MOF Samples Research Articles

Bioactive glass doped with zinc-based metal–organic frameworks (Zn/MOF) nanoparticles for antibiotic delivery applications

Zn-MOF/bioactive glass nanoparticles were successfully prepared using quick–alkali-modified sol–gel and tested for gentamicin drug delivery. Samples of 0 and 0.8 mol% Zn MOF contents (BG and BG/Zn MOF, respectively) were characterized using XRD, FTIR, TEM, and SEM/EDX. In addition, zeta characteristics and surface area parameters were also evaluated. Moreover, the cell viability of the prepared samples was tested against the osteosarcoma MG-63 cell line to evaluate the ability of prepared samples for bone regeneration. In addition, the antimicrobial activity of glass samples with and without antibiotics was determined against different microorganisms. Finally, the samples were loaded with gentamicin drug, and drug release profile and kinetics were studied too. XRD and FTIR results confirmed the physicochemical properties of the prepared samples. TEM results showed that particles were in the nano-sized range in both samples; however, the presence of Zn MOF increased the dispersity of particles. Both samples were bioactive, as indicated by hydroxyapatite formation on their surfaces. Cytotoxicity estimation of prepared materials exhibited their safe and nontoxic nature. BG/Zn MOF sample demonstrated prolonged drug release and excellent antimicrobial activity in comparison to BG alone. Therefore, the present study provides promising preliminary results regarding the usage of BG/Zn MOF nanoparticles loaded with gentamicin as an effective approach for bone regeneration.Graphical

Efficient removal of piroxicam and ketoprofen by acid-modulated iron(III) metal–organic frameworks

Pharmaceutical substances such as piroxicam and ketoprofen have been detected in worldwide water sources, posing an emerging risk to environmental health. Therefore, developing a low-energy and efficient method to remove these pollutants from the environment is necessary. Herein, the adsorption of piroxicam and ketoprofen from water has been investigated by using a series of modulated metal–organic frameworks, namely MIL-126 synthesized in the presence of various amounts of acetic acid. The material synthesized with 1 equivalent of the acid modulator, MIL-126-1AA, has been found to show impressive adsorption activities, irrespective of its lower surface area than the other MOF samples studied. MIL-126-1AA exhibits maximum adsorption capacities of 209.65 mg g−1 for piroxicam and 452.49 mg g−1 for ketoprofen, respectively. Such high adsorption capacities can be attributed to the permanent porosity of MIL-126, an optimal amount of defects, as well as a delicate balance of non-covalent interactions between the MOFs and the adsorbates, as revealed from the adsorption studies and X-ray photoelectron spectroscopic analysis. Additionally, the durability of the adsorbents allows them to be reusable after multiple cycles without significant decrease in the adsorptive performance, further highlighting their potentials for the remediation of pharmaceuticals and other organic pollutants from the environment.

Highly efficient metal-organic framework based intumescent poly(L-lactic acid) towards fire safety, ignition delay and UV resistance

Developing multifunctional biodegradable PLA with ignition delay, high efficient fire retardancy, and UV resistance properties is a challenging task owing to its high flammability, and mutually exclusive phenomenon between the latter two properties. In this work, we report a superior efficient synergistic action combining piperazine pyrophosphate (PAPP) and a Co based metal-organic framework (ZIF-67). Results illustrated that with merely 0.06 wt% ZIF-67, intumescent PLA containing 4.96 wt% PAPP reached UL-94 V0 rating. The PLA/4.9PAPP/0.1MOF sample possessed a limiting oxygen index (LOI) value at 33 %, exhibited a 28 % reduction in peak heat release rate (pHRR) and a 67 % increase in fire propagation index (FPI). Moreover, the presence MOF delayed the ignition time of PLA by 12 s due to the highly porous structure of MOF and its chemical heat-sink performance. Insightful reaction to fire mechanism in the condensed phase via TG-FTIR and Raman revealed that a crack free protective intumescent char layer with higher graphitization degree was formed, which effectively enhanced the barrier effect and minimize the heat and fuel transfer. In addition, the UV resistance of PLA composites is enhanced, remaining at and below 5 % transmittance in the UVA and UVB areas. This work provides a green production way of multifunctional degradable materials and broadens their application fields.

