A simple, direct method for generating a nanohybrid of CdS quantum dots (QDs) in functionalized waste polymer shows good optical properties combined with photocatalytic activities. Homogeneous sulfonation of expanded polystyrene waste (EPS) forms partially sulfonated polystyrene (PSS). Hydrogelation of the PSS facilitates the attachment of CdS QDs through sulfonic acid groups by ion-exchange mechanism, followed by trapping within the polymer network, ultimately generating an organic/inoganic nanohybrid. X-ray diffraction verifies the existence of the CdS nanocrystals and defines their cubic crystalline structure and crystallite size. High resolution transmission electron microscopy shows the formation of QDs in the nanohybrid. A blue shift in ultraviolet-visible absorption and photoluminescence confirm the QDs formation. The polymer chains effectively passivate the surface of CdS nanocrystals that exhibit exciton emission (455-471 nm) with less surface defect state emission (540 nm). In addition, the photocatalytic activity of the composite in degrading an organic dye is demonstrated.l