Homogeneous sub-nanophase network tailoring of dual organosilica membrane for enhancing CO2 gas separation

Dual organosilica membranes were synthesized to investigate the effects of differing molar ratios of bis (triethoxysilyl) ethane (BTESE)/glycidyl Polyhedral oligomeric silsesquioxane (glycidyl POSS) on the membrane performance. The reaction mechanism behind CO2 capture using the organosilica membranes under ambient conditions was also investigated. A facile in-situ framework synthesis approach was introduced for the copolymerization reaction of dual organosilica. BTESE has a smaller molecular size than that of glycidyl POSS, and the Si–C–C–Si linkage is the main structure contributing to its high CO2 affinity. Additionally, the dimensional and mechanical stability were maintained at high doping levels owing to the inclusion of glycidyl POSS. Consequently, the free volume of the resulting hybrid networks increased owing to the cage structure and high cross-link density, which was attributed to the coexistence of epoxy ring-opening polymerization and condensation polymerization. The characterization and permeation tests revealed that the 1B0.5P gel with the best copolymerization effect exhibits a high CO2 permeance of 5.74 × 10−8 mol m−2 s−1 Pa−1 at 25 °C and ideal selectivity values of 11.61, 37.55 and 63.67 for CO2/H2, CO2/CH4 and CO2/N2, respectively. Moreover, a new analytical technique was proposed to investigate the surface microstructure of organosilica membranes for the first time using optical microscopy.