM. The possible mechanism with the quenched PA detection efficiency was based on fluorescence energy transfer and photoinduced electron transfer. Moreover, the observed results were supported by the optimized structures of the compounds using the DFT/B3LYP/6-311G/LanL2DZ method. Eventually, the pyrazoline derivative BP was further utilized for natural water samples, showing recoveries in the 87.62-101.09% and RSD was less than 3%.

A Novel Composite of Zinc-based Metal Organic Framework Embedded with SnO2 Nanoparticle as a Photocatalyst for Methylene Blue Dye Degradation as well as Fluorometric Probe for Nitroaromatic Compounds Detection.

A facile bottom up synthesis technique is opted for the preparation of novel composite SnO2@Zn-BTC. This synthesized composite is fully characterized by Fourier Transform Infrared (FTIR) Spectroscopy, Powder X-Ray Diffraction (PXRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDS), and Elemental mapping techniques. Optical analysis was performed using UV-Visible absorption spectroscopy and fluorescence studies. Further this composite was utilized for the first time as a photocatalyst for methylene blue (MB) dye degradation under sunlight irradiation. This photocatalyst shows degradation efficiency of 89% within 100 min of exposure of sunlight. In addition to that, the synthesized composite can be utilized as a fluorescence probe for detection of NACs via 'turn-off" quenching response. This composite is extremely sensitive towards 3-NA in aqueous medium with quenching efficiency of 75.42%, which is highest quenching rate till reported. There occurs no interference for detecting 3-NA in the presence of other NACs. The linear fitting of the Stern-Volmer plot for 3-NA shows large quenching constant (KSV) of 0.0115 ppb-1 with correlation coefficient R2 = 0.9943 proves higher sensitivity of composite in sensing process. The outstanding sensitivity of composite for 3-NA is certified by the low detection limit (LOD) of 25 ppb (0.18 µM). Photoinduced Electron Transfer (PET) and Fluorescence Resonance Energy Transfer (FRET) are the mechanisms used for clarification of quenching response of PL intensity by NACs via density functional theory (DFT) calculations and extent spectral overlap, respectively. Hence, synthesized composite is verified as multi-component system to act as excellent photocatalyst as well as fluorescent sensor.

A Luminescent Cu(II)-MOF with Lewis Basic Schiff Base Sites for the Highly Selective and Sensitive Detection of Fe3+ Ions and Nitrobenzene.

A Schiff base functionalized Cu(II)-based metal-organic framework (MOF) denoted as Cu-L, was developed via a solvothermal method using low-cost starting material, i.e., Schiff base linker, 4,4'-(hydrazine-1,2-diylidenedimethylylidene)dibenzoic acid (L). Good crystallinity and thermal stability of synthesized Cu-L was confirmed by the crystallographic and thermogravimetric studies. An excellent photoluminescent properties of Cu-L ensure their suitability for the ultrafast detection of Fe3+ ions and nitrobenzene via a turn-off quenching response. The remarkable sensitivity of Cu-L towards Fe3+ ions and nitrobenzene was certified by the low limit of detection (LOD) of 47 ppb and 0.004 ppm, respectively. With incorporated free azine groups, this MOF could selectively capture Fe3+ ions and nitrobenzene in aqueous solution. The plausible mechanistic pathway for the quenching in the fluorescence intensity of the Cu-L in the presence of Fe3+ ions and nitrobenzene have been explained in detail through the density functional theory calculations, photo-induced electron transfer (PET), fluorescence resonance energy transfer (FRET), and competitive energy adsorption. This present study open a new avenue to synthesize novel crystalline MOF-based sensing materials from cheap Schiff base linkers for fast sensing of toxic pollutants.

Novel SnO2@Cu3(BTC)2 Composites as a Highly Efficient Photocatalyst and Fluorescent Sensor.

