The First Kr‐Selective Carbon Molecular Sieve for Inverse Adsorption of Krypton Over Xenon at Ambient Temperature

Abstract The efficient adsorption‐based separation of krypton (Kr) and xenon (Xe) is of paramount importance but is challenged by their similar physicochemical properties. While carbon adsorbents are theoretically promising for Kr/Xe sieving, practical success has remained elusive. Here, a series of ultramicroporous carbon molecular sieves synthesized from sucrose‐derived hydrochar is reported. The study employs careful characterization and controlled thermal pyrolysis to tailor ultramicropore formation and elucidate the evolution of the carbon framework. The leading material, C‐Suc‐750, has an ideal pore size of ≈4.0 Å. In particular, C‐Suc‐750 has achieved a remarkable Kr/Xe uptake ratio of 39.3 at ambient conditions, setting a new benchmark for selective Kr adsorption and molecular sieving of Kr/Xe. Breakthrough experiments further confirm the superior molecular sieving performance of C‐Suc‐750, highlighting its potential for Kr recovery in nuclear waste treatment. Moreover, molecular dynamics (MD) simulations demonstrate the critical role of narrow slit‐pore of the carbon molecular sieve in molecular sieving separation of Kr/Xe, providing insights into the mechanism driving this selectivity.