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)] 5 ·{AsMo 4 V Mo 6 VI V 2 V O 40 (V IV O)[V IV O(H 2 O)]}·2H 2 O ( 1 ), as catalyst. The POMOF catalyst was constructed by the connection of reduced {AsMo 10 V 4 } 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 {AsMo 10 V 4 } clusters. Significantly, the transition of electrons from Cu(I)-MOF to {AsMo 10 V 4 } clusters (Cu → Mo/V) greatly inhibits the recombination of photogenerated carriers, thereby advancing electron transfer. More importantly, the {AsMo 10 V 4 } clusters are not only adsorption sites but also catalytically active sites. This causes the fast transfer of photogenerated electrons from Mo/V to UO 2 2+ (Mo/V → O → U) via the surface oxygen atoms. The shorter electron transmission distance between catalytic active sites and UO 2 2+ 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 {AsMo 10 V 4 } clusters.