CO2 Capture and Gas Storage Capacities Enhancement of HKUST-1 by Hybridization with Functionalized Graphene-like Materials.

The role of graphene related material (GRM) functionalization on the structural and adsorption properties of MOF-based hybrids was deepened by exploring the use of three GRMs obtained from the chemical demolition of a nanostructured carbon black. Oxidized graphene-like (GL-ox), hydrazine reduced graphene-like (GL), and amine-grafted graphene-like (GL-NH2) materials have been used for the preparation of Cu-HKUST-1 based hybrids. After a full structural characterization, the hybrid materials underwent many adsorption-desorption cycles to evaluate their capacities to capture CO2 and store CH4 at high pressure. All the MOF-based samples showed very high specific surface area (SSA) values and total pore volumes, but different pore size distributions attributed to the instauration of interactions between the MOF precursors and the specific functional groups on the GRM surface during MOF growth. All the samples showed a good affinity toward both gases (CO2 and CH4) and a comparable structural stability and integrity (possible aging was excluded). The trend of the maximum storage capacity values of the four MOF samples toward CO2 and CH4 was HKUST-1/GL-NH2 > HKUST-1 > HKUST-1/GL-ox > HKUST-1/GL. Overall, the measured CO2 and CH4 uptakes were in line with or higher than those already reported in the open literature for Cu-HKUST-1 based hybrids evaluated in similar conditions.

Dynamic behavior of metal nanoparticles in MOF materials: analysis with electron microscopy and deep learning.

Electron microscopy is a key characterization technique for nanoscale systems, and electron microscopy images are typically recorded and analyzed in terms of the morphology of the objects under study in static mode. The emerging current trend is to analyze the dynamic behavior at the nanoscale observed during electron microscopy measurements. In this work, the study of the stability of MOF structures with different compositions and topologies under conditions of an electron microscope experiment revealed an unusual dynamic behavior of M NPs formed due to the electron-beam-induced transformation of specific frameworks. The transition to the liquid phase led to spatial movement, rapid sintering, and an increase in the M NPs size within seconds. In the case of copper nanoparticles, instantaneous sublimation was observed. The dynamic behavior of Co NPs was analyzed with a computational framework combining deep learning and classic computer vision techniques. The present study for the first time revealed unique information about the stability of a variety of MOFs under an electron beam and the dynamic behavior of the formed M NPs. The formation of Fe, Ni, Cu, and Co NPs was observed from a molecular framework with a specific subsequent behavior - a stable form for Fe, excessive dynamics for Co, and sublimation/condensation for Cu. Two important outcomes of the present study should be mentioned: (i) electron microscopy investigations of MOF samples should be made with care, as decomposition under an electron beam may lead to incorrect results and the appearance of "phantom" nanoparticles; and (ii) MOFs represent an excellent model for fundamental studies of molecular-to-nano transitions in situ in video mode, including a number of dynamic transformations.

Outstanding energy storage performance in Co[sbnd]Fe bimetallic metal-organic framework spindles via decorating with reduced graphene oxide nanosheets

Reduced graphene oxides (rGOs; 3 and 5 wt%) decorated on CoFe bimetallic metal-organic framework (CoFe-MOF) have been synthesized by the ultrasonic-assisted solvothermal method. XRD patterns did not show any significant amendment in crystalline structure of MIL-88A and 3 % rGO@CoFe-MOF revealed better crystallinity than other samples. TEM and FESEM images clearly demonstrated that the rGO nanosheets are coated on the CoFe-MOF spindles. BET and BJH analyzes showed that the 3 % rGO@CoFe-MOF composite had the highest specific surface area (149 m2 g−1) and mean pore size (1.79 nm) compared to the other samples. The MOF and rGO decorated on MOF samples were deposited on Ni foam (NF) and their electrochemical performance as binder-free electrodes was evaluated in 3 M KOH electrolyte. The 3 % rGO@CoFe-MOF/NF electrode exhibits outstanding specific capacitance of 2069.1 F g−1 at a current density of 0.5 A g−1 and good cycling stability with 91.3 % capacitance retention at a high current density of 10 A g−1 after 5000 cycles. The assembled 3 % rGO@CoFe-MOF//activated carbon asymmetric supercapacitor device delivers a maximum energy density of 75.8 Wh kg−1 at a power density of 700 W kg−1. The results exhibit that the 3 % rGO@CoFe-MOF can be a propitious electrode material in energy storage devices.

