The nanoporous crystalline phase of a cheap commercial polymer shows, already at room temperature, large uptake of gas molecules (e.g., butadiene and carbon dioxide) leading to polymer/gas clathrate phases. These clathrate phases have been characterized by X-ray diffraction and infrared linear dichroism measurements. Gas release kinetics are strongly reduced as a consequence of clathrate formation and can be further reduced by (010) orientation of the host phase, i.e., by placing the ac layers of close-packed enantiomorphous polymer helices nearly parallel to the film plane. The reported results indicate that this robust and easy-to-process polymeric crystalline framework is suitable for gas storage and controlled release.