Microporous metal–organic frameworks with open metal sites and π-Lewis acidic pore surfaces for recovering ethylene from polyethylene off-gas†
There is an urgent demand for recovering ethylene (C2H4) from polyethylene off-gas since it allows for a more efficient conversion of monomers with high economic value. Herein, we report a three-dimensional (3D) porous MOF [Cu2(L)(H2O)2]·5DMF·dioxane·3H2O (FJU-101, H4L = N,N′-bis(5-isophthalic acid)naphthalenediimide, DMF = N,N′-dimethylformamide) with π-Lewis acidic pore surfaces and superior gas storage/separation performance. Under ambient conditions, the activated FJU-101a exhibits a high C2H4 uptake of 142 cm3(STP) per g and more importantly, the dynamic fixed-bed breakthrough test indicates that the recovery of C2H4 from simulated polyethylene off-gas through a column packed with FJU-101a adsorbent can be efficiently achieved. Such a separation is essential to recycle ethylene for its commercial usage. In addition, FJU-101a also exhibits an extraordinarily high gravimetric uptake of CO2 (219.1 cm3 g−1) at 273 K and 1 bar, which is only slightly lower than that of the best CO2 adsorption material, namely, MgMOF-74 (230 cm3 g−1) under similar conditions.