Isomorphous Cobalt\nCoordination Frameworks: Enhancing\nElectrocatalytic Oxygen Evolution Reaction through Coordinated Solvent\nVariations

Oxygen evolution reaction (OER) is a key electrochemical\nredox\nreaction involved in metal–air batteries and water-splitting\ndevices. Reducing the energy barrier of these reactions accentuates\nthe necessity in designing competent electrocatalysts. There is an\nurgent demand for affordable and durable catalysts utilizing non-noble\nmetals, specifically Ni, Co, and Fe, for the OER. In this context,\nthree following cobalt(II) coordination frameworks based on a pyridyl\ncarboxylic acid ligand were synthesized: [Co<sub>3</sub>(μ<sub>3</sub>-OH)(PCA)<sub>4</sub>(DMF)<sub>2</sub>(H<sub>2</sub>O)](NO<sub>3</sub>)·DMF·3H<sub>2</sub>O (<b>1</b>), [Co<sub>3</sub>(μ<sub>3</sub>-OH)(PCA)<sub>4</sub>(EtOH)<sub>3</sub>](NO<sub>3</sub>)·3EtOH·3H<sub>2</sub>O (<b>2</b>), and [Co<sub>3</sub>(μ<sub>3</sub>-OH)(PCA)<sub>4</sub>(DMA)<sub>2</sub>(H<sub>2</sub>O)] (ClO<sub>4</sub>)·DMA·H<sub>2</sub>O) (<b>3</b>) using a solvothermal method. The single-crystal\ndiffraction studies confirm the similarity in the three-center cobalt\nsecondary building unit (SBU) and the final 3D topology. These frameworks\nare investigated as potential catalysts for the OER under alkaline\n(1 M KOH) conditions. Compound <b>1</b> shows extraordinary\nOER activity demonstrating an overpotential value of 0.37 V at 10\nmA cm<sup>–2</sup> and a Tafel slope of 78.9 mV. The alternation\nin the coordination sphere resulting from the difference in coordinated\nsolvent emerges as an intriguing reason contributing to the exceptional\nactivity of a coordination network. The effective electronic modulation\nwithin the cobalt trinuclear center induced by the changes in the\ncoordination sphere has lowered the free energy barrier for the desorption\nof the oxygen produced. This work emphasizes the significant influence\nand effect of the coordination environment in catalytic activity,\nserving as a template for designing advanced electrocatalysts that\nare free from noble metals.