Absorption performance and mechanism of volatile organic compounds by phosphonium ionic liquids with different anions

Abstract

AbstractBACKGROUNDThe emission of volatile organic compounds (VOCs) seriously harms the environment and human health. The prevention and control of VOC pollution is a major challenge in the research field. Aiming at VOC pollution treatment using green solvents, the absorption of trichloromethane by synthesized tributyl(propyl)phosphonium bis(trifluoromethylsulfonyl)imide ([P4443] [Tf2N]), tributyl(propyl)phosphonium tetrafluoroborate ([P4443] [BF4]), tributyl(propyl)phosphonium trifluoroacetic acid ([P4443] [CF3COO]) and xylene by trioctyl(propyl)phosphonium bis(trifluoromethylsulfonyl)imide ([P8883] [Tf2N]) and trioctyl(propyl)phosphonium tetrafluoroborate ([P8883] [BF4]) were experimentally measured. The mechanism of trichloromethane and xylene absorption by phosphonium‐based ionic liquids (PILs) with different anions was further discussed through simulation calculation.RESULTSPILs process excellent absorption capacity, such as [P4443] [CF3COO], with static saturation absorbing capacity up to 2.843 g g−1 for trichloromethane. PILs have a certain selective absorption ability for xylene, which has the highest absorption for o‐xylene, reaching 1.462 g g−1. The absorption energy data also prove that [CF3COO]− anion preferentially interacts with trichloromethane. Combined with the most stable structures of VOCs absorbed by PILs, the results of the Mulliken charge and frontier molecular orbitals indicate that PIL anions play a major role in chlorinated alkanes, and form hydrogen bonds with them. In addition, the cation can form CH···π bond interaction with xylene.CONCLUSIONThe experimental and calculated results showed that PILs are a promising adsorbent for trichloromethane and xylene. The study provides a reference for PILs designed to deal with VOCs in the future. © 2024 Society of Chemical Industry (SCI).