A recyclable luminescent MOF sensor for on-site detection of insecticide dinotefuran and anti-Parkinson's drug entacapone in various environmental and biological specimens.

The monitoring and precise determination of pesticides and pharmaceutical drugs and their residues have become increasingly important in the field of food safety and water contamination issues. Herein, a fluorescent aluminium MOF sensor (1) was developed for the selective recognition of neonicotinoid insecticide dinotefuran and anti-Parkinson's drug entacapone. Guest-free MOF 1' exhibited ultra-fast response (< 5 s) and ultra-low detection limits of 2.3 and 7.6 nM for dinotefuran and entacapone, which are lower than the previously reported MOF sensors. In the presence of other competitive analytes, great selectivity was achieved towards both analytes. The probe was recyclable up to five cycles. The sensing ability was explored towards entacapone in human serum, urine and dinotefuran in real soil, rice, honey samples, different fruits, vegetables, real water specimens and a wide range of pH media. A low-cost, handy MOF-based polymer thin-film composite (1'@PVDF-PVP) was developed for the on-site detection of dinotefuran and entacapone. Mechanistic studies involving analytical techniques and theoretical calculations suggested that FRET and PET are the probable reasons for entacapone sensing whereas IFE is responsible for dinotefuran detection. The entire work presents a low cost, multi-use photoluminescent sensor of entacapone and dinotefuran to address the environmental pollution.

Naphthalimide functionalized metal-organic framework for rapid and nanomolar level detection of hydrazine and anti-hypertensive drug nicardipine.

The increasing utilization of hydrazine and its derivatives across diverse sectors highlights the pressing need for efficient detection methods to safeguard human health and the environment. Likewise, nicardipine, a widely used medication for heart diseases, necessitates accurate sensing techniques for clinical research and therapeutic monitoring. Here, we propose a novel approach using a naphthalimide-functionalized Zr-MOF as a fluorometric probe capable of detecting both hydrazine and nicardipine in aqueous medium. Our designed probe exhibited a significant 31-fold increase in fluorescence intensity upon interaction with hydrazine. At the same time, nicardipine induced 86% fluorescence quenching with an exceptionally rapid response time (100 s for hydrazine and 5 s for nicardipine). The designed probe has the ability to detect both analytes at nanomolar concentrations (LOD for hydrazine is 1.11 nM while that for nicardipine is 9.6 nM). Investigation across various wastewater samples and pH conditions further validated its practical utility. The mechanism behind fluorometric sensing of nicardipine was thoroughly investigated using modern instrumentation. Our study presents a versatile and effective approach for detecting hydrazine and nicardipine, addressing crucial needs in both industrial and biomedical contexts.

Functional Group-Assisted Fluorescence Sensing Platform for Nanomolar-Level Detection of an Antineoplastic Drug and a Neurotransmitter from Environmental Water and Human Biofluids.

A fast, sensitive, selective, and biocompatible dual sensor of an antineoplastic medication (methotrexate) and a neurotransmitter (adrenaline) is still being searched by present-day scientists. To overcome this issue, we have designed a functionalized, robust, bio-friendly luminescent MOF for the sensitive, selective, and rapid monitoring of methotrexate and adrenaline. This probe is the first ever reported MOF-based fluorescence sensor of methotrexate and second only for adrenaline. This fluorescence probe has a very low limit of detection (LOD) of 0.34 and 11.2 nM for adrenaline and methotrexate, respectively. The sensor can detect both the targeted analytes rapidly within 5 s. It can also detect adrenaline and methotrexate from human blood serum and urine accurately and precisely. This reusable sensor is equally efficient in detecting methotrexate from environmental water specimens. Biocompatible, user-friendly, and inexpensive chitosan@MOF@cotton composites were fabricated for the detection of adrenaline and methotrexate from the nanomolar to the micromolar range by the naked eye under a fluorescence lamp. This probe displayed high reproducibility, precision, and accuracy in sensing methotrexate and adrenaline. Fluorescence resonance energy transfer (FRET) and the inner filter effect (IFE) are the possible mechanisms for adrenaline and methotrexate sensing, respectively. The possible mechanism was supported by using required instrumental techniques and theoretical simulations.

