A Zn-based MOF for efficient C3H6/C2H4 separation with high C2H4 productivity

Abstract

The methanol-to-olefins (MTO) process has emerged as a pivotal technology for ethylene (C 2 H 4 ) production, rendering the development of highly efficient propylene (C 3 H 6 ) adsorbents for the separation of MTO products and the acquisition of polymer-grade C 2 H 4 an urgent research imperative. Despite the reported high C 3 H 6 /C 2 H 4 selectivity or substantial C 3 H 6 adsorption capacity exhibited by certain metal-organic frameworks (MOFs), the inherent trade-off between these two properties often results in a suboptimal yield of high-purity C 2 H 4 . In this study, we have synthesized a novel zinc-based metal-organic framework (Zn-ICA) featuring a cage-like porous architecture through the utilization of a 1H-indazole-5-carboxylic acid ligand. This MOF exhibits an exceptionally high C 3 H 6 adsorption capacity (199.6 ​cm 3 ​g −1 at 100 ​kPa and 298 ​K) coupled with a favorable C 3 H 6 /C 2 H 4 selectivity (8.8), surpassing numerous benchmark MOFs that have been previously documented for C 3 H 6 /C 2 H 4 separation applications. Molecular simulation analyses reveal that the enhanced interaction between C 3 H 6 and the framework is attributable to the presence of π-bonds and accessible N/O sites within the ligand. Notably, breakthrough experiments have unequivocally demonstrated that this MOF is capable of achieving a record-breaking productivity (124.6 ​L ​kg −1 ) of polymer-grade C 2 H 4 (≥99.95 ​%) when employed for the separation of an equimolar C 3 H 6 /C 2 H 4 mixture, thereby positioning it as a highly promising advanced adsorbent for MTO product separation. • The MOF exhibits high C 3 H 6 adsorption capacity and high C 3 H 6 /C 2 H 4 selectivity. • Significant C 2 H 4 productivities can be achieved within a single separation cycle. • The presence of supramolecular binding sites facilitates the interaction between C 3 H 6 and the MOF. • The MOF exhibits favorable adsorption cycling performance along with a relatively low adsorption heat.