Aerogels and Xerogels from Biogenic Phenols and Furfural

Abstract

Both climate change and the depletion of fossil feedstocks drive the demand for high performance materials based on renewable natural resources. Due to their remarkable thermally insulating and light-weight properties that can be traced back to their unique microstructure, aerogels and xerogels based on phenolics, such as resorcinol-formaldehyde (RF), have received increasing attention.[1] Furthermore, high char yields resulting from carbonization of RF gels render them attractive precursors for porous carbons, which- in turn- are interesting for electrochemical applications. However, RF is made from fossil precursors, and thus biogenic alternatives to these phenolic aerogels are highly sought-after. In that context, we report on three phenolic aerogels and xerogels made from bio-based monomers, namely cardanol-furfural, thymol-furfural, and eugenol-furfural.[2] We have investigated the conditions of gelation, solvent exchange, and drying, and characterized properties such as chemical structure, density, surface area, pore size and -volume, microstructure, thermal stability and wetting behavior. Furthermore, we report on the carbonization of these bio-based aerogels and xerogels. Especially carbon xerogels based on eugenol-furfural show promising pore characteristics and significantly higher char yield when compared to carbons based on cellulose aerogels. These gels can, thus, be considered attractive candidates for larger scale production and further studies in electrochemical applications.

[1] X. Lu, M. C. Arduini-Schuster, J. Kuhn, O. Nilsson, J. Fricke, R. W. Pekala, Science 1992, 255, 971-972. [2] T. Anklam, Dissertation “Hydrophobe Aerogele und Xerogele – Substitution von Phenolen durch Phenolether und Alkylphenole“, 2024, University of Cologne.