Hf-Based MOF for Rapid and Selective Sensing of a Nerve Agent Simulant and an Aminophenol: Insights from Experiments and Theory.

The metal-organic framework (MOF) Hf-DUT-52 was prepared with diamino functionality by the solvothermal method. This material displayed fluorometric sensing ability toward a nerve agent simulant (diethyl chlorophosphate (DCP)) and 3-diethylaminophenol (3-DEAP). It is the first-ever reported fluorescent MOF sensor for DCP and 3-DEAP. Apart from a fast response (<5 s), the sensor had a very low detection limit for both DCP and DEAP (limit of detection (LOD) values for DCP and 3-DEAP sensing were 9 and 125 nM, respectively). The obtained detection limit is the second lowest among all of the reported optical sensors for DCP. The sensor also displayed its capability to identify the presence of trace amount of DCP in various natural water specimens with good selectivity. Moreover, MOF@cotton composites were developed for visual, on-site, nanomolar-level detection of both targeted analytes. Furthermore, a MOF@PVA thin film was fabricated and successfully utilized for the detection of highly volatile and deadly poisonous DCP in the vapor phase. The sensor was also recyclable for up to five cycles without losing appreciable efficiency. Density functional theory (DFT)-based periodic and cluster calculations were performed to shed light on the sensing ability of the MOF by studying the interactions of DCP and DEAP with the MOF. Our theoretical results reveal the importance of linker defects and water chemisorption on the adsorption/complexation of the analytes at uncoordinated Hf sites.

MOF-Fabric Composites Based on a Multi-Functional MOF as Luminescent Sensors for a Neurotransmitter and an Anti-Cancer Drug.

A biocompatible, reliable, fast, and nanomolar-level dual-functional sensor for a neurotransmitter (e.g., adrenaline) and an anti-cancer drug (e.g., 6-mercaptopurine (6-MP)) is still far away from the hand of modern-day researchers. To address this issue, we synthesized an aqua-stable, bio-friendly, thiourea-functionalized Zr(IV) metal-organic framework (MOF) for selective, rapid sensing of adrenaline and 6-MP with ultra-low limit of detection (LOD for adrenaline = 1.9 nM and LOD for 6-MP = 28 pM). This is the first MOF-based fluorescent sensor of both the targeted analytes. The sensor not only can detect adrenaline in HEPES buffer medium but also in different bio-fluids (e.g., human urine and blood serum) and pH media. It also exhibited 6-MP sensing ability in aqueous medium and in various wastewater specimens and pH solutions. For the quick and on-site detection of this neuro-messenger (adrenaline) and the drug (6-MP), cost-effective sensor-coated cotton fabric composites were fabricated. The MOF@cotton fabric composite is capable of detecting both the analytes up to the nanomolar level by the naked eye under UV light. The sensor can be recycled up to five times without significantly losing its efficiency. The Förster resonance energy transfer in the presence of adrenaline and inner-filter effect in the presence of 6-MP are the most likely reasons behind the quenching of the MOF's fluorescence intensity, which were proved with the help of appropriate instrumental techniques.

Functionalized Metal-Organic Framework for Selective Fluorometric Detection of Sodium Dodecyl Sulfate and Vitamin B12 Using MOF@Cotton Composites and Lewis Base-Catalyzed Condensation Reaction.

A zirconium(IV)-based metal-organic framework (MOF) fluorophore containing the 2,5-diaminoterephthalic acid (H2BDC-(NH)2) linker was synthesized and characterized. The physicochemically stable, porous (SBET = 504 m2 g-1) MOF (1') exhibited selective and sensitive fluorescence turn-on behavior toward the sodium dodecyl sulfate (SDS) surfactant and turn-off response toward vitamin B12. This is the first ever reported MOF-based dual optical sensor of SDS and vitamin B12. Other competitive analytes did not interfere in the detection of both the analytes. Along with the lowest ever reported limit of detection (LOD) values (LOD for SDS = 108 nM and LOD for vitamin B12 = 45.3 nM), 1' displayed short response time for SDS (50 s) and vitamin B12 (5 s) detection. The MOF was able to detect SDS in various real water samples and vitamin B12 in various bio-fluids (urine and serum) and pH media. A MOF-coated cotton composite was fabricated, which displayed a visible color change under UV light even after treating it with a nanomolar concentration of both the analytes. The sensor displayed excellent reusability up to five cycles of sensing. Various experimental outcomes evidenced that the electrostatic interaction between the -NH2 groups of the linker and the -SO3- group of SDS is the possible reason for the selective SDS sensing. For vitamin B12, the energy transfer from the probe to vitamin B12 resulted in fluorescence quenching. In addition, the catalytic performance of 1' was investigated in the condensation reaction between benzaldehyde derivatives with cyanoacetamide with high yields in ethanol at 70 °C. The solid was used for three cycles with no decrease in its activity and selectivity. PXRD and FESEM analysis before and after the reaction suggested the retention of the crystallinity of 1', thus indicating catalyst stability.

