Engineering defective trimetallic metal-organic framework nanosheets for advanced water oxidation electrocatalysis.

Limited by single metal active sites and low electrical conductivity, designing nickel-based metal-organic framework (MOF) materials with high activity and durability remains a challenge. Here, a novel class of two-dimensional trimetallic MOF nanosheets with plentiful active sites, rich metal defects, and facilitated mass and electron transfer channels is developed as efficient electrocatalysts for boosting oxygen evolution reaction (OER). The unique 2D nanosheet structure enlarges the active area; meanwhile, the organic ligand in the MOF can work as a pillar to enlarge the interplanar space to boost the ion and electron transportation, and the synergistic effect between multi-metal active sites can effectively promote the electrocatalytic activity. Interestingly, after an electrochemical activation process, the optimized NiFeZn MOF nanosheets can yield abundant metal defects, enabling them to deliver a low overpotential of 233 mV at 10 mA cm with a much smaller Tafel slope of 37.8 mV dec. More importantly, this method is also universal for the synthesis of the NiFe-MOF family for achieving outstanding electrocatalytic OER performance. These findings present a universal strategy for the construction of a novel class of 2D trimetallic MOF nanosheets for the OER.