One of the most frequent modifications to tune the chemistry of MOFs is linker functionalization -e.g. UiO-66, NH 2 -UiO-66, Cl-UiO-66, yet there are very limited studies on the effect of positional isomerism of these functional groups to the resulting (absorption) properties. In general functionalization adds more binding sites to the MOF structure. But adding functional groups may or may not lead to a better separation capability due to steric hindrance and / or altered pore or window size. Therefore, a methodology is needed to understand the potential diversity in positional functional group isomerism, and how these isomers affect the resultant properties of the framework molecules, eventually leading to design rules for a particular application.