A Dynamic Organic Structuring-Directing Agent for Pure-Silica-Zeolite AST and LTA Syntheses

Pure-silica-zeolite (PSZ) AST and LTA are synthesized successfully by using the same structure-directing agent (SDA) molecule, but at different concentrations. A dynamic organic SDA is proposed to discuss the mechanism of phase discrimination between AST and LTA. Data suggest that the SDA molecules can self-assemble into dimer or trimer complexes at different concentrations by π-π interactions, and these differences can be taken advantage of to selectively synthesize either PSZ AST or LTA. These deviations from the Liebau's rules indicate that small changes in SDA chemistry, structure, and order in solution can have a great impact on the structure selectivity of the zeolite synthesis.