Adsorptive Separation of Acetylene from Ethylene in Isostructural Gallate-Based Metal-Organic Frameworks

The separation of acetylene from ethylene is of paramount importance in the purification of chemical feedstocks for industrial manufacturing. Herein, an isostructural series of gallate-based metal-organic frameworks (MOFs), M-gallate (M=Ni, Mg, Co), featuring three-dimensionally interconnected zigzag channels, the aperture size of which can be finely tuned within 0.3 Å by metal replacement. Controlling the aperture size of M-gallate materials slightly from 3.69 down to 3.47 Å could result in a dramatic enhancement of C₂ H₂ /C₂ H₄ separation performance. As the smallest radius among the studied metal ions, Ni-gallate exhibits the best C₂ H₂ /C₂ H₄ adsorption separation performance owing to the strongest confinement effect, ranking after the state-of-the-art UTSA-200a with a C₂ H₄ productivity of 85.6 mol L^-1 from 1:99 C₂ H₂ /C₂ H₄ mixture. The isostructural gallate-based MOFs, readily synthesized from inexpensive gallic acid, are demonstrated to be a new top-performing porous material for highly efficient adsorption of C₂ H₂ from C₂ H₄ .