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

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 = N,N-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.