A flexible zinc tetrazolate framework exhibiting breathing behaviour on xenon adsorption and selective adsorption of xenon over other noble gases

Abstract

Given the fact that traditional cryogenic rectification is highly energy and capital intensive for the purification of xenon, effective selective adsorption of xenon over other noble gases at room temperature using porous materials is a critical and urgent issue. Here, we present a flexible zinc tetrazolate framework ([Zn(mtz)₂]), which exhibits a high capture capacity for xenon and selective adsorption of xenon over other noble gases at room temperature. Due to its high adsorption enthalpy for xenon, a suitable pore size that matches well with the xenon atom, as well as the high polarizability of Xe, [Zn(mtz)₂] shows breathing behaviour on xenon adsorption, which is confirmed by the experimental adsorption isotherms of xenon and thermodynamic analysis of breathing transition. The isosteric heats of adsorption and S(DIH) calculations indicate that [Zn(mtz)₂] has significantly higher adsorption affinity and capacity for Xe compared with Kr, Ar and N₂. The high capture capacity of Xe (2.7 mmol g⁻¹) in an idealized PSA process and high Xe/Kr selectivity (15.5) from breakthrough experiment promise the potential application of [Zn(mtz)₂] in Xe capture and separation from Xe–Kr gas mixtures.