Search

Herein, we report the covalent organic framework supported metal–organic framework (COF–MOF) from melamine and terephthalaldehyde as the COF and 1,2,4,5-tetrabenzenecarboxylic acid as the MOF moiety, as porous catalyst for the one-pot preparation of 2-aryl substituted 2,3-dihydroquinazoline-4(1H)-one and 2,3-diphenyl-2,3-dihydroquinazolin-4(1H)-one's derivatives. COF–MOF was characterized by FTIR, EDX, TGA, FESEM, XRD and BET. This methodology offers several advantages including solvent-free and eco-friendly conditions high yield of the products, short reaction time, simple work-up procedure, and ease of recyclability of the catalyst. Three-component reaction of isatoic anhydride (1), aromatic aldehydes (2), aniline (3) or ammonium acetate (5) and COF–MOF for the one-pot preparation of 2,3-diphenyl-2,3-dihydroquinazolin-4(1H)-ones (4a–j) and 2-Aryl Substituted 2,3-Dihydroquinazoline-4(1H)-one derivatives (6a–j) [ABSTRACT FROM AUTHOR]

Acetylene terminated polymers are gaining interest due to the need for easily processable thermally stable networks. The Metal Organic Frameworks (MOFs)—aluminum fumarate (Al_FA_A) and copper fumarate (Cu_FA_A) MOFs were synthesized and blended with bispropargyl ether (bis (4-propargyloxyphenyl) sulfone—SPE). The (SPE + 1% MOFs) blends were characterized and thermally polymerized to give P(SPE + MOFs). The synthesized materials were characterized using FTIR, DSC, TG and TG-FTIR. The addition of both MOFs decreased the enthalpy of fusion and enthalpy of curing by 60%. The addition of copper MOF to SPE drastically reduced the temperature at which the thermal curing was maximum (300 °C to 252 °C). The 2-H chromenes were formed from bispropargyl ethers by Claisen-type sigmatropic rearrangement. Compared to pure SPE, the polymers resulting from hybrid systems show a slower thermal degradation rate. The sulfone as a swivel group in SPE and the involvement of fumarate π-bonds of MOFs during polymerization make the material more versatile. The investigation concluded that these novel inorganic–organic hybrid blends may be a good start for low-temperature curable sufficiently thermally stable matrix resin systems having a wide scope of applicability in the field of filler-reinforced composites. [ABSTRACT FROM AUTHOR]

A water-dispersible Tb(III)-based metal organic framework (TBP) was produced by diffusion technique using benzene-1,3,5-tricarboxylic acid (BTC) and pyridine as easily accessible ligands at low cost. The as-synthesized TBP with a crystalline structure and rod-shaped morphology has exhibited thermal stability up to 465 °C. Elemental analysis confirmed the presence of carbon, oxygen, nitrogen, and terbium in the synthesized MOF. TBP was used as a fluorescent probe for detection of danofloxacin (DANO) in an aqueous medium with significant enhancement of fluorescence intensity as compared to various fluoroquinolone antibiotics (levofloxacin (LEVO), ofloxacin (OFLO), norfloxacin (NOR), and ciprofloxacin (CIPRO)) with a low detection limit of 0.45 ng/mL (1.25 nm). The developed method has successfully detected DANO rapidly (i.e., response time = 1 min) with remarkable recovery (97.66–101.96%) and a relative standard deviation (RSD) of less than 2.2%. Additionally, TBP showcased good reusability up to three cycles without any significant performance decline. The in-depth mechanistic studies of the density functional theory (DFT) calculations and mode of action revealed that hydrogen bonding interactions and photo-induced electron transfer (PET) are the major factors for the turn-on enhancement behavior of TBP towards DANO. Thus, the present work provides the quick and precise identification of DANO using a new fluorescent MOF (TBP) synthesized via a unique and facile diffusion technique. [ABSTRACT FROM AUTHOR]

