Interfacial solar desalination is an emerging technology for freshwater production, but the finding of novel solar evaporators is still challenging. In the present research, graphitic carbon foam (CF) was synthesized from the upcycling of waste plastic polyethylene terephthalate (PET) waste bottles functionalized with carrollite CuCo2S4 as a photothermal layer. Analytical characterization [X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS)] confirms the functionalization of carrollite CuCo2S4 on graphitic carbon foam. The UV-Vis spectroscopy analysis showed an enhanced optical absorption in the UV-Vis-near IR region (>96%) for functionalized CuCo2S4-CF foam compared to carbon foam (67%). The interfacial solar desalination experiment presented a significantly enhanced evaporation rate of 2.4 kg·m−2·h−1 for CuCo2S4-CF compared to that of CF (1.60 kg·m−2·h−1) and that of CuCo2S4 (1.60 kg·m−2·h−1). The obtained results proved that the newly synthesized CuCo2S4-CF from the upcycled plastic into new material for the photothermal desalination process can enhance the practice of a circular economy to produce fresh water.