A microporous mixed-metal (Na/Cu) mixed-ligand (flexible/rigid) metal–organic framework for photocatalytic H2 generation

Abstract

For the first time, we report a cost-effective mixed-metal (Na/Cu) mixed-ligand (flexible/rigid) metal–organic framework H_1.5[Na_0.5Cu₂(L₁)(L₂)(H₂O)]·5.5H₂O (Na/Cu-MOF; H₂L₁ = 4,4′-(4-(4H-1,2,4-triazol-4-yl)phenylazanediyl)dibenzoic acid; and H₄L₂ = citric acid). The 3D microporous framework of the Na/Cu-MOF consists of 10.28 Å × 10.07 Å quadrilateral channels and 14.52 Å × 6.72 Å triangular channels, which exhibits highly efficient photocatalytic H₂ generation (4650 μmol g⁻¹ h⁻¹) under visible-light irradiation. Emission quenching and transient photocurrent experiments confirm the charge separation and transfer process for the possible reaction mechanism in the photocatalytic system. Control experiments using a similar single-metal single-ligand MOF [Cu₂(L₂)(H₂O)₂] (Cu-MOF; H₄L₂ = citric acid) have been performed for comparison, which demonstrates the potential of mixed-metal mixed-ligand MOFs in the practical utilization of light.