Self-Assembly of Hollow, Pompon-Like and Nanosheet-Structured Carbon Nitride for Photodegradation of Tetracycline Hydrochloride

A hollow pompon-like carbon nitride (hp-CN), composed of nanosheets, is prepared and used for photocatalytic degradation of tetracycline hydrochloride (TC). The synthesis is done by a supramolecular self-assembly method, using melamine and cyanuric acid as precursors. The hollow pompon-like morphology and nanosheet structure promote both the textural (e.g., crystallinity, surface area) and electronic properties (e.g., electron-hole separation efficiency, number of excited electrons, and impedance) of hp-CN, compared to these of graphitic carbon nitride (g-CN) synthesized by direct polycondensation of melamine. The hp-CN-6 (heating for 6 h) is highly active for photodegradation of TC, with 96.3% conversion obtained within 15 min when conducted at pH 1.86, and no appreciable activity loss is detected within 4 cycles. Quenching experiments suggest that superoxide radicals (center dot O-2(-)) are the primary active reaction species. A comparison in the activity of hp-CN-6 and g-CN for photocatalytic TC degradation is made, and a possible mechanism is proposed.