Hybrid organosilica membrane with high CO2 permselectivity fabricated by a two-step hot coating method

• Sol particle size and microstructure are important for fabricating the membrane.
• Two-step hot coating method can combine the superior properties of two sols.
• CO2 separation performance of the membrane is partly controlled by CO2 adsorption.
• The as-prepared BTESE-derived membrane shows a high separation performance for CO2.

Using 1, 2-bis (triethoxysilyl) ethane as a precursor, a hybrid organosilica membrane with high CO2 permselectivity, has been prepared by a two-step hot coating method. Here two sols with different sol particle sizes and microporous structures were prepared by tuning the dose of acid. By combining the two sols in the coating process using the two-step hot coating method, a thin and dense hybrid organosilica layer can be obtained. Single gas permeation experiments of the as-prepared membrane show a high permeance of 1.3×10−6 mol m−2 s−1 Pa−1 for CO2, with excellent CO2/N2 and CO2/CH4 separation factor of 23.5 and 31.5, respectively. Based on the mixture gas permeation experiments, the selectivities of CO2/N2 and CO2/CH4 at 20 °C were measured to be 10.5 and 17.5, respectively. The high perm-selectivity indicates that the as-prepared membrane contains only few defects. Furthermore, we demonstrate that the CO2 separation performance of the as-prepared membrane is greatly controlled by its CO2 adsorption properties.