Highly porous nanostructured materials face applications for separation techniques and catalysis. Their nanostructure substantially influences their mechanical properties and thus their potential as functional materials. The present thesis deals with the characterisation of porous carbon- and silica-based materials with complex structure at several levels of hierarchy. The aim is to contribute to a better understanding of porous nanomaterials produced by templating processes, and the correlation between structure and functions, especially their mechanical properties. In the first part, X-ray scattering techniques using synchrotron radiation as well as Raman spectroscopy and nanoindentation were used to study carbon-based materials made of pyrolysed wood. The results provided a general kinetics law for the thermal degradation of cellulose, and it was shown that the orientation of native cellulose and the developing graphene sheets of carbon were parallel to the axial direction of the wood cells. The changes of mechanical properties were correlated with the structural transformations due to thermal treatment. In the second part, in-situ synchrotron radiation investigations of sorption phenomena in mesoporous silica-based materials provided quantitative information of pore structure, liquid film formation and growth in confined geometry. Furthermore, it was shown that the pore walls deform reversibly due to capillary condensation.