Pyridine-induced caused structural reconfiguration forming ultrathin 2D metal–organic frameworks for the oxygen evolution reaction

Abstract

Two-dimensional metal–organic frameworks (2D MOFs) as an ideal prototype material for the electrocatalytic oxygen evolution reaction (OER) can expose more metal active sites due to their ultrathin 2D structure. Herein, a two-dimensional Co₃BDC₆Py₃DMF₁ (termed Co MOF-Py₃, BDC = 1,4-benzene dicarboxylic acid, Py = pyridine, and DMF = N,N-dimethylformamide) catalyst was prepared by a solvothermal bottom-up method by introducing pyridine to replace the triethylenediamine organic coordination in three-dimensional (3D) Co₂(BDC)₂(DABCO)·4DMF·H₂O (termed Co MOF, DABCO = 1,4-diazabicyclo[2.2.2]octane). Compared to the 3D columnar Co MOF, the overpotential of ultrathin 2D nanosheet Co MOF-Py₃ at 10 mA cm⁻² decreased by 55 mV to 307 mV, and the Tafel slope was 52.14 mV dec⁻¹. To further improve the catalytic capability of Co MOF-Py₃, the Fe element was introduced into Co MOF-Py₃ by impregnation to obtain a Co₃Fe₁ MOF-Py₃ catalyst, which exhibited excellent OER performance with a low overpotential of 269 mV at 10 mA cm⁻² and a small Tafel slope of 45.29 mV dec⁻¹. Structural characterization reveals that the addition of a specific quantity of pyridine could completely replace the triethylenediamine ligands, thus leading to structural reconfiguration of the entire MOF, resulting in a structural alteration from 3D to 2D and enhancing the number of metal active sites to catalyze the OER.