Boosting Near-Infrared Photothermal Conversion by Intermolecular Interactions in Isomeric Cocrystals

Organic cocrystal exhibits excellent photothermal conversion (PTC), but how the intermolecular interactions of cocrystals regulate the PTC is obscure. Here, two isomeric donor molecules (phenanthrene and anthracene) and two electron-withdrawing molecules (7,7,8,8,8-tetracyanodimethylquinone and 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinone dimethane) are self-assembled into the four cocrystals (PTQ PFQ ATQ and AFQ). By changing the molecular configuration of the donor and the electronwithdrawing ability of the acceptor, the intrinsic influencing factors of the intermolecular interaction on the PTC were explored. Under near-infrared laser (808 nm) irradiation, the PTC efficiencies of PTQ PFQ AFQ and ATQ are 35.85, 44.74, 57.00, and 60.53%, respectively. Based on the single-crystal X-ray diffraction, ultrafast time-resolved transient absorption, and excited-state theoretical calculations, we found that the pi-pi stacking in ATQ and AFQ is conducive to promoting the near-infrared light-harvesting ability and the p-pi interaction of cocrystals can regulate the nonradiative rotation of -C(C N)(2) groups, resulting in a tunable near-infrared PTC via the isomeric cocrystals. Accordingly, the evaporation rate of the porous polyurethane-AFQ foam can reach 1.33 kg.m(-2).h(-1) in the simulated solar-driven water evaporation system. This work provides a strategy to boost the PTC by the intermolecular interactions of cocrystal materials.

Automated summary

This study explores the intermolecular interactions of cocrystals in regulating photothermal conversion efficiency, demonstrating that pi-pi stacking and p-pi interactions play crucial roles in enhancing near-infrared light absorption. The findings offer a strategy to boost photothermal conversion efficiency by tuning the interactions between cocrystal materials.