Abstract: It is provided a water-saturated carbon molecular sieve membrane obtainable by a) providing a hydrophilic carbon molecular sieve membrane (CMSM) comprising pores of a pore size from 0.25 nm to 0.55 nm for molecular sieving, pores of a pore size from 0.55 nm to 0.90 nm for adsorption diffusion and a negligible amount of pores larger than 0.90 nm such that a plot of N2 permeance versus pressure of permeation at room temperature and at a pressure from 1 to 4 bar has zero or negative slope; and b) humidifying the membrane until obtaining a water-saturated carbon molecular sieve membrane. It is also provided a process for the separation of a gas from a gas mixture with such a water-saturated membrane, and its use for solvent dehydration, and as a membrane reactor.