A fluorophore anchored MOF for fast and sensitive sensing of Cu(II) and 3-nitrotyrosine in a physiological medium.

We report the solvothermal synthesis of a dansyl anchored hafnium based fluorescent metal-organic framework (MOF) having the formula [Hf6O4(OH)4(L)6]·H2O·6DMF (H2L = 2-((5-(dimethylamino)naphthalene)-1-sulfonamido)terephthalic acid). The synthesized material showed high fluorescence emission properties as well as high thermal (stable up to 330 °C) and chemical stability. It also exhibited a wide range of pH tolerance as well as a high BET surface area of 703 m2 g-1. The activated MOF showed ultra-fast (detection time < 10 s) and ultra-sensitive sensing properties towards Cu(II) and the biologically important biomarker 3-nitrotyrosine (3-NTyr) in a HEPES medium at a physiological pH of 7.4. Along with high selectivity, very low detection limits of 229 nM and 539 nM were obtained for Cu(II) and 3-NTyr respectively. Furthermore, this probe was utilised for the detection and quantification of Cu(II) and 3-NTyr in biosamples (urine and serum) with very low RSD values (2.3-4.8%). Additionally, this probe was employed to detect the presence of Cu(II) as a pollutant in various environmental water samples. Furthermore, for rapid economic detection of Cu(II), a MOF coated fluorescent paper strip was demonstrated. Thorough mechanistic investigations displayed that a complexometric interaction between Cu(II) and the probe is the main reason for the quenching of fluorescence intensity. This proposed mechanism was well supported by experimental evidence. On the other hand, the FRET mechanism is proposed based on the experimental observations for dynamic quenching of the fluorescence intensity of the probe in the presence of 3-NTyr.

Metal-Organic-Framework-Based Chemosensor for Ultrafast and Ultrasensitive Detection of Pd2+ Ions in Water, Real Specimens, and Test Strips.

A new ultrasensitive and ultrafast Al(III) metal-organic-framework (MOF)-based probe (1) was constructed to detect Pd2+ ions. Extremely selective recognition of Pd2+ ion was demonstrated by the guest-free compound 1 (called 1') using a fluorescence signal. The quenching in the fluorescence signal was observed due to the weak interaction between the linker alkyne-π bond and Pd2+. The mechanism of isophthalic alkyne-π and Pd2+ interaction was systematically examined with the help of isothermal titration calorimetry (ITC), X-ray photoelectron spectroscopy (XPS), and UV-vis spectroscopy. The response time of the MOF for sensing of Pd2+ was 30 s, which is the lowest response time for MOF-based Pd2+ sensing to date, with an ultralow detection limit (102 nM) and Stern-Volmer constant (4.39 × 103 M-1), evidencing the outstanding ability to sense Pd2+ ion by this probe. The Pd2+ detection limit falls among the lowest values. Activated MOF (1') also showed considerable recyclability up to five steps with a constant sensing ability. In different water resources (Milli-Q water, lake water, river water, and tap water), the probe also showed excellent sensing ability. A paper-strip device was developed for the applicability of our material for the real field sensing application of Pd2+. The relevance of 1' is not only up to Pd2+, but it could also sense palladium in other possible oxidation states.

Diamino group-functionalized Zr-based metal-organic framework for fluorescence sensing of free chlorine in the aqueous phase and Knoevenagel condensation.

