Lignin‐Based Photothermal Materials: Bridging Sustainability and High‐Efficiency Energy Conversion

Photothermal materials can effectively absorb light and convert it into heat, providing sustainable solutions to mitigate environmental pollution and energy shortages. Compared to traditional photothermal materials, lignin has garnered significant attention due to its wide availability, low cost, biocompatibility, renewability, and sustainability. Consequently, lignin-based materials are considered ideal candidates for the development of eco-friendly photothermal systems, aligning well with the increasing demand for sustainable energy solutions. This review discusses the potential of lignin-based photothermal materials, highlighting their unique molecular structure and the photothermal properties imparted by their aromatic rings, which facilitate effective energy conversion through non-radiative vibrational relaxation. Discussed the latest advances in the applications of lignin photothermal materials in photothermal drive, solar desalination, and biomedicine. Despite the significant potential of lignin, challenges such as structural variability, long-term stability, and scalability remain critical. This paper integrates recent progress and proposes strategies to optimize the photothermal performance of lignin-based materials, while emphasizing important directions for sustainable development, thereby providing a roadmap to fully realize the potential of lignin in next-generation green technologies.