Electrochemical Exfoliation of the Two-Dimensional Conjugated Metal–Organic Framework for High-Performance Urea Electrooxidation

Two-dimensional (2D) conjugated metal–organic frameworks (c-MOFs) have attracted extensive interest in electrochemical fields due to their inherent electrical conductivity. However, the severe interlayer stacking still poses barriers toward their potential applications. The reliable synthesis of ultrathin c-MOF nanosheets is crucial yet remains challenging. Herein, we demonstrate an electrochemical exfoliation approach to obtain ultrathin nanosheets from layer-stacked c-MOF crystals. Our results reveal the electric field-induced ion intercalation mechanism and provide a viable method for the synthesis of ultrathin M-HHTP (M = Ni, Cu, Co; HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene) nanosheets. To prove utility, the obtained Ni-HHTP nanosheets as urea oxidation reaction (UOR) catalysts achieve an ultrahigh current density of 165.7 mA cm–2 at 1.35 V versus a reversible hydrogen electrode and nearly 100% selectivity of N-products. Experimental characterization and theoretical calculations reveal that the fully exposed square planar NiO4 active centers effectively reduce the energy barrier of C–N bond cleavage for UOR and suppress the parasitic oxygen evolution reaction.