Exploring Electron Transfer Mechanism in Synergistic Interactional Reduced Polyoxometalate-Based Cu(I)-Organic Framework for Photocatalytic Removal of U(VI).

Photocatalytic reduction of U(VI) is a promising method for removing uranium containing pollutants. However, using polyoxometalate-based metal-organic frameworks (POMOFs) for photoreduction of U(VI) is rare, and the relevant charge transfer pathway is also not yet clear. In this article, we demonstrate a highly efficient strategy and revealed a clearly electron transfer pathway for the photoreduction of U(VI) with 99% removal efficiency by using a novel POMOF, [Cu(4,4'-bipy)]·{AsMoMoVO(VO)[VO(HO)]}·2HO (), as catalyst. The POMOF catalyst was constructed by the connection of reduced {AsMoV} clusters and Cu(I)-MOF chains through Cu-O coordination bonds, which exhibits a broader and stronger light absorption capacity due to the presence of reduced {AsMoV} clusters. Significantly, the transition of electrons from Cu(I)-MOF to {AsMoV} clusters (Cu → Mo/V) greatly inhibits the recombination of photogenerated carriers, thereby advancing electron transfer. More importantly, the {AsMoV} clusters are not only adsorption sites but also catalytically active sites. This causes the fast transfer of photogenerated electrons from Mo/V to UO(Mo/V → O → U) via the surface oxygen atoms. The shorter electron transmission distance between catalytic active sites and UO achieves faster and more effective electron transport. All in all, the highly effective photocatalytic removal of U(VI) using the POMOF as a catalyst is predominantly due to the synergistic interaction between Cu(I)-MOFs and reduced {AsMoV} clusters.