Construction of a novel nickel-based MOF with accessible oxygen sites for efficient CH4/N2 separation

Abstract

Enriching coal-bed methane to provide pure methane is promising and attractive. However, it is challenging due to the similar properties of CH₄ and N₂. In this work, a novel nickel-based metal–organic framework (named TUTJ-201Ni) with a high density of accessible oxygen sites was synthesized for CH₄/N₂ separation. From the structure, oxygen atoms from ligands and μ₂-hydroxyl are densely distributed on the surface of rhombic channels. Gas adsorption measurements showed that TUTJ-201Ni exhibited high CH₄ uptake over N₂. CH₄/N₂ selectivity at 298 K and 1.0 bar was calculated to be 7.2. Modeling studies indicated that the pore centers surrounded with accessible oxygen atoms are the optimal bonding sites. The stronger adsorption affinity of CH₄ can be attributed to multiple hydrogen bonding. The exceptional CH₄/N₂ separation performance of this material was further evaluated using breakthrough experiments.