Atomically dispersed Cu on aryl amino substituted g-C3N4 (Cu@f-gC3N4) was prepared through a two-step process by involving successive impregnation and calcination without any assistance from a template. In a typical synthesis, dicyandiamide (DCDA, 9 g) and 2-amino-5-(trifluoromethyl) benzonitrile (0.150 g, 1.6 wt%) were homogeneously mixed with Cu(NO3)2•3H2O (0.019 g, 0.2 wt%). The mixture was then stirred and heated in water (45 mL) at 95-100 °C until it was completely dried. The resulting mixture was removed, grounded in an algae mortar, and loaded onto a stainless-steel chamber. Subsequently, the GERO carbolite tube furnace chamber was kept heated for 244 min (~ 4 hr) until it reached to 550 °C under aerobic atmosphere (S2.1, ESI). Then the temperature was maintained for 4 h. After that, the cooling process started and reached to room temperature in another 6 hr. After synthesizing Cu@f-gC3N4, several characterization techniques were employed to examine its structural and electronic properties. At first, Ultraviolet-visible diffuse reflectance spectra (UV-Vis DRS) and Mott-Schottky measurements were collected to determine the electronic band structure of the photocatalyst (Figure ). The band gap of Cu@f-gC3N4 was determined to be 2.65 eV from the Tauc plot. The positive slope of the Mott-Schottky curve suggested that the photocatalyst was n-type. The conduction band potential (Efb) of Cu@f-gC3N4 was approximately -1.40 V (vs SCE), as determined from the intersection between the Mott-Schottky plot and the baseline. In general, the bottom potential of the conduction band (CB) for an n-type semiconductor is considered to have a similar value to Efb. Therefore, the valence band (VB) of Cu@f-gC3N4 was at ca. +1.25 V.