CdO and CdS nanocrystals have been prepared via simple thermal treatment of coordination polymers, viz., [Cd(dca)2(Mim)2]n and [Cd(SCN)2(Bim)2]n (where Bim and Mim are benzimidazole and 1-methylimidazole respectively) as precursors at 600-650 °C in air for 2 h. A variety of techniques like infrared spectroscopy, X-ray diffraction, scanning electron microscopy and thermal gravimetric analysis have been employed to carry out structural characterization of these nanoparticles. The optical band gap of these materials, estimated to be about 2.43 and 2.50 eV respectively, establish a relationship between energy band gap of bulk and nanomaterials. Photocatalytic reactivity of these nanomaterials are evaluated by studying the degradation of C. I. Reactive Yellow 84, a popular and widely used reactive dye in cotton industry.