A novel SnO2@Cu3(BTC)2 composite was synthesized using a quick and affordable bottom-up approach via impregnation of SnO2 nanoparticles into the porous Cu3(BTC)2 metal-organic framework (MOF). This composite material is characterized by Fourier transform infrared (FTIR) spectroscopy, powder X-ray diffraction (PXRD) spectra, scanning electron microscope (SEM) analysis, and energy-dispersive X-ray spectroscopy (EDS) analysis. SnO2@Cu3(BTC)2 degraded the methylene blue (MB) dye within 80 min under sunlight with a maximum degradation efficiency of 85.12%. This composite easily recyclable up to five cycles with the retention of its MB degradation efficiency. Moreover, SnO2@Cu3(BTC)2 can be also used efficiently for fast sensing of 2,4,6-trinitrophenol (TNP) in water with noticeable turn-off quenching response. Its limits of detection (LOD) for TNP was 2.82 µM with enhanced selectivity toward TNP (over other NACs) as verified by competitive nitro explosive tests. Density functional theory (DFT) calculations and spectral overlap were used to assess the sensing mechanism. This composite fluorescent sensing system for TNP are demonstrated to have high selectivity and sensitivity. Our findings imply that the prepared low cost SnO2@Cu3(BTC)2 composite can be used as a superior fluorescence sensor and photo catalyst for large scale industrial applications.

Synthesis, Characterization, Analytical Application, and Theoretical Studies of a Schiff Base, (E)-2-(2-aminophenylthio)-N-(Thiophen-2-yl-methylene) Benzenamine.

In this study, a new Schiff base, (E)-2-(2-aminophenylthio)-N-(thiophen-2-yl-methylene) benzenamine was synthesized for selective detection of Hg2+. This Schiff base was characterized by proton nuclear magnetic resonance (1HNMR), carbon-13 nuclear magnetic resonance (13CNMR), and Fourier-transform infrared (FTIR) spectroscopy. Binding interaction between (E)-2-(2-aminophenylthio)-N-(thiophen-2-yl-methylene)benzenamine and various metal ions has been studied by UV-Vis spectroscopic measurements and shows promising coordination towards Hg2+ and almost no interference from other metal ions (Ag+, Mn2+, Fe3+, Al3+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Fe2+ and Cr3+).This Schiff base exhibiting detection limit of 3.8 × 10- 8 M. The Schiff base newly synthesized in this study was successfully applied to the determination of Hg2+ in water samples. In addition to the experimental study, a theoretical study was conducted using Gaussian 09 program to support the experimental findings. FTIR, NMR, bond angle, bond length, torsional angles, and structural approximation were studied using theoretical consideration.

Amine-decorated Zirconium Based Metal Organic Framework for Ultrafast Detection of 2,4,6-Trinitrophenol in Aqueous Samples.

An amine-decorated zirconium based metal organic framework (MOF) UiO-66-NH2 with rod shape morphology was synthesized by solvothermal process using 2-aminoterephthalic acid as an organic linker. Crystallinity of synthesized MOF material was confirmed with PXRD technique. MOF was employed as selective and sensitive sensor for ultra-trace detection of 2,4,6-trinitrophenol (TNP) in aqueous matrix, even in coexistence with other competitive nitroaromatic analytes. High value of Stern-Volmer quenching constant Ksv (1.106 × 105 M- 1), plausible photoluminescent quenching efficiency (97.8%) and lower detection limit (0.95 µM/217ng mL- 1) ascertained extraordinary sensitivity of developed MOF for TNP. Density functional theory calculations and electrostatic interactions (i.e. ionic interaction, H-bonding and π-π interaction) indicated that electron and energy transfer processes play a key role in turn-off quenching response of UiO-66-NH2 sensor. Spiked real samples were analysed to validate the developed method, which satisfactorily established the developed MOF sensor as an efficient tool for analysis.

Efficient Turn-On Zr Based Metal Organic Framework Fluorescent Sensor for Ultrafast Detection of Danofloxacin in Milk Samples.

