The synthesis method for PEG/alkyl-based imidazolium/pyridinium ionic liquids was studied. Four steps were used to fabricate the membranes: polymerization, chloromethylation, linkage of the polymers with the pendent groups and membrane cast. Permeabilities and CO2/N2 selectivity of two membranes were examined and each showed remarkable CO2/N2 selectivity. CO2 permeability of the [PSM-MIM][Cl] membrane is better than that of the [PSM-MEIM][Cl] membrane, which is due to the steric hindrance of the methoxyethyl group. The syntheses of PEG/alkyl-based imidazolium/pyridinium ionic liquids (IL) were studied. PEG-based ILs were demonstrated to have better H2S solubilities than the alkyl-based ILs. H2S solubilities of the imidazolium ILs and pyridinium ILs were compared. The anion effects on H2S solubilities have been investigated, while the temperature effects on H2S solubilities will need to be studied in the near future.