Unveiling the Dynamic Pathways of Metal–Organic Framework Crystallization and Nanoparticle Incorporation for Li–S Batteries

Metal–organic frameworks (MOFs) present diverse building blocks for high-performance materials across industries, yet their crystallization mechanisms remain incompletely understood due to gaps in nucleation and growth knowledge. In this study, MOF structural evolution is probed using in situ liquid phase transmission electron microscopy (TEM) and cryo-TEM, unveiling a blend of classical and nonclassical pathways involving liquid–liquid phase separation, particle attachment–coalescence, and surface layer deposition. Additionally, ultrafast high-temperature sintering (UHS) is employed to dope ultrasmall Cobalt nanoparticles (Co NPs) uniformly within nitrogen-doped hard carbon nanocages confirmed by 3D electron tomography. Lithium–sulfur battery tests demonstrate the nanocage-Co NP structure's exceptional capacity and cycling stability, attributed to Co NP catalytic effects due to its small size, uniform dispersion, and nanocage confinement. The findings propose a holistic framework for MOF crystallization understanding and Co NP tunability through ultrafast sintering, promising advancements in materials science and informing future MOF synthesis strategies and applications.