Adsorption of gases and vapours in silica based xerogels

•Selective adsorption properties of xerogels for gases and vapours has been studied to a little extent.•Silica xerogels and hybrid organic/inorganic xerogels present different selectivity.•The change composition of xerogels can give reversed selectivity for the ethane/ethylene mixture.•Hybrid xerogels were able to differentiate the adsorption of the mono and di-branched hexane isomers.