Fig. 5

Optical and electronic properties of g-C₄₀N₃-COF. a UV/vis diffuse reflectance spectra (DRS) and steady-state photoluminescence (PL) spectra of g-C₄₀N₃-COF. The gray dash line represents solution UV/vis absorption spectra of DCTSP (model compound) recorded in dichloromethane. The upper inset shows the digital photograph of the sample under ambient light and 365 nm UV-lamp. b Band gap determined from the Kubelka–Munk-transformed reflectance spectra. c PL decay spectra monitored at 563 nm under 365 nm excitation at 298 K. d Mott-Schottky (M-S) plot for g-C₄₀N₃-COF measured in 0.2 M Na₂SO₄ (pH 6.8) with Ag/AgCl (+0.199 V vs. NHE) as the reference electrode in dark. e UPS spectrum of g-C₄₀N₃-COF. f Band positions of g-C₄₀N₃-COF (These vacuum level values were converted to electrochemical potentials according to: −4.44 eV vs. vacuum level is equal to −0.4 V vs. NHE at pH 6.8). g Chopped current–potential (I–V) curve of g-C₄₀N₃-COF photoelectrode under visible light (300 W Xenon light with cut-off filter λ > 420 nm). Electrolyte: Ar-saturated 0.2 M Na₂SO₄ aqueous solution. The applied potential was swept at +10 mV s⁻¹ under intermittent irradiation with a period of 5 s. Inset is chopped anodic photocurrent density vs. time recorded on a g-C₄₀N₃-COF photoanode at 1.0 V vs. RHE. h Electronic properties of g-C₄₀N₃-COF using DFT calculations and corresponding density of states (DOS). i The Kohn-Sham orbitals of HOMO and LUMO of g-C₄₀N₃-COF. C gray, N blue, H white