Mg-MOF-74 has attracted intense attention due to its high CO2 uptake ability. In this work, a new strategy by using magnesium oxide as seeds was developed to synthesize a dense, defect-free Mg-MOF-74 membrane with hydrogen-selectivity. The mixed gas separation factor of H-2/CO2 mixture could be improved by the post-modification of the Mg-MOF-74 membrane with ethylenediamine, since the modification with amine groups enhanced the strong adsorption of CO2 molecules, which reduces the permeance of CO2. The separation factors for both as-synthesized and amino-functionalized Mg-MOF-74 membranes reduce gradually with increasing temperature. After amination of the open Mg sites, the separation performance of the Mg-MOF-74 membrane was remarkably enhanced, and the H-2/CO2 selectivity increased from 10.5 to 28 at room temperature. (C) 2014 Elsevier Ltd. All rights reserved.