Superior electrochemical water oxidation in vacancy defect-rich 1.5 nm ultrathin trimetal-organic framework nanosheets

Engineering the 2D metal-organic framework (MOF) material can enrich the metal-unsaturated edges as active sites for catalysis, however, introducing multiple heterointerfaces and vacancy defects into 2D MOF and exploring their effects on electrocatalytic oxygen evolution reaction (OER) remain a major challenge. Here we construct ultrathin and highly curved 2D FeCoNi trimetal-organic framework nanosheets (FeCoNi-MOFs) with only approximately 1.5 nm thickness and abundant oxygen vacancies. The formed defect-rich FeCoNi-MOFs display outstanding OER performance with a much smaller overpotential of 254 mV at 10 mA cm−2 and remarkable stability for over 100 h in alkaline solutions. This is the highest OER activity level attained for direct-MOF catalysts. Theoretical analysis of FeCoNi MOFs with rich oxygen vacancies further suggests that the increased Fermi level with multiple heterointerfaces and the addition of oxygen vacancies co-facilitate the pre-oxidation of low-valence metals and the reconstruction/deprotonation of intermediate metal−OOH, thus enhancing electron transport efficiency.