This work presents a combined molecular simulation and experimental study to understand the effect of graphene on the packing and gas adsorption performance of a new class of polymers, known as polymers of intrinsic microporosity (PIMs). PIMs can be processed to membranes or other useful forms and their chemistry can be tailored for specific applications. Their rigid and contorted macromolecular structures give rise to a large amount of microvoids attractive for small molecule adsorption. We show that the presence of graphene in the composite affects the structure of the membrane as evidenced by the change in colour and SEM micrographs, but it does not reduce significantly the adsorption capacity of the material. (C) 2014 The Authors. Published by Elsevier Inc.