Microporous Metal-organic Framework Research Articles

Microporous metal–organic framework with open Cu2+ functional sites and optimized pore size for C2H2 storage and CH4 purification

A microporous metal–organic framework (MOF), Cu6(ABTC)3(H2O)6·(DMA)7(H2O)12 (Cu-ABTC, H4ABTC = 3,3′,5,5′-azobenzenetetracarboxylic acid) was solvothermal obtained and structurally characterized. The activated Cu-ABTC-a exhibits high BET specific surface area of 2366 m2/g. Due to optimized pore space and open Cu2+ functional sites, Cu-ABTC-a displays high C2H2 storage capacity of 208 cm3 g−1 at 298 K and separation selectivities for equimolar C2H2/CH4 and CO2/CH4 at 298 K, respectively.

Kinetic separation of propylene over propane in a microporous metal-organic framework

Propylene (C3H6)/propane (C3H8) separation is one of the most challenging as well as most energy-intensive separation processes in the petrochemical industry. Herein we report a microporous metal–organic framework ELM-12 with appropriate channels where efficient separation of C3H6 over C3H8 is achieved via the kinetic separation effect. Time-dependent kinetic adsorption, density-functional theory calculation and breakthrough experiments collaboratively demonstrate that the considerable diffusivity difference between C3H6 and C3H8 accounts for the excellent separation performance of ELM-12. The high kinetic C3H6/C3H8 separation factor (204 at 298 K), large breakthrough time interval, and easy regeneration process of this MOF, make it a promising adsorbent for this important separation task. Furthermore, this material is highly stable under ambient condition and its production can be easily scaled up, rendering it quite favorable for practical industrial application.

Evaluation of the BET Theory for the Characterization of Meso and Microporous MOFs

AbstractSurface area determination with the Brunauer–Emmett–Teller (BET) method is a widely used characterization technique for metal–organic frameworks (MOFs). Since these materials are highly porous, the use of the BET theory can be problematic. Several researchers have evaluated the BET method to gain insights into the usefulness of the obtained results and interestingly, their findings are not always consistent. In this review, the suitability of the BET method is discussed for MOFs that have a diverse range of pore widths below the diameters of N2 or Ar and above 20 Å. In addition, the surface area of MOFs that are obtained by implementing different approaches, such as grand canonical Monte Carlo simulations, calculations from the crystal structures or based on experimental N2, Ar, or CO2 adsorption isotherms, are compared and evaluated. Inconsistencies in the state‐of‐the‐art are also noted. Based on the current literature, an overview is provided of how the BET method can give useful estimations of the surface areas for the majority of MOFs, but there are some crucial and specific exceptions which are highlighted in this review.

Postsynthetic Metalation Metal-Organic Framework as a Fluorescent Probe for the Ultrasensitive and Reversible Detection of PO43- Ions.

The self-assembly of a zinc salt with the novel ligand 4,4',4″-[(1,3,5-triazine-2,4,6-triyl)tris(sulfanediyl)]tribenzoic acid generated 3D microporous metal-organic frameworks (MOFs), namely, {[Zn4(L3-)2(O2-)(H2O)2]·4EtOH} n. The frameworks with multiple Lewis basic sites exhibit easily sensitized properties. After encapsulation of the Tb3+ cation in this Zn-MOF, the as-obtained fluorescent-functionalized Tb@Zn-MOFs not only maintain distinguished chemical stabilities but also exhibit strong characteristic emissions of trivalent terbium ions. Interestingly, Tb@Zn-MOF has been chosen to be a potential highly selective and sensitive luminescent platform for the reversible detection of PO43- ions in aqueous and living cell buffer solutions with a fast response time of 10 s and a low detection limit (0.1 ppm). Strikingly, this work presents the first example of a fluorescent sensor that can quantitate PO43- in simulated biological fluids and monitor these ions in the water system in a wide range of concentrations from 10-6 to 10-3 M.

