Ion-Induced Delamination of Layered Bulk Metal–Organic Frameworks into Ultrathin Nanosheets for Boosting the Oxygen Evolution Reaction

Creating ordered two-dimensional (2D) metal–organic framework (MOF) nanomaterials is conducive to understanding the structure–property relationship for rationally designing high-efficiency electrocatalysts. However, the controllable synthesis of ultrathin MOF nanosheets with predesigned structures and anticipative properties is still a great challenge. Here, we reported an electrolyte-assisted electrochemical approach to in situ exfoliate the intrinsic 2D MOF crystals with the Ni4Ln cluster as a secondary building unit (SBU) into ultrathin metal–organic nanosheets. Notably, the electric current density of the oxygen evolution reaction rapidly increases from 9.4 to 31.0 mA cm–2 at 1.8 V and the Tafel slope reduces from 150 to 87 mV dec–1, originating from electrochemically delaminating the thick 2D MOF precursors into ultrathin (∼4 nm) nanosheets to expose more catalytic active sites. Furthermore, the electrocatalytic oxygen evolution reaction (OER) activity of these 2D heterometallic MOF nanosheets can be effectively manipulated through precisely altering the lanthanide component of the Ni4Ln SBU in the layered MOFs. Density functional theory calculations reveal that the lanthanide ion of the SBU affects the adsorption and desorption capacity of active nickel centers to OER-relevant species, leading to the difference of the catalytic activity.