In this work, a nanopowder of porous molybdenum (Mo) oxides with different polymorphs were prepared by anodizing the Mo sheet in ethylene glycol solution containing fluoride at 60, 70, and 80 V for 30 min. Synthesized Mo oxides showed remarkable changes in their structural parameters and morphology upon the anodization voltage which were confirmed using X-ray diffraction, energy dispersive X-ray, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, N₂ adsorption-desorption, and field emission scanning electron microscopic. Anodized Mo is composed of α-MoO₃, β-MoO₃, β-MoO₂, and β-Mo₉O₂₆ phases. Synthesized Mo oxides were used, as a catalyst, for the photodegradation of methylene blue (MB), and results were compared to the literature. The maximum observed efficiency, ∼65%, towards MB was achieved using anodized Mo at 70 V (MO70) under UV–visible irradiation for 85 min. The N₂ adsorption-desorption analysis revealed that MO70 exhibits the smallest particle size and greatest surface area among other samples. The performance of MB adsorption was investigated using several kinetic adsorption models and the pseudo-second-order model being the ideal one. The maximum adsorption constant is 1.4 × 10⁻² g/(mg min) and the amount of MB that degraded at equilibrium is 5.52 mg/g for MO70. The anodization of Mo generated various polymorphs semiconductors which provide an excellent platform for the removal of toxic organic dyes from the wastewater.