Coupling graphitic carbon nitrides with tetracarboxyphenyl porphyrin molecules through π-π stacking for efficient photocatalysis

Graphitic carbon nitride (g-C3N4) photocatalysts have attracted dramatically growing attention due to their attractive electronic structure, relatively low cost, high physicochemical stability, and earth-abundant features, but their practical applications are hindered by the fast recombination of photogenerated carriers, low conductivity, and lack of absorption towards longer wavelengths. In this work, a simple and effective strategy is demonstrated to highly promote the photocatalytic performance of the g-C3N4 by modifying with tetrakis (4-carboxyphenyl) porphyrin (TCPP) molecules, which can be tightly adsorbed on the g-C3N4 surfaces through pi-pi stacking. The typical TCPP/g-C3N4 photocatalyst with 0.1% TCPP content shows a highly enhanced photocatalytic degradation rate of 0.0591 min(-1) towards Rhodamine B (RhB), which is more than two times higher than the 0.0224 min(-1) for the pristine g-C3N4. Detailed investigations elucidate that the highly improved photocatalytic performance is contributed by the broadened visible light absorption and improved electron-hole separation efficiency and carrier migration efficiency induced by coupling TCPP molecules. Besides, RhB molecules prefer to be adsorbed on the TCPP/g-C3N4 surfaces, which is beneficial for the oxidative degradation reaction with the active species near the surfaces. This study may pave a new avenue to prepare highly efficient photocatalysts based on g-C3N4 by coupling conjugated molecules.