Photocatalytic Chlorination of Methane Using Alkali Chloride Solution

The development of direct conversion for selective functionalization of inert methane plays an important role in the chemical sciences. Here, we report a photocatalytic approach to successfully convert methane into methyl chloride over NaTaO3 photocatalyst using an alkali chloride solution as the chlorine source under ambient conditions, which can overcome disadvantages of toxicity and corrosiveness in the traditional chlorination of methane. Various noble metals and oxide cocatalysts (Pt, Pd, Au, Ag, and Ag2O) and different chloride ion solutions (NaCl, KCl, LiCl, MgCl2, BaCl2, CaCl2, CuCl2, FeCl3, ZnCl2, etc.) are investigated to optimize the photocatalytic chlorination processes. Ag2O/NaTaO3 is the best photocatalyst, giving the maximum CH3Cl yield of 152 μmol g–1 h–1 in aqueous NaCl solutions and an apparent quantum yield of 7.2% under 254 nm monochromatic light irradiation. The target product CH3Cl is verified to be formed by a direct combination of the photoinduced species •CH3 and •Cl on the Ag2O surface. This work provides a meaningful approach for the conversion of methane into chloromethane under normal conditions.