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 2 H 2 ) removal from ethylene (C 2 H 4 ) is a crucial step in the production of polymer‐grade C 2 H 4 but remains a daunting challenge because of the similar physicochemical properties of C 2 H 2 and C 2 H 4 . Currently energy‐intensive cryogenic distillation processes are used to separate the two gases industrially. A robust ultramicroporous metal–organic framework (MOF), Ni 3 (pzdc) 2 (7 Hade) 2 , is reported for efficient C 2 H 2 /C 2 H 4 separation. The MOF comprises hydrogen‐bonded linked one‐dimensional (1D) chains, and features high‐density open metal sites (2.7 nm −3 ) 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 2 H 2 at 0.01 bar with a high C 2 H 2 uptake of 60.6 cm 3  cm −3 and C 2 H 2 /C 2 H 4 selectivity.