A pacs-type metal–organic framework with high adsorption capacity for inverse C2H6/C2H4 separation

Abstract

Separation of the mixture of ethylene (C₂H₄) and ethane (C₂H₆) to produce polymer-grade C₂H₄ is of prime importance in the petrochemical industry. In this context, metal–organic frameworks (MOFs) featuring tunable pore metrics and surface chemistry, especially those with inverse C₂H₆/C₂H₄ adsorption selectivity, hold great promise in energy-effective purification of C₂H₄ by adsorptive separation, but often encounter the well-known trade-off between adsorption selectivity and capacity. In this work, we report two new MOFs by deploying the pore-space-partition (PSP) strategy for the purpose of reducing the pore aperture size while retaining the gas-accessible pore volume. As a result, Ni-bodc-tpt (bodc = bicyclo[2.2.2]octane-1,4-dicarboxylic acid, tpt = 2,4,6-tri(4-pyridyl)-1,3,5-triazine) by combining optimal pore size, large cage pore volume, and rich C–H binding sites exhibits concurrently high C₂H₆ adsorption capacity (131.65 cm³ g⁻¹) and C₂H₆/C₂H₄ selectivity (1.8) at 298 K and 1 bar, which is superior or comparable to many benchmark C₂H₆-selective MOFs. A dynamic breakthrough experiment demonstrates that high-purity C₂H₄ (>99.9%) can be harvested in one step from a binary mixture of C₂H₆/C₂H₄ (50/50, v/v), attesting to the feasibility of this new MOF as a prospective C₂H₄ purification agent.