A porous metal–organic framework based on an asymmetric angular diisophthalate for selective adsorption of C₂H₂ and CO₂ over CH₄

Abstract

A new copper-based metal-organic framework [Cu₂L(H₂O)₂]·5DMF·2H₂O (ZJNU-56) has been solvothermally synthesized using a custom-designed asymmetric rigid bent diisophthalate ligand, 5,5'-(1-amine-naphthyl-2,4-diyl) diisophthalic acid (H₄L), and structurally determined by single-crystal X-ray diffraction. ZJNU-56 features a three-dimensional (3D) open framework incorporating three different types of metal-organic cages and two distinct types of one-dimensional channels. With a moderate BET surface area of 1655 m² g^-1, optimized pore structure, and functional sites (open copper sites and Lewis basic amine groups) on the cage surface, ZJNU-56 after desolvation exhibits highly selectively adsorptive separation of C₂H₂ and CO₂ over CH₄ under ambient conditions. At 298 K, the predicted IAST selectivities are 35.7-72.9 for an equimolar C₂H₂/CH₄ gas mixture and 6.8-7.0 for an equimolar CO₂/CH₄ gas mixture at pressures varying from 1 to 109 kPa, respectively, which are among the highest reported to date for copper-based MOFs.