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 Fe4L6 capsule containing a hydrophobic cavity, which can be used to encapsulate and separate propylene/propane. The successful encapsulation of propylene and propane by the Fe4L6 cage in a water solution was documented by NMR spectroscopy. The binding constants K for the Fe4L6 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 D2O 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 Fe4L6 cage as a separation material in a U‐shaped glass tube. This work provides a new strategy for the separation of olefin/paraffin. A water‐soluble tetrahedral Fe4L6 metal‐organic cage has been successfully used to separate propane and propylene under ambient conditions. Mixed gases of C3H6 and C3H8 were captured by Fe4L6 at the gas‐liquid interface in a U‐shaped glass tube. Governed by the guest binding affinity, C3H6 is released first after transport of the gases to the receiving arm of the tube.