Encapsulating Polyoxometalates inside Single-Walled Carbon Nanotubes for Efficient Solar-Driven Interfacial Evaporation

Abstract

Polyoxometalates (POMs) display great potential for application in the photothermal field. However, the high water-solubility of POMs restricts their use for solar-driven interfacial evaporation. Therefore, controlling the stability of POMs and fully utilizing their photothermal characteristics is a challenge. Hence, a strategy is proposed through confining POMs with single-walled carbon nanotubes (SWCNTs), which serve as a photothermal layer of a metal-organic frameworks-modified wood evaporator for solar steam generation. POMs are effectively protected by SWCNTs, and concurrently narrow the bandgap of SWCNTs to increase light absorption. Furthermore, the molecular dynamics simulations indicate that the metal-organic frameworks in wood substrate can lower the enthalpy of evaporation by regulating microenvironment of hydrogen bonds. With this ingenious design, the evaporation rate reaches 2.53 kg m⁻² h⁻¹ under 1 sun, which exceeds most wood-based evaporators. Meanwhile, the evaporator also exhibits good purification performance for seawater and wastewater. This work provides precise regulation from the molecular level, and can be extended to create more efficient solar evaporators.