Two-dimensional heterostructures built from ultrathin CeO 2 nanosheet surface-coordinated and confined metal-organic frameworks with enhanced stability and catalytic performance.

Two-dimensional (2D) metal-organic framework (MOF) based heterostructures will be greatly advantageous to enhance catalytic performance because they increase the contact surface and charge transfer. Herein, a novel 2D heterostructure named CeO 2 @NiFe-MOFs, in which monolayer NiFe-MOFs is coordinated with ceria (CeO 2 ) to improve catalytic and stability performance, is successfully constructed by the strategy of in situ growth on the surface of ultrathin CeO 2 nanosheets being functionalized with monolayer carboxylic acid groups. The 2D heterostructure possesses a sandwich structure, where monolayer NiFe-MOFs are coordinated to both the top and bottom surface of CeO 2 nanosheets via joining carboxylic acid groups. In particular, CeO 2 with robust coordination plays a significant role in the anchoring of carboxylic acid groups and binding strength of heterostructures. The 2D CeO 2 @NiFe-MOF heterostructure with a joint effect of metal-ligand coordination not only presents good structural stability but also significantly enhances the oxygen evolution reaction (OER) efficiencies in comparison to bare NiFe-MOFs, achieving a current density of 20 mA cm -2 at a low overpotential of 248 mV as well as durability for at least 40 h. Meanwhile, the electronics, optics, band gap energy and local strains of CeO 2 decorated with 2D NiFe-MOFs are different to the properties of bare CeO 2 . Our study on the construction of an ultrathin CeO 2 surface-coordinated and confined MOF layer may pave a new way for novel 2D MOF composites/heterostructures or multi-functional 2D CeO 2 materials to be used in energy conversion or other fields.