Upcycled PET‐Derived Carbon Foam Functionalized with Cu₃SbS₄–Sb₂S₃ Heterostructures for Efficient Interfacial Solar Desalination

Solar desalination is an emerging technique to produce fresh water utilizing renewable solar energy. However, the engineering of efficient photothermal material is a significant obstacle. In the present study, a carbon foam is synthesized from the upcycling of waste PET and hydrothermally functionalized with a heterostructure composed of Cu 3 SbS 4 and Sb 2 S 3 . Material characterizations demonstrated the successful decoration of nanochannels on graphitic carbon foam (CF). The analysis of the optical properties in the UV/Vis‐NIR spectral range demonstrated excellent absorption properties of 96% for Cu 3 SbS 4 ‐Sb 2 S 3 /CF compared to Sb 2 S 3 /CF (48%) and CF (68%) in near‐IR. Photothermal desalination results reveal the evaporation rate of 2.82 kg m −2 h −1 for Cu 3 SbS 4 ‐Sb 2 S 3 /CF compared to 1.4 kg m −2 h −1 for Sb 2 S 3 /CF and 1.58 kg m −2 h −1 for CF, with 99% salt removal in condensed water. The formation of the composite leads to a high surface temperature and enhanced evaporation rate. The contact angle analysis confirmed the hydrophilic nature of the material that plays a crucial role in the solar desalination process. These findings elucidate the effective photothermal performance achieved through chalcogenide heterostructure engineering supported on upcycled carbon foam derived from waste PET, demonstrating a practical application aligned with circular economy principles in solar desalination.