title: Hydrocarbon adsorption in the flexible metal organic frameworks MIL-53(Al, Cr).
abstract: A general study of the adsorption of n-alkanes in the flexible metal organic framework (MOF) MIL-53 is presented. The roles of the length of the alkyl chain (n = 1-9), the nature of the metal (Al, Cr), and temperature were investigated. The shape of the adsorption curves is driven by the alkyl chain length of the n-alkanes. While traditional type-I isotherms are observed for short alkanes (n = 1, 2), adsorbates with longer chains induce clear substeps in the isotherm curves whose positions depend on the chain length. Such substeps are due to a breathing phenomenon, as proven by ex situ X-ray diffraction analysis. They strongly depend on the amount of adsorbate in the pores and on the nature of the metal (Al, Cr), which, for a given alkane, leads to a strong change in the substep positions despite the similar characteristics of the two metals. The adsorption kinetics are highly sensitive to small variations in temperature. Their detailed analysis in different regions of the isotherms shows in some cases the existence of distinct diffusion regimes and/or conformations within the flexible phases.
authors.affiliation: MACS, Institut Charles Gerhardt, UMR 5253 CNRS/ENSCM/UM2/UM1, 34296 Montpellier cedex 5, France.
authors.forename: Thuy Khuong
authors.initials: TK
authors.lastname: Trung
authors.forename: Philippe
authors.initials: P
authors.lastname: Trens
authors.forename: Nathalie
authors.initials: N
authors.lastname: Tanchoux
authors.forename: Sandrine
authors.initials: S
authors.lastname: Bourrelly
authors.forename: Philip L
authors.initials: PL
authors.lastname: Llewellyn
authors.forename: Sandra
authors.initials: S
authors.lastname: Loera-Serna
authors.forename: Christian
authors.initials: C
authors.lastname: Serre
authors.forename: Thierry
authors.initials: T
authors.lastname: Loiseau
authors.forename: François
authors.initials: F
authors.lastname: Fajula
authors.forename: Gérard
authors.initials: G
authors.lastname: Férey