All‐Weather Solar‐Powered Desalination and Synchronous Cs⁺ Extraction for Salt‐Lake Water Enabled by Crown‐Ether‐Decorated Phase‐Change Microcapsules

Abstract Solar‐powered interfacial evaporation is recognized as an emerging technology for desalination of salt‐lake water but suffers from insufficient evaporation mass under intermittent sunlight illumination. Meanwhile, salt‐lake water contains abundant noble metal ions; however, there is no effective strategy to extract them during evaporation. Hereby, an interfacial evaporator integrated with crown‐ether‐functionalized phase‐change microcapsules (Crown‐MicPCM) is designed to realize all‐weather desalination and synchronous caesium ion (Cs⁺) extraction of salt‐lake water. Crown‐MicPCM is constructed with an n‐docosane core for photothermal energy storage, a magnetic SiO₂/Fe₃O₄ composite shell for easy recyclability, a polydopamine inner coat for sunlight absorption, and a crown ether outer coat for selective Cs⁺ adsorption. Through integrating the functions of solar energy harvest, latent heat storage, and selective Cs⁺ adsorption within Crown‐MicPCM, such an innovative design boosts the evaporation and adsorption performance of the developed evaporator significantly. The developed Crown‐MicPCM‐integrated evaporator exhibits a considerable improvement in freshwater production and Cs⁺ extraction, achieving a Cs⁺ adsorption capacity of 32.6 mg g⁻¹ and an evaporation rate of 1.43 kg m⁻² h⁻¹ under one‐sun illumination. Compared with the evaporator without a phase‐change material, the Crown‐MicPCM‐integrated evaporator obtains an increase in freshwater yield by 47% and in adsorption efficiency of Cs⁺ by 12% under natural sunlight illumination.