Enhanced CO₂ separation performance for tertiary amine-silica membranes via thermally induced local liberation of CH₃Cl

A facile method for the fabrication of amine-silica membranes with enhanced CO₂ separation performance was proposed via the thermally induced liberation of small molecules from quaternary ammonium salt. Quaternary ammonium-silica (QA-SiO_1.5) xerogel powders/films were fabricated via sol-gel processing and their thermal stability was systematically studied using thermogravimetric mass spectrometer, Fourier transform infrared, energy dispersive spectroscopy, and positron annihilation lifetime spectroscopy analysis. CO₂ sorption performances of QA-SiO_1.5 derived xerogel powders were quantitatively compared after assigning their relevant parameters to a dual-mode sorption model. The gas permeation performances of membranes derived from QA-SiO_1.5 were evaluated in terms of kinetic diameter and temperature dependence of gas permeance, and activation energy (E_p) required for gas permeation. The results indicate that liberation of the CH₃Cl molecules from these membranes significantly improved both CO₂ permeation and CO₂/N₂ separation capabilities. Therefore, the present study provides insight that should be useful in the development of high-performance CO₂ separation membranes via the effect of the thermally induced liberation of small molecules.