Figure 4.

Syntheses of 2D polymer nanosheets through different bottom–up methods. a) Schematic illustration of the hydrogen bond‐directed 2D polymerization reaction to produce crystalline 2D polymer nanosheets. Reproduced with permission.^{[ 41 ]} Copyright 2019, American Chemical Society. b) Synthesis of CAP by the metal‐surface‐mediated polymerization and corresponding STM, AFM, and height images. Reproduced with permission.^{[ 51 ]} Copyright 2017, Springer Nature. c) Synthesis of imine‐linked COF nanosheets at the liquid/solid interface. Reproduced with permission.^{[ 53 ]} Copyright 2019, Royal Society of Chemistry.