To fabricate an oil-water separation material that is rich in source, eco-friendly, and responsive, in this study, we successfully developed a collagen-based sponge for application to oil-water separation based on a green and facile strategy. In this design, widely-available collagen (COL) was used as the substrate: it was immersed in polydimethylsiloxane (PDMS) suspension with candle soot (CS) nanoparticles, followed by hot curing. The resultant sponge (CS/PDMS-COL) possessed good hydrophobicity with a water contact angle of 148.3° under a low PDMS concentration of 2%. The results from field emission scanning electron microscope, Fourier transform infrared spectrometer, X-ray photoelectron spectrometer, and X-ray diffractometry demonstrated the successful coating of CS and PDMS on the surface of COL substrate. The CS/PDMS-COL can adsorb eight oils, with the adsorption capacity for trichloromethane reaching 95 g/g. With benzene as the target adsorbent, the separation efficiency was maintained at no less than 95% even after recycling 20 times. CS/PDMS-COL was also used to separate oil-in-water emulsion. Moreover, the sponge killed bacteria effectively due to its excellent near-infrared photothermal responsiveness. This study provides new insight into the preparation of facile oil-water separation materials based on naturally occurring biomaterials effortlessly.