Sub‐Ångstrom Pore Engineering in Carbon Molecular Sieves Realizes Diffusion‐Gated Kinetic Sieving of Alkenes from Alkanes

Abstract Sub‐Ångstrom pore engineering offers a new paradigm for molecular separations. Here, we report sucrose‐derived carbon molecular sieves (CMSs) with precisely tailored sub‐Ångstrom slit pores that enable diffusion‐gated kinetic sieving for the challenging separation of alkenes from alkanes. The optimized materials, C‐Suc‐650 and C‐Suc‐750, set new industry‐leading standards for the kinetic separation of C 3 H 6 /C 3 H 8 and C 2 H 4 /C 2 H 6 , respectively. Through a combination of breakthrough experiments, pressure swing adsorption (PSA) simulations, and molecular dynamics (MD) modeling, we demonstrate that these sieves consistently achieve >99.9% alkene purity, with outstanding selectivity, rapid uptake kinetics, and remarkably low energy consumption. Mechanistic studies reveal that slit pore architecture uniquely enhances alkene diffusion while hindering alkane movement, establishing a clear design principle for next‐generation, energy‐efficient gas separations. These results provide a blueprint for exploiting diffusion‐gated kinetic sieving at the sub‐Ångstrom scale to address longstanding challenges in industrial gas purification.