In this work, a mesoporous c-Al 2 O 3 membrane was synthesised on an a-Al 2 O 3 substrate by a solgel dip coating process. The membranes were characterised using SEM, field emission SEM, Xray diffractometry and N 2 adsorption/desorption measurements (Brunauer-Emmett-Teller analyses). The characterisation results revealed that a flawless c-alumina membrane layer with 3?5 mm thickness and 2?1 nm average pore size was achieved. Subsequent separation tests indicated that CO 2 could be separated from N 2 by the mesoporous c-Al 2 O 3 membrane. In spite of the difficulties of the separation, the optimised microstructure achieved for the prepared membrane led to desirable and regular permeation behaviour. It was also observed that separation could be more efficient in high pressure permeation conditions. The prepared substrate fulfilled the required strength and permeability for the thin c-Al 2 O 3 membrane film under these conditions. Accordingly, an optimised completely ceramic membrane structure, applicable for CO 2 separation applications, was achieved.