Herein, the synthesis, optical, and electrochemical characteristics of the spinel CuAl2O4 synthesized by co-precipitation are the focus of this research. As per to the X-ray diffraction (XRD), the obtained sample crystallizes in a cubic symmetry (SG: fd-3m) with a lattice constant of 8.0790 Å. The TEM image revealed spherical nanoparticles with an average build of ∼9 nm and d-spacing of 0.248 nm of the reticular the planes (3 1 1), suggesting the formation of the CuAl2O4 crystalline structure. The optical and dielectric constants, including the extinction coefficient (k), refractive index n (λ), optical conductivity (σopt), dissipation factor (tan δ) and relaxation time (τ) were determined based on diffuse reflectance. The (C−2 - E) graph, plotted in Na2SO4 showed that CuAl2O4, is feature of n-type conduct with a flat band potential of 0.42 VRHE. The EIS spectroscopy displays a semicircle feature with the presence of a constant phase element (CPE) and a bulk resistance of 558 Ω cm2 that lowers to 462.7 Ω cm2 under visible irradiation. As application, the catalytic performance of CuAl2O4 was examined in the breakdown of Methyl violet dye (MV) under sunlight. Within 3 h, an abatement of 89% was obtained, and the oxidation of MV (10 mg/L) follows a first-order kinetic model with a half-life of 82 min. The catalyst can be reused without loss of activity for the first four cycles where •OH and •O2− are accountable of the MV oxidation. © 2022 Elsevier B.V.