The beauty of being complex: Prussian blue analogues as selective catalysts and photocatalysts in the degradation of ciprofloxacin

We investigate the performance of four Prussian blue analogues (PBAs) as catalysts for the selective degradation of ciprofloxacin in water, under both dark and illumination conditions. We show that no light is actually needed to induce a selective degradation of the molecular target, while light irradiation spurs the process, without, however, resulting in the commonly reported photolysis-supported breaking down. We present a systematic characterization of the PBAs aiming at interpreting the catalytic outcomes in the light of a classic coordination chemistry analysis, empowered by the most recent findings in literature. We show that varying the transition metal binding the N atom of the cyanide bridge is key to promote photoinduced charge generation and transfer, which effectively disrupts the molecular target. The analysis of the materials before and after the irradiation with solar simulated light results in a change of the lattice parameters, indicating the possibility of a light-induced spin cross-over.