Suspension Processing of Microporous Metal-Organic Frameworks: A Scalable Route to High-Quality Adsorbents

SummaryMetal-Organic Frameworks (MOFs) have been intensively studied for applications such as gas storage, gas separation, catalysis, drug delivery, and more. Typically, the development of MOFs involves a post-synthetic solvent exchange process, which usually requires a significant investment of time, energy, labor, and resources. Herein, we propose a novel post-synthetic processing methodology for commercial and laboratory-scale MOFs called “Suspension Processing.” Suspension processing is a non-destructive, agitation-based technique that provides efficient solvent exchange, pore cleaning, and surface defect removal in MOFs. Suspension processing has shown the capability to significantly improve the surface area and gas uptake properties of microporous MOFs, including PCN-250, UiO-66, and HKUST-1. Suspension processing displays improved time, energy, and labor efficiency, as well as considerably enhanced product quality. These findings confirm suspension processing as a straightforward methodology with applicability as a universal technique for the production of high-quality microporous materials.

Highly Selective Gaseous and Liquid-Phase Separation over a Novel Cobalt(II) Metal–Organic Framework

The mild recognition sites of oxygen atoms and phenyl rings from 5-(4-pyridyl)-methoxyl isophthalic acid (5,4-PMIA2-) moieties and tetrakis(4-pyridyloxymethylene) methane (TPOM) linkers inside the channels of a novel three-dimensional microporous metal-organic framework (MOF) [Co2(5,4-PMIA)2(TPOM)0.5]· xsolvent (1) are presumed to provide pore environments with moderate contacts toward guests, as indicated by grand canonical Monte Carlo simulations, which appear to be beneficial for adsorption and separation applications. As expected, 1 represents one of the rare examples that show both high storage capacity of C2H n and good adsorption selectivity of C2H n/CH4 and CO2/CH4 under ambient conditions, and yet, it has significantly lower energy consumption for regeneration. In addition, a validated submicro-1-based microsolid-phase extraction (μ-SPE) method for the determination of trace monohydroxylated polycyclic aromatic hydrocarbons in complex human urine was developed with satisfactory sensitivity and good precision by online coupling to liquid chromatography-mass spectrometry, which represents the first example of a mixed-ligand MOF applied as an efficient sorbent for μ-SPE.

A Trifunctional Luminescent 3D Microporous MOF with Potential for CO2 Separation, Selective Sensing of a Metal Ion, and Recognition of a Small Organic Molecule

A 3D microporous luminescent metal–organic framework {[Zn(oba)(L)0.5]·dma}n (IITKGP‐9, IITKGP represents the Indian Institute of Technology Kharagpur; L = 3,3′‐azodipyridine, H2oba = 4,4′‐oxydibenzoic acid) with 1D rhombus‐shaped channels has been synthesized by employing a bent organic linker with an unexploited azo‐functionalized N,N′ spacer. The metal–organic framework (MOF) exhibits potential for highly selective sorption of CO2 with excellent selectivity of CO2 from CO2/N2 (291 at 273 K and 118 at 295 K) and CO2/CH4 (17.5 at 273 K and 4.8 at 295 K) at a pressure of 1 bar, as demonstrated by ideal adsorbed solution theory (IAST) calculations. Such high separation ability, especially at 273 K for CO2/N2, can be attributed to the microporous (5.8 × 6.6 Å2) nature of this MOF and the enhanced interactions of the adsorbed CO2 molecules with the functional azo groups decorating the pore channels. This MOF is highly emissive at 374 nm upon excitation at 310 nm. The free azo groups exposed in the channels serve as functional sites for the sensing of metal ions and the recognition of small organic molecules through the quenching of fluorescence. Fluorescence measurements revealed that this MOF can selectively sense Fe3+ and also detect toxic nitromethane with high sensitivity. Elemental mapping by energy‐dispersive X‐ray spectroscopy and powder XRD analysis of the Fe3+‐loaded MOF material, recyclability tests, and a plausible quenching mechanism are presented. Thus, this MOF demonstrates potential as a trifunctional MOF material for three different applications, namely selective gas separation, selective ion sensing, and selective recognition of organic molecules.

Synthesis, crystal structure and adsorption property of a microporous Cd(II) metal–organic framework based on 1H-imidazo[4,5-f][1,10]phenanthroline

A microporous metal–organic framework (MOF), [Cd(IP)Cl]n (1, HIP = 1H-imidazo[4,5-f][1,10]phenanthroline), with 1D square channels along the c axis was constructed through the solvothermal method. Because of the polar nitrogen atoms and the π-electron-rich ligand, activated MOF 1a presents a strong interaction with CO2, showing selective capture of CO2 from a mixture of CO2/N2. Additionally, MOF 1a also shows significant selective capture of CO2 from CO2/CH4 and CO2/C2H4 mixtures due to the sieving effect of the 1D channels. The column breakthrough experiment results further confirmed that microporous MOF 1a could be used as a potential porous material for selective CO2 adsorption.