Metal organic framework, UiO-67 was synthesized by coordinating Zr(IV) with 4,4'-biphenyldicarboxylic acid (BPDC) ligand. Morphology and crystallinity of MOF was confirmed with FE-SEM and PXRD procedure. Danofloxacin (DANO), a veterinary fluoroquinolone antibiotic, was detected in milk by employing UiO-67 as "turn-on" fluorescent sensor. Original photoluminescent (PL) efficiency of UiO-67 sensor was enhanced on its electronic interaction with DANO molecule. Significant PL efficiency enhancement, lower detection limit 0.49 ng/mL (1.37 nM), swift detection (time < 1 min), and excellent linear correlation (R2 = 0.9988) indicated extraordinary sensitivity of developed UiO-67 sensor for DANO. Selectivity and performance of sensor was unaltered in presence of interfering species and detection results were obtained under permissible variation limits. Method applied successfully for ultra-trace detection of DANO residues in milk samples.

Schiff base-functionalized metal-organic frameworks as an efficient adsorbent for the decontamination of heavy metal ions in water.

Adsorptive removal of heavy metal ions from water is an energy- and cost-effective water decontamination technology. Schiff base functionalities can be incorporated into the pore cages of metal-organic frameworks (MOFs) via direct synthesis, post-synthetic modification, and composite formation. Such incorporation can efficiently enhance the interactions between the MOF adsorbent and target heavy metal ions to promote the selective adsorption of the latter. Accordingly, Schiff base-functionalized MOFs have great potential to selectively remove a particular metal ion from the aqueous solutions in the presence of coexisting (interfering) metal ions through the binding sites within their pore cages. Schiff base-functionalized MOFs can bind divalent metal ions (e.g., Pb(II), Co(II), Cu(II), Cd (II), and Hg (II)) more strongly than trivalent metal ions (e.g., Cr(III)). The adsorption capacity range of Schiff base-functionalized MOFs for divalent ions is thus much more broad (22.4-713 mg g-1) than that of trivalent metal ions (118-127 mg g-1). To evaluate the adsorption performance between different adsorbents, the two parameters (i.e., adsorption capacity and partition coefficient (PC)) are derived and used for comparison. Further, the possible interactions between the Schiff base sites and the target heavy metal ions are discussed to help understand the associated removal mechanisms. This review delivers actionable knowledge for developing Schiff-base functionalized MOFs toward the adsorptive removal of heavy metal ions in water in line with their performance evaluation and associated removal mechanisms. Finally, this review highlights the challenges and forthcoming research and development needs of Schiff base-functionalized MOFs for diverse fields of operations.

Experimental and Theoretical Studies of the Pyrazoline Derivative 5-(4-methylphenyl)-3-(5-methylfuran-2-yl)-1-phenyl-4,5-dihydro-1H-Pyrazole and its Application for Selective Detection of Cd2+ ion as Fluorescent Sensor.

A simple fluorescent chemosensor 5-(4-methylphenyl)-3-(5-methylfuran-2-yl)-1-phenyl-4, 5-dihydro-1H-pyrazole (PY) has been synthesized for the detection of Cd2+ ion.The fluorescent probe PY shows high selectivity for Cd2+in the presence of othermetal ions (Co2+, Cu2+, Hg2+, Mn2+, Zn2+, Fe3+, Pb2+, Ni2+, and Al3+). The fluorescence intensity of the PY has been strongly quenched with increasing concentration of Cd2+ (0-0.9 µM)via photoinduced electron transfer mechanism. The binding constant of Cd2+ to PY for the 1:1 complex isfound to be 5.3 × 105 M-1with a detection limit of 0.09 µM. The chemosensor was successfully applied for determination of Cd2+ in different water samples (tap, river, and bottled water) showing good recovery values in the range of 94.8-101.7% with RSD less than 3%. Density functional theory (DFT) calculations were also performed to investigate electronic and spectral characteristics which are quite agreeable with the experimental value. The results show that the synthesized fluorescent chemosensor shows good selectivity towards Cd2+ and can be readily applied for the detection of Cd2+ in real samples including water samples.

A Novel Method for the Synthesis of MOF-199 for Sensing and Photocatalytic Applications.

