Structure Solution and Defect Analysis of Extra-Large Pore Zeolite with UTL Topology by Electron Microscopy.

Defects within zeolites are of crucial importance in order to explain their physicochemical behavior. UTL zeolite, with a pillared layer structure, has been widely used in zeolite crystal engineering to assembly new structures from its layer structural units, but fundamental understanding of its defect remains unknown. Here, we report a newly synthesized UTL framework zeolite, UTL-DBU, with a commercially available superbase 1,8-diazabicyclo [5.4.0] undec-7-ene (DBU) as a template. Its structure was determined by the combination of three-dimensional electron diffraction tomography and high-resolution (scanning) transmission electron microscopy. By transmission electron microscopy, two types of defects, stacking disorder and edge dislocation-like planar defect, were discovered. Based on the analysis of the electron diffraction and imaging the layer stacking sequence together with the structural and mathematical models of the micro-twinning were successfully built up. Unraveling these defects will provide new insights to the rational design of targeted zeolites utilizing UTL.