Construction of robust open metal-organic frameworks with chiral channels and permanent porosity

Four new metal-organic frameworks (MOFs) containing chiral channels have been synthesized using an achiral, triazine-based trigonal-planar ligand, 4,4',4' '-s-triazine-2,4,6-triyltribenzoate (TATB), and an hourglass secondary building unit (SBU): Zn3(TATB)2(H2O)2.4DMF.6H2O (1); Cd3(TATB)2(H2O)2.7DMA.10H2O (2); [H2N(CH3)2][Zn3(TATB)2(HCOO)].HN(CH3)2.3DMF.3H2O (3); [H2N(CH3)2][Cd3(TATB)2(CH3COO)].HN(CH3)2.3DMA.4H2O (4). MOFs 1 and 2 are isostructural and possess (10,3)-a nets containing large chiral channels of 20.93 and 21.23 A, respectively, but are thermally unstable due to the easy removal of coordinated water molecules on the SBU. Replacement of these water molecules by formate or acetate generated in situ leads to 3 and 4, respectively. Formate or acetate links SBUs to form infinite helical chains bridged by TATB to create three-dimensional anionic networks, in which one of the two oxygen atoms of the formate or acetate is uncoordinated and points into the void of the channels. This novel SBU-stabilization and channel-functionalization strategy may have general implications in the preparation of new MOFs. Thermogravimetric analysis (TGA) shows that solvent-free 3' is thermally stable to 410 degrees C, while TGA studies on samples vapor-diffused with water, methanol, and chloroform show reversible adsorption. MOF 3 also has permanent porosity with a large Langmuir surface area of 1558 m2/g. All complexes exhibit similar strong luminescence with a lambdamax of approximately 423 nm upon excitation at 268.5 nm.     

Nanotubular metal-organic frameworks with high porosity based on T-shaped pyridyl dicarboxylate ligands

Two nanotubular metal-organic frameworks (MOFs), {Cu(L1)·2H(2)O·1.5DMF}(∞) (1) and {Cu(2)(L2)(2)(H(2)O)(2)·7H(2)O·3DMF}(∞) (2), with novel topologies have been constructed based on Cu(2+), 5-(pyridin-4-yl)isophthalic acid (L1) and 5-(pyridin-3-yl)isophthalic acid (L2), respectively. Two MOFs were characterized by IR spectroscopy, thermogravimetry, single-crystal, and powder X-ray diffraction methods. Network analysis reveals a two-nodal (3,6)-connected (4·6(2))(2)(4(2)·6(10)·8(3)) net and a three-nodal (3,4)-connected (4·8(2))(4)(4(2)·8(2)·10(2))(2)(8(4)·12(2)) net. Interpenetration is inherently prevented by both of the topologies of the frameworks. The porosity of MOF 1 was confirmed by N(2) and CO(2) gas adsorption investigations. MOF 1 exhibits remarkable hydrogen sorption hysteresis at low pressure and a H(2) uptake capacity of 1.05 wt% at 77 K and 1 atm.     

A mesoporous metal-organic framework with permanent porosity

A mesoporous metal-organic framework possessing permanent porosity has been synthesized and characterized for the first time.     

Influence of connectivity and porosity on ligand-based luminescence in zinc metal-organic frameworks

Applications of metal-organic frameworks (MOFs) require close correlation between their structure and function. We describe the preparation and characterization of two zinc MOFs based on a flexible and emissive linker molecule, stilbene, which retains its luminescence within these solid materials. Reaction of trans-4,4'-stilbene dicarboxylic acid and zinc nitrate in N,N-dimethylformamide (DMF) yielded a dense 2-D network, 1, featuring zinc in both octahedral and tetrahedral coordination environments connected by trans-stilbene links. Similar reaction in N,N-diethylformamide (DEF) at higher temperatures resulted in a porous, 3-D framework structure, 2. This framework consists of two interpenetrating cubic lattices, each featuring basic zinc carboxylate vertices joined by trans-stilbene, analogous to the isoreticular MOF (IRMOF) series. We demonstrate that the optical properties of both 1 and 2 correlate with the local ligand environments observed in the crystal structures. Steady-state and time-resolved spectroscopic measurements reveal that the stilbene linkers in the dense structure 1 exhibit a small degree of interchromophore coupling. In contrast, the stilbenoid units in 2 display very little interaction in this low-density 3-D framework, with excitation and emission spectra characteristic of monomeric stilbenes, similar to the dicarboxylic acid in dilute solution. In both cases, the rigidity of the stilbene linker increases upon coordination to the inorganic units through inhibition of torsion about the central ethylene bond, resulting in luminescent crystals with increased emission lifetimes compared to solutions of trans-stilbene. The emission spectrum of 2 is found to depend on the nature of the incorporated solvent molecules, suggesting use of this or related materials in sensor applications.     

