Broad Optical Absorption and Photochromism in a Metal-Tripyridinium Cage Glass via Acid Perturbation for Efficient...

Solar-thermoelectric generation (STEG) offers a promising route to meet growing energy demands, but its practical application is constrained by the narrow photoresponse and low efficiency of conventional photothermal materials. Here, we report an ultrastable metal-tripyridinium cage photochromic glass (1g) with outstanding photothermal performance, synthesized through an acid perturbation strategy. A π-extended tripyridinium-based tricarboxylic acid ligand was designed, integrating a rigid pyridine-centered aromatic scaffold for cage assembly with flexible N-CH₂-aryl linkers to facilitate glass formation. Pair distribution function analyses reveal that the resulting coordination cage glass stabilizes radical states and optimizes charge transfer, enabling broad optical absorption beyond 2000 nm. Consequently, 1g achieves a photothermal conversion efficiency of 93.1 ± 1.2% under 1060 nm laser irradiation at 0.6 W cm^{- 2}, with a stable surface temperature of 97.8 °C. Excited-state dynamics calculations and femtosecond transient absorption spectra show that disorder-induced LLCT-to-MLCT transitions, reduced energy gaps, enhanced reorganization energy, and suppressed radiative decay underlie its exceptional performance. Integrated with thermoelectric modules, the system generates a 50.6°C temperature difference and 2.53 V under 8.0 kW m^-2 irradiation, powering multicolor LEDs and dual fans. This work establishes an efficient, stable radical-based photothermal material and an integrated photo-thermo-electric platform for practical STEG applications.