Hybrid organic inorganic silica membranes are interesting candidates for gas-separation applications due to their excellent hydrothermal stability. However, up to now these membranes lack the separation performance required to separate hydrogen from carbon dioxide. In this work a procedure for doping zirconia into the hybrid silica matrix is reported, resulting in an improved H-2/CO2 permselective membrane compared with non-doped hybrid silica membranes. Zirconia doped 1,2-bis(triethoxysilyl)ethane (Zr-BTESE) was synthesized by sal-gel chemistry, using zirconyl nitrate as the zirconium source. By optimization of the sol reaction conditions (i.e. reaction time and temperature) a homogenous sol was obtained. Defect-free membranes were obtained by adjusting the concentration of the dip-coating solution. The doped membranes showed a slight decrease in hydrogen permeance from 4.4 x 10(-7) to 1.8 x 10(-7) mol m(-2) S-1 Pa-1 as compared to an undoped BTESE membrane, but a large increase in H-2/CO2 (from 4 to 16) and H-2/N-2 (from 12 to 100) permselectivity was observed. (C) 2015 Elsevier B.V. All rights reserved.