Ionothermal synthesis : a new synthesis methodology using ionic liquids and eutectic mixtures as both solvent and template in zeotype synthesis

Abstract

The aim of this thesis was to research the new synthesis methodology of ionothermal synthesis, used for the synthesis of zeolite type materials, mainly aluminophosphates. An ionic liquid or eutectic mixture is to act as both the organic template and the solvent, hence eliminating the space filling effects in the reaction from the water. Initial reactions were carried out using the ionic liquid 1-ethyl-3-methylimidazolium bromide which acted as the solvent and template in the production of four three-dimensional structures and one layered structure. The addition of cobalt into the aluminophosphate framework was investigated and resulted in three different cobalt-aluminophosphates being synthesised, including one new zeolite framework. Experiments were carried out into the effect of altering the imidazolium cation alkyl chain. It appears likely that in the presence of fluoride, some of the imidazolium cations undergo a metathesis reaction forming 1,3-dimethylimidazolium which acts as a template in the formation of an aluminophosphate. Preliminary investigations have also been started into the effects of changing the ionic liquid anion from bromide to phosphorus hexafluoride and bis((trifluoromethyl)sulfonyl)amide. The use of these anions resulted in the production of several different one and two-dimensional structures. The use of eutectic mixtures as solvent and template was also investigated as a cheaper, more easily synthesised solvent than the ionic liquids. The results show a new methodology of eutectic mixtures acting as template delivery agents through the slow, in situ decomposition of the urea derivative of the eutectic mixture. This synthesis method resulted in the formation of nine one and two-dimensional aluminophosphates.