Highly selective adsorption of light hydrocarbons in a HKUST-like MOF constructed from spirobifluorene-based octacarboxylate ligand by a substitution strategy

Metal-organic frameworks (MOFs) with HKUST-like tbo structures have been paid specific attention for gas sorption and separation because of their specific pore features. According to the geometric similarity of spirobifluorene and [Cu₂(O₂CR)₄] paddlewheel secondary building units (Cu2 SBUs) in HKUST-1, we attempted to rationally construct a HKUST-like MOF by a substitution strategy. Using a judiciously designed octatopic carboxylate ligand, a copper-organic framework, JUC-220, was synthesized. The crystals of JUC-220 exhibited characteristic features in cubic with disorder, possibly due to the disorder substitution and high symmetry of tbo topology. Two related HKUST-like structure models were considered. Thanks to the suitable pore size and specific pore shapes, the adsorption selectivities of JUC-220 for C₃H₈/CH₄ (5/85) and C₂H₆/CH₄ (10/85) gas mixtures were as high as 736 and 46 respectively at 298 K and 1 bar. Specially, JUC-220 exhibited excellent trace adsorption performance of C₃H₈ and C₂H₆ as well as reverse adsorption behavior of C₂H₆/C₂H₄. Thus, JUC-220 serves as an example of HKUST-like MOF with disorder for light hydrocarbons separation and the implementation of substitution which can be used to explore more porous MOFs.