Multifunctional Cu (II)-based Metal Organic Framework (MOF) [Cu3(BTC)2] has been synthesized by a facile electrochemical method. Crystallographic and morphological characterizations of synthesized MOF have been done using Powder X-ray Diffractometer and Scanning Electron Microscope (SEM), respectively, whereas Fourier Transform Infrared Spectroscopy (FT-IR), Energy Dispersive X-ray Spectroscopy (EDS), UV-Vis Absorption Spectroscopy and Energy Resolved Luminescence Spectroscopic studies have been used for the detailed qualitative, quantitative as well as optical analyses. Sharp PXRD peaks indicate the formation of highly crystalline MOF with face centered cubic (fcc) structure. Flakes (average length = 0.71 µm and width = 0.10 µm) and rods (average aspect ratio = ((0.1:8.3) µm) like morphologies have been observed in SEM micrographs. The presence of C, O and Cu has been confirmed by EDS analysis. Photocatalytic activity potential of the synthesized MOF has been tested using methylene blue dye (MB) as a test contaminant in aqueous media under sunlight irradiation. Selective and sensitive fluorescent sensing of different Nitroaromatic compounds (NACs) like 4-Nitroaniline (4-NA), 2-Nitroaniline (2-NA), 3-Nitroaniline (3-NA), 4-Nitrotoulene (4-NT), 2,4-Dinitrotoulene (2,4-DNT), 1,3-Dinitrobenzene (1,3-DNB), 2,6- Dinitrotoulene (2,6-DNT) has been done by exploring the photoluminescent behaviour of chemically stable Cu3(BTC)2. Synthesized MOF is extremely sensitive towards 4-NA, which is having PL quenching efficiency of 82.61% with highest quenching rate till reported. Indeed, a large quenching coefficient KSV = 34.02 × 10-7 M-1 and correlation coefficient R2 = 0.9962 in KSV plot have been elucidated with limit of detection (LOD) = 0.7544 ppb. The possible ways of luminescence quenching are successfully explained by the combination of Photoinduced Electron Transfer (PET) and Resonance Energy Transfer (RET) mechanisms. Additionally, the Density Functional Theory (DFT) calculations have been employed to support the experimental results. Cu3(BTC)2 fully demonstrates the power of a multi component MOF, which provides a feasible pathway for the design of novel material towards fast responding luminescence sensing and photocatalytic degradation of pollutants.

Synchronous Fluorescence Determination of Al3+ Using 3-Hydroxy-2-(4-Methoxy Phenyl)-4H-Chromen-4-One as a Fluorescent Probe.

A simple synchronous fluorescent chemosensor 3-hydroxy-2-(4-methoxyphenyl)-4H-chromen-4-one (3-HC) has been synthesized for the selective analysis of Al3+. On the addition of Al3+, 3-HC displayed a redshift with a change in wavelength of emission maximum from 436 to 465 nm along with enhancement in fluorescence intensity, which formed the basis for its sensitive detection. Under optimized conditions, 3-HC was applied for the determination of Al3+ in the concentration range of 1 × 10-7-1 × 10-6 M. The limit of detection (LOD) and limit of quantification (LOQ) values were found out to be 1.69 × 10-8 and 5.07 × 10-8 M respectively. Further, the developed method was applied for the analysis of Al3+ in real water samples (tap water, bottled water, and tube well water) which showed good recovery values in the range of 95-99.7% with RSD less than 4%.

Fluorescence "Turn-off" Sensing of Iron (III) Ions Utilizing Pyrazoline Based Sensor: Experimental and Computational Study.

A simple pyrazoline-based ''turn off'' fluorescent sensor 5-(4-methoxyphenyl)-3-(5-methylfuran-2-yl)-1-phenyl-4,5-dihydro-1H-pyrazole (PFM) was synthesized and well characterized by different techniques such as FT-IR, 1H-NMR, 13C-NMR, and mass spectrometry. The synthesized sensor PFM was utilized for the detection of Fe3+ ions. Fluorescence emission selectively quenched by Fe3+ ions compared to other metal ions (Mn2+, Al3+, Fe2+, Hg2+, Cu2+, Co2+, Ni2+, Cd2+, Pb2+, and Zn2+) via paramagnetic fluorescence quenching and showed good anti-interference ability over the existence of other tested metals. Under optimum conditions, the fluorescence intensity of sensor quenched by Fe3+ in the range of 0 to 3 µM with detection limit of 0.12 µM. Binding of Fe3+ ions to PFM solution were studied by fluorescent titration, revealed formation of 1:1 PFM-Fe metal complex and binding constant of complex was found to be of 1.3 × 105 M-1. Further, the fluorescent sensor has been potentially used for the detection of Fe3+ in environmental samples (river water, tap water, and sewage waste water) with satisfactory recovery values of 99-101%.

