First low-temperature 15N nuclear magnetic resonance study of nitrogen physisorption/condensation in microporous solids

Abstract

Low-temperature ¹⁵N NMR has been used to study the nuclear environment of the nitrogen as it fills the pores of a microporous zeolite. A phase transition from a liquid-like condensate to a restricted/confined liquid with reduced molecular motion is inferred from changes in the NMR signal. However, the transition from this state (phase) to a solid phase is not evident as the temperature is lowered to below 11 K. The micropores restrict the molecular motion and, at the same time, change (depress the transition temperature for) the liquid–solid equilibrium of the condensing nitrogen.