The invention relates to a nanowire structural element suitable for installing, for example, in a microreactor system or microcatalyst system. A template-based method is used for producing the nanowire structural element, wherein electrochemical deposition of the nanowires takes place in nanopores, preferably continuing at least until caps have formed and at least partially grown together. After reinforcing the two cover layers, the structured hollow space between the two cover layers is exposed by dissolving the template foil and removing the dissolved template material, wherein the two cover layers remain intact. The result is a stable, sandwich-like nanostructure having a two-dimensional, open-celled hollow space structure, bounded on two sides by the cover layers and penetrated by the nanowires in a columnar manner in the plane parallel to the cover layers.