wileyonlinelibrary.comsuch as the mono-branched hexane isomer 3MP are usually still present and contribute to decrease the performance of the process. To overcome this drawback, there is a crucial need to search for alternative porous solids able to more selectively adsorb di-branched compounds such as the 22DMB from the mono-branched 3MP and linear nHEX.As a typical example, it was demonstrated that zeolite BETA could be used to upgrade the actual TIP processes by partially separating mono from di-branched hexane isomers in a dual layer pressure swing adsorption (PSA) bed with 5A zeolite, [ 3 ] leading to an enhancement of the RON number of the fi nal stream from 86 to 92, a value similar to the one obtained in the Hexsorb process of Axens. The achievement of higher upgrading thus calls for the design of more effi cient porous adsorbents. Metal organic frameworks (MOFs) are the latest class of crystalline porous solids. [ 6 ] These are built up from the linkage of inorganic sub-units and organic ligands, and constitute a versatile class of porous materials due to their large chemical and structural diversity, paving the way for their use in many societally relevant applications (gas storage, separation, catalysis, sensing, biomedicine, etc.) [ 7,8 ] In the fi eld of fl uid separation, it was shown for instance that MOFs could be of a great interest to separate propane from propylene, [ 9 ] xylene or alkane isomers, [ 10 ] carbon dioxide fromThe separation ability of branched alkane isomers ( n HEX, 3MP, 22DMB) of the fl exible and functionalized microporous iron(III) dicarboxylate MIL-53(Fe)-(CF 3 ) 2 solid is evaluated through a combination of breakthrough experiments (binary or ternary mixtures), adsorption isotherms, X-ray diffraction temperature analysis, quasi-elastic neutron scattering measurements and molecular dynamics simulations. A kinetically controlled molecular sieve separation between the di-branched isomer of hexane 22DMB from a mixture of paraffi ns is achieved. The reported total separation between mono-and di-branched alkanes which was neither predicted nor observed so far in any class of porous solids is spectacular and paves the way towards a potential unprecedented upgrading of the RON of gasoline.

International audienceThe adsorption properties of linear long chain alkanes (from n-pentane to n-nonane) within the rigid MOF MIL-47 (V) have been explored by combining gravimetry measurements and molecular simulations. Both experimental absolute isotherms and enthalpies of adsorption for all n-alkanes were compared with those obtained by configurational bias grand canonical Monte Carlo simulations (CB-GCMC) based on two different force fields. From a fair agreement between experimental and simulated data, a further step consisted of investigating the microscopic adsorption mechanism in play to shed some light onto the preferential orientations and conformations of all investigated n-alkanes. Whereas the trans conformation is predominantly observed for all n-alkanes, the proportion of the n-alkane conformations lying parallel to the direction of the tunnel significantly increases with the chain length, emphasizing that the confinement effect is stronger for the longer chain n-alkanes. Finally, molecular dynamics simulations allowed us to emphasize that all n-alkanes follow a pathway along the direction of the tunnel, leading to a 1D type diffusion mechanism, the motions being mainly centered around the middle of the pores at low loading, whereas they are significantly shifted toward the pore wall when the alkane concentration increases