Effect of thermal treatment on gas transport properties of hyperbranched polyimide-silica hybrid membranes

► Thermotreated hyperbranched polyimide membranes for gas separation were investigated. ► The thermotreated membranes showed high gas permeability and selectivity. ► The CO2/CH4 separation ability was improved by hybridization with silica. ► The improved separation ability were caused by enhanced free volume elements.