Pure and Sm-loaded brookite nanoparticles and thin films were prepared using TiCl4 as precursor of TiO2. The samples were characterized by X-ray diffraction (XRD), specific surface area (SSA) determination, diffuse reflectance spectroscopy (DRS) and photoluminescence (PL) measurements. The photocatalytic activity of the powders was investigated by employing the photodegradation of 4-nitrophenol in a liquid–solid system whilst the photoreactivity of the films was tested by evaluating the rate of degradation of 2-propanol in a gas–solid system. Loading with Sm resulted in a significant improvement of the photoreactivity of brookite and the beneficial effect was attributed to an increased separation efficiency of the photogenerated electron–hole pairs. The content of samarium was an important factor affecting the photocatalytic activity. The optimum amount of samarium was 1% for the powders and 0.1% for the films. There is a relationship between PL spectra and photoactivity, namely, the lower the PL intensity, the higher the photocatalytic activity