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

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 C₃H₆/C₃H₈ and C₂H₄/C₂H₆, 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.