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

Abstract

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.