Bio‐Based Mechanically Strong Covalent Adaptable Networks for Stable‐Response Solar Harvesting

ABSTRACT Lignin‐based photothermal conversion materials provide effective solutions for advancing next‐generation photothermal generators. However, recently reported lignin‐based photothermal conversion materials face significant challenges due to poor mechanical strength, unstable solar energy collection, and difficulty in recycling. In response, high‐performance photothermal materials based on lignin–tung oil covalent adaptive networks (LTs) are produced. The dynamic β‐hydroxyl esters and multiple hydrogen bonds confer LTs with mechanical robustness, high adhesive strength, swelling resistance, and cycle processing performance. The π–π conjugation of aromatic rings imparts efficient photothermal conversion performance to LTs. Under xenon light irradiation (200 s, 1.2 W cm −2 ), LTs achieved a photothermal temperature exceeding 125°C. Furthermore, LTs demonstrated excellent maximum temperature stability over five light‐heating and cooling cycles. The generator voltage remained stable within four cycles under leaf occlusion or real sunlight and could be artificially regulated when integrated into a thermoelectric generator. Consequently, the bio‐based, mechanically strong, highly efficient, and stable‐responding photothermal materials produced via a simple strategy hold significant potential for next generation solar thermal generators, suitable for industrial scale and large‐scale production.