A large‐scale quantity of copper oxalate nanoparticles were successfully obtained via a facile and green solid‐state chemical reaction. Copper oxalate nanoparticles were obtained by ball‐milling between copper chloride, Liquorice(Glycyrrhiza glabra), and ascorbic acid at ambient conditions. The size and morphology of copper oxalate nanoparticles powder was studied by transmission and scanning electron microscopy. The prepared nanoparticles were semi‐spherical in shape and ranged from 5 to 15 nm in size. UV/Vis spectroscopy, Fourier transforms infrared spectroscopy, and X‐ray photoelectron spectroscopy measurements were carried out to characterize the prepared samples. Copper oxalate nanoparticles were evaluated as a catalyst in the catalytic degradation of 4‐nitrophenol, bromophenol blue, reactive yellow, and mixture of the three pollutants. The present study combined solid‐state reaction and green requirements for the mass‐production of nanomaterials. The proposed reaction is performed in simple steps, inexpensive, low energy consuming, solvent‐free, and minimizes the emission of secondary wastes.