A Self-Assembled Capsule for Propylene/Propane Separation

The development of energy-saving technology for the efficient separation of olefin and paraffin is highly important for the chemical industry. Herein, we report a self-assembled Fe₄ L₆ capsule containing a hydrophobic cavity, which can be used to encapsulate and separate propylene/propane. The successful encapsulation of propylene and propane by the Fe₄ L₆ cage in a water solution was documented by NMR spectroscopy. The binding constants K for the Fe₄ L₆ cage toward propylene and propane were determined to be (5.0±0.1)×10³  M^-1 and (2.1±0.7)×10⁴  M^-1 in D₂ O at 25 °C, respectively. Experiments and theoretical studies revealed that the cage exhibited multiple weak interactions with propylene and propane. The polymer-grade propylene (>99.5 %) can be obtained from a mixture of propylene and propane by using the Fe₄ L₆ cage as a separation material in a U-shaped glass tube. This work provides a new strategy for the separation of olefin/paraffin.