A Hexaiminohexaazatrinaphthalene-Based 2D Conjugated Metal-organic Framework with Regulable Dual Metal Active Sites...

In recent years, 2D π-d conjugated metal-organic frameworks (2D cMOFs) have attracted great attention in the field of electrocatalysis due to their superior conductivity. The bimetallic synergistic strategy is an efficient method to improve the electrocatalytic activity of 2D cMOFs. However, the construction of bimetallic sites in 2D cMOFs for most works is uncontrollable, which cannot precisely regulate the active sites of 2D cMOFs. Herein, Fe₃(Co₃HAHATN)₂ (HAHATN = hexaiminohexaazatrinaphthalene) with regulable Fe─N₄ and Co─N₂Cl₂ dual metal active sites is fabricated. Through adjusting the pH of the reaction system, the metal ions could precisely choose to coordinate with the phenanthroline N or amino N of HAHATN. Fe₃(Co₃HAHATN)₂ exhibits outstanding oxygen evolution reaction (OER) activity (an overpotential of 220 mV vs. RHE at 10 mA cm^-2 and a Tafel slope of 61.87 mV dec^-1). Both experimental and theoretical results demonstrate that the synergistic effect between Fe─N₄ and Co─N₂Cl₂ sites contributes to its prominent OER activity, in which the Fe─N₄ site energetically prefers the absorption of OH^- and the Co─N₂Cl₂ site is in favor of the decrease of the rate-determining step free energy of Fe₃(Co₃HAHATN)₂. This work provides a new avenue for the synthesis of highly efficient 2D cMOFs-based electrocatalysts with precisely regulable dual metal active sites.