This study reports the performance of Zr-based MOF, UiO-66, modified by Dimethyl Ethylenediamine (UiO-66-mmen) for anticancer methotrexate drug (MTX) uptake. This post-synthetic modified MOF is kind of a support for carrying a medicine in biological media. The surface morphology and characteristics of the modified MOF were analyzed using SEM, EDX, FTIR, PXRD and BET. Also, the optimum values of three effective parameters including pH, MOF dosage and contact time were calculated by response surface methodology (RSM) and central composite design (CCD). The results showed that the best conditions for pH, MOF dosage and time were 3, 0.15 g and 89 min, respectively while MTX uptake efficiency was 88.54%. The results show that the Langmuir isotherm model (qm = 1000 mg g−1) can better fit the equilibrium data, demonstrating the monolayer adsorption of MTX on UiO-66-mmen. Besides, it was revealed that three predominant mechanisms including H-bonding, interaction between Zr-sites of UiO-66 and carboxyl groups of MTX, and π–π stacking interactions govern MTX uptake on UiO-66-mmen. The kinetic data also exhibited that the Lagergren model is the predominant kinetic model and MTX adsorption on UiO-66-mmen is physical type. Moreover, the thermodynamic analysis proved that MTX uptake is spontaneous, endothermic and physical type. [ABSTRACT FROM AUTHOR]

Zeolitic imidazolate framework/carbon nanotube (ZIF-67/CNTs) was prepared by precipitation method. ZIF-67/CNTs maintained the characteristics of large specific surface area and high porosity of ZIFs, showing stable cubic structure. The adsorption capacities of ZIF-67/CNTs for Cong red (CR), Rhodamine B (RhB) and Cr(VI) were 36.82 mg/g, 1421.29 mg/g and 716.67 mg/g under the conditions of 2:1, 3:1 and 1:3 masses of ZIF-67 and CNTs, respectively. The optimum adsorption temperature of CR, RhB and Cr(VI) were 30 °C, and the removal rates at the adsorption equilibrium were 81.22%, 72.87% and 48.35%. The adsorption kinetic model of the three adsorbents on ZIF-67/CNTs was consistent with the quasi-second order reaction model, and the adsorption isotherms were more consistent with adsorption law of Langmuir. The adsorption mechanism for Cr(VI) was mainly electrostatic interaction, and the adsorption mechanism for azo dyes was the combination of physical and chemical adsorption. This study would provide theoretical basis for further developing metal organic framework (MOF) materials for environmental applications. [ABSTRACT FROM AUTHOR]

Ionic liquids (ILs) containing colloidal metal organic frameworks (MOFs) have been used as gas chromatography stationary phases to provide distinct separation properties. The behavior of four different organic frameworks in 18 ionic liquids was investigated. Metal organic frameworks flocculated, degraded, or formed colloidal dispersions in ionic liquids. The newly developed stationary phase consisted of colloidal ZIF-8 uniformly dispersed in an imidazolium-based dicationic ionic liquid which provided the first separation of permanent gases via hybrid gas–liquid chromatography. In addition, various groups of alkanes, ketones, alcohols, ethers, and Rohrschneider-McReynolds compounds were separated on this newly developed hybrid stationary phase. Equations for the three-phase model were derived to determine the behavior of solutes with this pseudophase system. Using this model, the distribution constants between all three phases were calculated. It was shown that the metal organic framework had a significant effect on solute partitioning to the stationary phase. [ABSTRACT FROM AUTHOR]

