Pressure-Induced Argon Insertion into an Auxetic Small Pore Zeolite

We report that natrolite,Na16Al16Si24O48·16H2O, a small pore auxetic zeolite can incorporate significant amounts of Argon under moderate pressure- and temperature conditions resulting in Na16Al16Si24O80·16H2O·6Ar. This material has a ∼6.5% larger unit cell than natrolite at ambient conditions and its structure is related to Na16Al16Si24O80·24H2O, an intermediate superhydrated natrolite referred to as para-natrolite. Argon insertion under pressure into auxetic frameworks such as natrolites is an important and overlooked confinement mechanism with potential applications and implications.