Cellulose foams, or sponges, are produced from solutions in ionic liquids by the aqueous acid mediated decomposition of 1-alkyl-3-methylimidazolium-2-carboxylates, where the alkyl group and acid may be selected such that the by-product is the ionic liquid solvent: a by-productless foaming.
Scott, J. L., Unali, G., & Perosa, A. (2011). A "by-productless" cellulose foaming agent for use in imidazolium ionic liquids. Chemical Communications, 47(10), 2970-2972. https://doi.org/10.1039/c0cc05057a