The present invention relates to a process for the separation of at least one unbranched C4-C2O hydrocarbon from a fluid mixture containing the unbranched hydrocarbon and at least one branched isomer of the unbranched hydrocarbon, which comprises the step of-contacting the fluid mixture with an adsorbent comprising a porous metal organic framework material, which material comprises at least one at least bidentate organic compound coordinately bound to at least one metal ion, to get the unbranched hydrocarbon adsorbed, wherein the at least one at least bidentate organic compound is a monocyclic, bicyclic or polycyclic ring system which is derived from at least one heterocycle selected from the group consisting of pyrrole, alpha-pyridone and gamma-pyridone and has at least two ring nitrogens and is unsubstituted or bears one or more substituents selected independently from the group consisting of halogen, Ci-6-alkyl, phenyl, NH2, NH(d-6-alkyl), N(C1-6-alkyl)2, OH, Ophenyl and OCi-6-alkyl, where the substituents Ci_6-alkyl and phenyl are unsubstituted or bear one or more substituents selected independently from the group consisting of halogen, NH2, NH(d-6-alkyl), N(C1-6-alkyl)2, OH, Ophenyl and OCi-6-alkyl. The present invention also relates to the use of said porous metal-organic framework material in a process for the separation of unbranched hydrocarbons from their branched isomers.