Terephthalate acid decorated TiO2 for visible light driven photocatalysis mediated via ligand-to-metal charge transfer (LMCT)

A novel terephthalate acid (TPA) and TiO2 system was developed by chemically bonding between the -COOH groups on TPA and -OH groups on the surface of TiO2 under hydrothermal conditions. The crystallization, morphology and photochemical properties of TiO2-TPA were studied by XRD, FTIR, XPS, TEM, UV-vis absorption spectroscopy measurements, respectively. The prepared TiO2-TPA nanoparticles exhibited excellent photoactivity under visible light by a ligand-metal charge transfer (LMCT) mechanism. Even though TPA is often used as a ligand for titanium-organic frameworks, there has been no report about the fact that TiO2-TPA is capable of forming an LMCT complex. The optimized TiO2-TPA (molar ratio of 0.5) composite showed a superior photodegradation than TiO2. The removal rate of Rhodamine B (RhB) was 94.10 % in 60 min, which were 31.3 times than that of pure TiO2 (3.34 %). The result indicated that TiO2 and TPA had tight synergistic effect. In detail, TPA-modified composite showed a smaller band gap and stronger light respond under visible range. Meanwhile, the charge transfer from TPA to TiO2 reduced the recombination rate of electron holes.