Ultrafast Solar Dehalogenation of Aromatic Halides in Water Via Diradical Transformation in Organic Semiconductors

Abstract

The aqueous dehalogenation of aromatic halides, particularly the challenging task of removing low-substituted carbon-halogen bonds, has historically been associated with prolonged treatment cycles and high energy and economic costs. In this study, we present a novel Zn0.8Cd0.2S/PDI composite photocatalyst that achieves complete dehalogenation of deca-BDE in water within just 2 min under concentrated natural sunlight. This catalyst utilizes the conduction band electrons of Zn0.8Cd0.2S nanoparticles to achieve in-situ PDI→:PDI2- transformation, fully exploiting the solar spectrum with improved near-infrared absorption, and introducing additional diradical catalytic sites, facilitating ultrafast dehalogenation cycles. The radical-attack pathway initiated by :PDI2- predominates, overcoming the bottleneck of the slow protonation pathway in traditional inorganic catalysts. This advancement leads to dehalogenation efficiencies ranging from 92% to 99% for eleven typical aromatic halides, presenting a highly efficient, cost-effective, and rapid method for the solar-driven mineralization of organic halogenated wastewater.

Keywords: Dehaogenation, Perylene Diimide, Diradical Intermediate, Aromatic Halides, Photocatalysis