Collapse-Resistant Large-Sized 2D Metal-Organic-Framework-Derived Nitrogen-Doped Porous Ultrathin Carbon Nanosheets for High-Performance Supercapacitors

Metal-organic-framework (MOF)-derived two-dimensional materials have attracted tremendous attention in energy storage, because of their unique layered structure and abundant active sites. However, the facile synthesis of carbon materials simultaneously having large-sized, ultrathin-layered nanosheets and ultrahigh specific surface area remains a challenge. In this work, we develop a simple carbon protection strategy for efficiently stabilizing the ultrathin carbon nanosheets against structure degradation. The optimized as-prepared sample (UPZCNs-K4) exhibits a flat morphology with a large size (ca. 10 μm), a thickness of 2.8 nm, high pore volume, and a high capacitance of 402 F g⁻¹ at 1 A g⁻¹ in 6.0 M KOH aqueous electrolyte. An assembled symmetric supercapacitor delivers 16.18 W h kg⁻¹ and 21.89 W h kg⁻¹ output in KOH aqueous solution and Na₂SO₄ electrolytes, respectively. The excellent performances of the optimized sample can be attributed to the combination of ultrahigh specific surface area for ions storage and ultrathin structure with large size for a short ion diffusion distance. We believe this work will aid in designing ultrathin porous carbon nanosheets with new nanostructures toward energy-related applications.