Topology and pore-surface engineering of a Zr-MOF for ethylene purification and propylene recovery from MTO products

Abstract

Efficient separation of light hydrocarbons from methanol-to-olefins (MTO) product streams, typically consisting of ethylene (C2H4), propylene (C3H6), and ethane (C2H6), is pivotal for sustainable olefin production but remains challenged by the trade-off between selectivity and capacity. Herein, we report a highly robust zirconium-based metal–organic framework, NKU-400, constructed from 12-connected Zr6 clusters and tetratopic carboxylate ligands, featuring a unique (4,4,12)-connected topology with aromatic-rich and N/O-functionalized pore surfaces. The tailored pore environment affords a pronounced thermodynamic preference for C3H6 over C2H4 through synergistic pore confinement and multiple C–H⋯π/O/N interactions, while a more modest discrimination between C2H6 and C2H4 develops at finite loading. Consequently, NKU-400 exhibits high adsorption capacities for C3H6 (6.01 mmol g−1) and C2H6 (4.29 mmol g−1), together with high C3H6/C2H4 IAST selectivities of 9.83–10.67 at 298 K. Dynamic breakthrough experiments further demonstrate highly effective binary C3H6/C2H4 separation, delivering polymer-grade C2H4 (≥99.95%) with a productivity of 94.45 L(STP) kg−1 and enabling the subsequent recovery of high-purity C3H6 (≥99.5%) with a productivity of 77.62 L(STP) kg−1 from an equimolar mixture. Furthermore, NKU-400 enables the one-step purification of polymer-grade C2H4 from ternary C3H6/C2H6/C2H4 mixtures, followed by the recovery of high-purity C3H6 with a productivity of 59.72 L(STP) kg−1 within a single adsorption–desorption cycle. Combined with its excellent chemical robustness, these results establish NKU-400 as a promising adsorbent for the purification of MTO-derived light hydrocarbons and highlight the effectiveness of integrating topology design with pore-surface engineering for challenging hydrocarbon separations.