Fractionation of essential oils is technically challenging due to enormous scaffold diversities and structural complexities as well as difficulties in the implementation of the fractionation in the gas phase. Packing beads with multi-dimensional hierarchical nanostructures have been developed herein to pack fractional columns for atmospheric distillations. Activated alumina beads were coated with a porous TiO2 thin film. Growth of Cu-BTC (benzene-1,3,5-tricarboxylate) crystals in resultant porous surfaces leads to the generation of new nanopores and increased metal centers for differential coordination with diverse components of essential oils. The TiO2 thin film is not only an integral part of the composites but also induces the oriented growth of Cu-BTC metal organic framework (MOF) crystals through coordinative interactions. These Al2O3@TiO2@Cu-BTC MOF beads show very strong absorptive capability for major components of essential oils, except for a single cyclic ether eucalyptol with steric hindrances. The eucalyptol was fractionated by using the column packed with those modified alumina beads from raw materials of Artemisia argyi, and Rosmarinus officinalis with high purities up to 96% and 93%, respectively. [ABSTRACT FROM AUTHOR]

The absence of stable and highly active non-precious metal electrocatalysts as a substitute to precious metal i.e., Pt (state-of-the-art) for methanol oxidation reaction in the application of direct methanol fuel cell considerably impedes the commercialization of these energy devices. In this work the electrocatalytic investigation of Fe-In MOF and its g-C3N4-based composites (i.e., 5–8 wt% g-C3N4@ Fe-In MOF) for methanol oxidation is reported. All the catalysts were prepared via solvothermal method. XRD, SEM, EDX, and FTIR were used to characterize the Fe-In MOF and its 5–8wt% g-C3N4 composites. In comparison to other prepared g-C3N4 based Fe-In MOF composites, the 7wt% g-C3N4 @ Fe-In MOF catalyst showed much greater electrochemical activity (i.e., 95.54 mA/cm2) and stability of 72.45% in 1 M NaOH and 3 M CH3OH. Due to graphitic carbon nitride specified high catalytic activity, intercalation, ion exchange, and redox properties. Further, the availability of iron (Fe) and indium (In) may also show a significant role in enhancing the electrocatalytic performance of 7wt% g-C3N4 @ Fe-In MOF over Fe-In MOF. They could be viewed as stable and economical electrocatalysts due to their numerous advantageous characteristics in structure, content, and nitrogen doping level. [ABSTRACT FROM AUTHOR]

The separation of carbon dioxide and methane is vital for biogas upgradation and natural gas sweetening applications. Membrane separation is one of the techniques used for CO2 and CH4 separation for biogas upgradation and natural gas sweetening owing to its energy efficiency, low capital cost, portable, and ease of operation. Polymer membranes and inorganic membranes have a trade-off relationship between permeability and selectivity. A new class of membranes known as Mixed Matrix Membranes (MMMs) is being explored to overcome this trade-off by dispersing inorganic fillers in the polymer matrix. However, the addition of filler poses new interfacial morphological difficulties, such as poor dispersion, very strong interaction between filler and polymer, and formation of voids. These challenges can be tackled by suitable choice of filler and polymer, functionalization of filler and polymer, polymer blending. The hybrid membranes separation process or use of two or more strategies can lead to the formation of defect-free membranes with improved separation performance. In this review article, we provide a concise literature review and analysis of the strategies for improving the transport properties of MMMs based on MOF as filter materials for CO2/CH4 separation. [ABSTRACT FROM AUTHOR]

