The incessant emission of CO₂ and its accumulation in the atmosphere are among the primary concerns of environmental boards in society, urging fundamental studies that encourage the use of nanotechnology for CO₂ utilization to produce chemicals or alternative fuels. In this context, batches of SnO₂/Cu-metallic nanomaterials were synthesized using a simple sol-gel route and applied in the catalytic CO₂ photoreduction reaction in water. The catalysts were analyzed before and after the reaction to unveil the structural transformations and chemical interactions throughout the process. The characterization techniques allowed the identification of a UV-driven phase transition from metallic copper to its respective oxides, with emphasis on the crystalline phase growth of Cu₂O. This transition has a significant impact on catalyst selectivity, and despite the decrease in C₂ compounds, Methanol was the main product. This result may evidence the active phase for this valuable chemical, contributing to future research in the field of catalyst design and its application.