Immobilizing Functional Sites into Isoreticular Zinc-Based MOFs To Tune Pore Environment for Highly Efficient Methanol-to-Olefins (MTO) Product Separation

The separation of C3H6/C2H4 mixtures is a critical process in MTO reactions, which remains a great challenge because of their similar physicochemical properties. Immobilizing functional groups in MOFs has emerged as an effective strategy for tuning pore environments and improving the C3H6/C2H4 separation performance. Herein, two isoreticular and functionalized Zn-MOFs are successfully designed and constructed to separate MTO products, namely, CH3-decorated JLU-MOF125 and NH2-decorated JLU-MOF126. The two MOFs feature moderate pore volumes, micropore structures, and rich N/O sites, which collectively contribute to exceptional C3H6/C2H4 separation efficiency. Ultrahigh polymer-grade (>99.9%) C2H4 (1146.1 and 1138.6 L/kg, respectively) can be obtained from the dynamic breakthrough experiments of JLU-MOF125 and JLU-MOF126, and 29.6 and 48.9 L/kg of C3H6 (>99.5%) can be recovered, respectively. More importantly, both MOFs exhibit remarkable stability and the breakthrough curves remain nearly unchanged after 5 cycles, which makes them promising materials for the separation of MTO products in industrial application.