Ionic Liquid-Based Route for the Preparation of Catalytically Active Cellulose–TiO₂ Porous Films and Spheres

The present work evaluates the possibilities of processing cellulose with ionic liquids and functional nanoparticles like TiO₂ toward a new generation of porous nanocomposites, shaped as films or spheres, which may find direct application in water purification, catalysis, and self-cleaning materials. The focus was set on the factors controlling the formation of the porous film structure during the nonsolvent induced phase separation process from polymer solutions in ionic liquids via immersion in water and during the porous film drying step. Temperature and cosolvent addition facilitate cellulose solubilization and help control the phase separation by improving the mass transfer. The complex relation between the catalytic activity of the porous TiO₂–cellulose nanocomposite materials obtained under different processing conditions and their structure has been studied during the photodegradation of model organic dyes like rhodamine B and methylene blue. After drying, the catalytic activity of the nanocomposites decreases as a consequence of the reformation of the intra- and intermolecular hydrogen bonds in cellulose which diminish the flexibility and the mobility of the fine cellulose fibrils network.