The Eclear catalyst is prepared using a unique flame combustion process, and the nanoparticles can complete the reaction in a high-temperature flame at 1800 ℃ for only 5-10 milliseconds. The short residence time allows the particle size of the nanoparticles to be accurately controlled within the range of 5-15 nanometers. At the same time, in-situ doping of elements such as Au, Ag, Mn, Fe, and Zn can regulate the absorption wavelength of nanoparticles and improve their absorption capacity, making the product nano photocatalyst have extremely excellent catalytic performance. Suitable for photocatalytic treatment of benzene containing organic waste gases and toxic and harmful waste gases such as ammonia, hydrogen sulfide, and methyl mercaptan emitted from industries such as printing, baking, painting, and garbage deodorization.