Zn-based metal-organic framework with confined pore aperture and inert pore environment for efficient one-step separation of methanol-to-olefins products

Zn-BDC-dmtrz with confined nonpolar pores preferentially adsorbs C 3 H 6 and C 2 H 6 over C 2 H 4 for MTO separation. • Zn-BDC-dmtrz delivers high C 3 H 6 uptake of 6.4 mmol g −1 and superior C 3 H 6 /C 2 H 4 IAST selectivity of 9.7. • Pore confinement and synergistic host–guest interactions jointly govern selective gas recognition. • One-step MTO purification by Zn-BDC-dmtrz yields polymer-grade C₂H₄ (>99.9%) and high-purity C₃H₆ (>99.5%). The efficient separation of propylene (C 3 H 6 ) from ethylene (C 2 H 4 ) and ethane (C 2 H 6 ) in methanol-to-olefins (MTO) product streams is of great industrial and economic significance, yet remains highly challenging due to their similar molecular sizes and physicochemical properties. Herein, we report a microporous zinc-based metal-organic framework, Zn-BDC-dmtrz, featuring a large pore volume, a confined pore aperture (∼5.6 Å), and a relatively nonpolar pore environment. These structural features enable preferential adsorption of C 3 H 6 and C 2 H 6 over C 2 H 4 , making Zn-BDC-dmtrz particularly suitable for the purification of MTO-derived hydrocarbon mixtures. At 298 K and 100 kPa, Zn-BDC-dmtrz exhibits a high C 3 H 6 uptake of 6.4 mmol g −1 , together with a C 3 H 6 /C 2 H 4 IAST selectivity of 9.7 and a separation potential (ΔQ) of 4.7 mmol g −1 , outperforming many representative MOF adsorbents reported for C 3 H 6 /C 2 H 4 separation. In situ FT-IR spectroscopy, GCMC simulations, and DFT-D calculations reveal that the superior adsorption of C 3 H 6 originates from synergistic pore confinement and favorable host-guest interactions within the framework. Dynamic breakthrough experiments further demonstrate that Zn-BDC-dmtrz enables the direct production of polymer-grade C 2 H 4 (>99.9%) and the recovery of high-purity C 3 H 6 (>99.5%) from binary and ternary mixtures representative of MTO effluents, with excellent recyclability over multiple adsorption-desorption cycles. This work highlights Zn-BDC-dmtrz as a promising adsorbent for one-step MTO product purification and provides design principles for porous materials combining confined pore sizes with chemically inert pore environments for challenging light-hydrocarbon separations. Schematic illustration of the one-step separation and purification of ethylene as well as recyclable recovery of high-purity propylene from MTO product streams benefiting from the unique structural advantages of Zn-BDC-dmtrz. Download: Download high-res image (157KB) Download: Download full-size image