Atomic-scale insights into topotactic transformations in extra-large pore silicate zeolites using time-resolved 3D electron diffraction

Understanding the atomic scale structural dynamics of phase transformations is crucial for developing new materials and tailoring the properties of the materials. However, many materials are obtained as polycrystalline powders with large unit cells and/or complex structures, making it challenging to investigate detailed structural changes using conventional X-ray diffraction techniques. Here, we employ time-resolved 3D electron diffraction (3D ED) to unravel the topotactic reactions and transformations of extra-large pore silicate zeolites ECNU-45 to ECNU-46. Notably, ECNU-45 features 3D interconnecting 24×10×10-ring channels, while ECNU-46 exhibits 1D 24-ring channels connected to 10-ring pockets. ECNU-45 and ECNU-46 are the first reported examples of pure silicate zeolites with pores larger than 22-rings. Our findings showcase detailed changes at six distinct tetrahedral Si sites, involving atom displacement, addition, and removal of framework atoms through bond breakage and formation. This work not only presents the discovery of novel zeolites but also provides unprecedented atomic-level insights into the dynamic processes of topotactic reactions. Our results have significant implications for advancing materials engineering and understanding complex solid-state reactions at an atomic scale.