Four different lanthanide (Ce, Dy, Lu, and Sm) doped TiO2 mesoporous materials were synthesised using the sol–gel method with titanium (IV) isopropoxide as the precursor. All of the synthesized materials were characterised using different analytical techniques, BET, PXRD, TEM, SEM-EDX, Raman, FTIR, photoluminescence, and UV-DRS spectroscopy. Photocatalytic activity and efficacy of the materials in the degradation of caffeine in aqueous solutions was investigated under visible light illumination. Although all materials showed good photocatalytic activity, Ce-doped TiO2 exhibited relatively better activity than the other three catalysts. High photoactivity of the catalysts was attributed to the presence of lanthanides and their ability to generate ions that scavenge electrons under visible light, thereby enhancing photodegradation of caffeine. All materials proved to be good and were recyclable without loss of catalytic activity up to three runs. An intermediate [N-1,3,6-trimethyl-2,4-dioxo-1,2,3,4-tetrahydropyrimidin-5-yl)formamide] (TDTF) and two products (6-amino-1,3-dimethyl-2,4-dioxo-1,2,3,4-tetrahydropymidin-5-ly)-(methyl)-carbamic acid (ATCA) and N-methyl-N-(methylcarbomoyl)-2-oxoacetamide (MMO) were identified by the LC–MS spectra.

The photocatalytic activity of bare titania and ceria supported mesoporous titania (CeO2/TiO2) catalysts were assessed for the degradation of caffeine by visible light irradiation in absence of the oxidants. Different wt% metal loaded (bare, 0.1, 0.5 and 1.0) materials were synthesised by a sol-gel method using anionic surfactants. Various instrumentation techniques were used to characterise the prepared photo-catalysts such as P-XRD, BET, TEM, SEM-EDX, FT-IR, Raman, UV-DRS and photoluminescence spectroscopy. 0.5% CeO2 doped titania exhibited excellent efficiency in photo degradation of caffeine in aqueous solution relative to all the other prepared heterogeneous catalysts. All the materials showed good efficiency and were recyclable without loss of catalytic activity up to three times. Analysis of degradation products was carried by Liquid chromatograph-mass spectrometry. Two reaction products 6-amino-1,3-dimethyl-2,4-dioxo-1,2,3,4-tetradropymidin-5-ly)-methylcarbamic acid (ATCA) and N-methyl-N-(methylcarbomoyl)-2-oxoacetamide (MMO) were positively identified.