Efficient Trapping of Trace Acetylene from Ethylene in an Ultramicroporous Metal-Organic Framework: Synergistic Effect of High-Density Open Metal and Electronegative Sites.

Acetylene (C H ) removal from ethylene (C H ) is a crucial step in the production of polymer-grade C H but remains a daunting challenge because of the similar physicochemical properties of C H and C H . Currently energy-intensive cryogenic distillation processes are used to separate the two gases industrially. A robust ultramicroporous metal-organic framework (MOF), Ni (pzdc) (7 Hade) , is reported for efficient C H /C H separation. The MOF comprises hydrogen-bonded linked one-dimensional (1D) chains, and features high-density open metal sites (2.7 nm ) and electronegative oxygen and nitrogen sites arranged on the pore surface as cooperative binding sites. Theoretical calculations, in situ powder X-ray diffraction and Fourier-transform infrared spectroscopy revealed a synergistic adsorption mechanism. The MOF possesses S-shaped 1D pore channels that efficiently trap trace C H at 0.01 bar with a high C H uptake of 60.6 cm  cm and C H /C H selectivity.