(363ac) Tracking the Unique Structural Evolution of Aei-Type Zeolites Synthesized By Faujasite Interzeolite Transformation

Interzeolite transformations can occur by design using metastable zeolites as seeds or as a natural process during organic-free syntheses. Zeolite faujasite (FAU) is commonly used as a meststable zeolite for the preparation of other crystalline materials, such as zeolite SSZ-39 (AEI). The latter is similar to commercial SSZ-13 (CHA), which consists of interconnected cages connected by 8-membered rings micropore (aperture size of 3.8×3.8 Å) and double six membered rings (D6R). The alternating orientation of the D6R of AEI results in a medium size cage that can include spheres up to 7.3 Å, which exhibits high potential for C1 catalysis (e.g., methane to methanol, methanol to olefins, and NH₃ selective catalytic reduction of NOx). Zeolite AEI has attracted recent attention as a potential alternative to SSZ-13; and although progress has been made to identify different synthesis routes, including FAU-to-AEI interzeolite transformation, its mechanism of crystallization is not fully understood.

There have been studies exploring different metastable seeds for interzeolite transformation (e.g., MFI, FER, *BEA), different synthesis conditions, as well as a broad range of organic structure-directing agents (OSDAs). In this presentation, my research interest is the synthesis of ultrathin SSZ-39 nanosheets using a new OSDA. Moreover, I will show how subtle modifications to OSDA chemistry results in distinct synthesis pathways. Notably, our findings reveal that the introduction of defects creates intermediate AEI morphologies (e.g., rod-like crystals) that undergo structure rearrangements to plate-like final products with distinct physicochemical properties. Testing of these materials in benchmark catalytic reactions reveal differences in the performance of SSZ-39 depending on the selection of OSDA, thus providing insight into design strategies for synthesizing AEI catalysts with optimal properties compared to state-of-the-art small-pore zeolites.