Hexamethylenetetramine multiple catalysis as a porosity and pore size modifier in carbon cryogels

Hexamethylenetetramine (HMTA) base catalysis is used to control the porosity and pore size of resorcinol furaldehyde cryogels synthesized in tert-butanol. While HMTA produces ammonia and formaldehyde in aqueous media, other carbon–nitrogen molecular units are possible in non-aqueous solvents. The results suggest that at least two paths are possible from this decomposition, a reactive catalyst in pure tert-butanol or a base like catalyst in an aqueous mix. Due to the catalytic effect under high catalysis in tert-butanol the samples promoted high macroporosity > 70%, reduced shrinkage < 20% and had lower syneresis compared to specimens with low concentration of HMTA. On the other hand the use of water mixtures was shown to reduce the mesopore size up to 50%, and reduce the macroporosity to 20%, when compared to the tert-butanol case. Nitrogen physisorption, TEM and FTIR are used to characterize the chemical and structural properties of the cryogels.