Isoreticular interpenetrated pillared-layer microporous metal-organic framework as a highly effective catalyst for three-component synthesis of pyrano[2,3-d]pyrimidines

Two isoreticular microporous Zn(II)-MOFs, [Zn2(NH2-BDC)2(4-bpdh)]·3DMF (TMU-16-NH2) and [Zn2(BDC)2(4-bpdh)]·3DMF (TMU-16), (NH2-BDC = amino-1,4-benzenedicarboxylate, BDC = 1,4-benzenedicarboxylate and 4-bpdh = 2,5-bis(4-pyridyl)-3,4-diaza-2,4-hexadiene) were used as heterogeneous catalysts. The TMU-16-NH2 was used as an efficient heterogeneous base catalyst for the three-component cyclocondensation of 1,3-dimethylbarbituric acid, aryl aldehydes and malononitrile, giving rise to pyrano[2,3-d]pyrimidines. The ease of catalyst synthesis, excellent conversions and reusability of the catalyst for five consecutive cycles without a significant degradation in its catalytic activity, suggests significant future potential of this metal-organic framework for a wide range of base catalyzed reactions.

Separation of Acetylene from Carbon Dioxide and Ethylene by a Water-Stable Microporous Metal-Organic Framework with Aligned Imidazolium Groups inside the Channels.

Separation of acetylene from carbon dioxide and ethylene is challenging in view of their similar sizes and physical properties. Metal-organic frameworks (MOFs) in general are strong candidates for these separations owing to the presence of functional pore surfaces that can selectively capture a specific target molecule. Here, we report a novel 3D microporous cationic framework named JCM-1. This structure possesses imidazolium functional groups on the pore surfaces and pyrazolate as a metal binding group, which is well known to form strong metal-to-ligand bonds. The selective sorption of acetylene over carbon dioxide and ethylene in JCM-1 was successfully demonstrated by equilibrium gas adsorption analysis as well as dynamic breakthrough measurement. Furthermore, its excellent hydrolytic stability makes the separation processes highly recyclable without a substantial loss in acetylene uptake capacity.

Separation of Acetylene from Carbon Dioxide and Ethylene by a Water‐Stable Microporous Metal–Organic Framework with Aligned Imidazolium Groups inside the Channels

AbstractSeparation of acetylene from carbon dioxide and ethylene is challenging in view of their similar sizes and physical properties. Metal–organic frameworks (MOFs) in general are strong candidates for these separations owing to the presence of functional pore surfaces that can selectively capture a specific target molecule. Here, we report a novel 3D microporous cationic framework named JCM‐1. This structure possesses imidazolium functional groups on the pore surfaces and pyrazolate as a metal binding group, which is well known to form strong metal‐to‐ligand bonds. The selective sorption of acetylene over carbon dioxide and ethylene in JCM‐1 was successfully demonstrated by equilibrium gas adsorption analysis as well as dynamic breakthrough measurement. Furthermore, its excellent hydrolytic stability makes the separation processes highly recyclable without a substantial loss in acetylene uptake capacity.

Made in Water: A Stable Microporous Cu(I)-carboxylate Framework (CityU-7) for CO2, Water, and Iodine Uptake.

Using water as the sole solvent, the bifunctional molecule tetrakis(methylthio)-1,4-benzenedicarboxylic acid (TMBD) was reacted with Cu(CH3CN)4BF4 to form a robust microporous metal-organic framework (MOF, CityU-7) featuring Cu(I) ions being simultaneously bonded to the carboxyl and thioether donors. The MOF solid is stable in air and can be easily activated by heating, without the need for treatment with organic solvents. The subnanoscopic pores (ca. 0.6 nm) of the host net allow for uptake of CO2 and H2O but exhibit lesser sorption for N2 at 77 K. The microporous net can also be penetrated by I2 molecules.

Monodisperse Metal-Organic Framework Nanospheres with Encapsulated Core-Shell Nanoparticles Pt/Au@Pd@{Co2(oba)4(3-bpdh)2}4H2O for the Highly Selective Conversion of CO2 to CO.

