Photocatalysts for oxidation reactions are crucial for a wide variety of industrial activities. Here, we describe a framework consisting of silver nanomaterials atop Mg-doped lithium niobate. This substrate under white light irradiation is demonstrated to support the oxidation of compounds, such as p-aminothiophenol, through the activation of charge transfer processes. This study highlights the use of doped lithium niobate materials as semiconductor platforms for plasmonic photocatalysis.