Cryo-EM for nanomaterials: Progress and perspective

Cryogenic electron microscopy (cryo-EM) has extensively boosted structural biology research since the "resolution revolution" in the year of 2013 which was soon awarded the Nobel Prize in Chemistry in 2017. The advances in camera techniques and software algorithms enabled cryo-EM to routinely characterize the three-dimensional structures of biomolecules at near-atomic resolution. Biomolecules are basically sensitive to electron irradiation damage, which can be minimized at cryo-temperature. This principle has inspired material scientists to characterize electron beam- or air-sensitive materials by cryo-EM, such as the electrodes in the lithium-ion battery, metal-organic frameworks (MOFs), covalent-organic frameworks (COFs) and zeolites. In addition, the reaction systems can be fast-frozen at vitreous ice in cryo-EM, which correspondingly preserves the materials at the close-to-native state. Herein, we summarized the development and applications of both the cryo-EM technique and other emerging cryo-techniques in materials science, and energy storage and conversion. Cryo-EM techniques, capable of the direct observation of sensitive materials and electrochemical reaction processes, will greatly renew our understanding of materials science and related mechanisms.