Acid-tailored self-assembled perylene diimide supramolecular for visible-light-driven activation of peroxymonosulfate towards efficient degradation of iohexol

The presence of iohexol (IOX) in the environment has attracted widespread attention. Acetic acid, hydrochloric acid, and nitric acid tailored self-assembled perylene diimides (PA, PC and PN) were prepared and utilized in different visible-light-driven activation of peroxymonosulfate (PMS/Vis) systems for the degradation of IOX. As an electron acceptor, PMS can significantly hinder the recombination of photogenerated electron-hole pairs. The removal rate of 5 mg/L IOX by PC/PMS/Vis system reached 99.1% at 30 min, which was 2.0 times and 1.3 times higher than that of PA/PMS/Vis and PN/PMS/Vis system. The boosted oxidation activity with PC was due to the pH dependence of perylene diimide (PDI) self-assembly and the small amount of Cl- (0.56%) absorbed on PC, which can promote the transfer of electron-hole pairs, change the surface charge distribution and energy band position, and enhance pi-electron conjugation. Based on density functional theory and electrostatic potential calculation, the Cl- adsorbed on the surface of PDI brings an effect on the electrostatic potential distribution. Furthermore, the built-in intermolecular electric field leads to accelerated charge transfer of PDI. In the PC/PMS/ Vis system, holes, singlet oxygen and superoxide radical were perceived as the dominant contributors. The degradation of IOX carried out via pathways of amide hydrolysis, amino oxidation, hydrogen abstraction, dei-odination reaction, and center dot OH attack. This work provides a new method for the pollution control of IOX and sci-entific guidance for the tailored self-assembly of organic supramolecules.