Oxygen Evolution\nEnhancement of Oxalate-Based Nickel–Iron\nMOF through Bipyridine Coordinated Strategy

The catalytic performance of oxalate-based Ni–Fe\nmetal–organic\nframeworks (MOFs) in the oxygen evolution reaction (OER) was investigated\nvia a coordination strategy. The bidentate chelating ligand 2,2′-bpy\n(2,2′-bipyridine), was utilized to improve the catalytic kinetics\nunder ambient conditions. The results revealed that a MOF-to-MOF transformation\nincluding the formation of [M(2,2′-bpy)<i><sub>n</sub></i>]<sup>2/3+</sup> (M = Ni/Fe, <i>n</i> = 1–3)\ncould boost alkaline OER, giving an impressive ultralow overpotential\nof 220 mV at a current density of 10 mA/cm<sup>2</sup> in a 1 M KOH\nsolution, surpassing the performance of control group activity of\noxalate-based Ni–Fe MOF. However, excessive addition of the\nligand had a negative effect, leading to decreased activity. Further\ninvestigation revealed the double role of 2,2′-bpy: Both promote\nand suppress catalytic reactions. The catalytic mechanism was then\ndiscussed, highlighting the potential of secondary ligands to effectively\nfine-tune the catalytic behavior of these materials.