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

Acetylene (C2H2) removal from ethylene (C2H4) is a crucial step in the production of polymer‐grade C2H4 but remains a daunting challenge because of the similar physicochemical properties of C2H2 and C2H4. Currently energy‐intensive cryogenic distillation processes are used to separate the two gases industrially. A robust ultramicroporous metal–organic framework (MOF), Ni3(pzdc)2(7 Hade)2, is reported for efficient C2H2/C2H4 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 C2H2 at 0.01 bar with a high C2H2 uptake of 60.6 cm3 cm−3 and C2H2/C2H4 selectivity. Trace acetylene can be efficiently separated from ethylene via the synergistic effect of high‐density open metal and electronegative sites in an ultramicroporous metal–organic framework (MOF). The specific binding sites in the MOF afford an excellent acetylene uptake at 0.01 bar by maximizing the host–guest interactions.