fig3

Figure 3. The electronic structure and optical properties of 2D COFs and their related molecular building blocks mentioned in Figure 2. (A) Energy band diagram of COFs; (B) HOMO and LUMO energy level diagram of the molecular building blocks; (C) Absorption coefficients of COFs. 2D: Two dimensional; COFs: covalent organic frameworks; HOMO: highest occupied molecular orbital; LUMO: lowest unoccupied molecular orbital.