Constructing energetic covalent organic frameworks with high stability and low sensitivity

Developing new functional explosives that display high stability, good energy performance, and low sensitivity are one of the key directions of energetic materials research. In this work, two-dimensional(2D)Schiff-based energetic covalent organic frameworks(COFs) are prepared based on triaminoguanidine salts with different anions as building blocks. Benefiting from the robust covalent bond in 2D extended polygons and strong π-π interactions in the eclipsed interlayers, the synthesized energetic ...     

Twelve-connected porous metal-organic frameworks with high H(2) adsorption

The twelve-connected metal-organic frameworks {[Ni(3)(OH)(L)(3)].n(solv)}(infinity) and {[Fe(3)(O)(L)(3)].n(solv)}(infinity) [LH(2) = pyridine-3,5-bis(phenyl-4-carboxylic acid)] have been prepared and characterised: these materials can be desolvated to form porous materials that show adsorption of H(2) up to 4.15 wt% at 77 K.     

Elaboration of metallic compacts with high porosity for mechanical supports of SOFC

The development of third generation Solid Oxide Fuel Cells (SOFC) with metallic mechanical supports presents several advantages over that of ceramic stacks by offering a lower cost and longer lifetime of the stacks. As a consequence, it is necessary to prepare metallic porous compacts that remain stable at the operating temperature of the SOFC (700–800 °C) under reductive atmosphere. This paper presents an innovative process to elaborate iron, nickel and cobalt porous compacts. The process is based on the thermal decomposition of metal oxalate precursors with controlled morphology into metallic powders with coralline shape. Uniaxial compaction of such powders (without binder addition to the powders) under low uniaxial pressures (rising from 20 to 100 MPa) gave rise to green compacts with high porosity and good mechanical properties. After annealing at 800 °C under H₂ atmosphere, the compacts still present interconnected porosity high enough to allow sufficient gas flow to feed a SOFC single cell in hydrogen: the porosity rises from 25 to 50% for iron compacts, from 20 to 50% for cobalt compacts, and is higher than 40% for nickel compacts. Results from physicochemical characterization (XRD, SEM, gas permeation, Hg porosimetry) corroborated the process for SOFC application.     

Activated carbon aerogels with high bimodal porosity for lithium/sulfur batteries

Activated carbon aerogels (ACAs) with high bimodal porosity were obtained for lithium/sulfur batteries by potassium hydroxide (KOH) activation. Then sulfur–activated carbon aerogels (S–ACAs) composites were synthesized by chemical deposition strategy. The S–ACAs composites were characterized by field emission scanning electron microscopy (FESEM), transmission electron microscopy, and N₂ adsorption/desorption measurements. It is found that the activated carbon aerogels treated by KOH activation presents a porous structure, and sulfur is embedded into the pores of the ACAs network-like matrix after a chemical deposition process. The Li/S–ACAs (with 69.1 wt% active material) composite cathode exhibits discharge capacities of 1,493 mAh g^?1 in the first cycle and 528 mAh g^?1 after 100 cycles at a higher rate of C/5 (335 mA g^?1). The S–ACAs composite cathode exhibits better electrochemical reversibility, higher active material utilization, and less severe polysulfide shuttle than S–CAs composite cathode because of high bimodal porosity structure of the ACAs matrix.     

A guest-dependent approach to retain permanent pores in flexible metal-organic frameworks by cation exchange

Two anionic metal-organic frameworks were successfully prepared based on pre-designed flexible multicarboxylate ligands and indium cations. Owing to the flexibility of the bridging organic linkers, which could not themselves sustain the frameworks, both of the frameworks showed thermal instability and shrinkage after removal of guest solvent molecules. Inspired by bamboo, we used a guest-dependent approach to tune the permanent porosity of the MOFs. In this approach, several tetraalkyammonium cations of different sizes were introduced into the channels by cation exchange to act as partitions and to support the main frameworks. This approach significantly enhanced the stability of the framework and its permanent porosity. Moreover, the gas-adsorption properties (such as gate sorption, hysteresis, and selectivity) of the MOFs were also modulated by the judicious choice of guest cations.     

