Tetrahydroxybenzoquinone-Based Two-Dimensional Conductive Metal–Organic Framework via π-d Conjugation Modulation for Enhanced Oxygen Evolution Reaction

Abstract

2D conductive metal–organic frameworks (2D c-MOFs) have attracted significant interest as efficient electrocatalysts for the oxygen evolution reaction (OER). However, effectively regulating their catalytic activity remains a significant challenge. Herein, density functional theory (DFT) was performed to explore the effect of π-d conjugation modulation on the electronic structure of the tetrahydroxy-1,4-benzoquinone-based 2D c-MOFs. The computational results indicate that the strong π-d conjugation caused by orbital hybridization between Co and Fe widens and enhances the hybridization between the d_xz/d_yz orbitals at the metal sites and the p orbitals of the ligands, thereby affecting the reconstruction of the MOFs during the OER process. Experimentally, CoFe-THQ with various atomic ratios was synthesized. The results indicated that the synthesized Co_0.6Fe_0.4-THQ powders only needs an overpotential of 247 mV to reach a current density of 10 mA cm^–2 for the OER in alkaline medium, which is much lower than most reported transition metal-based electrocatalysts and even better than that of the benchmark RuO₂ electrocatalyst. Furthermore, in situ Raman and in situ Fourier transform infrared spectroscopy analyses revealed that Co_0.6Fe_0.4-THQ undergoes a different reconstruction evolution during the OER process compared to Co-THQ, with the mixed (Co, Fe) bimetallic oxides ((Co, Fe)₃O₄ and α-(Co, Fe)₂O₃) formed after reconstruction identified as the true active species. This study opens up an effective avenue for the rational design of high-activity 2D c-MOF electrocatalysts.