Copper-Metal organic framework (Cu-MOF) and melamine/Cu-MOF (MCu-MOF) samples were prepared by the hydrothermal process. The produced powder was dried and characterized by using the FTIR, X-ray techniques. The thermal-gravimetry (TG) analysis was performed to detect the thermal stability of the product. On other hand, the morphology and the surface area of this powder were carried. The bioactivity of the powder was carried by measuring the inhibition zone diameter around samples in (mm). The results of characterization showed that on the IR spectra a series of absorption peaks at 970, 1500 and 1640 cm−1 were appeared which characterized the formation of Cu-MOF, while an addition peaks were observed at 3121, 3324, 3415 and 3467 cm−1 and attributed to the incorporation of melamine into Cu-MOF. X-ray patterns of the prepared samples show sharp peaks at 7.4 and 8.5 specified to Cu-MOF. The intensity of these peaks increases by adding melamine which indicate the improving the crystanility. Moreover two peaks at 26, 30attributed to the incorporate melamine in the Cu-MOF. The surface area of Cu-MOF is equal to 1350 m2 g−1while increase to 1410 m2 g−1 by incorporates melamine into the Cu-MOF. The thermal behavior (TG) of the Cu-MOF showed three sequence stages attributed to the moisture evaporation, degradation of the Cu-MOF and forming the Cu–O as end product respectively. For melamine incorporated to Cu-MOF (MCu-MOF), the TG profile split the main degradation into two parts resulting from the presence of melamine. To study the morphology of these samples by both FESEM and HRTEM were examined. The bioactivities of the both samples were tested against microbial strains. The results showed that the Cu-MOF and MCu-MOF have insignificant antimicrobial activity against gram positive of bacteria and Fungi. While for gram negative of bacteria it is observed a considerable effect. [ABSTRACT FROM AUTHOR]

Metal organic frameworks (MOFs) nanoporous innovative materials as particulate reinforcing materials for high-temperature epoxy resins are designed and fabricated. Aqueous synthesis of MOFs is always the need of this hour. This paper focuses on the synthesis of aluminum-based MOFs in gram quantities by optimizing both the reaction temperature and time. The MOFs are annealed at different temperatures. The structures are characterized by several analytical techniques. The structural rearrangement during thermal treatment leads to increase in particle size and decrease in crystallinity. The improvement in mechanical (3.5%) and electrical properties for hybrid aluminum MOF-based di/tri-epoxy composites was discussed. [ABSTRACT FROM AUTHOR]

The design and construction of a novel magnetic resonance sensor (MRS) is presented for bisphenol A (BPA) detection. The MRS has been built based on the core component of magnetic Fe3O4 nanoparticles (~ 40 nm), which were uniformly distributed in nanoporous carbon (abbreviated as Fe3O4@NPC). The synthesis was derived from the calcination of the metal organic framework (MOF) precursor of Fe-MIL-101 at high temperature. Fe3O4@NPC was confirmed with enhanced transversal relaxation with r2 value of 118.2 mM−1 s−1, which was around 1.7 times higher than that of the naked Fe3O4 nanoparticle. This enhancement is attributed to the excellent proton transverse relaxation rate of Fe3O4@NPC caused by the reduced self-diffusion coefficient of water molecules in the vicinity of Fe3O4 nanoparticles in the nanoporous carbon. BPA antibody (Ab) and antigen (Ag)-ovalbumin (OVA) were immobilized onto the Fe3O4@NPC to form Ab-Fe3O4@NPC and Ag-Fe3O4@NPC, respectively. These two composites can cause the three-dimensional assembly of Fe3O4@NPC via immunological recognition. The presence of BPA can compete with antigen-OVA to combine with Ab-Fe3O4@NPC, thereby breaking the assembly process (disassembly). The difference in the change of the T2 value before and after adding BPA can thus be used to monitor BPA. The proposed MRS not only revealed a wide linear range of BPA concentration from 0.05 to 50 ng mL−1 with an extremely low detection limit of 0.012 ng mL−1 (S/N = 3), but also displayed high selectivity towards matrix interferences. The recoveries of BPA ranged from 95.6 to 108.4% for spiked tea π, and 93.4 to 104.7% for spiked canned oranges samples, respectively, and the RSD (n = 3) was less than 4.4% for 3 successive assays. The versatility of Fe3O4@NPC with customized relaxation responses provides the possibility for the adaptation of magnetic resonance platforms for food safety development. [ABSTRACT FROM AUTHOR]

