Cis–Trans Selectivity of Haloalkene Isomers in Nonporous Adaptive Pillararene Crystals
2019
Zhou, Yujuan | Jie, Kecheng | Zhao, Run | Huang, Feihe
The separation of haloalkene cis–trans isomers is difficult to achieve, yet highly desired in the chemical industry. Here, we report an energy-efficient adsorptive separation of 1,4-dichloro-2-butene (DCB) cis–trans isomers using nonporous adaptive crystals of perethylated pillararenes. Adaptive perethylated pillar[6]arene (EtP6) crystals separate the trans-DCB isomer from its cis isomer with high selectivity while perethylated pillar[5]arene (EtP5) crystals adsorb cis–trans DCB isomers without selectivity. The selectivity of EtP6 derives from the difference in the thermodynamic stabilities of guest-loaded EtP6 crystal structures upon capture of cis–trans DCB isomers, while the structural similarity of guest-loaded EtP5 leads to the loss of selectivity. EtP6 is highly recyclable due to the reversible transformations between guest-free and guest-loaded structures.
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