Conjugated donor-acceptor (D-A) supramolecule catalyst for visible-light-driven photocatalytic removal of bromate in water

To guarantee drinking water security, removal of bromate (BrO₃ ⁻) has garnered plenty of attention in water treatment. In current study, we have developed a novel conjugated donor-acceptor (D-A) photocatalyst (4,4′'-bis(diphenylamino)-[1,1′:4′,1′'-terphenyl]-2′,5′-dicarbaldehyde, BDTD) with supramolecule architecture assembling via intermolecular C–H···O hydrogen bonds and C–H···π interactions. Both diffuse reflectance spectrum (DRS) and density functional theoretical (DFT) calculations gave the bandgap of E_g = 2.21 eV, clearly indicating the visible-light response of BDTD supramolecule. The calculations showed that BDTD supramolecule could induce nearly 100% removal of BrO₃ ⁻ stably at pH-neutral condition driven by visible light, accounting for a first-order kinetic constant being one order of magnitude higher than most of the photocatalysts previous reported. As demonstrated by our electron scavenger experiment and DFT calculations, the BDTD supramolecule should undergo the photocatalytic reduction of BrO₃ ⁻ through direct reduced by the lowest unoccupied molecular orbital of conduction band (potential of −1.705 V versus standard hydrogen electrode) electron. The BDTD supramolecule may serve as an attractive photocatalyst by virtue of response to visible light, efficient charge transfer and separation as well as high photocatalytic activity, which will make the removal of BrO₃ ⁻ in water much easier, more economical and more sustainable.