High performance hydrogen photoproduction using a Co-doped CuBDC metal organic framework

Abstract

In this study, defect-rich CuBDC metal organic frameworks (MOFs) were engineered by combining the 4-formylbenzoic acid (4-FBA) defective linker with Ni²⁺ or Co²⁺ dopants. After solvothermal synthesis, Ni²⁺ and Co²⁺ cations were found to be homogeneously distributed in CuBDC and the sheet-like structure of the MOF is preserved after doping but its three-dimensional organization is modified. The defects generated by the dopants improve both the optical absorption and the lifetime of photogenerated charge carriers compared to CuBDC as demonstrated by UV-visible absorption spectra and photoluminescence. Electrochemical impedance spectroscopy measurements also show that the charge carrier transfer and separation are improved by doping. The photocatalytic activity of the MOFs was evaluated for hydrogen production under visible light irradiation. The highest production rate of H₂ (11 176 μmol H₂ g⁻¹ h⁻¹, based on the mass of the MOF) is obtained for Co–CuBDC, with a value ca. 3.8 times higher than that of CuBDC. This work demonstrates that doping of CuBDC with Co²⁺ cations is an effective strategy to prepare photocatalysts with high performance for H₂ evolution.