# Using Hybrid PDI-Fe3O4 Nanoparticles for Capturing Aliphatic Alcohols: Halogen Bonding vs. Lone Pair–π Interactions

## TL;DR

This study explores how halogenated perylene diimides on Fe3O4 nanoparticles capture alcohols through noncovalent interactions.

## Contribution

The paper introduces a comparison between halogen bonding and lone pair–π interactions in VOC capture using hybrid nanoparticles.

## Key findings

- VOC retention increases with longer alkyl chains, favoring interaction with the PDI aromatic surface.
- Tetrachlorinated PDIs showed higher VOC retention times than tetrabrominated PDIs.
- Computational tools helped clarify the roles of halogen bonding and lone pair–π interactions in VOC capture.

## Abstract

In this study, Fe3O4 nanoparticles (FeNPs) decorated with halogenated perylene diimides (PDIs) have been used for capturing VOCs (volatile organic compounds) through noncovalent binding. Concretely, we have used tetrachlorinated/brominated PDIs as well as a nonhalogenated PDI as a reference system. On the other hand, methanol, ethanol, propanol, and butanol were used as VOCs. Experimental studies along with theoretical calculations (the BP86-D3/def2-TZVPP level of theory) pointed to two possible and likely competitive binding modes (lone pair–π through the π-acidic surface of the PDI and a halogen bond via the σ-holes at the Cl/Br atoms). More in detail, thermal desorption (TD) experiments showed an increase in the VOC retention capacity upon increasing the length of the alkyl chain, suggesting a preference for the interaction with the PDI aromatic surface. In addition, the tetrachlorinated derivative showed larger VOC retention times compared to the tetrabrominated analog. These results were complemented by several state-of-the-art computational tools, such as the electrostatic surface potential analysis, the Quantum Theory of Atoms in Molecules (QTAIM), as well as the noncovalent interaction plot (NCIplot) visual index, which were helpful to rationalize the role of each interaction in the VOC···PDI recognition phenomena.