Here, we show how a membrane can be designed and operated to achieve 'uphill' permeation of carbon dioxide against its own chemical potential difference by employing the transport of carbonate ions with coupled 'downhill' permeation of oxygen. Absolute values of the carbon dioxide permeability of the order of 10(6) Barrers are achieved experimentally over more than 200 h of operation. These permeabilities are some four orders of magnitude greater than polymeric gas separation membranes. We believe that these high permeabilities are due to the effective use of the oxygen chemical potential difference across the membrane as a driving force for carbonate transport. (C) 2015 The Authors. Published by Elsevier B.V.