Poly(amidoamine) (PAMAM) dendrimers showed high CO2 separation properties and were successfully immobilized in a poly(ethylene glycol) (PEG) network upon photopolymerization of PEG dimethacrylate. The PAMAM dendrimer incorporation ratio was readily controlled, and a stable self-standing membrane containing up to 75 wt.% PAMAM dendrimer was obtained. The CO2 separation properties over smaller H-2 were investigated by changing the PAMAM dendrimer content or generation and CO2 partial pressure (Delta P-CO2) under atmospheric conditions. Especially, a polymeric membrane containing 50 wt.% PAMAM dendrimer (0th generation) exhibited an excellent CO2/H-2 selectivity of 500 with CO2 permeability of 2.74 x 10(-14) m(3)(STP)m/(m(2) s Pa) or 3.65 x 10(3) barter (1 barrer = 7.5 x 10(-18) m(3) (STP)m/(m(2) s Pa)) when a mixture gas (CO2/H-2:5/95 by vol.) was fed at 25 degrees C and 100 kPa with 80% relative humidity. This polymeric materials are promising for a novel CO2 separation membrane. (C) 2008 Elsevier B.V. All rights reserved.