Cyclic Trinickel(II) Clusters in a Metal‐Azolate Framework for Efficient Overall Water Splitting

Herein, a stable metal‐azolate framework with cyclic trinickel(II) clusters, namely [Ni3(μ3‐O)(BTPP)(OH)(H2O)2] (Ni‐BTPP, H3BTPP=1,3,5‐tris((1H‐pyrazol‐4‐yl)phenylene)benzene), achieved a current density of 50 mA cm−2 at a cell voltage of 1.8 V in 1.0 M KOH solution, while the current density of 20%Pt/C@NF||IrO2@NF is just 35.8 mA cm−2 at 2.0 V under the same condition. Moreover, no obvious degradation was observed over 12 hours of continuous operation at a large current density of 50 mA cm−2. Theoretical calculations revealed that the μ3‐O atom in the cyclic trinickel(II) cluster serves as hydrogen‐bonding acceptor to facilitate the dissociation of a H2O molecule adsorbed on the adjacent Ni(II) ion, giving a lower energy barrier of H2O dissociation compared with Pt/C; meanwhile, the μ3‐O atom can also participate in the water oxidation reaction to couple with the adjacent *OH adsorbed on Ni(II) ion, providing a low‐energy coupling pathway, thus Ni‐BTPP achieves a high performance for overall water splitting. A cyclic trinickel(II) cluster‐based metal‐azolate framework is reported as a high‐performance bifunctional catalyst for overall water splitting.