Stabilizing Radicals in Aggregation-Induced Emission Rotor-Polyoxometalate Crystals for Efficient Photothermal Conversion.

The rational design of photothermal materials with well-defined molecular structures and efficient solar energy conversion is crucial for advancing renewable energy technologies, particularly in harnessing the near-infrared region (∼54% of the solar spectrum). Despite significant progress, existing systems often compromise structural precision and fabrication control in pursuit of performance. Achieving the combination of broadband absorption, high conversion efficiency, and precise crystalline structure remains a critical challenge. Here, we report a one-pot synthesis of a crystalline photothermal material, namely APC, formed within minutes through the assembly of polyoxometalates (POMs) clusters with amino-modified tetraphenylethylene, a representative molecular rotor with an aggregation-induced emission (AIE) feature. This represents the first demonstration of AIE rotor-POM assemblies for photothermal conversion. Trace peroxides at ppm levels in the solvent oxidize AIE rotors during assembly, initiating rapid radical formation that is stabilized by the crystalline matrix. The resulting air-stable radicals enable broadband absorption beyond 2000 nm, while the intramolecular motion of AIE rotors efficiently converts absorbed energy into heat, achieving an exceptional photothermal conversion efficiency of 88.7% under 808 nm laser irradiation. Mechanistic studies reveal that strong intermolecular charge transfer between AIE rotors and POMs drives radical generation, stabilized by spatial confinement and partial SOMO-HOMO inversion. Under 1 sun illumination, APC achieves a high solar-to-vapor water evaporation efficiency of 97.5%, highlighting its promise for solar-driven desalination. This study introduces a rational design strategy for crystalline photothermal hybrids and establishes the mechanistic connections among molecular assembly, charge transfer, and radical stabilization.