In this study, biomass derived activated carbon (AC) was utilized to enhance the electrochemical properties of copper benzene-1, 3, 5-tricarboxylate metal organic framework (Cu-BTC MOF). Dried leaves (Lantana) were activated with phosphoric acid (H3PO4) for preparation of AC. Cu-MOF was pyrolyzed with different ratios of AC (1:1) under a reduction atmosphere of mixture of argon and hydrogen gases (90:10) in a tube furnace. These freshly produced composite materials were examined by X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy and thermal gravimetric analysis. The synthesized catalysts were tested for its electro catalytic activity for oxidation reduction reaction (ORR) in three electrode system by cyclic voltammetry, Tafel polarization and electrochemical impedance spectroscopy. The electrochemical parameters calculated by film coated glassy carbon electrode exhibit impact of activated carbon on oxidation reduction reaction catalyzed by Cu-BTC MOF. The composite Cu@AC (1:1) reported the highest current density of 2.11 mA cm−2 at 0.9 V potential with a scan rate of 50 mV s−1 in 0.1 M KOH which is better than commercial grade Pt/C having highest current density of 1.37 mA cm−2 at 0.86 V potential. The electrochemical activity and intensified constancy is due to synergistic influence of MOF and AC-composite. [ABSTRACT FROM AUTHOR]

In present work the development of copper benzenetricarboxylic acid metal organic framework (Cu-BTC MOF) based electrocatalyst and the effect of graphene oxide on catalytic activity of metal organic framework were studied for methanol oxidation reaction. Cu-MOF was prepared by a facile hydrothermal method and graphene oxide flakes were synthesized via improved Hummer's method. Surface morphological studies of catalyst were analyzed through scanning electron microscopy technique, which revealed cubic structure of crystals, while the crystallinity and functional groups present were characterized through X-ray Diffraction and FTIR spectroscopy respectively. Electrochemical studies were conducted by using cyclic voltammetry, electrochemical impedance spectroscopy, and chronoamperometry techniques. Among all series of catalyst, 5 wt% GO/Cu-MOF exhibit highest current density of 120 mA/cm2 at a scan rate value of 50 mV/s at a voltage of 0.9 V. [ABSTRACT FROM AUTHOR]

Butanol is a second generation biofuel with high potential to replace fossil fuels in the future. The main drawbacks in biobutanol production are the low yields of operation and high cost of separation. In this study, n-butanol recovery from its aqueous solutions was carried out by pervaporation as an alternative separation process using polyimide supported polydimethylsiloxane membranes, which were especially prepared for this purpose. To enhance the separation efficiency of the membrane, metal organic framework fillers of MOF-199 were included in its structure. Several combinations of polyimide supported PDMS active layered membranes were prepared with the fillers in each layer of the membrane, in both layers of membrane and membranes without fillers. Thus, the effect of the fillers on the separation performance was investigated. It was found that the inclusion of MOF-199 enhances the membrane performance; meanwhile, the support layer also contributes to mass transfer of n-butanol. Furthermore, the effect of the process parameters on the pervaporation performance was investigated. Results of pervaporation tests indicate that the developed membranes have a good potential for n-butanol recovery from aqueous mixtures. [ABSTRACT FROM AUTHOR]

In this work, the adsorption of benzoic acid (BA) over metal organic framework of chromium-benzenedicarboxylates (MIL-101) is reported for the first time. The influences of pH, contact time, initial concentration, and temperature of BA solution on the adsorption behavior were investigated. The Langmuir adsorption isotherm was adequate to represent the experimental data (R > 0.99) and the adsorption kinetics was well-represented by a pseudo-second order kinetic model (R > 0.96). The zeta potential of MIL-101 decreased with increasing pH confirming the importance of electrostatic interactions between MIL-101 and BA as well as the importance of the large pore volume (1.32 m/g) and large surface area (2390 m/g) of MIL-101 for adsorption interaction. The thermodynamics analysis indicated negative free energy, enthalpy, and entropy changes suggesting that the adsorption of BA on MIL-101 is spontaneous and exothermic. The adsorption capacity of BA adsorption over MIL-101 was compared with those for other conventional adsorbents. The maximum capacities of BA uptake on MIL-101, activate carbon, and multiwall carbon nanotubes were 769.2, 406.5, and 341.2 mg/g, respectively, suggesting the superiority of MIL-101 as an adsorbent. Adsorption of real wastewaters containing other organic compounds in addition to BA confirmed the versatility of MIL-101 as a suitable adsorbent in wastewater treatment compared with conventional adsorbents. [ABSTRACT FROM AUTHOR]

