Hierarchical silica monolith prepared using cellulose monolith as template

Silica monoliths with a continuous porous structure have received much attention in biomedical and environmental applications owing to their high-performance separation/adsorption behaviors. However, it is difficult to maintain a porous structure in silica monoliths because their synthesis often involves complicated phase separation in sol-gel reactions. Herein, for the first time, we used an ecofriendly cellulose material as a template to prepare a hydrophilic and hierarchically porous silica monolith. The cellulose monolith template was prepared from cellulose acetate by a thermally induced phase separation method. The silica was then prepared in the presence of the cellulose monolith by a typical sol-gel reaction of tetraethyl orthosilicate (TEOS) to form the composite monolith, which was converted to the silica monolith by burning in air to remove the cellulose monolith. Owing to the hierarchically porous structure of the cellulose monolith template, the obtained silica monolith showed a similar hierarchically porous structure, as confirmed by scanning electron microscopy and nitrogen adsorption-desorption analyses. The pore structure could be controlled by changing the fabrication parameters, such as the kind of cellulose monolith and TEOS concentration. The surface-modified silica monolith was developed for further applications.