Synthesis of efficient cobalt-metal organic framework as reusable nanocatalyst in the synthesis of new 1,4-dihydropyridine derivatives with antioxidant activity.

Efficient cobalt–metal organic framework (Co-MOF) was prepared via a controllable microwave-assisted reverse micelle synthesis route. The products were characterized by SEM image, N2 adsorption/desorption isotherm, FTIR spectrum, and TG analysis. Results showed that the products have small particle size distribution, homogenous morphology, significant surface area, and high thermal stability. The physicochemical properties of the final products were remarkable compared with other MOF samples. The newly synthesized nanostructures were used as recyclable catalysts in the synthesis of 1,4-dihydropyridine derivatives. After the confirmation of related structures, the antioxidant activity of derivatives based on the DPPH method was evaluated and the relationship between structures and antioxidant activity was observed. In addition to recyclability, the catalytic activity of Co-MOF studied in this research has remarkable effects on the synthesis of 1,4 dihydropyridine derivatives.

Efficient nitro-aromatic sensor via highly luminescent Zn-based metal-organic frameworks

Highly stable zinc-based luminescent metal-organic framework (LMOF) [(Zn2-(NDC)2(bpy)·Gx) where NDC-2,6-naphthalene dicarboxylic acid, bpy - 4,4' bipyridine, and G - guest solvent molecules] is synthesized via solvothermal method at different synthesizing temperatures (120, 150 and 180∘C) for the detection of nitro-aromatics. Sample structure and presence of ligands is confirmed by X-ray diffraction and FTIR measurements, respectively. The photoluminescence properties of synthesized LMOF samples show the strong emission intensity in ethanol at 376 nm when it is excited at 240 nm. The detection limit is calculated using fluorescence quenching for the various nitro-analytes (2,4-DNP, 2-Nitrotoulene, 4-Nitrophenol, and Nitrobenzene) revealed that it is least for the sample synthesized at 150∘C with the maximum percentage in fluorescence decay. The thermal stability of as-synthesized samples is analysed using thermogravimetry analysis (TGA) which reveals that sample synthesized at 150∘C is the most stable sample. The TGA analysis also shows that on further heating from 526∘C to 980∘C decomposition of zinc metal and formation of zinc oxide takes place. FE-SEM confirms the cuboidal morphology with an average particle size of 12.62 nm, corroborated by the TEM analysis. The fluorescence quenching mechanism is explained on the basis of dipole-dipole and π-stacked interactions between the MOF and nitro-aromatics that play a prominent role in the sensing of nitro-analytes. Synthesized MOF samples show excellent recyclability in fluorescence quenching even after the fourth cycle, i.e. more than 95% and is sensitive to detect nitro-aromatics even upto 0.284 µM, and the results can generalize the explosive sensor technology and sensing various nitro-based pollutants.

Metal–organic frameworks encapsulated with an anticancer compound as drug delivery system: Synthesis, characterization, antioxidant, anticancer, antibacterial, and molecular docking investigation

