Confinement effects on molecular diffusion in zeolites: mechanisms and perspectives

Zeolites exemplify a quintessential class of confined systems, where well-defined molecular-scale channels impose precise spatial constraints on guest species, profoundly altering their diffusion behavior and catalytic properties. This review systematically examines confinement effects on molecular diffusion in zeolites, elucidating fundamental mechanisms such as orders-of-magnitude variations in diffusivity, the reconstruction of diffusion pathways, and emergent phenomena including the levitation effect, molecular trajectory control, the molecular trapdoor effect, and thermal resistance effects, among others. We summarize the synergistic effects of framework topology, guest molecular conformation, acid-site interactions, loading, and temperature on diffusion within these confined environments. Furthermore, we highlight the critical interplay between diffusion and catalytic performance, emphasizing confinement-driven shape selectivity and reaction enhancement. Finally, we outline key challenges and opportunities in designing zeolites with tailored diffusion properties for advanced applications in catalysis, separation, and energy conversion. By bridging atomic-scale mechanistic insights with practical implications, this comprehensive analysis provides a roadmap for the development of next-generation zeolite catalysts.