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

Abstract

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 C₃H₈ via 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.