Selective adsorption of aldehyde impurities from propylene oxide using perethylated pillar[5]arene enabled by spatial size matching effect

Effective removal of acetaldehyde and propionaldehyde from propylene oxide is important for polyether industry but remains a significant challenge due to their similar molecular sizes and relatively close volatilities. Herein, we studied flexible molecular materials, perethylated pillar[n]arene crystals (n = 5, 6), which can be used to separate acetaldehyde and propionaldehyde in propylene oxide. Through a space size matching effect, perethylated pillar[5]arene demonstrates excellent adsorption selectivity of 95 % and 100 % for aldehydes in ternary mixture and binary mixture of propylene oxide, acetaldehyde and propionaldehyde, respectively. These impressive selective adsorption is achieved based on their differential host–guest interactions. Density functional theory calculations provide a comprehensive explanation of the adsorption process, revealing that the adsorption mechanisms of perethylated pillar[5]arene for acetaldehyde and propionaldehyde primarily involve C-H···O hydrogen bonding and C-H···π interactions. This study also provides a novel method for achieving one-step purification of propylene oxide in industrial applications.