We developed a porous diamino group-functionalized Zr(IV) metal-organic framework (MOF). The synthesized MOF has a similar structure to DUT-52 (DUT = Dresden University of Technology), which has a face-centered cubic structure with an Fm3̄m space group. The synthesized material (DUT-52-(NH2)2-1) was solvent exchanged with methanol (MeOH) and activated at 100 °C overnight. Both the as-synthesized and activated materials (DUT-52-(NH2)2-1') are thermally stable until 300 °C. The Brunauer-Emmett-Teller (BET) surface area of DUT-52-(NH2)2-1' was found to be 413 m2 g-1. DUT-52-(NH2)2-1' showed a significant quenching of fluorescence response after coming in contact with free chlorine (ClO-) in an aqueous medium. The selectivity of DUT-52-(NH2)2-1' towards ClO- was not significantly hampered in the presence of any competitive ion. The limit of detection (LOD) value was found to be 0.08 µM in phosphate-buffered saline (PBS, pH = 7.4). DUT-52-(NH2)2-1' is recyclable and very sensitive towards ClO-. Moreover, the paper strip method was developed for onsite identification of ClO-. Furthermore, the catalytic activity of DUT-52-(NH2)2-1' was tested in the Knoevenagel condensation between benzaldehyde and cyanoacetamide. The experimental results clearly indicate that DUT-52-(NH2)2-1' exhibits high activity with very high selectivity towards condensation products. The solid was reusable three times with no decay in its activity, as evidenced by powder X-ray diffraction (PXRD), field emission scanning electron microscopy (FE-SEM) and fourier transform infrared (FT-IR).

Ultrafast and nanomolar level detection of H2S in aqueous medium using a functionalized UiO-66 metal-organic framework based fluorescent chemosensor.

Here, we present a 4-nitrophenyl functionalized Zr-UiO-66 MOF (MOF = metal-organic framework) and its applications towards the selective, sensitive and rapid detection of H2S both in the aqueous medium and vapour phase. The MOF material was synthesized using the 2-(nitrophenoxy)terepththalic acid (H2BDC-O-Ph-NO2) linker and ZrCl4 salt in the presence of a benzoic acid modulator. It was carefully characterized by thermogravimetric analysis (TGA), elemental analysis, powder X-ray diffraction (PXRD), FT-IR spectroscopy and surface area analysis. Noticeable thermal stability up to a temperature of 390 °C under air and the considerable chemical stability in different liquid media (H2O, 1 M HCl, glacial acetic acid, NaOH in the pH = 8 to 10 range) confirmed the robustness of the MOF. The BET surface area (1040 m2 g-1) indicated the porous nature of the MOF. Remarkable selectivity of the MOF towards H2S over other potential congeners of H2S was observed in the aqueous medium. A very high fluorescence increment (∼77 fold) was observed after adding an aqueous Na2S solution to the MOF suspension. The MOF probe displayed the lowest limit of detection (12.58 nM) among the existing MOF-based chemosensors of H2S. Furthermore, it exhibited a very quick (60 s) response towards H2S detection. The MOF compound could also detect H2S in the vapour phase as well as in real water samples. Furthermore, we developed inexpensive MOF-coated paper strips for the naked-eye sensing of H2S. A thorough investigation was carried out in order to elucidate the fluorescence turn-on sensing mechanism.

A Zr-Based Metal-Organic Framework with a DUT-52 Structure Containing a Trifluoroacetamido-Functionalized Linker for Aqueous Phase Fluorescence Sensing of the Cyanide Ion and Aerobic Oxidation of Cyclohexane.

A zirconium (Zr) metal-organic framework having a DUT-52 (DUT stands for Dresden University of Technology) structure with face-centered cubic topology and bearing the rigid 1-(2,2,2-trifluoroacetamido) naphthalene-3,7-dicarboxylic acid (H2NDC-NHCOCF3) ligand was prepared, and its solid structure was characterized with the help of the X-ray powder diffraction (XRPD) technique. Other characterization methods like thermogravimetric analysis (TGA) and Fourier transform infrared (FT-IR) spectroscopy were applied to verify the phase purity of the compound. In order to get the solvent-free compound (1'), 1 was stirred with methanol for overnight and subsequently heated at 100 °C overnight under vacuum. As-synthesized (1) and activated (1') compounds are thermally stable up to 300 °C. The Brunsuer Emmett-Teller (BET) surface area of 1' was found to be 1105 m2 g-1. Fluorescence titration experiments showed that 1' exhibits highly selective and sensitive fluorescence turn-on behavior toward cyanide (CN-) anion. The interference experiments suggested that other anions did not interfere in the detection of CN-. Moreover, a very short response time (2 min) was shown by probe 1' for CN- detection. The detection limit was found to be 0.23 µM. 1' can also be effectively used for CN- detection in real water samples. The mechanism for the selective detection of CN- was investigated systematically. Furthermore, the aerobic oxidation of cyclohexane was performed with 1' under mild reaction conditions, observing higher activity than the analogous DUT-52 solid under identical conditions. These experiments clearly indicate the benefits of hydrophobic cavities of 1' in achieving higher conversion of cyclohexane and cyclohexanol/cyclohexanone selectivity. Catalyst stability was proved by two consecutive reuses and comparing the structural integrity of 1' before and after reuses by the XRPD study.

