Abstract

Solid-state NMR spectroscopy in conjunction with theoretical calculation was employed to investigate the adsorbent–adsorbate host–guest interactions during propane/propylene separation on ZIF-8. 1H NMR chemical shifts of free gaseous and adsorbed propane/propylene are unambiguously assigned with the assistance of two-dimensional (2D) 1H-1H correlation spectroscopy (COSY) MAS NMR spectra. Meanwhile, the adsorption selectivity for propane/propylene mixtures on ZIF-8 at a pressure in range of 1.9–9.6 bar is quantitatively determined using 1H MAS NMR experiments, which agreed well with the ideal adsorbed solution theory (IAST) predictions. The preferential adsorption of propane compared with propylene on ZIF-8 is directly visualized from the 2D 1H-1H spin diffusion homo-nuclear correlation (HOMCOR) MAS NMR spectroscopy. Moreover, the preferential adsorption sites for propane and propylene are deduced from the 1H-1H spin diffusion buildup curves, which is further confirmed by DFT theoretical calculations. This work provides insights to understand the structure–property relationship during the propane/propylene separation on ZIF-8 as adsorbent.

link：https://pubs.rsc.org/en/Content/ArticleLanding/2022/CP/D1CP05931A