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

Abstract

Abstract Purification of C 2 H 4 from an C 2 H 4 /C 2 H 6 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 Å 3 ) and ethane (3.81×4.08×4.82 Å 3 ) through molecular cross‐section size differentiation. Co‐gallate shows an unprecedented IAST selectivity of 52 for C 2 H 4 over C 2 H 6 with a C 2 H 4 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 C 2 H 4 /C 2 H 6 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.