The joint effect of naphthalene-system and defects on dye removal by UiO-66 derivatives

We report the results of the application of UiO-66 derivates for dye removal. This complex process includes two parallel mechanisms. The first one is the adsorption of the dye into the pores of MOF. The second one is photocatalytic degradation. We used two linkers for MOF synthesis: 1,4-benzene dicarboxylate and 1,4-naphthalene dicarboxylate. The introduction of these molecules in various ratios into the UiO-66-type structure allowed us to trace the effect of naphthalene species on the methylene blue removal. It was shown that a conjugated π-system of naphthalene rings led to charge transfer from linker to zirconium ions. It reduces the bandgap of the material and, therefore, results in higher photocatalytic performance. We also traced the effect of defects in the MOF structure on methylene blue degradation. It was shown that unsaturated zirconium ions in defect pores effectively catalyze dye cleavage and direct this process to the oxidative demethylation pathway. Obtained results could be applied to improve the photocatalytic properties of UiO-66 derivates.