Donor–Acceptor Organic Photothermal Material with Vibrant Molecular Motion for Highly Efficient Water Evaporation and Electricity Generation

Organic photothermal materials have demonstrated significant potential for seawater desalination. However, the poor photobleaching resistance and low photothermal conversion efficiency restrict their widespread use. In this study, by incorporating the vigorous donor and acceptor structure and the vibrant molecular motion groups, BPBA-BID demonstrates good photobleaching resistance and outstanding photothermal conversion ability, reaching 235 °C only within 5 s under 0.4 W cm –2 of 808 nm irradiation. Under one-sun irradiation, BPBA-BID acquires a great photothermal conversion efficiency of 33.4%, surpassing many organic photothermal materials. When incorporated into a loofah substrate, the BPBA-BID-based two-dimensional (2D) solar-driven water evaporator achieves a water evaporation rate of 1.44 kg m –2 h –1 with an evaporation efficiency of 99.1%, suggesting remarkable water evaporation performance. Seawater desalination experiments using this evaporator show a significant reduction in major ion concentrations. After evaporating methylene blue and methyl orange aqueous solutions, residual dyes in collecting water are negligible, confirming the effective desalination and water purification capability. Additionally, we also developed a water–electricity cogeneration device that can effectively transform solar energy into both thermal and electrical power. Utilizing BPBA-BID as an organic small-molecule photothermal material offers a potential probability for water purification and electricity supply, contributing to the sustainable development of green energy.