Synthesis of cyclotriphosphazene-containing polymeric nanotubes and their use as metal-free photocatalysts for methylene blue degradation

Highly cross-linked, organic-inorganic hybrid polymer nanotubes with primary amine groups on the surface have been successfully prepared through a facile polycondensation of hexachlorocyclotriphosphazene and melamine in absence of any surfactants or template agents. Then, these nanotubes were used as visible light photocatalysts for the degradation of methylene blue (MB) in water and the physicochemical properties of catalysts were characterized by several techniques. The as-synthesized nanotubes were closed at one end with a micrometer-scale in length (about 3-10 μm), 200-300 nm in the diameter, and the inner diameters of the two ends of each nanotube was 100-200 nm and 5-10 nm, respectively. A large amount of free radicals (OH) were generated in aqueous phase under visible light irradiation, which can photocatalytically oxidize and eventually mineralize. And, the progress of degradation was similar with semiconductor materials. The simple preparation method and photocatalytic performance of the cyclotriphosphazene-containing polymeric nanotubes represent an important step towards photocatalytic reaction in general where artificial conjugated polymer semiconductors can be used as energy transducers.