A gas separator, a method for producing the gas separator, and a method for separating gases based on a property of inelasticity of the gases. The inventive gas separator is a permeable porous material for separating a mixture of gases by selectable pore size exclusion, comprising pores formed with at least one nanostructured compound. In other words, the inventive porous material can be used to separate a mixture of gases based upon the different working diameter of each of the gases. By selecting specific nanostructured compounds, the porous material can be tailored to contain pores of a predetermined size which allow gases having a working diameter smaller than the size of the pores to pass through the material while preventing the passage of gases having a working diameter greater than the size of the pores.