Polymer monolithic open tubular columns are presented as a solid adsorbent for fast and efficient gas phase separations. A porous monolithic layer of polystyrene–divinylbenzene was formed inside a capillary through an in situ polymerisation method creating a long, open bore column with high flow through permeability. The mechanical stability and chromatographic performance of the column was tested, showing the phase to be extremely stable up to 270 °C and capable of fast separations with efficiencies of almost 4000 theoretical plates per meter.