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

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.