Low-energy electron-driven functionalization of benzene–water ices to phenol

¹ Université Lyon 1, CNRS, Institut de Physique des 2 Infinis, UMR5822, F-69100 Villeurbanne, France
² Univ Rennes, CNRS, IPR (Institut de Physique de Rennes), UMR 6251, F35000 Rennes, France
³ Université Lyon 1, CNRS, Institut Lumière Matière, UMR5306, F-69100 Villeurbanne, France

^★ Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 26 January 2026
Accepted: 21 April 2026

Abstract

Low-energy electrons abundantly generated by galactic cosmic radiation are expected to play a central role in the radiation chemistry of interstellar and cometary ices, yet their capacity to drive specific bond-forming reactions in simple aromatic systems remains poorly constrained. Here, sub-12 eV electrons were used to irradiate mixed benzene (C₆H₆)–water ices under cryogenic conditions, which led to the selective formation of phenol (C₆H₅OH) via C–O bond formation at the aromatic ring. Energy-resolved measurements show that the phenol yield is governed by resonant processes, consistently with dissociative electron attachment and electronically excited states of the condensed benzene–water matrix. Temperature-programmed desorption combined with mass-spectrometry diagnostics allowed the direct quantification of phenol production. These results demonstrate that low-energy electrons alone can promote net hydroxylation of benzene in icy environments, providing a previously underappreciated route to phenolic species in dense clouds, star-forming regions and irradiated icy bodies, and highlighting electron-induced functionalization as a key driver of aromatic complexity in astrochemical ices.