An efficient and unique route for the fabrication of highly condensed oxygen-doped carbon nitride for the photodegradation of synchronous pollutants and H2O2 production under ambient conditions

N2-assisted thermal polycondensation of a novel supramolecular self-assembly based on melamine, cyanuric acid, and thiourea produced S-doped carbon nitride. Molecular dynamics simulation estimated nonbonding energies between the melamine-cyanuric acid adduct and thiourea. The C–S functional group was efficiently converted to C–O by facile calcination in a static air atmosphere, which gave a highly condensed O-doped carbon nitride nanosheet (O-CN). Density functional theory (DFT) calculations and experimental results confirmed that the oxygen-doped site is more stable and provides midgap states near the conduction band position of CN compared with sulfur doping. O-CN exhibited excellent visible light harvesting and photocatalytic activities toward removal of tetracycline and rhodamine B in an initial 15 min while producing a highly stable amount of H2O2 under an open atmosphere without a sacrificial agent. These outstanding performances result from synergistic approaches that lead to the modified polycondensation process, unprecedented reduction ability, and enhanced optical properties. [Display omitted] •A facile and efficient synthesis of O-doped carbon nitride nanosheet was proposed.•O-doped carbon nitride was prepared from a novel supramolecular precursor.•The photocatalyst completely degraded TC and RhB in a very short time.•Significant H2O2 production rate of 168.1 μmol g−1 h−1 was also obtained.•Photocatalytic mechanism and toxicity of TC intermediates were assessed in detail.