Efficient separation of CH4/C2H6/C3H8 enabled by an indium-tetracarboxylate MOF with cross-channel and amino sites.

The highly efficient purification of CH4 from natural gas is critical for energy applications but remains a major separation challenge. Porous frameworks featuring high adsorption performance for C3H8 and C2H6 over CH4 offer a promising approach. Herein, we report the design and synthesis of a novel indium-based metal-organic framework, NUC-301, containing tetracarboxylic acid ligands, cross-channel structures, and amino functional groups, for efficient adsorption and separation of CH4/C2H6/C3H8 mixtures. Single-component adsorption isotherms show that NUC-301 preferentially adsorbs C2H6 and C3H8, with capacities of 39.6 and 52.3 cm3 g-1, respectively, at 298 K and 1 bar, while the capacity for CH4 is only 9.5 cm3 g-1. This is accompanied by high adsorption selectivity of 22 for C2H6/CH4 and 612 for C3H8/CH4. GCMC simulations reveal that the synergistic effect of cross-channels and amino groups enables efficient recognition of C2H6 and C3H8via C-H⋯O and C-H⋯N interactions. Transient breakthrough simulations with a simulated natural gas mixture (CH4/C2H6/C3H8 = 85/10/5) were conducted to evaluate the separation performance of NUC-301, demonstrating great potential for practical separation applications.