AbstractMetal organic framework (MOF) hybrid materials could be one of the answers in this investigation. We describe a simple and effective encapsulation of doxorubicin (DOX), an anticancer drug, inside Zr‐MOF, which have been little studied as drug delivery organizations. We investigated the measured release of the drug from Zr‐MOF in response to external incentives such as pH changes and interaction with biomimetic schemes. Zr‐MOF with encapsulated doxorubicin (DOX@Zr‐MOF) can be manufactured in one pot by addition the anticancer medication DOX to the reaction combination. They demonstrated pH‐responsive medication release and cancer cell killing capability. MOFs can be designed as multifunctional distribution vehicles for a diversity of loads, including medicinal and imaging agents, using our simple one‐pot approach. Fourier transform infrared (FTIR), X‐ray diffraction, scanning electron microscopy, and N2 sorption isotherm were used to analyze MOF and the developed drug delivery (DOX@Zr‐MOF) scheme. It investigated the effects of MOF and a bespoke drug delivery system on the feasibility of patient breast as well as liver tumor cell lines. At pH 5, the trapped drug can be released more quickly than at pH 7.4. Zr‐MOF nanoparticles had modest cytotoxicity; however, DOX@Zr‐MOF has higher cytotoxicity in MCF‐7 and HepG‐2 cells than DOX at concentrations greater than 31.25 μg ml−1. These results were discovered that DOX@Zr‐MOF could be a promising technique for delivering medicines to cancer cells. Furthermore, using the agar well dispersion technique, Zr‐MOF, DOX, and captured DOX@Zr‐MOF samples were assessed for their potential antibacterial activity against pathogenic bacteria in comparison to traditional antibiotics. In compared to the reference medication Gentamycin, the DOX@Zr‐MOF exhibits a large inhibitory zone against Gram negative organisms (Escherichia coli). The docking active place interactions were assessed to see if DOX might bind to the breast cancer 3hb5‐oxidoreductase receptor, prostate cancer protein 2q7k, and SARS‐CoV‐2 protease 6YB7 for anticancer and anticovid‐19 activities.

Facile synthesis of M2(m‐dobdc) (M = Fe and Mn) metal‐organic frameworks for remarkable hydrogen storage

AbstractMetal‐organic frameworks (MOFs) are emerging as promising candidates for hydrogen storage material because of their porosity and adjustable hydrocarbon structures coordinated with the metal element. Present work explore the synthesis of M2(m‐dobdc) (M = Fe and Mn; m‐dobdc4− = 4,6‐dioxido‐1,3‐benzenedicarboxylate) metal‐organic frameworks via solvothermal method for the purpose of hydrogen storage application. The X‐ray diffraction, transmission electron microscope, scanning electron microscope, energy dispersive X‐ray analysis, and nuclear magnetic resonance spectroscopic studies have been done to ensure the synthesized material is M2(m‐dobdc) (M = Fe and Mn) MOFs. The Brunauer‐Emmett‐Teller (BET) analysis reveals the average pore size of 36.271 nm for Mn2(m‐dobdc) MOF whereas the average pore size for fe2(m‐dobdc) MOF was found to be 2.1992 nm. The as‐prepared MOF samples are in the mesoporous range based on pore size distribution (internal pore diameter greater than 2 nm) with spherical pore geometry. Hydrogen storage studies shows that Fe2(m‐dobdc) has a hydrogen storage capacity of 0.18 wt% at ambient temperature (30°C) under 100 atm H2 pressure, whereas the hydrogen storage capacity for Mn2(m‐dobdc) is 1.38 wt% under identical conditions of temperature and pressure. The hydrogen storage capacity at liquid nitrogen temperature (−196°C) under 100 atm H2 pressure for Fe2(m‐dobdc) and Mn2(m‐dobdc) is 4.31 and 8.21 wt%, respectively.

Synthesis of Al-Based Metal-Organic Framework in Water With Caffeic Acid Ligand and NaOH as Linker Sources With Highly Efficient Anticancer Treatment.

In this study, novel nanostructures of aluminum base metal-organic framework (Al-MOF) samples were synthesized using a sustainable, non-toxic, and cost-effective green synthesis route. Satureja hortensis extract was used as an effective source of linker for the development of the Al-MOF structures. The Fourier-transformed infrared (FTIR) spectrum confirmed the presence of characterization bonds related to the Al-MOF nanostructures synthesized by the green synthesis route. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses revealed that the sample synthesized by Na2-CA was composed of multilayers, although it was agglomerated, but it had dispersed and occurred in spherical particles, indicating active organic matter. N2 adsorption/desorption isotherms demonstrated the significant porosity of the Al-MOF samples that facilitate the high potential of these nanostructures in medical applications. The anticancer treatment of Al-MOF samples was performed with different concentrations using the MTT standard method with untreated cancer cells for 24 and 48 h periods. The results exhibited the significant anticancer properties of Al-MOF samples developed in this study when compared with other MOF samples. Thus, the development of a novel Al-MOF and its application as a natural linker can influence the anticancer treatment of the samples. According to the results, the products developed in this study can be used in more applications such as biosensors, catalysts, and novel adsorbents.