Metal-Organic Framework (MOF) Derived Recyclable, Superhydrophobic Composite of Cotton Fabrics for the Facile Removal of Oil Spills.

Marine oil spill cleanup is one of the major challenges in recent years due to its detrimental effect on our ecosystem. Hence, the development of new superhydrophobic oil absorbent materials is in high demand. The third-generation porous materials, namely metal-organic frameworks (MOFs), have drawn great attention due to their fascinating properties. In this work, a superhydrophobic MOF with UiO-66 (SH-UiO-66) topology was synthesized strategically with a new fluorinated dicarboxylate linker to absorb oil selectively from water. The fully characterized superhydrophobic MOF showed extreme water repellency with an advancing water contact angle (WCA) of 160° with a contact angle hysteresis (CAH) of 8°. The newly synthesized porous MOF (SBET = 873 m2 g-1) material with high WCA found its promising application in oil/water separation. The superhydrophobic SH-UiO-66 MOF was further used for the in-situ coating on naturally abundant cotton fiber to make a superhydrophobic MOF@cotton composite material. The MOF-coated cotton fiber composite (SH-UiO-66@CFs) showed water repellency with a WCA of 163° and a low CAH of 4°. The flexible superhydrophobic SH-UiO-66@CFs showed an oil absorption capacity more than 2500 wt % for both heavy and light oils at room temperature. The superoleophilicity of SH-UiO-66@CFs was further exploited to separate light floating oil as well as sedimentary heavy oil from water. SH-UiO-66@CFs material can also separate oil from the oil/water mixture by gravity-directed active filtration. Hence, the newly developed MOF-based composite material has high potential as an oil absorbent material for marine oil spill cleanup.

An Anthracene-Based Metal-Organic Framework for Selective Photo-Reduction of Carbon Dioxide to Formic Acid Coupled with Water Oxidation.

A Zr-based metal-organic framework has been synthesized and employed as a catalyst for photochemical carbon dioxide reduction coupled with water oxidation. The catalyst shows significant carbon dioxide reduction property with concomitant water oxidation. The catalyst has broad visible light as well as UV light absorption property, which is further confirmed from electronic absorption spectroscopy. Formic acid was the only reduced product from carbon dioxide with a turn-over frequency (TOF) of 0.69 h-1 in addition to oxygen, which was produced with a TOF of 0.54 h-1 . No external photosensitizer is used and the ligand itself acts as the light harvester. The efficient and selective photochemical carbon dioxide reduction to formic acid with concomitant water oxidation using Zr-based MOF as catalyst is thus demonstrated here.

An acetoxy functionalized Al(III) based metal-organic framework showing selective "turn on" detection of perborate in environmental samples.

Here, we have described the design, preparation and detailed characterization of a new acetoxy functionalized aluminium based metal-organic framework (MOF) called CAU-10-OCOCH3 (1) (CAU stands for Christian-Albrechts-University). The desolvated compound was employed for the detection of perborate in a pure aqueous environment. The presented MOF based perborate sensing probe (1) was synthesized by employing 5-acetoxyisophthalic acid and AlCl3·6H2O as the linker molecule and metal salt source, respectively, in DMF/H2O medium at 120 °C for 12 h. The material (1') showed a very selective fluorescent turn-on response towards perborate in aqueous medium with the coexistence of several competitive analytes. A dramatic increment (65 fold) in emission intensity of the probe was observed within 5 min of the addition of perborate. A chemo-selective reaction between perborate and the acetoxy functionality and subsequent hydrolysis of the acetoxy group to the hydroxy group is the main cause of the turn-on nature of detection. The material showed a detection limit of 1.19 µM. The probe was also applied for the recognition of perborate in several environmental water samples. The material is the first ever MOF based probe for selective detection of perborate.

