Solar-driven organic solvent purification enabled by the robust cubic Prussian blue

Abstract

Organic solvent purification and molecular separation play a remarkable role in textile, petrochemical and pharmaceutical industries, which is usually an energy intensive process, e.g. high temperature-driven distillation or high pressure-driven organic solvent nanofiltration. Here, we provide a promising alternative solar-thermal evaporation for organic solvent recovery and purification, an economic and green technology due to the sustainability and inexhaustibility of solar energy. To achieve that, cubic Prussian blue (PB) nanocrystals are elaborately synthesized and in situ loaded on cotton fibers (CFs) to form stable solar-thermal materials. The so-assembled composite PB@CF shows great light absorption, photothermal conversion and solvent self-pumping capacity, which was successfully used for photothermal purification of a library of organic solvents with the dielectric constant from 2.38 to 37.78 and a high rejection up to 99.9%. The vaporization flux ranges from 29.2 L m⁻² h⁻¹ for acetone to 0.73 L m⁻² h⁻¹ for N-methylpyrrolidone under one sun illumination, negatively correlating with the evaporation enthalpy change. The interfacial solar evaporation rate is significantly improved by 4.0–11.5 times compared to the bare solvent evaporation without the photothermal material. More practically, the composite PB@CF with excellent organic solvent resistance undergoes stable solar evaporation, even after immersion in a highly polar solvent such as N,N-dimethylacetamide for 3 months. Thus, such a robust PB@CF composite offers a prospective energy economic alternative to solving the organic solvent related issue, e.g. solvent recovery, catalyst recycle, molecular separation in petrochemical and pharmaceutical industries.