In this paper, an overview is given on membranes with oxygen facilitated transport properties to enrich the oxygen content in air. Special emphasis is paid to recent developments of oxygen carrier systems and carrier containing membranes. Concepts leading to a structural evolution of supported liquid membranes are discussed in view of ion as well as gas separation processes. As a new concept, micro-encapsulated liquid membranes are introduced, in which a mobile carrier operates in the interior of liquid droplets that are encapsulated and dispersed in a solid polymer matrix and routes to prepare the new membranes described.