Low-Dimensional Zeotypes Templated by Stacked Cyclic Benzimidazolium Revealed by Electron Crystallography.

The structural diversity of zeolites depends strongly on the use of organic structure-directing agents (OSDAs) that guide their formation. Low-dimensional zeolitic materials, such as layered or chain-like phases, can serve as key intermediates in topotactic condensation pathways, yet the mechanisms governing their formation and transformation remain poorly understood. Here, we report three low-dimensional zeolitic materials, EMM-75P, EM-L01, and EM-L02, synthesized using benzimidazolium cations as OSDAs. Their structures were determined by three-dimensional electron diffraction (3D ED), including the atomic structure of the OSDAs, revealing their confinement within the framework to shed light on their structure-directing role. The bulky benzimidazolium OSDAs prevent the formation of materials with three-dimensional framework structures and instead direct the formation of low-dimensional zeotypes. Upon calcination, the two-dimensional layered aluminosilicate zeotype EMM-75P undergoes topotactic condensation to form a three-dimensional zeolite, EMM-75, with a previously unreported zeolite framework topology. Aluminosilicate EM-L01 is a 2D analogue of