Most membranes show carbon dioxide perm-selectivity at low temperatures (such as the room temperature). High temperature carbon dioxide permeable membranes offer advantages for effective carbon dioxide capture from fossil fuel burning power plants at high temperatures. The paper will focus on a new group of dual-phase membranes that permeate only carbon dioxide at high temperatures (>500oC). These dual-phase membranes consist of a metal or oxygen ionic conducting oxide phase and a molten carbonate phase which conduct respectively electrons or oxygen ions and carbonate ions. The paper will summarize key properties of the dual-phase membranes, including the effects of the ionic conductivity of materials, pore structure of the ceramic phase, membrane thickness and the operation conditions on the permeance of carbon dioxide. Applications of these membranes in membrane reactors for water gas shift reaction or dry-reforming of methane for pre- or post-combustion carbon dioxide capture will be discussed. Finally, the paper will address the key issues of the stability of the membranes in industrially related atmospheres.