Dye-sensitized NH₂-UiO-66 anchored with copper ions for tandem visible-light-driven hydrogen evolution

Metal-organic frameworks (MOFs) have attracted exciting application prospects in photocatalytic hydrogen (H-2) evolution due to the diversity of organic ligands and metal ions. However, the inappropriate conduction band position of pristine MOFs and corresponding large overpotential for H-2 evolution restrict the H-2 production under visible light. Herein, a dye-sensitized NH2-UiO-66 anchored with copper ions (EY-6Cu-NU-66) was synthesized by in-situ Cu anchoring followed by Eosin Y sensitization. The H-2 production activity showed that EY-6Cu-NU-66 reached 3579.82 mu mol center dot g(-1)center dot h(-1) under visible light, which was four times higher than that of dye-sensitized pristine NU-66 (EY-NU-66) and 99-fold higher than that of 6Cu-NU-66 free of dye sensitization. A series of characterizations and theoretical computations indicated that photo-generated electrons first transfer from the excited Eosin Y to the lowest unoccupied molecular orbital (LUMO) of the NU-66, then further transfer to the transition Cu-II/Cu-I metal center that is formed by Cu anchored on-NH2. This tandem mechanism not only improves the visible-light absorption ability of NU-66 but also promotes its separation efficiency of photo-generated carriers, thus greatly reducing the overpotential for H-2 evolution. This work provides a new strategy for visible-light-driven H-2 production by dye-sensitized MOF-based materials without noble metal loading.