Notably, the highly-twisted molecular conformation of carbazole unit can weaken interlayer π-π stacking, leading to easy formation of nanosheets. As we expected, JUC-557-nanosheet displayed a graphene-like morphology (Fig. and Supplementary Figs. ). Lattice fringes between layers (~ 0.4 nm) can be observed by the high-resolution transmission electron microscopy (HR-TEM, Fig. ). The atomic force microscopy (AFM) measurements further confirmed a molecular-level understanding of anticipated ultrathin nanostructure. The thickness of JUC-557-nanosheet was in the range of 2.2~2.6 nm, and thus the number of layers was speculated to be 5~6 layers (Figs. 2e, 2f and Supplementary Fig. ). The homogeneous lateral size of JUC-557-nanosheet ranged from 0.5 to 1.0 µm (Supplementary Fig. ).