This work presents an extreme biomimetics route for the modification of the surface of fibre-based scaffolds of poriferan origin by the creation of novel nanostructured multiphase biocomposites. The exceptional thermal stability of the nanostructured sponge chitin allowed for the formation of a novel nanocrystalline chitin-(Ti,Zr)O-2 composite with a well-defined nanoscale structure under hydrothermal conditions (160 degrees C). Using a combination of experimental techniques, including X-ray diffraction, scanning electron microscopy, high resolution transmission electron microscopy, EDX mapping and near edge electron loss spectroscopy (ELNES) in TEM and thermogravimetryidifferential scanning calorimetry coupled with mass spectrometry; we showed that this bioorganic scaffold facilitates selective crystallization of TiO2, predominantly in form of anatase, over the monoclinic zirconium dioxide (baddeleyite). The control of the crystal morphology through the chitin templates is also demonstrated. Obtained samples were characterized in terms of their photoluminescent properties and photocatalytic performance. These data confirm the high potential of the extreme biomimetics approach for developing a new generation of multiphase biopolymer-based nanostructured materials. (C) 2016 Elsevier B.V. All rights reserved.