Flexible Microporous Copper(II) Metal–Organic Framework toward the Storage and Separation of C1–C3 Hydrocarbons in Natural Gas

Abstract

A flexible and robust microporous copper(II) metal-organic framework (MOF) based on a methyl-functionalized ligand, namely, [Cu₃(μ₃-OH)₂(L)₂(DMF)] (LIFM-ZZ-1; L = 2,2'-dimethyl-4,4'-biphenyldicarboxylic acid and DMF = <i>N</i>,<i>N</i>-dimethylformamide), was constructed. Its sorption performance for the separation of CH₄, C₂H₆, and C₃H₈ was investigated. LIFM-ZZ-1 showed a breathing behavior that led to a transition between large- and narrow-pore states. The sample also showed outstanding water stability. Gas adsorption experiments revealed that desolvated LIFM-ZZ-1 exhibited higher adsorption capacities for C₂H₆ and C₃H₈ (2.80 and 4.06 mmol·g^-1) than for CH₄ (0.39 mmol·g^-1) at 298 K and 1 bar. Breakthrough experiments showed that a CH₄/C₂H₆/C₃H₈ mixture was completely separated at 298 K, demonstrating the promising potential applications of this material for separating low contents of C2/C3 hydrocarbons from natural gas.