Methane adsorption on the Zr-BDC metal-organic framework structure at supercritical temperatures and pressures

Methane adsorption by the sample of the metal-organic framework structure (MOF) Zr-BDC (BDC is benzene-1,4-dicarboxylate) containing zirconium ions was studied in a pressure range of 0.1–40 MPa at 303, 313, 323, and 333 K. The excess adsorption isotherms Γ(P,T) and adsorption isotherms of total amount a(P, T) were calculated, and the adsorption volume W was determined. The adsorption isosteres were constructed on the basis of these isotherms, and the isosteric qst(a,T) and initial q(0,T) heats of adsorption were calculated. The average isosteric heats of adsorption q st * (a, T) were determined taking into account the dependence of qst(a,T) on the amount adsorbed. These values were compared with the average heats of adsorption q(E) calculated with allowance for the characteristic energy of adsorption E(T), which were determined, in turn, from the adsorption isotherms a(P,T). Two calculation methods were used: via the characteristic curve and via the adsorption isotherm presented in the linear coordinates of the Dubinin—Astakhov equation. In both cases, new parameters were introduced in the adsorption equation to determine E(T): “Ps” that replaces the vapor pressure at saturation and critical temperature Tc. The Zr-BDC MOF sample is a microporous adsorbent, which can be used for methane storage.

Simultaneous neutron powder diffraction and microwave characterisation at elevated temperatures.

The use of simultaneous neutron powder diffraction (NPD) and microwave characterisation can provide more information than the use of either technique individually; for example, it enables the differentiation of physisorbed and metal-coordinated species. Many possible experiments using these combined techniques can benefit from the addition of a heat source for sample heating, such as real-time measurements of solvent removal, or chemical and catalytic reactions. This paper documents the design of equipment to conduct simultaneous NPD and 2.5 GHz microwave cavity resonance techniques at elevated temperatures and confirms the use of this equipment for successful desolvation of a metal-organic framework (MOF) sample at 150 °C. The high sensitivity of microwave characterisation of lossy and polar materials is demonstrated at levels much lower than those that can be detected using crystallographic techniques.

Core-shell Co-MOF-74@Mn-MOF-74 catalysts with Controllable shell thickness and their enhanced catalytic activity for toluene oxidation

A series of core-shell Co-MOF-74@Mn-MOF-74 samples with different shell thicknesses were prepared by the seed growth method, which were characterized by powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), inductively coupled plasma mass spectrometry (ICP-MS), X-ray photoelectron spectroscopy, nitrogen adsorption-desorption and scanning electron microscopy (SEM). The shell thickness of these MOF samples were successfully controlled by adjusting the mass ratio between MnCl2·4H2O and Co-MOF-74. On this basis, these MOFs were applied to the catalytic oxidation of toluene. The results showed that with the growth of Mn-MOF-74 in the outer layer of Co-MOF-74, the oxidative selectivity of the substrate to benzaldehyde was greatly improved for the synergy between the core layer and shell layer. The conversion of toluene was 22.4%, and the selectivity of benzaldehyde was 98.1%. In addition, the catalyst can transform various substituted toluene into the corresponding aldehydes in highly selectivity and still keep good stability after four catalytic cycles. The selectivity of the corresponding aldehyde is generally above 80%.

Mechanochemistry of Metal-Organic Frameworks under Pressure and Shock.

