Two　isostructural　Zirconium　MOFs,　PFC-14　and　PFC-15,　based　on　linear　ligand　bearing　different　alkyl　chains　on　backbones,　have　been　synthesized　under　solvothermal　reaction　conditions.　These　two　MOFs　have　the　same　structures　with　UiO-66　series　but　display　two-fold　interpenetration　in　structure.　In　situ　powder　X-ray　diffraction　during　the　gas　loading　process　demonstrates　that　the　interpenetration　and　the　alkyl　side　chains　on　linkers,　reduces　the　surface　area　though,　creates　adsorption　sites　to　accommodate　CO2　and　CH4　molecules　as　indicated　by　in　situ　XRD　studies.　The　work　presented　here　provides　insight　on　rational　design　of　MOFs　for　gas　adsorption　and　separation.