A facile, versatile and reproducible sol–gel process to make microporous organosilica membranes by using 1,2-bis (triethoxysilyl) ethane (BTESE) as a precursor is reported. The influence of process parameters on sol particle size and rheology of BETSE-derived sols was investigated to produce defect-free composite membranes by a single dipping procedure and subsequent calcination. The microporous structure of a BTESE layer on mesoporous alumina supports enabled selective molecular sieving of gas molecules. Single gas permeation (SGP) experiments, performed at 200 C, showed that a H2/CH4 permselectivity of 24 was reproducibly achieved. NoSF6 gas permeance through these membranes proof the presence of a defect-free microstructure. SEM cross-section analysis showed a hybrid selective layer with a thickness dependent on the sol precursor concentration.