Preparation of polybenzoxazole-silica hybrid membranes for CO2/CH4 separation

The gas transport properties of novel polybenzoxazole (PBO)-silica hybrid membranes prepared via a sol-gel reaction and different thermal treatment protocols were investigated. The thermal decomposition and glass transition temperatures of the hybrids increased with increasing silica content, indicating improved thermal stability by hybridization with silica. With increasing silica content and higher thermal treatment temperature, the hybrids showed enhanced CO2 permeability and CO2/CH4 selectivity, which tended to intersect with the upper-bound trade-off line. The improved CO2/CH4 separation ability of the PBO-silica hybrid membranes might be due to the increased intermolecular chain distance and free volume holes favorable for CO2/CH4 separation created around the polymer/silica interfacial area.