A highly connected metal–organic framework with stretched inorganic units for propylene/ethylene separation

Abstract

Separating propylene from ethylene in the product mixture derived from the methanol-to-olefin conversion process in an energy-efficient way is challenging, and adsorptive separation utilizing porous materials such as metal–organic frameworks (MOFs) provides a potential solution. Herein, we constructed a highly connected MOF structure with “stretched” [Zn₈SiO₄] as metal nodes and mixed binding groups (carboxylate and pyrazolate) as linkers. The mixed binding groups adapted well to the increase in the inter-metal distance caused by the insertion of SiO₄⁴⁻ in the nodes, enabling the formation of a highly symmetrical 12-connected net with high porosity and suitable pore apertures. This framework exhibited an impressive C₃H₆ adsorption capacity of 180.5 cm³ g⁻¹ and a calculated C₃H₆/C₂H₄ selectivity of 8.6 at 298 K and 100 kPa, which was attributed to the abundant N/O sites on the pore surface that generated stronger interactions with C₃H₆. Furthermore, dynamic breakthrough experiments demonstrated that the framework was capable of effectively separating C₃H₆/C₂H₄ under various conditions, making it a promising benchmark adsorbent for industrial applications.