Utilizing the gate-opening mechanism in ZIF-7 for adsorption discrimination between N₂O and CO₂

Abstract

N₂O is a greenhouse gas with tremendous global warming potential, and more importantly it also causes ozone depletion; thus, the separation of N₂O from industrial processes has gained significant attention. We have demonstrated that N₂O can be selectively separated from CO₂ using the zeolite imidazolate framework ZIF-7. The adsorption/desorption isotherms of both N₂O and CO₂ in ZIF-7 indicate the gate-opening mechanism of this material and surprisingly, the threshold pressure for the gate opening with N₂O is lower than that with CO₂. Theoretical calculations indicate that both gas–host and gas–gas interaction energies for N₂O are more favorable than those for CO₂, giving rise to the difference in the threshold pressure between N₂O and CO₂ in ZIF-7. Breakthrough experiments for N₂O/CO₂ mixtures confirm that ZIF-7 is capable of separating N₂O and CO₂ mixtures under the optimized conditions, in reasonable agreement with simulation results, making it a promising material for industrial applications.