Polycatenated Molecular Cage-Based Propane Trap for Propylene Purification with Recorded Selectivity

The propane (C 3 H 8 )-selective adsorption technology is recognized as a promising energy-efficient way to directly afford high-purity propylene (C 3 H 6 ). Here, a novel strategy via cage construction, combining with multiple interaction and shape selectivity, was raised to achieve preferential C 3 H 8 adsorption. We revealed that the polycatenated molecular cage within a microporous framework of [Ni(bpe) 2 (WO 4 )] (bpe = 1,2-bis(4-pyridyl)ethylene) showed preferential C 3 H 8 adsorption behavior with recorded C 3 H 8 /C 3 H 6 selectivity (1.62–2.75), as well as the high adsorption enthalpy around 42 kJ mol –1 . The cage afforded dense electronegative binding sites, enabling the multiple C δ− —H δ+ . . .C δ− interaction with C 3 H 8 molecule and thus the higher affinity for C 3 H 8 than C 3 H 6 . Additionally, the cage exhibited shape selectivity to oblate C 3 H 8, and was unfavorable to C 3 H 6 with relatively planar configuration as indicated by modeling studies. The high purity propylene (99.6%) was directly obtained without the extra adsorption–desorption cycles through the column breakthrough experiment.