Versatile polyimide composite aerogels for highly efficient interfacial solar steam generation through controlling the molecular polarity

In this study, an efficient interfacial solar steam generation (ISSG) system has been designed from the viewpoints of molecular design and crystallization kinetics, and fabricated to produce clean water and remove various hazardous substances. With incorporating of polar side unit (–COOH) into PI molecule, the composite aerogel offered sufficient water transporting capacity through capillary force compared to composite aerogel with inert side unit (–CH 3 ), although the same hybrid photo-thermal materials (carbon fiber and polyaniline) were adopted. Meanwhile, by controlling the freezing rate and ice crystal growth, the porosity increased from 63.2 % to 89.9 %, and pore size decreased from 150 to 60 μm, which provided much more photo-thermal interfacial area to evaporate water molecules. As a result, a new record of evaporation rate of 5.17 kg m -2 h −1 has been achieved for ISSG system based on PI aerogel irradiated by xenon light with an intensity of 1000 W m −2 , which is far higher than that of ISSG system based on –CH 3 composite aerogel (0.62 kg m -2 h −1 ). Excitingly, the designed composite aerogel also shows excellent capacity to adsorb various heavy metal ions (83.3 mg g −1 for Cu 2+ , 79.8 mg g −1 for Ni 2+ and 68.8 mg g −1 for Cr 6+ ) and outstanding removal efficiency of organic dyes (approaching to 100 %) with the help of synergistic effect of electrostatic adsorption, hydrogen bonding interaction, metal–ligand coordination, chelation effect and redox. More importantly, this ISSG system possesses long-term stability, the evaporation rate is nearly unchanged even it has been treated for 100 h under 1 kW m −2 irradiation owing to the robust morphology and durability of polar group. As a typical case, the PI composite aerogel possesses a good thermal insulation in a broad temperature range from −25 to 200 °C and excellent flame retardancy. Overall, this work provides a prospective strategy to construct highly efficient clean water generation system with versatile and stable performances for practical application.