Recently it was shown that enzymatic and mechanical processing of macroscopic cellulose fibers lead to disintegration of long and entangled native cellulose I nanofibers in order to form mechanically strong aqueous gels (Pa ¨a ¨kko ¨et al., Biomacromolecules, 2007Biomacromolecules, , 8, 1934. Here we demonstrate that (1) such aqueous nanofibrillar gels are unexpectedly robust to allow formation of highly porous aerogels by direct water removal by freeze-drying, (2) they are flexible, unlike most aerogels that suffer from brittleness, and (3) they allow flexible hierarchically porous templates for functionalities, e.g. for electrical conductivity. No crosslinking, solvent exchange nor supercritical drying are required to suppress the collapse during the aerogel preparation, unlike in typical aerogel preparations. The aerogels show a high porosity of $98% and a very low density of ca. 0.02 g cm À3 . The flexibility of the aerogels manifests as a particularly high compressive strain of ca. 70%. In addition, the structure of the aerogels can be tuned from nanofibrillar to sheet-like skeletons with hierarchical micro-and nanoscale morphology and porosity by modifying the freeze-drying conditions. The porous flexible aerogel scaffold opens new possibilities for templating organic and inorganic matter for various functionalities. This is demonstrated here by dipping the aerogels in an electrically conducting polyaniline-surfactant solution which after rinsing off the unbound conducting polymer and drying leads to electrically conducting flexible aerogels with relatively high conductivity of around 1 Â 10 À2 S cm À1 . More generally, we foresee a wide variety of functional applications for highly porous flexible biomatter aerogels, such as for selective delivery/separation, tissue-engineering, nanocomposites upon impregnation by polymers, and other medical and pharmaceutical applications.

Chemical vapor deposition of a thin titanium dioxide (TiO 2 ) fi lm on lightweight native nanocellulose aerogels offers a novel type of functional material that shows photoswitching between water-superabsorbent and water-repellent states. Cellulose nanofi brils (diameters in the range of 5-20 nm) with native crystalline internal structures are topical due to their attractive mechanical properties, and they have become relevant for applications due to the recent progress in the methods of their preparation. Highly porous, nanocellulose aerogels are here fi rst formed by freeze-drying from the corresponding aqueous gels. Well-defi ned, nearly conformal TiO 2 coatings with thicknesses of about 7 nm are prepared by chemical vapor deposition on the aerogel skeleton. Weighing shows that such TiO 2 -coated aerogel specimens essentially do not absorb water upon immersion, which is also evidenced by a high contact angle for water of 140 ° on the surface. Upon UV illumination, they absorb water 16 times their own weight and show a vanishing contact angle on the surface, allowing them to be denoted as superabsorbents. Recovery of the original absorption and wetting properties occurs upon storage in the dark. That the cellulose nanofi brils spontaneously aggregate into porous sheets of different length scales during freeze-drying is relevant: in the water-repellent state they may stabilize air pockets, as evidenced by a high contact angle, in the superabsorbent state they facilitate rapid water-spreading into the aerogel cavities by capillary effects. The TiO 2 -coated nanocellulose aerogels also show photooxidative decomposition, i.e., photocatalytic activity, which, in combination with the porous structure, is interesting for applications such as water purifi cation. It is expected that the present dynamic, externally controlled, organic/inorganic aerogels will open technically relevant approaches for various applications.

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In this study, H-beta zeolite-supported iridium catalysts were prepared by atomic layer deposition (ALD) and characterized as such and after different activation treatments. A reference catalyst was prepared by wet impregnation. The samples were tested in decalin ring opening reaction. ALD samples were clearly more active and selective in decalin ring opening compared to impregnated sample. The differences observed in characteristics and activities between ALD samples and impregnated sample are discussed.