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·{AsMo4VMo6VIV2VO40(VIVO)­[VIVO­(H2O)]}·2H2O (1), as catalyst. The POMOF catalyst was constructed by the connection of reduced {AsMo10V4} 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 {AsMo10V4} clusters. Significantly, the transition of electrons from Cu­(I)–MOF to {AsMo10V4} clusters (Cu → Mo/V) greatly inhibits the recombination of photogenerated carriers, thereby advancing electron transfer. More importantly, the {AsMo10V4} clusters are not only adsorption sites but also catalytically active sites. This causes the fast transfer of photogenerated electrons from Mo/V to UO22+(Mo/V → O → U) via the surface oxygen atoms. The shorter electron transmission distance between catalytic active sites and UO22+ 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 {AsMo10V4} clusters.