This study presents the development of a heterojunction electrocatalyst by growing Ir nanoparticles on ultrathin NiFe-MOF nanosheets supported by nickel foam (NF) through a solvothermal approach and subsequent redox strategy. The optimized Ir@NiFe-MOF/NF catalyst exhibits superior bifunctional performance for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in 1.0 m KOH solution, outperforming commercial and recently reported electrocatalysts. Density functional theory (DFT) calculations are used to investigate the electronic interactions between Ir nanoparticles and NiFe-MOF nanosheets, revealing that the strong Ir–O—Ni/Fe bonds at the heterojunction interface modulate the electronic structure and enhance the catalytic activity. The catalyst's excellent electrochemical performance, including low overpotentials for HER and OER, and long-term stability, make it a promising candidate for efficient overall water splitting.This study presents the development of a heterojunction electrocatalyst by growing Ir nanoparticles on ultrathin NiFe-MOF nanosheets supported by nickel foam (NF) through a solvothermal approach and subsequent redox strategy. The optimized Ir@NiFe-MOF/NF catalyst exhibits superior bifunctional performance for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in 1.0 m KOH solution, outperforming commercial and recently reported electrocatalysts. Density functional theory (DFT) calculations are used to investigate the electronic interactions between Ir nanoparticles and NiFe-MOF nanosheets, revealing that the strong Ir–O—Ni/Fe bonds at the heterojunction interface modulate the electronic structure and enhance the catalytic activity. The catalyst's excellent electrochemical performance, including low overpotentials for HER and OER, and long-term stability, make it a promising candidate for efficient overall water splitting.