Chitosan templated synthesis of porous metal oxide microspheres with filamentary nanostructures

This work describes a versatile strategy for fabricating highly porous and nanofibrous titania, zirconia, alumina and tin oxide. Taking advantage from chitosan polysaccharide microspheres as nano-assembling system during sol–gel mineralization of monomeric alkoxides and the beneficial effect of supercritical CO2 drying to avoid the collapse of the transient hybrid material network, all targeted metal oxides were created, after calcinations, as fibrous filaments featuring dual meso- and macro-porous network with surface areas ranging from 110 to 310 m2g−1. Chitosan alcogels were found to be the best mould for this replication alleviating the problems associated with the rapid kinetic growth encountered with hydrogels and those of diffusion limitations in dried aerogels. From mechanistic point of view, amino-metal coordination NH2 → M (M = Ti, Zr, Al, Sn) and hydrogen bonding between hydroxyl group and oligomeric metal oxide play a pivotal role during the mineralization process.

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► Natural and available template (chitosan) was used to fabricate porous inorganic oxide microspheres.
► High surface areas were obtained ranging from 110 to 310 m2 g−1.
► The replication led to nanometric objects with filamentary structures.