The invention relates to gas separation, in particular to separation of C02 from C02-rich liquids, particularly from C02 absorption liquids used in the removal of C02 from off-gases or product flows, such as natural gas or synthesis gas. According to the invention, C02 is separated from a C02-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 C02 is transported from the liquid through the membrane.