Stable metal-organic frameworks with high catalytic performance in the cycloaddition of CO2 with aziridines

Based on the mixed ligands XN(4′-(4-pyridine)4,2′:2′,4′′-terpyridine) and isophthalic acid(IPA), three new metal-organic frameworks(MOFs) {[M_2(XN)_2(IPA)_2]·2 H_2O}_n(M=Co(1), Mn(2), Ni(3)) were assembled and structurally characterized,presenting 3 D pillar-chain feature structures. Stability measurements demonstrate that these compounds possess high thermostability and can endure different organic solvents as well as various acid/base solutions with pH range of 1 to 14. Importantly,compounds 1–3 can serve as high-efficiency catalysts for the transformation of CO_2 and aziridines to form high-value oxazolidinones under mild conditions, exhibiting excellent cyclicity at least five times.     

Metal-organic frameworks with exceptionally high capacity for storage of carbon dioxide at room temperature

Metal-organic frameworks (MOFs) show high CO2 storage capacity at room temperature. Gravimetric CO2 isotherms for MOF-2, MOF-505, Cu3(BTC)2, MOF-74, IRMOFs-11, -3, -6, and -1, and MOF-177 are reported up to 42 bar. Type I isotherms are found in all cases except for MOFs based on Zn4O(O2C)6 clusters, which reveal a sigmoidal isotherm (having a step). The various pressures of the isotherm steps correlate with increasing pore size, which indicates potential for gas separations. The amine functionality of the IRMOF-3 pore shows evidence of relatively increased affinity for CO2. Capacities qualitatively scale with surface area and range from 3.2 mmol/g for MOF-2 to 33.5 mmol/g (320 cm3(STP)/cm3, 147 wt %) for MOF-177, the highest CO2 capacity of any porous material reported.     

A novel asymmetric activated carbon electrode doped with metal-organic frameworks for high desalination performance

Journal of Solid State Electrochemistry - In this work, we synthesized metal-organic framework Cu3(BTC)2 which was applied as the doping materials of anode electrodes in capacitive deionization...     

New type of spherical pore Al alloy foam with low porosity and high strength

The Ultra Light Metal Structure with variouskinds of pores (open, close) realizes the lightness andmultifunction of structural material. The functionsinclude lightness (ρ < 1), high specific strength, highenergy absorption, sound insulation, heat insulationand electromagnetism shield. It is one of the hotspotsin material research nowadays[1— . The requirements 6]of high speed movement and high technology make Alalloy foam, which has higher specific st…     

Metal-assisted salphen organic frameworks (MaSOFs) with high surface areas and narrow pore-size distribution

The one-pot three component synthesis of metal containing microporous organic polymers with high BET surface areas is presented. The metal salphen units were built during the formation of the porous polymers. Selective gas adsorption depending on the metal ions is discussed.     

Continuous synthesis for zirconium metal-organic frameworks with high quality and productivity via microdroplet flow reaction

A series of Zr-based metal-organic frameworks were continuously synthesized with high quality and high productivity through microdroplet flow reaction.     

Aqueous dispersions of colloidal poly(3-hexylthiophene) gel particles with high internal porosity

This work outlines the development of nano-porous, sub-micron poly(3-hexylthiophene) (P3HT) gel particles as solution-processable inks for applications in polymer solar cells. These dispersions are produced by emulsifying bulk P3HT organogels into water containing surfactant. The optical characteristics and stability of the resulting gel particles are assessed and their structure characterized. The P3HT within the gel particles is shown to retain its crystallinity with no evidence of doping. The gel particles are shown to be stable against aggregation due to the presence of surfactant at the oil/water interface. The fracture of the gel network during emulsification produces a bimodal distribution of particles that increase in size with increasing P3HT concentration in the 'parent' organogel. Small Angle Neutron Scattering measurements show that the particles maintain the structure of the bulk gels with high specific surface area. Spray-coating the gel particle dispersions produces uniform thin-films, which have been used to fabricate polymer/fullerene solar cells with a fully spray-coated active layer.     

The first systhesis of a chromia-pillared layered niobate with porosity, acidity and high thermostability

Although the hydrated niobic acid is an unusual solid acid and making an impact onits application in catalysis, it is usually nonporous and has a rather low surface area andweak acidity upon heat treatment. To overcome these shortcomings, the layered nio-bate had been pillared with thermostable inorganic oxides such as alumina and silica.Chromia is also a suitable inorganic oxide which can be used as pillar and contributesnew properties to the resultant materials. Here, we report the first synthesis of achromia-pillared layered niobate with porosity, acidity and thermostability.