A microporous MOF Zn(BDC)(4,4'-Bipy)0.5 (MOF-508b, BDC = 1,4-benzenedicarboxylate, 4,4'-Bipy = 4,4'-bipyridine) was examined for the separation and removal of CO2 from its binary CO2/N-2 and CO2/CH4 and ternary CO2/CH4/N-2 mixtures by fixed-bed adsorption. With one-dimensional pores of about 4.0 x 4.0 angstrom to induce their differential interactions with the three components, MOF-508b exhibits highly selective adsorption to CO2 with the,adsorption capacity of 26.0 wt % at 303 K and 4.5 bar. This is the first example of microporous MOFs for the separation and removal of CO2 from its binary and ternary mixtures by fixed-bed adsorption, establishing the feasibility of the emerging microporous MOFs for their potential. applications in this very important industrial and environmental process.

a b s t r a c tAn adsorption study of hexane and xylene isomers mixtures was addressed in a rigid zirconium terephthalate UiO-66 (UiO for University of Oslo) with octahedral and tetrahedral cavities of free diameter close to 1.1 nm and 0.8 nm, respectively. Multicomponent equimolar breakthrough experiments show that the adsorption hierarchy of structural isomers in UiO-66 is opposite to the one observed in conventional adsorbents. For hexane isomers, it was found that the amount adsorbed increases with the degree of branching, being 2,2-dimethylbutane (22DMB) and 2,3-dimethylbutane (23DMB) the more retained molecules. Regarding the xylene isomers, the results show that the adsorption of the bulkier ortho-xylene (oX) is favoured compared to its homologues. The structural similarity between MOF UiO-66 and zeolite MCM-22 suggests that the reverse shape selectivity observed in the adsorption of hexane and xylene isomers might be attributed to the rotational freedom of the molecules inside the small cavities.

A three-dimensional microporous metal-organic framework Zn(BDC)(Dabco)(0.5) (BDC = 1,4-benzenedicarboxylate, Dabco = 1,4-diazabicyclo [2,2,2]octane), having two types of intersecting pores to encapsulate linear hexane and to block branched hexanes, and thus exhibiting highly selective sorption with respect to n-hexane, has been successfully applied to the kinetic separation of hexane isomers by fixed-bed adsorption. Document Type: Article Language: English

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.