ConspectusMetal-organic framework solids (MOFs) are synthetic nanoporous materials that have drawn intense efforts in synthesis and characterization of chemical properties, most notably for their ability to adsorb liquids and gases. They are constructed as "node-spacer" nanostructured materials: metal centers (ions or clusters) connected by organic linkers (commonly containing carboxylate or imidazolate groups) to form crystalline, extended, often highly nanoporous structures. MOFs exhibit a variety of advantages over conventional porous materials: rationally designed synthesis of desired crystal structures and crystal engineering become feasible; great synthetic versatility and ease of incorporating different chemical functionalities are realized; and the use of lightweight organic linkers allows for ultrahigh surface area and porosity previously not accessible to conventional materials (i.e., zeolites and porous carbon). As a consequence, MOFs show great promise for a rapidly expanding collection of applications such as gas storage, separations, catalysis, sensing, and drug delivery.The mechanochemistry of MOFs and their response to shock waves, which we discuss in this Account, have been only partially explored. Mechanochemistry, the connection between the mechanical and the chemical worlds, has ancient origins. Rubbing sticks together to start a fire is mechanochemistry. Only in the past decade or so, however, has mechanochemistry gained a notable focus in the chemical community. In the following discussion, we present a general introduction to the complex mechanochemical behavior of MOFs both under quasi-static compression and under shock loading created by high-speed impact. During elastic deformation, MOFs undergo reversible structural or phase transitions. Plastic deformation of MOFs can result in mechanochemistry and can permanently modify the crystal structure, the pore dimensions and configuration, and the chemical bonding. The large energies required to induce bond rearrangement during plastic deformation suggest an interesting potential of MOFs for shock wave mitigation applications.MOFs are promising materials for shock energy dissipation because of the high density of nanopores which can absorb shock energy as they collapse. We have recently developed a platform to assess shock wave energy attenuation by MOFs and other powdered materials. It uses a tabletop laser-driven flyer plate to impact MOF samples at velocities of up to 2.0 km/s. The pressure of the shock waves that break out from the MOF sample can be measured by photon Doppler velocimetry. By measuring the shock profiles of MOF layers with different thicknesses, we can determine the shock pressure attenuation by the MOF layer. We have identified the two-wave structure of shocks in MOFs caused by nanopore collapse. Electron micrographs of recovered shocked MOFs show distinct zones in the shocked material corresponding to shock powder compaction, nanopore collapse, and chemical bond destruction.

Discerning Detection of Mutagenic Biopollutant TNP from Water and Soil Samples with Transition Metal-Containing Luminescence Metal-Organic Frameworks.

Two luminescent MOFs, Mn@MOF and Cd@MOF, have been reported herein, which are capable of selectively detecting 2,4,6-trinitrophenol (TNP), one of the potent organic water pollutants in the class of mutagenic explosive nitroaromatic compounds (epNACs). It is perceived that the d10-based Cd(II)-constituting MOF shows a better response in the realm of TNP-like nitroaromatic sensing in comparison to the d5-based Mn@MOF which may possess lower electron density over the conjugated building blocks. The sensing competences of these chemosensors have been explored by means of various spectroscopic experimentations, and it is observed that for both d5 and d10-containing MOFs, the initial fluorescence intensity is significantly quenched in response to an aqueous solution of TNP. However, Cd@MOF is more selective and sensitive toward TNP over several other epNACs than Mn@MOF. The high chemical stability of the MOF samples, as well as its amusing sensing efficiency of Cd@MOF, further instigated to investigate the sensing ability in various environmental specimens like soil and water culled from several zones of West Bengal, India.

Ethylenediamine-incorporated MIL-101(Cr)-NH2 metal-organic frameworks for enhanced CO2 adsorption

Ethylenediamine (EA)-incorporated MIL-101(Cr)-NH2 adsorbents were prepared for CO2 adsorption. First, MIL-101(Cr)-NH2 was directly prepared by the solvothermal method, followed by the EA incorporation inside the pores of MIL-101(Cr)-NH2. The prepared samples were characterized by N2 porosimetry, field-emission scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectrometry, thermogravimetric, and powder X-ray diffraction analyses. The effects of ethylenediamine loading in MIL-101(Cr)-NH2 on the CO2 adsorption capability were systematically investigated. EA-incorporated MIL-101(Cr)-NH2 showed CO2 adsorption capacity of ca. 3.4 mmol/g, which was ∼62% higher than the pristine MIL-101(Cr)-NH2. In addition, the amine-grafted MOF samples showed good regenerability and stability after consecutive adsorption-desorption cycles at ambient conditions. These suggest that introduction of alkylamine molecules into the pores of metal-organic frameworks can be a promising strategy to improve the CO2 soprtion ability of MOFs.

