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

Abstract

Metal-organic frameworks (MOFs) have attracted exciting application prospects in photocatalytic hydrogen (H2) 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 H2 evolution restrict the H2 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 H2 production activity showed that EY-6Cu-NU-66 reached 3579.82 μmol·g−1·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 CuII/CuI 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 H2 evolution. This work provides a new strategy for visible-light-driven H2 production by dye-sensitized MOF-based materials without noble metal loading.