Potassium-doped carbon nitride: Highly efficient photoredox catalyst for selective oxygen reduction and arylboronic acid hydroxylation

• A novel self-assembly supramolecular aggregates and further calcination method was developed for potassium-doped carbon nitride (KCMCN). • The potassium-intercalated in carbon nitride provides a new channel for charge transfer and reduces the adsorption energy of oxygen for efficient photocatalytic oxygen reduction reaction. • The H 2 O 2 yield of KCMCN is approximately 10.7 times higher than MCN in 0.5% isopropanol aqueous solution. • The in-situ generated superoxide radical anion (·O 2 - ) species serve as the oxidant for photocatalytic hydroxylation of arylboronic acids to corresponding aryl alcohols. Photocatalytic two-electron oxygen reduction reaction for hydrogen peroxide production, a promising liquid energy carrier and an environmentally friendly oxidant, is regard as a promising process owing to its low-cost and environment-friendly advantages compared to the state-of-art anthraquinone oxidation for H 2 O 2 production. Herein, a potassium-doped carbon nitride photocatalyst has been successfully synthesized by the copolymerization of self-assembly supramolecular cyanuric acid and melamine aggregates with introduction of potassium chloride (KCMCN), wherein its band structure was carefully tuned and a new channel for charge transfer was created. Notably, DFT calculations pointed out that a lower absorption energy of oxygen (E ads = 0.27 eV) over KCMCN was estimated than that of MCN (E ads = 1.02 eV) with the introduction of K into carbon nitride framework, which is beneficial for superior H 2 O 2 evolution. The H 2 O 2 yield of KCMCN (317.9 µmol·L -1 ·h -1 ) was about 10.7 times higher than bulk carbon nitride at low concentration of sacrificial agent (0.5% isopropanol aqueous solution) and the apparent quantum efficiency (AQE) of KCMCN reached to 7.5% at 420 nm. Furthermore, in-situ photoinduced superoxide radical anion (·O 2 - ) species were generated from dioxygen in KCMCN, which were reacted with arylboronic acids to produce corresponding aryl alcohols through a hydroxylation process under visible light irradiation. This work opens up prospects for providing guidance for other organic synthesis based on the oxidative effect of H 2 O 2 and exploring novel heterogeneous photocatalysts in the field of value-added products formation.