Lizhen Liu

Microporous metal-organic framework 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.

Robustness, Selective Gas Separation, and Nitrobenzene Sensing on Two Isomers of Cadmium Metal–Organic Frameworks Containing Various Metal–O–Metal Chains

Poor stability has been one of the major difficulties affecting to the practical application of metal-organic frameworks (MOFs). In this work, we obtained two 3D structurally isomeric Cd-MOFs, {[Cd6(NH2Me2)2(PTB)4(HCOO)2(H2O)]·(DMF)13·(H2O)4} n (FJU-35) and {[Cd6(NH2Me2)2(PTB)4(HCOO)2]·(DMF)6·(H2O)2} n (FJU-36) (H3PTB = pyridine-2,4,6-tribenzoic acid) containing different CdII-O-CdII chains by varying the addition agents. FJU-35 with coordinated solvent and formate in asymmetric μ3-η1:η2 coordination mode within the CdII-O-CdII chains is vulnerable to external attacks and is apt to collapse after activation, while FJU-36 with no coordinated solvent in the CdII-O-CdII chains but fully protected by the carboxylates from the ligands and the symmetric formate in the coordination mode μ3-η2:η2 is stable, and its activated sample shows efficient separation of C2H2/CH4 and C2H2/CO2 mixtures. Conversely, FJU-35 with more vulnerability is more sensitive to the detection of nitrobenzene than FJU-36.