Gas separation membrane

A method of forming a gas separation membrane including: depositing a first hydrophilic polymer solution; depositing on top of the firs hydrophilic polymer solution a second, different hydrophilic polymer solution thereby forming a two-layer polymer solution; forming the two-layer polymer solution into one of a forward osmosis membrane and a pressure retarded osmosis membrane by bringing the second, different hydrophilic polymer solution into contact with water to form the dense layer; coating one of the forward osmosis membrane and the pressure retarded osmosis membrane with a thin layer of a third, different, hydrophilic polymer more pH tolerant than the first and second hydrophilic polymer solutions to form a dense rejection layer thereon; and exposing one of the coated forward osmosis membrane and the coated pressure retarded osmosis membrane to a high pH solution. A gas separation membrane formed from the foregoing process.