Separation of Bromoalkanes Isomers by Nonporous Adaptive Crystals of Leaning Pillar[6]arene

Abstract

Haloalkanes are important chemicals in synthetic chemistry and petrochemical industry, but the separation of their isomers is a big hurdle. Herein, we report a facile energy-efficient adsorptive separation strategy using a new class of nonporous adaptive crystals based on leaning pillar[6]arene. Desolvated perethylated leaning pillar[6]arene crystals (EtLP6) with interesting nonporous character show a preference for 1-bromoalkane isomers over 2-bromoalkane isomers. EtLP6 is capable of separating 1-bromopropane, 1-bromobutane, and 1-bromopentane from the corresponding 1:1 (v/v) mixtures of 1/2-positional isomers with purities from 89.6 % to 96.3 % in only one adsorption cycle. The selectivity is endowed by the different host-guest binding modes and different stabilities of EtLP6 crystalloids loaded with 1- and 2-positional isomers. Significantly, the guest-adsorbed assemblies are highly stable at room temperature and EtLP6 can be reused many times without any decrease in performance.

Keywords: host-guest systems; isomers separation; leaning pillar[6]arene; nonporous adaptive crystals; supramolecular chemistry.