Rational design of a functionalized aluminum metal-organic framework as a turn-off fluorescence sensor for α-ketoglutaric acid.

A 3D metal-organic framework (MOF) called Al-DUT-5-N2H3 (1) (DUT: Dresden University of Technology) was prepared hydrothermally using Al(iii) salt and a hydrazinyl functionalized linker called 2-hydrazinyl-[1,1'-biphenyl]-4,4'-dicarboxylic acid (BPDC-N2H3). Material 1 was successfully characterized by X-ray powder diffraction (XRPD), FT-IR spectroscopy, N2 sorption (BET) experiment, thermogravimetric analysis (TGA), EDX and FE-SEM analyses. The activated form of material 1 (called 1') was achieved by a direct heating process. Material 1' was successfully employed for the solution-phase fluorescence detection of α-ketoglutaric acid (α-KG). It showed high detection performance even when there were other competitive analytes present in the mixture. Material 1' is the first MOF-based fluorescent turn-off sensor for the detection of α-KG. The response time for α-KG is exceptionally low (60 s) as compared to any other reported α-KG sensor. The limit of detection (LOD) was found to be 0.61 µM, which is far better as compared to any other reported sensor for α-KG to date. The mechanism for α-KG sensing was thoroughly investigated and proposed to be PET (photoinduced electron transfer) process by TD-DFT (time-dependent DFT) calculations.

Rapid switch-on fluorescent detection of nanomolar-level hydrazine in water by a diacetoxy-functionalized MOF: application in paper strips and environmental samples.

Here, we present a new diacetoxy-functionalized UiO-66 metal-organic framework (MOF) for the trace level detection of hydrazine in water. The MOF material (1) was solvothermally prepared by the reaction between ZrOCl2·8H2O and 2,5-diacetoxy-1,4-benzenedicarboxylic acid (H2BDC-(OCOCH3)2). The desolvated material (1') showed a highly selective fluorescent turn-on signal towards hydrazine in water, which can be visualized by the naked eye under a UV lamp. Within 1 min of hydrazine addition, there was 14-fold fluorescence enhancement. The probe can detect hydrazine up to the nanomolar level (detection limit = 78.8 nM) in water. This detection limit is the lowest among MOF-based fluorescent probes for hydrazine. The material was also utilized for the sensing of hydrazine in paper strips and environmental water samples. Hydrazine-selective deprotection of ester groups anchored with the ligand is the principal reason behind the switch-on nature of sensing.

Post-synthetic modification of a metal-organic framework with a chemodosimeter for the rapid detection of lethal cyanide via dual emission.

A new Hf(iv) based metal-organic framework with the UiO-66 (UiO = University of Oslo) topology was prepared via a standard modulated solvothermal reaction. The weakly emissive MOF material was well characterized via various analytical techniques. The parent MOF was then post-synthetically modified with a highly emissive pyrene based chemodosimeter probe without altering the parent framework structure. The incorporation of the chemodosimeter in the modified MOF material was successfully confirmed by using FT-IR and 1H NMR spectroscopy. The emission behaviour of the parent MOF was changed drastically with a noticeable colour change after post-synthetic modification. After modification, the MOF material showed a very selective colorimetric and fluorometric dual-emissive response towards lethal cyanide ions. A large blue shift (Δλ = 127 nm) was observed in the emission spectra which can be also visualized with the naked eye under a hand held UV lamp. The presence of a vinyl functional group in the chemodosimeter can serve as a potential nucleophilic reaction centre, which was also confirmed by the DFT calculations. The reaction based sensing mechanism of the MOF material was successfully confirmed by 1H NMR spectroscopy. Furthermore, to apply the modified MOF material in real life, the test strip based sensing of cyanide in drinking water was demonstrated.

A Thiophene-2-carboxamide-Functionalized Zr(IV) Organic Framework as a Prolific and Recyclable Heterogeneous Catalyst for Regioselective Ring Opening of Epoxides.

