Biotemplated Lightweight γ-Alumina Aerogels

We present the biotemplating of γ-Al2O3 aerogels with chitosan nanofibrils. Aluminum–chitosan interactions cause the swelling of iridescent chitosan structures into helicoidal hydrogels and the subsequent aqueous dissolution of swollen fibrils to form Al–chitosan solutions. Viscous aqueous solutions of Al3+–chitosan hybrid nanofibers were freeze-dried to give lightweight cotton-like aerogels. Homogeneous incorporation of Al3+ ions into chitosan yields water-soluble nanofibrils that can serve as polymeric templates to support Al3+ ions in the aerogel composites. We investigated thermal removal of chitosan in the composites to obtain lightweight γ-Al2O3 nanocrystal aerogels that retain the weblike fiber networks of the chitosan template. These biotemplated alumina aerogel materials are promising candidates for catalyst supports and thermal insulation.