Architecting the Donor–Acceptor Units in UiO-68 for High-Efficiency Photocatalytic Pollutant Degradation

Direct degradation of pollutants by free radicals generated from a photocatalytic oxygen reduction reaction (ORR) has advantages of both thermodynamics and kinetics, but realizing the high degradation activity and selectivity still remains a great challenge. In this study, we successfully designed donor-acceptor (D-A) UiO-68 metal-organic frameworks (MOFs) by introducing different electron-withdrawing groups for enhanced photocatalytic degradation of pollutants. The electron-withdrawing group-functionalized UiO-68 was able to generate singlet oxygen (¹O₂) rather than hydrogen peroxide (H₂O₂) via the ORR process in the absence of a sacrificial agent. Theoretical and experimental results showed that the introduction of electron-withdrawing groups widened the visible-light absorption range and improved the intramolecular charge transfer, thus generating highly active and selective ¹O₂ for the degradation of Rhodamine B and methyl orange within 10 min. This study highlights the important role of the synergistic interaction between donor and acceptor units in promoting intramolecular charge transfer to increase the production efficiency of reactive oxygen species, providing a promising strategy for designing efficient photocatalysts and beyond.