Novel cake-like N-doped anatase/rutile mixed phase TiO₂ derived from metal-organic frameworks for visible light photocatalysis

Novel cake-like N-doped anatase/rutile mixed phase TiO₂ (A/R N-TiO₂) was successfully prepared through the pyrolysis of metal-organic frameworks MIL-125 and subsequent annealing in ammonia atmosphere. The morphology, structure and photocatalytic performance of A/R N-TiO₂ in the degradation of Rhodamine B (RhB) were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, UV–vis absorption spectroscopy and electrochemical impedance spectra, respectively. The results show that the A/R N-TiO₂ exhibits excellent photocatalytic performance. By optimizing the annealing temperature in ammonia atmosphere, a maximum RhB degradation rate of 93% under visible light irradiation is achieved. The improved photocatalytic performance is ascribed to the enhanced light absorption as well as the reduced electron-hole pair recombination after the N doping and the presence of stepwise energy levels in anatase and rutile TiO₂.