This study prepared titanium dioxide nanostructures modified with different boron (B-modified TiO2) concentrations. The percentage of the anatase was > 98 % and the rutile was < 1.1 % for pure samples or low boron concentrations. The brookite grew from 0.5 to 1.79 % with increasing boron concentration. The nanostructures with a diameter ≤ 25 nm and Egap ≤ 3.07 eV efficiently degraded 100 % of RhB up to 120 min or 45 min using UV-A or UV-C light, respectively. The most efficient material was used for the fluoxetine (FLX) photocatalysis. 3D spectrofluorimetry coupled with parallel factor analysis (PARAFAC) was applied to quantify FLX and the transformation product (TP). Therefore, LC-MS-Q-TOF analyses identified other TP and proposed a degradation mechanism. In general, our results show that modifying TiO2 with a low boron concentration is an excellent way to improve the photoactivity of this material for the degradation of organic contaminants.