Simultaneous C₂H₄ and C₃H₆ Purification via a MOF with Hierarchical Cages by Unique Combination of Coordination...

Separation in the methanol-to-olefins (MTO) process is crucial to producing pure olefin products (C₃H₆ and C₂H₄) in industry. The exploitation of advanced porous materials is becoming an important and challenging task for innovative adsorption separation technology. Herein, a new metal-organic framework (MOF)-Zn-ODIP is created through the differentiated coordination patterns of organic ligands and inorganic units. Its unique structure contains two different secondary building units (SBUs), forming different symmetries of hierarchical cages. While maintaining a high specific surface area (1385.4 m² g^-1) and porosity (70.1%), the material achieves selective adsorption for different light hydrocarbons through local coordination differences in cages. At 298 K, Zn-ODIP shows significantly more adsorption amounts for C₃H₆ and C₂H₆ compared to C₂H₄, with the loadings of 117.9, 79.6, and 67.5 cm³ g^-1, respectively, leading to a high C₃H₆/C₂H₄ selectivity of 12.3. Importantly, the material can completely separate and simultaneously obtain not only high-purity (>99.9%) C₂H₄ and C₃H₆ in one step from C₂H₄/C₃H₆ mixtures, but also the record C₃H₆ yield (47.6 L kg^-1) from C₂H₄/C₂H₆/C₃H₆ multi-component mixtures, greatly superior to existing MTO-products separation materials. This research exploits the differentiation of cage sizes as a new strategy for developing MOF design and efficient separation materials.