Boosting the photocatalytic performance of the oligo (phenylene vinylene) moiety by copolymerization for the heterogeneous degradation of indigo carmine dye

The copolymerization with flexible and rigid spacers of 4,4'-((1E, 1 ' E)-(2,5-dimethoxy-1,4-phenylene)bis (ethene-2,1-diyl))dibenzoic acid, as a promising phenylene vinylene-based (PV) organic photocatalyst, was examined as a strategy to validate the effect of such chemical modifications in the modulation of the photocatalytic properties of this organic pi-conjugated moiety. The polymers prepared here were fully characterized and evaluated as photocatalysts in the degradation of indigo carmine dye under two different irradiation scenarios (UVA and visible), consistently displaying a superior efficiency in contrast to their monomeric oligo (phenylene vinylene) (OPV) counterparts. Scavenging experiments confirmed that photocatalysis proceeds via the generation of superoxide radicals (O-2(center dot-)), singlet oxygen (O-1(2)), and direct oxidation. The obtained results proved that the insertion of an aromatic rigid spacer not only prompts an enhancement in the photocatalytic activity of the phenylene vinylene-based polymers but also increases the stability of the OPV moiety by minimizing the reaction of the vinyl fragments with reactive oxygen species. This was demonstrated with the reuse experiments, where 96% of the photocatalytic activity was preserved throughout the first five reuse cycles.