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

, 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.