Microporous metal–organic frameworks with open metal sites and π-Lewis acidic pore surfaces for recovering ethylene from polyethylene off-gas

Abstract

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.