A high-performance salt-rejecting and cost-effective superhydrophilic porous monolithic polymer foam for solar steam generation.

A direct solar desalination with the excellent solar photothermal efficiency, lower cost, and extend generator device lifetime is beneficial to increase potable water supplies. To address fundamental challenges in direct solar desalination, herein, we present a new and facile method to scalable fabrication of polymer porous foam (VMP) as salt-resistant photothermal materials, which was synthesized by using styrene and 1-vinyl-3-ethylimidazolium tetrafluoroborate as monomer, N, N'-Methylenebisacrylamide as cross-linking agent through a facile one-step hydrothermal method. The as-resulted VMP shows excellent mechanical property which could bear a compression strain of 30%, endowing its superior processability for practical operation. In addition, by taking advantage of its inherently well-controlled porous structure (porosity is 73.81 %), low apparent density and extremely low thermal conductivity (0.03204W/m-1K-1), the VMP foam exhibits excellent solar evaporation performance with a high solar photothermal efficiency of up to 88% obtained at a light density of 1 kWm-2. Moreover, the introduction of ionic liquid moiety (imidazolium tetrafluoroborate) into VMP endows its an interesting superhydrophilic wettability which can accelerate water transportation (wetting in 5s) and resolve the crystalline salt within 1.13h, by combination with its interconnected macropores of VMP which can be worked as water channels for replenishment of surface vaporized brine to prevent salt from adhering, the VMP show a salt-resistant performance, e.g. its solar evaporation efficiency nearly remains unchanged after 6h duration under 1 sun irradiation. Based on its simple and cost-effective manufacture process, excellent solar photothermal efficiency and salt-resistance, our VMP may be a promising candidate as photothermal materials for practical desalination from seawater and other wastewaters.