Experimental measurements and molecular simulations were conducted for two zeolitic imidazolate frameworks, ZIF-8 and ZIF-76. The transferability of the force field was tested by comparing molecular simulation results of gas adsorption with experimental data available in the literature for other ZIF materials (ZIF-69). Owing to the good agreement observed between simulation and experimental data, the simulation results can be used to identify preferential adsorption sites, which are located close to the organic linkers. Topological mapping of the potential-energy surfaces makes it possible to relate the preferential adsorption sites, Henry constant, and isosteric heats of adsorption at zero coverage to the nature of the host-guest interactions and the chemical nature of the organic linker. The role played by the topology of the solid and the organic linkers, instead of the metal sites, upon gas adsorption on zeolite-like metal-organic frameworks is discussed.

The objective of this work was to study the adsorption and separation of the most important families of hydrocarbon compounds on metal-organic frameworks (MOFs), in comparison with zeolites. For this purpose, we have selected four probe molecules, each of them representing one of these families, i.e., o- and p-xylene as aromatics, 1-octene as an alkene, and n-octane as an alkane. The separation of these four molecules was studied by binary breakthrough experiments. To represent the large diversity of MOF structures, the experiments were carried out with (i) two MOFs with coordinatively unsaturated metal sites (CUS), i.e., Cu-btc (HKUST-1) and CPO-27-Ni, (ii) a MOF with an anionic framework and extraframework cations, i.e. RHO-ZMOF, and (iii) two rather apolar zeolitic imidazolate framework (ZIF) materials with different pore sizes, i.e. ZIF-8 and ZIF-76. Zeolite NaY and zeolite β were used as polar and apolar reference adsorbents, respectively. The results can be briefly summarized as follows: ZIFs (not carrying any polar functional groups) behave like apolar adsorbents and exhibit very interesting and unexpected molecular sieving properties. CUS-MOFs behave like polar adsorbents but show the specificity of preferring alkenes over aromatics. This feature is rationalized thanks to DFT+D calculations. MOFs with extraframework cations behave like polar (cationic) zeolites.

The separation of paraffin isomers is a very important topic in the petrochemical industry. Zeolite 5A is industrially used to sieve alkane isomers, but its pore size does not allow the separation of monobranched and dibranched alkanes by a kinetic mechanism. In this publication, we compare three ZIF materials in the separation of C6-paraffin isomers: ZIF-8, ZIF-76, and a new material called IM-22. The performance of the materials is evaluated by a breakthrough curve of binary mixtures of n-hexane, 3-methylpentane, and 2,2-dimethylbutane. We show that ZIF-8 is a very attractive alternative to zeolite 5A because it exhibits a high (kinetic) selectivity for the adsorption of linear alkanes and at the same time a high adsorption capacity. The new material IM-22, a ZIF with CHA topology, seems to be particularly suited for the separation of mono-and dibranched paraffin isomers.

The "ZIF-8-water" system displays reproducible shock-absorber behaviour over several cycles with a stored energy of 13.3 J g(-1) and an energy yield close to 85%. The combination of the main features evidenced for ZIF-8, i.e. a quite low intrusion pressure and a high stored energy, opens a field for new applications.

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Current European regulations limit the sulfur content of gasoline to 10 ppmw. Such deep desulfurization levels can be achieved by catalytic hydrodesulfurization processes, but they are accompanied by excessive H2 consumption for unwanted side reactions, in particular, for the hydrogenation of olefins. Selective adsorption constitutes an attractive alternative to catalytic desulfurization. The main challenge is to find adsorbents able to remove the sulfur compounds with very high selectivity from a complex mixture of paraffins, naphthenes, olefins, and aromatic compounds. In the present contribution we present the screening of a large number of metal–organic frameworks (MOFs) for this purpose, using batch adsorption experiments. For the two most promising structures (HKUST-1 and CPO-27-Ni, two cus-MOFs, that is, with coordinatively unsaturated sites), the dynamic behavior, the impact of a model nitrogen-containing compound (pyridine) on the adsorption properties, as well as the regenerability were also evaluated by breakthrough experiments. The good results obtained in purification of our model feeds incited us to perform measurements with a real gasoline feed using batch measurements. The feasibility of adsorptive desulfurization of gasoline using MOFs is discussed on the basis of these results.

Metal–organic materials (MOFs) constitute very attractive materials for storage, separation, catalysis, and drug delivery because of their crystalline hybrid organic–inorganic structures and their large porous volume. Here, we report the energetic behavior, in term of storage/restoration of mechanical energy, of ZIF-8 upon high pressure intrusion–extrusion of aqueous KCl, LiCl, and NaCl solutions of variable concentration. Comparison with the energetic performances of the “ZIF-8–water” system is performed. Whatever the nature of the electrolyte (KCl, LiCl, NaCl), an increase of the intrusion pressures and thereby of the stored energy are observed with the increasing of salt concentration. However, the three studied systems differ, at least for the highest concentrations, by behaving as a shock-absorber for KCl and as a bumper for NaCl and LiCl. A combination of several characterization techniques used before and after intrusion–extrusion experiments, i.e., X-ray diffraction, solid state NMR, and N2 adsorption–desorption experiments, allows us to establish that the ZIF-8 network is preserved after such a treatment.

We report a structural and thermodynamic investigation of the phase behavior of Ga(OH,F)-MIL53, a gallium-based MOF having the MIL-53 topology containing 0.7 wt% fluorine bonded to the metal. Despite some small structural differences, especially for the hydrated form, the overall physical chemistry behavior of Ga(OH,F)-MIL-53 is very similar to standard fluorine free Ga-MIL-53 material. A combination of in situ X-ray diffraction, in situ Fourier transform infrared spectroscopy, differential scanning calorimetry and heat capacity measurements allowed to establish that Ga(OH,F)-MIL53 under vacuum (i.e. in the empty material) exhibits two stable phases: a nonporous narrow-pore (np) phase favored at low temperature and a large-pore (lp) phase favored at high temperature, accompanied by a huge hysteresis effect. Structure determination of the hydrated material Ga(OH,F)-MIL-53_np_H 2 O obtained after synthesis, activation and rehydration, was also performed. Density functional theory calculations show that it is not a stable structure of Ga(OH,F)-MIL53 in absence of adsorbed water molecules. Instead, this hydrated structure is a swollen variant of the np phase, where the flexible framework has expanded to accommodate water molecules.