Nanoporous 3D Graphene-like Zeolite-Templated Carbon for High-Affinity Separation of Xenon from Krypton

Nanoporous three-dimensional (3D) graphene-like carbons can be synthesized in MFI-, FAU-, and β-type zeolite templates, using the metal ion-catalyzed synthesis method. The carbon products obtained from the templates possessing distinct pore systems have large Brunauer–Emmett–Teller specific surface areas (700–3200 m2 g–1) and zeolite-like pore-structure ordering. The characteristic pore sizes of MFI-, FAU-, and β-zeolite-templated nanoporous carbons (ZTCs) were determined to be 0.5, 1.1, and 0.9 nm, respectively. The three ZTCs were studied for xenon–krypton adsorption according to the zeolite types. The MFI-ZTC exhibited the highest ideal adsorbed solution theory selectivity of 17 at an early coverage for xenon (Xe) over krypton (Kr) among the ZTCs. The β-ZTC exhibited one of the highest Xe/Kr uptake ratios and the highest Xe capacity, which originated from the high BET surface area of the 3D graphenic structure. We also demonstrate that the introduction of heteroatoms (e.g., O and N) in the same ZTC structure makes it more favorable for the separation of xenon over krypton. The gas separation performance of N-doped FAU-ZTC, as evaluated by xenon–krypton breakthrough experiments, exceeded that of activated carbon and undoped FAU-ZTC material.