Pore-Size Tuning of Plasma-Deposited Organosilica Membranes for Gas Separation

Organosilica membranes for gas separation were prepared by plasma-enhanced chemical vapor deposition (PECVD) using hexamethyldisiloxane (HMDSO), trimethylmethoxysilane (TMMS), and methyltrimethoxysilane (MTMS) as the silicon precursor. The gas permeation measurement revealed that MTMS-derived membrane had the highest He/N₂ selectivity, followed by the TMMS-derived and HMDSO-derived membranes. FT-IR characterization indicated that the HMDSO-derived membrane has the highest content of methyl group, while the methyl group content for the MTMS-derived membranes was the lowest. These results suggested that the pore size of organosilica membranes can be tuned by changing the chemical structure of the silicon precursor.