Preparation, characterization, and photocatalytic properties of composite materials of copper(II) porphyrin/TiO₂

Three new CuPp–TiO₂ composite materials were prepared by impregnating copper(II) porphyrin with different peripheral substituent (–OH, –COOC₂H₅, and –COOH) onto the surface of polycrystalline TiO₂ at room temperature and characterized by SEM, energy-dispersive X-ray spectrometry, X-ray diffraction, FT-IR, UV–Vis DRS, and photoluminescence. The effects of metalloporphyrins on the surface of TiO₂ have been detected by the photodegradation of 4-nitrophenol (4-NP) and rhodamine B (RhB). The loading of metalloporphyrins onto TiO₂ results in strong visible light absorption by the composite and, more importantly, a 1.47–2.47 times increase in visible light photocatalytic activity in the degradation of RhB. The metalloporphyrins dispersed on the TiO₂ surface can act as a small-band-gap semiconductor to absorb visible light, giving rise to electron–hole separation. What’s more, these CuPp–TiO₂ with different peripheral substituent (–OH, –COOC₂H₅, and –COOH) in meso-sites of porphyrin ring displayed different catalytic activities in the degradation of 4-NP and RhB, the CuPp containing –OH and –COOH showed better catalytic activity due to their strong interaction with TiO₂. A possible mechanism of these higher photocatalytic efficiencies was proposed based on the relative experiments.