The cooperation of charge transfer and electron transfer for manipulating photothermal behaviour of donor-acceptor co-crystals

Charge transfer complexes (CTCs) have become a promising and new class of photothermal conversion materials, in which the donor and acceptor can be regulated to control the energy gap, facilitating efficient absorption of near-infrared light. However, the successful co-crystallization of appropriate donor and acceptor pairs to form CTCs remains a challenging endeavor, as it requires addressing crucial issues including structural matching, co-assembly and crystallization conditions. Herein, on the basis of retaining the ‘autonomy’ of the assembly process, we leverage charge transfer and electron transfer processes of pyridinium building blocks to manipulate the photothermal behaviour in two distinct CTCs. Notably, CTC-1OH exhibits electron transfer initiated near-infrared photothermal conversion, while CTC-2OH has an intrinsic charge transfer-dependent photothermal effect with a photothermal efficiency as high as 35.4%. This work opens a new avenue for the development and optimization of the photothermal effect of CTCs.