In one aspect, the present invention provides a curable composition useful in the preparation of a gas separation membrane. The curable composition comprises a polyvinyl alcohol; an aliphatic polyamine; a polyglycidyl ether; and a salt of a C2 to C4 heterocyclic amino acid. In another aspect the present invention provides a composition comprising a crosslinked polyvinyl alcohol comprising structural units derived from a polyglycidyl ether, a polyamine and the salt of a C2 to C4 heterocyclic amino acid. The compositions are useful in the preparation of gas separation membranes in which the C2 to C4 heterocyclic amino acid in the form of its salt functions as a mobile carrier of carbon dioxide.