This study discusses about the photochemical, topological and textural properties of yttrium-doped titanium dioxide (TiO₂) photocatalysts. The mesoporous yttrium-doped TiO₂ substrates prepared in this research work operate efficiently via low-cost commercial 13-W UV lamps. A quantity of 2 wt% yttrium deposition on TiO₂ accelerates methyl orange UV decolourization kinetics. When Y content increases to 8 wt%, besides anatase, rutile is formed from 600°C. The Y₂Ti₂O₇ photoinactive compound emerges at 800°C. The P-123 surfactant mesopore templating treatment of TiO₂ xerogels (when concurrent with the sol–gel Y-doping of Ti alkoxides) features the following two correlated phenomena: (i) The surface area increases while the access to the inner porosity of the substrate becomes much easier, so that a larger portion of the surface is made accessible to the dye molecules as well as to the yttrium dopant; (ii) the inclusion of tubular instead of ink-bottle pores facilitates the transport of organic species in and out of the pore structure. The most active mesoporous substrate resulted to be made of 2 wt% Y; contrastingly, when Y= 8 wt%, photoinactivity arose because of Y₂Ti₂O₇ formation. The involvement of P123 was not the sole factor influencing the efficiency of TiO₂ mesoporous photocatalysts. There were additional key factors, such as the surging of co-ordination and nucleophilic species, during the dye photodegradation process, which were also induced by the presence of Y species on the surface of these substrates.