Optical determination of nitro phenol via ratiometric emission from Tb:Eu-MOFs: Chemical synthesis and spectral response

The present paper reported fluorescent detection of 2,4,6-trinitrophenol (PA) by controlling energy transfer finely between rare earth ions. Eu(III) and Tb(III) ions with different weight ratios were reacted with 1,3,5-benzenetricarboxylic acid to construct a MOF matrix. Corresponding MOF samples were characterized in detail with SEM, XRD, N2 adsorption and desorption to confirm their structure. Their photophysical performance was discussed in detail as well. It was found that these MOF samples showed weak Tb(III) green emission and strong Eu(III) red emission in the absence of PA, since the triplet state (T1) of 1,3,5-benzenetricarboxylic acid excited Eu(III) effectively compared to Tb(III). Given PA, T1 of 1,3,5-benzenetricarboxylic acid was increased to match Tb(III) energy level. Strong Tb(III) green emission and weak Eu(III) red emission were observed, showing ratiometric fluorescent sensing towards PA. Sensitivity and limit of detection were obtained as 4.34 and 0.28 μM, respectively. Unique selectivity and linear response towards PA were observed. The practical sensing performance was confirmed as well.

Tuning 1-hexene/n-hexane adsorption on MOF-74 via constructing Co-Mg bimetallic frameworks

A series of bimetallic CoxMg1-x-MOF-74 (x = 0, 0.12, 0.30, 0.57, 0.78, 1) structures were synthesized by using facile solvothermal systems having different binary metal compositions. All MOF samples were characterized carefully. Both adsorption affinity to n-hexane and 1-hexene and adsorption selectivity of 1-hexene over n-hexane were evaluated by static adsorption test coupled with computer simulation. It is indicated that the CoMg bimetallic MOF-74 frameworks can be successfully constructed via using well-designed reactant compositions. All bimetallic MOF-74 retain almost the same crystalline structure but higher porosity as compared to their monometallic samples. In addition, both of the adsorption capacity and selectivity of CoMg bimetallic MOF-74 samples are found strongly dependent on their metal compositions. Specifically, Co0.30Mg0.70-MOF-74 exhibits the largest 1-hexene adsorption capacity of 152.7 mg/g and the highest 1-hexene/n-hexane selectivity of 9.74, which are 2.1–2.3 and 4.1–8.9 times higher than those of monometallic Co or Mg-MOF-74 samples. Such improvement on adsorption ability and selectivity for olefin molecules can be attributed to the incorporation of more stable coordinatively unsaturated sites (CUS) within Mg-MOF-74 framework, leading to the synergetic effect of pore structure evolution as well as higher density of CUS metal sites in bimetallic frameworks. The tunable adsorption affinity to olefin/paraffin on MOF-74 by means of metal modification provides an approach to the efficient separation of olefins and paraffins from liquid hydrocarbon mixtures.

Density Measurement of Small Samples of Metal-Organic Frameworks Using Confocal Microscopy

A novel approach for precise density measurement of small samples with a weight in the mg-range has been developed recently [1]. Using this approach, a solid object is dropped into a semi-confined cylindrical cavity, which is filled with a nonvolatile liquid. To determine the volume of the sample the rise of the liquid meniscus is measured with confocal microscopy. During the development of new MOFs, the lack of an appropriate amount of material makes it often impossible to determine the bulk density of the new material. Here we demonstrate how the density of small MOF samples can be determined by this novel method. Even with samples in the range of 1.5 mg we can measure the density with an accuracy better than 1%. The effect of previous sorption of other liquids and the distinction of open and closed porosity will be addressed. 1.: Bulk Density Measurements of Small Solid Objects Using Laser Confocal Microscopy. A. Kilmametov, R. Gröger, H. Hahn, Th. Schimmel and S. Walheim: Advanced Materials Technology 2017, 2, 1600115