Gate-Opening Effect in a Flexible Metal–Organic Framework for Sieving Acetylene

Adsorptive separation employing porous materials is one of the most promising alternative technologies for C2H2 purification due to its energy-efficient and environmentally friendly advantages. Herein, we present the design and synthesis of a dicopper-paddle-wheel-based metal–organic framework (termed JNU-5-Me) with a carboxylate-azolate organic linker. The use of such a linker results in the axial positions of the dicopper paddle wheels being occupied by azolates, and therefore, a much-improved chemical stability of the framework structure. JNU-5-Me shows negligible adsorption of C2H4, C2H6, and CO2 at 1.0 bar and 298 K, while a gate-opening effect for C2H2 and a large C2H2 adsorption (4.7 mmol g–1) at 1.0 bar and 298 K. Dynamic breakthrough studies on JNU-5-Me demonstrate its excellent C2H2 separation performance from C2H2/CO2 (50/50, v/v) and C2H2/CO2/C2H4/C2H6 (70/10/10/10, v/v/v/v) mixtures. Additionally, in-situ infrared spectroscopy and Grand canonical Monte Carlo (GCMC) simulation reveal that the carboxylate oxygens and methyl groups on the framework are involved in the strong binding of C2H2, which may be attributed to the gate-opening effect of JNU-5-Me.