Exploring guest species in zeolites using transmission electron microscopy: a review and outlook

Zeolites, with their well-defined microporous frameworks, accommodate diverse guest species, including metal ions, atoms, clusters, complexes, and organic molecules. Direct imaging of these species and their interactions with the framework is crucial for understanding their structural and functional roles. Transmission electron microscopy (TEM), particularly aberration-corrected scanning TEM (STEM), has become an indispensable tool, offering atomic-resolution real-space insights. This review summarizes key (S)TEM techniques for probing guest species in zeolites, with a focus on low-dose strategies to minimize beam damage. We discuss the principles, applications, and limitations of various imaging modalities and highlight recent advances in visualizing metallic and organic species. Finally, we explore future directions for (S)TEM in zeolite research, emphasizing the opportunities and challenges of in situ, three-dimensional, and cryogenic imaging for resolving host-guest interactions with greater precision.