Synthetic dyes in industrial effluents are known to persist in the environment due to their stability and resistance to conventional biological and chemical treatments. As a result, there is a growing interest in alternative approaches such as photocatalysis, which is regarded as an efficient and environmentally friendly advanced oxidation process. Metal–organic frameworks (MOFs), particularly those incorporating copper, have recently shown great potential as photocatalysts due to their unique structural features, light-responsive behavior, and catalytic capabilities. This study focuses on the development and evaluation of a copper-based MOF, [Cu(4,4’-bipy)Cl]n, synthesized using a hydrothermal method with 4,4’-bipyridine as a linker, for the degradation of reactive blue dye under natural sunlight. Comprehensive characterization of the synthesized MOF was performed using Fourier Transform Infrared Spectroscopy (FTIR) to identify functional groups, Scanning Electron Microscopy (SEM) to analyze surface morphology, X-ray Diffraction (XRD) for phase identification, and UV–Visible Diffuse Reflectance Spectroscopy (DRS) to investigate optical properties. The impact of various operational parameters such as initial dye concentration, photocatalyst loading, and solution pH was examined to establish optimal degradation conditions. Under the best experimental conditions (0.4 mg/l dye concentration, 0.45 g catalyst, and pH 10), the Cu-MOF achieved a high degradation rate of 93.7%. Control tests confirmed that dye removal by photolysis was negligible and that dark adsorption accounted for approximately 30% removal. The catalyst’s stability was assessed over five reuse cycles, with degradation efficiency consistently exceeding 85%, indicating a modest reduction of approximately 8.7 % in performance. The findings demonstrate that the Cu-based MOF is a robust and efficient material for the photocatalytic treatment of dye-contaminated water, presenting a viable solution for sustainable wastewater remediation.