Three-in-One C₂H₂-Selectivity-Guided Adsorptive Separation across an Isoreticular Family of Cationic Square-Lattice MOFs

Energy-efficient selective physisorption driven C₂H₂ separation from industrial C2-C1 impurities such as C₂H₄, CO₂ and CH₄ is of great importance in the purification of downstream commodity chemicals. We address this challenge employing a series of isoreticular cationic metal-organic frameworks, namely iMOF-nC (n=5, 6, 7). All three square lattice topology MOFs registered higher C₂H₂ uptakes versus the competing C2-C1 gases (C₂H₄, CO₂ and CH₄). Dynamic column breakthrough experiments on the best-performing iMOF-6C revealed the first three-in-one C₂H₂ adsorption selectivity guided separation of C₂H₂ from 1:1 C₂H₂/CO₂, C₂H₂/C₂H₄ and C₂H₂/CH₄ mixtures. Density functional theory calculations critically examined the C₂H₂ selective interactions in iMOF-6C. Thanks to the abundance of square lattice topology MOFs, this study introduces a crystal engineering blueprint for designing C₂H₂-selective layered metal-organic physisorbents, previously unreported in cationic frameworks.