The structure of sodium-Y zeolite, Na56Si1360384A156, containing chemisorbed deuterated benzene has been studied for two different benzene coverages at 4 K and room temperature by powder neutron diffraction. The bare dehydrated zeolite has also been examined. The space group is Fd3m with cell parameters, at room temperature, of a = 24.85 (3) A, 24.83 (3) A, and 24.81 (3) 8, for the bare zeolite, low-coverage, and high-coverage samples, respectively. At 4 K a = 24.85 (3) 8, at low coverage and a = 24.81 (3) 8, for the high-coverage sample. The sodium ions are distributed over three sites whose positions at room temperature for the bare zeolite are Na(1) at 32e (x,x,x), x = 0.2345 (2); Na(2) at 32e, x = 0.0507 (4), and Na(3) at 16c (O,O,O), with fractional occupancies of 100 (2)%, 58 (2)%, and 44 (2)%, respectively.

Hybrid porous solids, with their tunable structures, their multifunctional properties and their numerous applications, are currently topical, particularly in the domain of adsorption and storage of greenhouse gases. Most of the data reported so far concern the performances of these solids in this domain, particularly in terms of adsorbed amounts of gas but do not explain at the atomic level why and how adsorption and storage occur. From a combination of structural, spectroscopic, thermodynamic experiments and of molecular simulations, this tutorial review proposes answers to these open questions with a special emphasis on CO(2) and CH(4) storage by some rigid and flexible hybrid porous materials.

No abstract

International audienceA combination of experimental (gravimetry, microcalorimetry, and quasi-elastic neutron scattering) measurements and molecular modeling was employed to understand the coadsorption of CO2 and CH4 in the zirconium terephthalate UiO-66(Zr) material from both the thermodynamic and kinetic points of view. It was shown that each type of molecules adsorb preferentially in two different porosities of the material, that is, while CO2 occupy the tetrahedral cages, CH4 are pushed to the octahedral cages. Further, a very unusual dynamic behavior was also pointed out with the slower molecule, that is, CO2, enhancing the mobility of the fast one, that is, CH4, that contrasts with those usually observed so far for the CO2/CH4 mixture in narrow window zeolites where the molecules are most commonly diffusing independently or slowing-down the partner species. Such behavior was interpreted in light of molecular simulations that evidenced a jump type mechanism involving a tetrahedral cages-octahedral cages-tetrahedral cages sequence that occurs more frequently for CH4 when in presence of CO2. The consequences in terms of CO2/CH4 selectivity and the possible use of this MOF-type material in a PSA process are then discussed. It is thus clearly emphasized that this MOF material combines several favorable features including a good selectivity, high working capacity, and potential easy regenerability that make it as a good alternative candidate of the conventional NaX Faujasite used in pressure swing adsorption

No abstract

One flue over the cuckoo's nest: A novel porous Zr‐based MOF combining a high chemical stability, easy “green” synthesis and scalability is prepared. This material incorporating carboxylic functions on its organic linkers has thermodynamically and kinetically very promising properties for CO2 capture from post‐combustion flue gas under real working conditions.

Channel tunnel: Diffusion of methane in the metal–organic frameworks MIL‐53(Cr) and MIL‐47(V) was elucidated by quasi‐elastic neutron scattering and molecular dynamics simulation, and 1D diffusion of CH4 along the channels was found in both materials. The self‐diffusivity of methane at low loading is very large, more than one order of magnitude higher than in zeolites. The picture shows CH4 molecules in a MIL‐53(Cr) channel.

No abstract