Solvent-induced framework-interpenetration isomers of Cu MOFs for efficient light hydrocarbon separation

Abstract

By tuning interpenetrated and non-interpenetrated frameworks, a pair of Cu-paddlewheel framework-interpenetration isomers (UPC-34, [Cu₃(L)₂(H₂O)₃]·2DMF·3EtOH·3H₂O and UPC-35, [Cu₃(L)₂(H₂O)₃]·2DMF·2Diox·3H₂O) based on a tripodal ligand (H₃L = 4,4′-((5-carboxy-1,3-phenylene)bis(ethyne-2,1-diyl))dibenzoic acid) has been synthesized and characterized. The interpenetrated framework (UPC-35) is more stable than the non-interpenetrated one (UPC-34). Due to the 2-fold interpenetration, UPC-35 has a pore size distribution of ∼4.5 Å, which is close to the kinetic diameters of light hydrocarbons (C₁–C₃), and thus exhibits high gas-uptake capacities for C₃H₆ and C₃H₈. Furthermore, UPC-35 is an effective adsorbent for the selective separation of C₃/C₂/C₁ light hydrocarbons.