A new thiophene-2-carboxamide-functionalized Zr-UiO-66 MOF (1) was synthesized by employing a traditional solvothermal procedure. Compound 1 displayed high thermal (up to 340 °C under an Ar atmosphere) and chemical stability (in water, 1 M HCl, and acetic acid). A nitrogen physisorption measurement with the activated form of 1 (denoted 1') exhibited a BET surface area (781 m2/g) despite attachment of a bulky side chain with the linker molecule. Compound 1' was able to heterogeneously catalyze the ring-opening reaction of epoxides with  amines. Catalyst 1' exhibited significant yields as well as wide substrate scope in the ring opening of epoxides by means of amines. It also displayed better catalytic performance in comparison to known MOF catalysts such as Cu3(BTC)2, Fe(BTC) (BTC: 1, 3, 5-benzenetricarboxylate), and Zr-UiO-66. Control experiments were performed with free linker,  Zr(IV) salt and without catalyst 1', confirming the exclusive role of 1' in the catalytic reaction. The reusability characteristics of catalyst 1' was established for up to five consecutive catalytic cycles. The synthesis and characterization of the linker molecule, material 1, and 1' and mechanism of the catalysis reaction were studied elaborately.

A functionalized UiO-66 MOF for turn-on fluorescence sensing of superoxide in water and efficient catalysis for Knoevenagel condensation.

In the present work, a new MOF material of the UiO-family called Zr-UiO-66-NH-CH2-Py (1) has been obtained by the solvothermal technique and successfully characterized. The MOF structure was assembled with 2-((pyridin-4-ylmethyl) amino) terephthalic acid (H2BDC-NH-CH2-Py) as linker and Zr4+ ion. The activated form of 1 (called 1') exhibits considerable thermal and chemical stability. Compound 1' showed a very rapid and selective response for the fluorometric sensing of superoxide (O2·-) in aqueous medium even in the presence of the potentially competitive reactive oxygen species (ROS). The limit of detection value for O2·- sensing is 0.21 µM, which is comparable with those of the reported O2·- sensors. This is the first MOF based fluorescent sensor for the detection of O2·-. The response time of this MOF sensor for O2·- is very short (240 s). On the other hand, 1' was employed as a solid heterogeneous catalyst for Knoevenagel condensation between benzaldehyde and ethyl cyanoacetate at 80 °C in ethanol resulting in a very high yield of the desired product. The effects of the esterified linker ((CH3)2BDC-NH-CH2-Py) and the corresponding metal salt (ZrCl4) on this catalytic reaction were examined separately. We have also tested the substrate scope elaborately for the catalytic reaction promoted by catalyst 1'.

Structural Diversity in Supramolecular Organization of Anionic Phosphate Monoesters: Role of Cations.

Syntheses and structures of anionic arylphosphate monoesters [ArOP(O)2(OH)]- (Ar = 2,6-CHPh2-4-R-C6H2; R = Me/Et/iPr/tBu) with different counter cations are reported. The counter cations were varied systematically: imidazolium cation, 2-methyl imidazolium cation, N-methyl imidazolium cation, N,N'-alkyl substituted imidazolium cation, 1,4-diazabicyclo[2.2.2]octan-1-ium cation, 4,4'-bipyridinium dication, and magnesium(II) dication. The objective was to examine if the supramolecular structure of anionic arylphosphate monoesters could be modulated by varying the cation. It was found that an eight-membered P2O4H2-hydrogen-bonded dimeric motif involving intermolecular H-bonding between the [P(O)(OH)] unit of the anionic phosphate monoester along with the counter cation is formed with 2-methyl imidazolium cation, N-methyl imidazolium cation, N,N'-alkyl substituted imidazolium cation, 1,4-diazabicyclo[2.2.2]octan-1-ium cation, and magnesium(II) dication; both discrete and polymeric H-bonded structures are observed. In the case of imidazolium cations and 1,4-diazabicyclo[2.2.2]octan-1-ium cation, the formation of one-dimensional polymers (single lane/double lane) was observed. On the other hand, two types of phosphate motifs, intermolecular H-bonded dimer and an open-form, were observed in the case of 4,4'-bipyridinium dication.