Host–Guest Charge‐Transfer Co‐Crystals With Record‐High Photothermal Conversion Efficiency for Solar‐Driven Interfacial Water Evaporation

ABSTRACT

Solar‐driven interfacial water evaporation using photothermal conversion materials is essential to address global freshwater scarcity. Organic charge‐transfer (CT) co‐crystals are effective for photothermal conversion, but their efficiency is often limited by suboptimal CT interactions. Here, we developed a host–guest‐enhanced CT interaction strategy in organic CT co‐crystals for efficient photothermal conversion. Two co‐crystals, TCNQ@An34C10 and F ₄ TCNQ@An34C10 , are prepared by employing an anthracene‐containing crown ether ( An34C10 ) as the electron donor host and two electron acceptor guests, 7,7,8,8‐tetracyanoquinodimethane ( TCNQ ) and 2,3,5,6‐tetrafluoro‐7,7,8,8‐tetracyanoquinodimethane ( F ₄ TCNQ ), respectively. Benefiting from the superior electron affinity of F ₄ TCNQ , F ₄ TCNQ@An34C10 achieves a record‐high photothermal conversion efficiency of 98.0% under 808 nm laser irradiation, far exceeding the 79.9% efficiency of TCNQ@An34C10 . This performance disparity is attributed to the distinct intermolecular interactions within the host–guest complexes, as revealed by combined experimental and theoretical calculations. Based on the exceptional photothermal properties, a composite foam is fabricated for solar‐driven interfacial water evaporation by loading F ₄ TCNQ@An34C10 onto porous polyurethane, which achieves a high water evaporation rate of 1.343 kg m ⁻² h ⁻¹ and a solar‐to‐vapor efficiency of 91.1% under 1 sun irradiation. This work provides new avenues for developing advanced photothermal materials toward efficient solar energy utilization.