Calix[4]arenes and nanotubes based on them convert NO2/N 2O4 gases into nonvolatile NO+ species and encapsulate them. In a one-electron reduction scheme with hydroquinone, the complexed NO+ transforms into NO gas. While NO is released, calixarenes are regenerated and can be loaded again. Supramolecular materials for generation, storage and release of NO can be potentially created, with high-capacity calixarene nanotubes holding a special promise. © Wiley-VCH Verlag GmbH & Co. KGaA, 2007.