Polymers of Intrinsic Microporosity (PIM-1) (Figure 1) are a unique class of organic polymers which are porous because of the presence of a spiro centre that prevents rotation of polymer chain which causes them to possess internal free volume (IFV)1. PIM-1 are unique compared to other porous carbon nanostructures because of the presence of regular C-N surface functionalities. The permeability and selectivity of PIM-1 for gas separation can be tuned via chemical modification of the nitrile group or photochemical modification of the spirocentre2, 3, 4. Because of such structural attributes these polymers possess a high surface area and can be probed for N2 adsorption and entrapment. Here, we explore the role of the CN surface functionalities of PIM-1 in inhibiting gas diffusivity, by providing a comparative study of N2 and Ar diffusion rates. (Figure Presented).