Halogen bonding-assisted adsorption of iodoperfluoroarenes on a strong anion exchanger and its potential application in solid-phase extraction

Abstract

The adsorption of iodoperfluoroarenes (IPFArs) by solid-liquid interfacial halogen bonding was investigated and preliminarily applied to solid-phase extraction (SPE). Based on 19F NMR titration experiments, UV spectrophotometric titrations, and chemical computations, silica gel functionalized with trimethylaminopropyl chloride (SAX) groups was chosen as a strong anion-exchanging adsorbent, since the solution-phase association ability of Cl− as halogen bond acceptor is superior to that of Br− or I−. Further explorations indicated that the adsorption of IPFArs is mainly driven by halogen bonding. The adsorption isotherms of 1,4-diiodotetrafluorobenzene (1,4-DITFB) and iodoperfluorobenzene (IPFB) were fitted by the Freundlich equation, while that of 1,2-diiodotetrafluorobenzene (1,2-DITFB) was fitted by the Langmuir equation. Such alternative adsorption models can meet the requirements of different self-assembly systems based on halogen bonding. In SPE applications, the adsorption efficiency of IPFArs on SAX is as follows: 1,4-DITFB≈1,2-DITFB>IPFB, with no significant adsorption of bromoperfluoroarenes. These results indicate promising applications of halogen bonding in the separation and enrichment of IPFArs.