Amino functionalisation of microemulsion templated mesoporous silica foams

Large pore microemulsion templated mesoporous silica foams (MCF), with spherical cell sizes of around 40 nm, were chemically modified via a reaction in dry solvent with (3-aminopropyl)triethoxysilane (APTES) and a vapour phase reaction with (3-aminopropyl)dimethylethoxysilane (APDMES). Nitrogen sorption measurements showed that in both cases the functionalised materials retained the underlying pore structure of the unfunctionalised MCF material, with the spherical cell size of the APTES-MCF material seen to be reduced by ∼ 2 nm. The nature of the chemical attachment was confirmed by ²⁹Si MAS NMR and differed in each case. APDMES-MCF showed a single additional peak over that of the framework silica, associated with the single chemical environment of the attached silane, whereas the APTES-MCF showed multiple overlapping peaks associated with the multiple chemical environments of the attached silane. Thermogravimetric analysis revealed the loading of organic material to be higher for APTES-MCF over APDMES-MCF, consistent with the proposed attachment mechanisms.