An investigation for H2/N2 adsorptive separation in SIFSIX-2-Cu-i

Hydrogen recovery from ammonia purge gas is a desirable method to relieve the pressure of increasing demand for hydrogen. Metal-organic frameworks (MOFs) are promising adsorbents for the separation of the H 2 –N 2 mixture. However, the separation of the H 2 –N 2 mixture using MOFs remains challenging due to the lack of adsorptive mechanism. Herein, the adsorption mechanism of the H 2 –N 2 mixture in SIFSIX-2-Cu-i has been systematically investigated with the method of a combination of excess adsorption experiments, molecular simulations , and DFT calculations. In the Grand Canonical Monte Carlo (GCMC) simulations, the polarizable force field was first applied to the adsorption of pure H 2 or N 2 and H 2 –N 2 mixture in SIFSIX-2-Cu-i. Ab Initio Molecular Dynamics (AIMD) was performed to investigate the distribution of the guest molecules in the pores of SIFSIX-2-Cu-i. Finally, Density functional theory (DFT) calculations were performed to predict the transfer of charge between MOF and guest molecules. Results revealed two binding sites of H 2 or N 2 in SIFSIX-2-Cu-i. A relatively high thermodynamic adsorption selectivity for N 2 over H 2 has been observed in SIFSIX-2-Cu-i. Furthermore, SIFSIX-2-Cu-i also exhibits a greater affinity with N 2 than with H 2 , which is probably because of the stronger induction interactions between F2 atoms and N 2 molecules. These findings are of significance to guide the design of the new highly selective adsorbents for the separation of H 2 /N 2 .