Selective sorption of amines by graphite oxide: Brønsted basicity is the major factor for selectivity

Abstract

Graphite oxide (GO) exhibits selective sorption of di-butylamine from a mixture of butylamine, di-butylamine and tri-butylamine. The selectivity is attributed to the higher basicity of di-butylamine in comparison to butylamine and tri-butylamine. Reaction of GO with a mixture of hexylamine and cyclohexylamine, two amines of similar basicity but different structures, suggests that in alkylamines, selectivity is predominantly due to the basicity of the amine with structural differences playing almost no role. However, when GO reacts with a mixture of aniline and cyclohexylamine (amines with a large difference in basicity) no selectivity is observed. The π-π interaction between the aromatic amine, aniline, and the aromatic regions of GO causes the sorption of aniline in its non-protonated form as much as cyclohexylamine with a far higher basicity.