Specific oriented metal-organic framework membranes and their facet-tuned separation performance

Modulating the crystal morphology, or the exposed crystal facets, of metal-organic frameworks (MOFs) expands their potential applications in catalysis, adsorption, and separation. In this article, by immobilizing the citrate modulators on Au nanoparticles and subsequently being fixed on solid copper hydroxide nanostrands, a well-intergrown and oriented HKUST-1 cube crystal membrane was formed at room temperature. In contrast, in the absence of Au nanoparticles, well-intergrown and oriented cuboctahedron and octahedron membranes were formed in water/ethanol and ethanol, respectively. The gas separation performances of these HKUST-1 membranes were tuned via their exposed facets with defined pore sizes. The HKUST-1 cube membrane with exposed {001} facets demonstrated the highest permeance but lowest gas binary separation factors, while the octahedron membrane with exposed {111} facets presented the highest separation factors but lowest permeance, since the window size of {111} facets is 0.46 nm which is smaller than 0.9 nm of {001} facets. Separation of 0.38 nm CO2 from 0.55 nm SF6 was realized by the HKUST-1 octahedron membrane. As a proof of concept, this will open a new way to design MOF-related separation membranes by facet controlling.

Crystal structure of 4,4'-bipyridine-1,1'-diium naphthalene-2,6-di-sulfonate dihydrate

The title hydrated mol-ecular organic salt, C10H10N2 (2+)·C10H6O6S2 (2-)·2H2O, crystallized with half a bipyridinium cation, half a naphthalene-2,6-di-sulfonate anion and a water mol-ecule in the asymmetric unit. The whole cation and anion are generated by inversion symmetry, the inversion centers being at the center of the bridging C-C bond of the cation, and at the center of the fused C-C bond of the naphthalene group of the anion. In the crystal, the anions and cations stack alternately along the a axis with π-π inter-actions [inter-centroid distance = 3.491 (1) Å]. The anions are linked via O-H⋯O(sulfonate) hydrogen bonds involving two inversion-related water mol-ecules, forming chains along [10-1]. These chains are bridged by bifurcated N-H⋯(O,O) hydrogen bonds, forming a three-dimensional framework structure. There are also C-H⋯O hydrogen bonds present, reinforcing the framework structure.

Zinc metal-organic frameworks: efficient catalysts for the diastereoselective Henry reaction and transesterification

Three new compounds bearing different flexible side functional groups, viz. 2-acetamidoterephthalic acid (H2L1), 2-propionamidoterephthalic acid (H2L2) and 2-benzamidoterephthalic acid (H2L3), were synthesized and their coordination reactions with zinc(II) were studied. X-ray crystallography showed the formation of novel metal organic frameworks with different dimensionalities, where the side functional groups of amidoterephthalic acid and/or auxiliary ligands were found to play significant roles. These frameworks [Zn2(L1)2(4,4'-bipyridine)2(H2O)(DMF)]n (1), [Zn4(L2)3(OH)2(DMF)2(H2O)2]n (2) and [Zn(L3)(H2O)2]n·n/2(1,4-dioxane) (3) act as heterogeneous polymeric solid catalysts not only for the diastereoselective nitroaldol (Henry) reaction of different aldehydes with nitroalkanes but also for transesterification reactions. These MOF-based heterogeneous catalysts can be recycled without losing their activity.

Zeolitic imidazolate framework composite membranes and thin films: synthesis and applications

The recent developments of zeolitic imidazolate framework (ZIF) membranes/films, ZIF–polymer mixed matrix membranes and their applications are reviewed in this article.

Multicycle water vapour stability of microporous breathing MOF aluminium isophthalate CAU-10-H

A long-time water vapour stability over 700 sorption cycles is proven for the first time for a breathing MOF, here CAU-10-H.

Advancement of sorption-based heat transformation by a metal coating of highly-stable, hydrophilic aluminium fumarate MOF

A 300 μm thick, polycrystalline, thermally well coupled coating of microporous aluminium fumarate was deposited on a metal substrate and found to be stable for at least 4500 ad-/desorption cycles with water vapour.

Influence of an amine group on the highly efficient reversible adsorption of iodine in two novel isoreticular interpenetrated pillared-layer microporous metal–organic frameworks

Two isoreticular two-fold interpenetrated microporous Zn(ii)-MOFs are compared with each other for the encapsulation of iodine.

Correlation of Gas Permeability in a Metal-Organic Framework MIL-101(Cr)-Polysulfone Mixed-Matrix Membrane with Free Volume Measurements by Positron Annihilation Lifetime Spectroscopy (PALS)

Hydrothermally stable particles of the metal-organic framework MIL-101(Cr) were incorporated into a polysulfone (PSF) matrix to produce mixed-matrix or composite membranes with excellent dispersion of MIL-101 particles and good adhesion within the polymer matrix. Pure gas (O₂, N₂, CO₂ and CH₄) permeation tests showed a significant increase of gas permeabilities of the mixed-matrix membranes without any loss in selectivity. Positron annihilation lifetime spectroscopy (PALS) indicated that the increased gas permeability is due to the free volume in the PSF polymer and the added large free volume inside the MIL-101 particles. The trend of the gas transport properties of the composite membranes could be reproduced by a Maxwell model.

A chiral mixed metal-organic framework based on a Ni(saldpen) metalloligand: synthesis, characterization and catalytic performances

A three-dimensional (3D) chiral mixed metal-organic framework [Cd4Cl(Ni-L)3(Ni-HL)(H2O)6(DMF)]·4DMF (CMOF 1) based on a new enantiopure dicarboxyl-functionalized Ni(saldpen) metalloligand Ni-H2L and a novel tetranuclear cadmium cluster [Cd4Cl(CO2)7(CO2H)] has been synthesized and characterized by elemental analyses, IR and UV-vis spectra, thermogravimetric analysis, nitrogen and carbon dioxide adsorption, powder and single-crystal X-ray diffractions. Each tetranuclear-cadmium cluster in 1 is linked by eight Ni-L ligands, and each Ni-L ligand is linked by two tetranuclear-cadmium clusters to generate a 3D framework with 1D open channels (∼1.1 × 0.9 nm(2)) along the b-axis. Based on its good stability, permanent porosity, Lewis acid sites and moderate uptake for CO2, 1 can be used as a self-supported heterogeneous catalyst for the synthesis of optically active propylene carbonate by asymmetric cycloaddition of CO2 with racemic propylene oxide under relatively mild conditions.