The sol–gel method was applied to Al-doped bis (triethoxysilyl) methane (BTESM, Si–C–Si unit) membranes. High C3H6 : C3H8 permeance ratios of approximately 40 at 200 °C were achieved through the precise control of the silica network size via a spacer method using Si–C–Si units as well as the incorporation of Al in BTESM-derived networks.
