A new eco-friendly method recently developed in our group has been further investigated for the preparation of gas selective silica-based molecular sieve membranes on/in macroporous tubular ceramic supports without any intermediate layer. The synthesis protocol under sub- and supercritical conditions was based on an "On-Stream Supercritical Fluid Deposition method" (OS-SFD) applying supercritical carbon dioxide (scCO(2)) as an attractive "green" solvent with easily adjustable properties enabling a controlled solubilisation/reaction of precursors and their transport to the ceramic support. Parameters influencing the final membrane characteristics such as permeates flow rate, calcination treatment and deposition steps have been examined for a selected reaction mixture, transmembrane pressure and defined deposition temperatures. On-line monitoring of the membrane formation process (deposition signature curve) was used in this process. Membrane characteristics are discussed in correlation with their gas permeation properties. The optimized crack-free silica membranes prepared at 50 degrees C have a compact microstructure but a thermal stability limited to 400 degrees C. A second deposition run allowed a recovery of the molecular sieving behaviour with a thermally activated transport for He up to 350 degrees C. These promising results demonstrate the potential of this novel method for the preparation of uniform molecular sieve membranes deposited directly on macroporous supports with virtually zero waste. (C) 2013 Elsevier B.V. All rights reserved.