Doping as a Strategy for Modulating Crystallinity and Optical Properties of Large Area Films of Semiconducting 2D-COFs

-phenylenediamine (PDA), benzene-1,3,5-tricarboxaldehyde (TCA), and melamine (Me) dopant, leading to significant alterations in both crystallinity and optical properties. Notably, the optical band gap shows a strong blue shift from ≈2.2 eV for the undoped 2D-COF to ≈2.6 eV for the optimally Me-doped 2D-COF. In addition, for the optimum ratio of melamine to PDA and TCA, we observed large, highly crystalline domains within the film. The effect of melamine doping on the structural and electronic modifications of the films was characterized using various spectroscopic and microscopic techniques and density functional theory calculations.