Metal-organic frameworks (MOFs) hybrid composites have recently attracted considerable attention in hydrogen storage applications. In this study a hybrid composite of zeolite templated carbon (ZTC) and Cr-based MOF (MIL-101) was synthesised by adding the templated carbon in situ during the synthesis of MIL-101(Cr). The obtained sample was fully characterized and hydrogen adsorption measurements performed at 77 K up to 1 bar. The results showed that the surface areas and the hydrogen uptake capacities of individual MIL-101 (2552 m g, 1.91 wt%) and zeolite templated carbon (2577 m g, 2.39 wt%) could be enhanced when a hybrid MIL-101(Cr)/ZTC composite (2957 m g, 2.55 wt%) was synthesized. The procedure presents a simple way for enhancement of hydrogen uptake capacity of the individual Cr-MOF and templated carbon samples. [ABSTRACT FROM AUTHOR]

Cellulose paper was coated with the metal-organic framework MIL-101(Cr) in a chitosan matrix and utilized for thin-film microextraction (TFME). The coated paper possesses excellent extraction efficiency for the triazine herbicides atraton, desmetryn, secbumeton, prometon, ametryn, dipropetryn, and dimethametryn. High-performance liquid chromatography-tandem mass spectrometry was applied to quantify target analytes. The effects of mass ratio of MIL-101(Cr) to chitosan, sample pH value, time of adsorption and desorption, and type and volume of desorption solvent on extraction efficiency were optimized. Under the optimal conditions, the method has limits of detection between 1.5 and 22 ng·L−1. The recoveries of triazines from spiked tap water, drinking water, lake water and river water range from 77.0 to 125.3%, with relative standard deviations of <17.4%. [ABSTRACT FROM AUTHOR]

Magnetite (Fe3O4) spheres acting as a core were evenly decorated with gold nanoparticles (AuNPs) and coated with a shell of a metal organic framework (MOF) of type MIL-100(Fe). The resulting hybrid nanomaterial of type Fe3O4-Au@MIL-100(Fe) hybrid is shown to be a viable new SERS substrate. The integration of magnetic core, build-in plasmonic gold nanoparticles and a MOF shell endows the Fe3O4-Au@MIL-100(Fe) with highly efficient magnetic separation and enrichment ability, abundant interparticle hotspots, and significant chemical enhancement effect. This leads to a large enhancement, and greatly improved reproducibility of the SERS signals as shown for Malachite Green (MG) and the fungicide thiram. MG in solution can be quantified with a 50-fold lower detection limit (0.14 nM for peak at 1398 cm−1) and largely improved reproducibility (RSD = 9%, 1398 cm−1) when compared to the use of (a) AuNPs anchored on MIL-100(Fe) (RSD = 27%, 1186 cm−1), or (b) AuNPs embedded in MIL-100(Fe) (RSD = 36%, 1398 cm−1). The method was applied to the quantitation of MG and thiram in spiked water samples. The lower limits of detection are 4.4 nM for MG (1398 cm−1) and 15 nM for thiram (1380 cm−1), respectively, and signals' RSDs are 13% (1398 cm−1) and 5% (1380 cm−1) for MG and thiram, respectively. The substrate is recyclable.Schematic illustration of the preparation and SERS molecule sensing application of Fe3O4-Au@MIL-100(Fe) hybrid. PMMA: poly(methacrylic acid; BPEI: branched poly(ethyleneimine); BTC: 1,3,5-tricarboxybenzene. [ABSTRACT FROM AUTHOR]