One of the main problems of gas storage in porous materials is that many molecules of interest adsorb too weakly to be retained effectively. To enhance gas storage in metal-organic frameworks (MOFs), we propose the use of kinetic trapping, i.e., a process where the guest gas is captured in the voids at loading conditions and not released immediately at normal conditions. In this approach, the diffusion-limiting pore size and the framework flexibility have to be matched to the gas, requiring flexible pore apertures to be smaller than the van der Waals diameter of the trapped guest. We selected the Metal-Organic Framework Ulm University-4 (MFU-4) with a pore aperture of 2.52 Å as a model coordination framework and used it for storage of xenon (with van der Waals diameter of 4.4 Å). Although xenon atoms are substantially larger than the MOF pore aperture, MFU-4 could be loaded with xenon by applying moderately high gas pressures. This is demonstrated to be due to the pore flexibility as confirmed by computational studies. The xenon loading could be tuned (from 0 wt % to more than 44.5 wt %) by changing the loading parameters such as pressure, temperature, and time, and the xenon atoms remained inside the pores upon exposing the material to air atmosphere at room temperature. To understand the material behavior, TGA, XRPD, and Xe NMR spectroscopy and computational studies were carried out.

Herein we present a new proton-conducting iron­(II) metal–organic framework (MOF) of an unusual structure formed by chains of alternating bistriazolate-p-benzoquinone anions and iron­(II) cations with four axially coordinated water molecules. These chains assemble via π–π stacking between the aromatic units to form a three-dimensional grid-like network with channel pores filled with water molecules. The material was structurally characterized by single-crystal XRD analysis, and its water and thermal stability was investigated. The proton conductivity was studied by impedance measurements on needle-like single crystals. A simple but efficient measurement setup consisting of interdigital electrodes was used. The influence of the crystal orientation, temperature, and humidity was investigated. The iron­(II)-MOF showed the highest proton conductivity of 3.3·10–3 S cm–1 at 22 °C and 94% relative humidity. Contrary to most known structures, the conductivity in this material is controlled by chemical properties of the pore system rather than by grain boundaries. The presented material is the starting point for further tailoring the proton-conducting properties, independent of morphological features which could find potential applications as membrane materials in proton-exchange membrane fuel cells.

Two organometallic pentanuclear zinc complexes, namely [ZnEt(Mebta)] and [ZnMe(Mebta)], containing tridentate N-donor ligands (5,6-dimethylbenzotriazolate, Mebta) were prepared by a one-pot synthesis. These compounds represent the first examples of organometallic complexes featuring a Kuratowski-type bond topology. Zinc ions were introduced as organometallic precursors (either diethylzinc or dimethylzinc was used), which upon mixing with the ligand yielded the desired complexes spontaneously. The organometallic complexes were characterized by a range of analytical techniques including NMR- and FT-IR spectroscopy, mass spectrometry, and elemental analysis. In addition, the structure of [ZnEt(Mebta)] could be solved by single-crystal X-ray analysis. The thermal and chemical stability of the complexes was studied by TGA, VT-XRPD and DRIFT, in addition to NMR and mass spectrometric investigations. The compounds were found to be unexpectedly stable under various conditions and to lack any reactivity with electrophilic reactants such as aldehydes, which commonly react easily with organozinc compounds. However, the basic alkyl groups could be reacted with strongly acidic compounds such as trifluoroacetic acid.

In this work, a metal–organic framework (MOF), namely MFU-4, which is comprised of zinc cations and benzotriazolate ligands, was used to entrap SF6 gas molecules inside its pores, and thus a new scheme for long-term leakproof storage of dangerous gasses is demonstrated. The SF6 gas was introduced into the pores at an elevated gas pressure and temperature. Upon cooling down and release of the gas pressure, we discovered that the gas was well-trapped inside the pores and did not leak out – not even after two months of exposure to air at room temperature. The material was thoroughly analyzed before and after the loading as well as after given periods of time (1, 3, 7, 14 or 60 days) after the loading. The studies included powder X-ray diffraction measurements, thermogravimetric analysis, Fourier-transform infrared spectroscopy, scanning electron microscopy, 19F nuclear magnetic resonance spectroscopy and computational simulations. In addition, the possibility to release the gas guest by applying elevated temperature, vacuum and acid-induced framework decomposition was also investigated. The controlled gas release using elevated temperature has the additional benefit that the host MOF can be reused for further gas capture cycles.

In this study, we investigate the potential of metal-organic frameworks (MOFs) for long-term gas storage at ambient conditions. Specifically, we selected a MOF ZIF-8 (with a 0.34 nm large pore...