Novel compositions suitable for fabrication of CO2-selective membranes are disclosed. In one aspect, the present invention is directed to compositions comprising polyimide/polyamine blends and copolymers, and to compositions comprising interfacially polymerized polyamides. In another aspect this invention is directed to novel CO2-selective membranes comprising such polyimide/polyamine blends and copolymers, and to novel CO2-selective membranes comprising interfacially polymerized polyamides. In yet another aspect, the present invention is directed to a novel water-gas-shift (WGS) reactor comprising the novel CO2-selective membranes. Advantageously, the use of the novel CO2-selective membrane allows alteration of the normal WGS reaction equilibrium, shifting the reaction towards production of H2. Carbon dioxide on the high pressure, feed gas side of the membrane reactor reacts with the novel membranes of the present invention at the interface between the feed gas and the membrane. The reaction product permeates through the membrane to the interface between the feed gas and the low pressure side of the membrane, where the CO2 desorbs into the low pressure side and is removed
