Ultrastable NIR Absorbing Imidazole-Based Open-Shell Diradicaloids for High-Efficiency Photothermal Steam and Power Generation

Open-shell diradicaloids are promising photothermal materials owing to their near-infrared absorption and efficient non-radiative energy dissipation. However, complex synthesis and inherent reactivity make them less relevant for practical applications. Herein, we report a stable, synthetically readily accessible pyrene-integrated imidazole-based open-shell diradical (PBQ) photothermal material. PBQ possesses a high diradical character, with a low ΔE_S-T of -2.8 kcal/mol, and strong solid-state absorption extending to ∼1600 nm. Under one-sun illumination for 10 min, PBQ attains a surface temperature of 71°C and exhibits high photothermal solar steam generation of 2.05 kg m^{- 2} h^{- 1} with a solar-to-vapour conversion efficiency of 98%. Notably, PBQ outperforms previously reported diradicaloid-based photothermal materials. PBQ exhibits excellent chemical- and photo-stability even after 40 days of water soaking and 14 days under natural sunlight, or under high-light intensity up to 2 suns for 120 mins. The high stability of PBQ is attributed to extensive delocalisation of the spin density across its large π-conjugated backbone and the presence of stabilising heteroatoms. Additionally, PBQ exhibits photothermal power generation and simultaneous cogeneration of steam and electricity. This work demonstrates an imidazole-linked diradicaloid as a high-performance photothermal material, offering a molecular platform for solar-driven water purification and energy conversion.