Bis(thiophen-2-yl-methylene) Benzene-1, 4-Diamine as Fluorescent Probe for the Detection of Fe3+ in Aqueous Samples.

A Schiff base bis(thiophen-2-yl-methylene)benzene-1, 4-diamine (L) was synthesized and used for selective and sensitive detection of Fe3+. L exhibited enhanced fluorescence response at excitation of 365 nm and emission wavelength of 440 nm for Fe3+. The formation of a 1:1 complex between L and Fe3+ was suggested by Job's plot by fluorescence titration and from optimized structures using Density functional theory (DFT). The fluorescence intensity was directly proportional to concentration of Fe3+ (R2 = 0.999) with the detection limit of 3.8 × 10-7 M and the binding constant of 1.20 × 104 M-1 at pH = 6.0. The probe was used to detect Fe3+ in different water samples with the percentage recovery of 99.7-103%. The interference of the other cations are < 5%.

Progress in pre-treatment and extraction of organic and inorganic pollutants by layered double hydroxide for trace-level analysis.

Continuous release of pollutants into the environment poses serious threats to environmental sustainability and human health. For trace-level analysis of pollutants, layered double hydroxide (LDH) is an attractive option to impart enhanced sorption capability and sensitivity toward pollutants because of its unique layered structure, tunable interior architecture, high anion-exchange capacities, and high porosity (e.g., Zn/Cr LDH/DABCO-IL, Ni/Al LDH, CS-Ni/Fe LDH, SDS-Fe3O4@SiO2@Mg-Al LDH, Boeh/Mg/Al LDH/pC, and Fe@NiAl LDH). In concert with the well-defined analytical methodologies (e.g., HPLC and GC), the LDH materials can be employed to detect trace-level targets (e.g., as low as âˆ¼ 20 fg/L for phenols) in aqueous environments. This review highlights LDH as a promising material for pre-treatment of a variety of organic and inorganic target pollutants in complex real matrices. Challenges and future requirements for research into LDH-based analytical methods are also discussed.

Synthesis of Copper Metal Organic Framework Based on Schiff Base Tricarboxylate Ligand for Highly Selective and Sensitive Detection of 2,4,6-Trinitrophenol in Aqueous Medium.

By using Schiff base tricarboxylate ligand 5-(4-carboxybenzylideneamino)isophthalic acid (H3CIP), a new imine functionalized copper metal organic framework (MOF) has been synthesized solvothermally. It was fully characterized by Fourier Transform Infrared (FTIR) Spectroscopy, Powder X-Ray Diffraction (PXRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDS), and elemental mapping techniques. The as-synthesized MOF has been utilized as fluorescent probe for detection of nitro aromatic explosives (NAEs). The results show that the copper MOF can be developed into highly selective and sensitive sensor for detection of TNP in the aqueous medium via the "turn-off" quenching response. The linear fitting of the Stern-Volmer plot for TNP offered large quenching constant of 1.07 × 104 M-1 for Cu-MOF indicating the high sensitivity of the sensing process. Outstanding sensitivity of prepared material towards TNP detection was further validated by the low detection limit of 80 ppb (0.35 µM). The detailed mechanistic studies for their mode of action and density functional theory (DFT) calculations reveals that photo-induced electron transfer (PET) and fluorescence resonance energy transfer (FRET) processes, as well as electrostatic interactions (i.e. H-bonding) are the key factors for the turn-off response toward TNP by this fluorescent sensor. Thus, this new LMOF owing to their high water stability and remarkable functional features are potential candidates which can be developed into selective and sensitive TNP detection devices.