Extreme Confinement of Xenon by Cryptophane‐111 in the Solid State

Abstract

Solids that sorb, capture and/or store the heavier noble gases are of interest because of their potential for transformative rare gas separation/production, storage, or recovery technologies. Herein, we report the isolation, crystal structures, and thermal stabilities of a series of xenon and krypton clathrates of (±)-cryptophane-111 (111). One trigonal crystal form, Xe@111⋅y(solvent), is exceptionally stable, retaining xenon at temperatures of up to about 300 °C. The high kinetic stability is attributable not only to the high xenon affinity and cage-like nature of the host, but also to the crystal packing of the clathrate, wherein each window of the molecular container is blocked by the bridges of adjacent containers, effectively imprisoning the noble gas in the solid state. The results highlight the potential of discrete molecule materials exhibiting intrinsic microcavities or zero-dimensional pores.

Reversible Encapsulation of Xenon and CH2Cl2 in a Solid‐State Molecular Organometallic Framework (Guest@SMOM)

“…Xenon finds application in structural biology as a probe for solvent and gas channels in metalloenzymes, due to its high atomic number and hydrophobicity . It also shows binding affinity in supramolecular cages, oxide frameworks, MOFs, cryptophanes, and porous coordination‐complex salts; and has been widely used as an NMR probe for the determination of pore size in framework materials, due to the sensitivity of δ( 129 Xe) to its local environment…”

Reversible Encapsulation of Xenon and CH2Cl2 in a Solid‐State Molecular Organometallic Framework (Guest@SMOM)

“…[15] Interestingly the 31 P{ 1 H} SSNMR spectrum now shows sharp signals at d À23. [21] It also shows binding affinity in supramolecular cages, [22] oxide frameworks, [23] MOFs, [24] cryptophanes, [25] and porous coordinationcomplex salts; [26] and has been widely used as an NMR probe for the determination of pore size in framework materials, [27] due to the sensitivity of d( 129 Xe) to its local environment. This transformation is reversible,a nd when [20] V Xe /V cavity = 0.43).…”

Ionization‐Facilitated Formation of 2D (Alumino)Silicate–Noble Gas Clathrate Compounds

“…The desorption temperatures increase to 498 K for Kr and to 673 K for Xe in the aluminosilicate (Figure E,F). This report of Xe atoms trapped in the nanocages up to 673 K constitutes, to the best of our knowledge, the most stable case of noble gas atoms in confinement so far …”