A new microporous metal-organic framework (MOF) with formula {Co2(oba)4(3-bpdh)2}4H2O [oba = 4,4'-oxybis(benzoic acid); 3-bpdh = N, N'-bis-(1-pyridine-3-yl-ethylidene)-hydrazine] was assembled, and its morphology was found to undergo a microrod-to-nanosphere transformation with temperature variation. Core-shell Au@Pd functional nanoparticles (NPs) were successfully encapsulated in the center of the monodisperse nanospheres, and Pt NPs were well-dispersed and fully immobilized on the surface of Au@Pd@1Co to build the Pt/Au@Pd@1Co composites, which exhibited NPs catalytic activity for the reverse water gas shift reaction. The core-shell Au@Pd NPs in MOF significantly enchanced the CO selectivity of the catalyst, and the Pt NP loading on the surface of the nanosphere afforded a desirable CO2 conversion.

Conversion of CO2 into liquid hydrocarbons in the presence of a Co-containing catalyst based on the microporous metal-organic framework MIL-53(Al)

A novel 10%Co/MIL-53(Al) nanohybrid based on the microporous metal-organic framework MIL-53(Al) prepared by MW-assisted synthesis exhibits the properties of a bifunctional catalyst with activity in CO2 hydrogenation to CO and consecutive synthesis of liquid hydrocarbons from carbon monoxide formed. The observed increase in the CO2 conversion in comparison with the thermodynamically possible conversion is assumed to be due to the expected shift of the equilibrium toward the formation of CO as a result of its further rapid conversion to hydrocarbons by the Fisher-Tropsch reaction.

A Moisture-Stable 3D Microporous CoII -Metal-Organic Framework with Potential for Highly Selective CO2 Separation under Ambient Conditions.

Selective adsorption and separation of CO2 from flue gas and landfill gas mixtures have drawn great attention in industry. Porous MOF materials are promising alternatives to achieve such separations; however, the stability in the presence of moisture must be taken into consideration. Herein, we have constructed a microporous metal-organic framework (MOF) {[Co(OBA)(L)0.5 ]⋅S}n (IITKGP-8), by employing a V-shaped organic linker with an azo-functionalized N,N' spacer forming a 3D network with mab topology and 1D rhombus-shaped channels along the crystallographic 'b' axis with a void volume of 34.2 %. The activated MOF reveals a moderate CO2 uptake capacity of 55.4 and 26.5 cm3 g-1 at 273 and 295 K/1 bar, respectively, whereas it takes up a significantly lower amount of CH4 and N2 under similar conditions and thus exhibits its potential for highly selective sorption of CO2 with excellent IAST selectivity of CO2 /N2 (106 at 273 K and 43.7 at 295 K) and CO2 /CH4 (17.7 at 273 K and 17.1 at 295 K) under 1 bar. More importantly, this MOF exhibits excellent moisture stability as assessed through PXRD experiments coupled with surface area analysis.

Iodine Adsorption in Metal Organic Frameworks in the Presence of Humidity.

Used nuclear fuel reprocessing represents a unique challenge when dealing with radionuclides such as isotopes of 85Kr and 129I2 due to their volatility and long half-life. Efficient capture of 129I2 ( t1/2 = 15.7 × 106 years) from the nuclear waste stream can help reduce the risk of releasing I2 radionuclide into the environment and/or potential incorporation into the human thyroid. Metal organic frameworks have the reported potential to be I2 adsorbents but the effect of water vapor, generally present in the reprocessing off-gas stream, is rarely taken into account. Moisture-stable porous metal organic frameworks that can selectively adsorb I2 in the presence of water vapor are thus of great interest. Herein, we report on the I2 adsorption capacity of two microporous metal organic frameworks at both dry and humid conditions. Single-crystal X-ray diffraction and Raman spectroscopy reveal distinct sorption sites of molecular I2 within the pores in proximity to the phenyl- and phenol-based linkers stabilized by the I···π and I···O interactions, which allow selective uptake of iodine.

