Radical-Assisted Nonradiative Processes to Couple Photothermy and Photosensitization for Solar-Driven Water Evaporation.

Nonradiative (NR) processes are pivotal in engineering materials with tailored properties for energy utilization. However, their intrinsic rapidity and competitiveness pose huge challenges in on-demand manipulation. Herein, radical-assisted multiple NR processes were achieved to couple photothermy and photosensitization based on a unique near-infrared-absorbing diradical-featured croconium (CR) dendrimer, CR-(DPA)-OMe. This dendrimer is well-designed by the direct covalent linkage between the flexible dendritic diphenylamine (DPA) and rigid diradical-featured CR units. The intrinsic diradical characteristics promote internal conversions in company with intramolecular donor-acceptor interactions, and the hyperfine coupling effect between the dimeric radical-ion pair excitons and adjacent magnetic nuclei assists intersystem crossing. Besides, the abundant intramolecular motions from the twisted and flexible dendritic diphenylamine groups facilitate vibrational relaxation and electron transfer. These processes endow CR-(DPA)-OMe with a photothermal conversion efficiency of 85.05% and superoxide anion generation capability under 808 nm laser irradiation. Thus, a water evaporation efficiency of 92.6% and antibacterial efficacy under one sunlight are obtained, comprehensively superior to previously reported organic small-molecule photothermal materials for solar-driven water evaporation. These findings highlight the importance of radicals in NR process manipulation, significantly boosting the development of organic functional materials with on-demand excited-state energy conversions.