Flexibility of the imidazolium based ionic liquids/water system for the synthesis of siliceous 10-ring containing microporous frameworks

Abstract

By using asymmetric di-substituted imidazolium molecules (1-Butyl-3-methylimidazolium (BMIM) and 1-Ethyl-3-methylimidazolium (EMIM) bromide) as the structure directing agents, in combination with simple changes in silica source or sodium/water content it is possible to prepare three pure phase microporous 10-ring siliceous zeolitic structures. The crystallizations are comparatively rapid with fully crystalline material resulting in 1–3 days at 443 K. In contrast to many recipes reported for pure silica materials, the synthesis is performed without the use of HF or without the need to alter the properties of the SDA, while significantly lower amounts of both ionic liquid and mineralizing agent are required. The results obtained indicate that effective phase control can be achieved from a primary gel composition by minor changes to either the silica source or the water/sodium content, with a strong specificity in the formation of topologies with interconnected 10-rings.