The present investigation describes a facile, in situ polymerization technique to fabricate starch-based hyper-branched polyurethane nanocomposites by incorporating palladium-reduced carbon dot (diameter, 10-15 nm) nanohybrid. The nanohybrid was prepared by a sunlight-driven one-pot approach by combining Pd nanoparticles with reduced carbon dots, without exhaustive condition and toxic chemicals. Fourier transform infrared, UV-visible, energy-dispersive X-ray, X-ray diffraction, and transmission electron microscopy analyses support the structure of the nanohybrid and nanocomposite. The nanocomposite is an efficient visible-light-assisted photo-catalyst for synthesis of biphenyl compounds via Suzuki-Miyaura coupling pathway under ambient and ligand-free conditions. It demonstrated enhancement in elongation at break (1.3-fold), tensile strength (2-fold), toughness (3.5-fold); and thermal stability (by 25 degrees C) over the pristine polymer. Thus, the nanocomposite is highly efficient for coupling aryl halides with various coupling partners to synthesize biphenyls and their derivatives, the important intermediates in organic chemistry that constitute the structural moiety of compounds with profound pharmacological activity.