Nanocomposite membranes are a class of innovative filtering materials made up of nanofillers embedded in a polymeric or inorganic oxide matrix that functionalized for the membrane. Thermally rearranged (TR) polymers are found to have a good blending of selectivity and permeability. Chemical iridization is a process for used to make HAB-6FDA polyimide from 3,3 dihydroxy-4,4 diamino-biphenyl (HAB) & 2,2-bis-(3,4-dicarboxyphenyl) hexafluoro propane dianhydride (6FDA). The sample is first changed from a pure polymer membrane to a silica nanofiller doped polymer layer and explain thermally rearrangement for gas permeability in polymer nanocomposite layers and its relationship with kinetic diameter of different gases. The selectivity is decreases as the permeability increases that shows on a trade-off relationship between permeability & selectivity. The CO2 permeability of the HAB-6FDA TR polymers is greater than that of other classes of polymers by equal free volume and indicating that these TR polymers have free volume distribution that supports high permeability. Thermally rearranged polymer nanocomposite exhibits higher gas permeability than that of silica doped and pure polymer. The selectivity for H2/N2 and H2/CO2 gas pairs exceeds towards Robeson's upper bound limit and in case of H2/CH4 gas pair this limit were crossed the Robeson’s upper bond limit. UV spectroscopy shows the change in transmission at higher wavelengths, while XRD show the reduction in FWHM with thermal treatment temperature. Polymer nanocomposite can be utilized to obtain high purity hydrogen gas for refinery and petrochemical applications.