Tannin-based xerogels with distinctive porous structures

Highly porous organic materials have been obtained from the gelation of a tannin-based resin at different pHs in the presence of F-127 Pluronic® surfactant. After subcritical drying in ambient conditions, and without the need of any solvent exchange step, the resultant xerogels had bulk densities typical of most organic aerogels. Their porous structures revealed unique features, depending on the initial pH, such as the possibility of getting either purely macroporous materials with narrow pore size distributions, or bimodal textures having a significant amount of mesoporosity. Correlations between porous texture and gelation time were clearly evidenced. On top of being easy to prepare, these xerogels are based on a cheap, renewable and abundant resource making them valuable precursors of porous carbon materials for a broad range of applications.