Solvo-thermal synthesis of a unique alkaline earth-transition Ba-Cd micro-porous coordination framework as hetero-metallic luminescent sensor for Cu2+ and real-time detection of benzaldehyde

In this work a unique hetero-metallic alkaline earth-transition Ba-Cd luminescent micro-porous metal-organic framework {[BaCd(μ6-tp)1.5(μ2-Cl)(H2O) (DMF)2]·0.75H2O}n (H2tp=terephthalic acid) (1) has been prepared under solvo-thermal conditions. In 1 infinite 1D {Ba-X-Cd} (X=O, Cl) inorganic chains are linked via these full de-pronated tp2− ligands forming a unique 3D I1O2 type micro-porous coordination framework. PXRD patterns of 1 have been determined confirming pure phases of 1. Luminescence investigations suggested that 1 exhibits highly selective and sensitive sensing for trace amounts of benzaldehyde in ethanol, which provides a facile method for real-time detection of benzaldehyde. Meanwhile 1 also exhibits highly selective and sensitive sensing for Cu2+ over other cations with high quenching efficiency Ksv value 1.15×104L·mol−1. As far as we know, 1 represents the first example of alkaline earth-transition hetero-metallic Ba-Cd micro-porous coordination framework as bi-functional luminescent probes for Cu2+ and benzaldehyde.

Fabrication of ultrathin MIL-96(Al) films and study of CO2 adsorption/desorption processes using quartz crystal microbalance

This contribution reports the fabrication and characterization of ultrathin films of nanoparticles of the water stable microporous Al tricarboxylate metal organic framework MIL-96(Al). The preparation of MOF dispersions in chloroform has been optimized to obtain dense monolayer films of good quality, without nanoparticle agglomeration, at the air-water interface that can be deposited onto solid substrates of different nature without any previous substrate functionalization. The MOF studied shows great interest for CO2 capture because it presents Al3+ Lewis centers and hydroxyl groups that strongly interact with CO2 molecules. A comparative CO2 adsorption study on drop-cast, Langmuir-Blodgett (LB) and Langmuir-Schaefer (LS) films using a Quartz Crystal Microbalance-based setup (QCM) has revealed that the CO2 uptake depends strongly on the film fabrication procedure and the storage conditions. Noteworthy the CO2 adsorption capacity of LB films is increased by 30% using a simple and green treatment (immersion of the film into water during 12 h just after film preparation). Finally, the stability of LB MOF monolayers upon several CO2 adsorption/desorption cycles has been demonstrated, showing that CO2 can be easily desorbed from the films at 303 K by flowing an inert gas (He). These results show that MOF LB monolayers can be of great interest for the development of MOF-based devices that require the use of very small MOF quantities, especially gas sensors.

Nanoscale Zr‐Based MOFs with Tailorable Size and Introduced Mesopore for Protein Delivery

AbstractIntroduction of large pore in the primitive microporous metal–organic frameworks (MOFs) with tailorable particle size can endow them with desired properties for potential applications in the intracellular delivery of membrane‐impermeable proteins. However, no research is found to focus on this topic until now. Herein, a monocarboxylic acid (MA) and organic base comodulation strategy is developed to synthesize the hierarchically porous UiO‐66 nanoparticles. MA of dodecanoic acid is utilized to control the pore size while trimethylamine (TEA) plays a key role in modulating the nucleation of crystallization to regulate the particle size. In comparison with microporous UiO‐66, a model protein of cytochrome c (Cyt c) could be efficiently loaded into the mesoporous MOFs (mesoMOFs). The size‐dependent cellular uptake is also evaluated, and it is verified that mesoMOFs with particle size of 90 nm could be endocytosed into living cells with highest efficiency. These outstanding merits enable the current mesoMOFs not only to exhibit efficient encapsulation of Cyt c but also facilitate the protein delivery into the cytosol and subsequent endosomal escape. Given the exceptional chemical stability, hierarchically porous structure as well as tunable particle size, the elaborated mesoUiO‐66 nanoparticles might offer a promising platform for a variety of biomedical applications.

Manufacturing Macroporous Monoliths of Microporous Metal–Organic Frameworks

We report the first use of a pressure-assisted sintering technique on metal–organic framework powders, allowing for the fast production of crystalline macroporous monoliths. Mechanical and microstructural characterization of the monoliths is presented. The interconnected macroporosity of the compacts can be adjusted, providing an immense interface for gas–solid interaction. The sintering technique is well-established and commercially available, allowing industrial scale-up of the process.