Charge‐Transfer Cocrystal via a Persistent Radical Cation Acceptor for Efficient Solar‐Thermal Conversion

Abstract Designing organic charge‐transfer (CT) cocrystals for efficient solar‐thermal conversion is a long‐sought goal but remains challenging. Here we construct a unique CT cocrystal by using a persistent 2,2′‐azino‐bis(3‐ethylbenzothiazoline‐6‐sulfonic acid) radical cation (ABTS +. ) as the electron acceptor. The strong persistency and electron affinity of ABTS +. endow a high degree of electron delocalization between ABTS +. and the 3,3′,5,5′‐tetramethylbenzidine donor. Together with the intrinsic long‐wavelength absorption of ABTS +. , the synthesized cocrystal can effectively capture the full solar spectrum and show distinguished photothermal efficiency. Such a cocrystal is further used for solar‐driven interfacial evaporation, and a high evaporation rate of 1.407 kg m −2 h −1 and a remarkable solar‐to‐vapor efficiency of 97.0 % have been achieved upon 1 sun irradiation. This work indicates the enormous prospects for charge transfer‐based functional materials through rational radical cation engineering.