The invention relates to gas separation, in particular to separation of CO2 from CO2-rich liquids, particularly from CO2 absorption liquids used in the removal of CO2 from off-gases or product flows, such as natural gas or synthesis gas. According to the invention, CO2 is separated from a CO2-rich liquid by a method comprising a step wherein, under elevated pressure, said liquid is contacted with a membrane based on polyacetylene substituted with trimethylsilyl groups such that the pressure across the membrane is at least 1 bar and that at least a part of the CO2 is transported from the liquid through the membrane.