Molecular Sieving of Ethane from Ethylene through the Molecular Cross-Section Size Differentiation in Gallate-based Metal-Organic Frameworks

Purification of C₂H₄ from an C₂H₄/C₂H₆ mixture, one of the most important while challenging industrial separation processes, is mainly through energy‐intensive cryogenic distillation. Now a family of gallate‐based metal–organic framework (MOF) materials is presented, M‐gallate (M=Ni, Mg, Co), featuring 3D interconnected zigzag channels, the aperture sizes of which (3.47–3.69 Å) are ideally suitable for molecular sieving of ethylene (3.28×4.18×4.84 ų) and ethane (3.81×4.08×4.82 ų) through molecular cross‐section size differentiation. Co‐gallate shows an unprecedented IAST selectivity of 52 for C₂H₄ over C₂H₆ with a C₂H₄ uptake of 3.37 mmol g⁻¹ at 298 K and 1 bar, outperforming the state‐of‐the‐art MOF material NOTT‐300. Direct breakthrough experiments with equimolar C₂H₄/C₂H₆ mixtures confirmed that M‐gallate is highly selective for ethylene. The adsorption structure and mechanism of ethylene in the M‐gallate was further studied through neutron diffraction experiments.