Sorption-based atmospheric water harvesting has the potential to address water scarcity by extracting fresh water from the air. The performance of this technology largely depends on the sorbent used. Hygroscopic salt-embedded composite materials (HSCMs) are promising sorbents for sorption-based atmospheric water harvesting because they combine the high sorption capacities of hygroscopic salts across all relative humidity levels with the salt-retaining structure and kinetics-enhancing properties of a porous or networked matrix. However, the interactions between the matrix and salts in HSCMs are not yet fully understood, which hinders the rational design of their sorption performance. This Review introduces a framework for understanding key sorption characteristics — capacity, enthalpy, kinetics and stability — of HSCMs, through an in-depth thermodynamic analysis of the interactions among hygroscopic salts, water and salt solutions. Using this framework, we analyse reported HSCMs and guide the design of future composites by considering factors such as salt content, pore structure and the carrying capacity of the matrix. We also examine the energy flow within the sorption and desorption cycles to explore potential designs for the matrix that could enhance both aspects. Looking forward, we emphasize the importance of designing sorbent materials and multifunctional device systems in tandem, integrating material design needs, local water demand and energy efficiency to fully leverage the untapped capabilities of atmospheric humidity.

基于吸附的大气水收集有可能通过从空气中提取淡水来解决水资源短缺问题。该技术的性能很大程度上取决于所使用的吸附剂。吸湿盐嵌入复合材料（HSCM）是基于吸附的大气水收集的有前途的吸附剂，因为它们结合了吸湿盐在所有相对湿度水平下的高吸附能力与多孔或网状结构的持盐结构和动力学增强特性。矩阵。然而，HSCM 中基质和盐之间的相互作用尚未完全了解，这阻碍了其吸附性能的合理设计。本综述介绍了一个框架，通过对吸湿盐、水和盐溶液之间相互作用的深入热力学分析，了解 HSCM 的关键吸附特性（容量、焓、动力学和稳定性）。使用这个框架，我们分析了报道的 HSCM，并通过考虑盐含量、孔隙结构和基体承载能力等因素来指导未来复合材料的设计。我们还检查了吸附和解吸循环内的能量流，以探索可以增强这两个方面的矩阵的潜在设计。展望未来，我们强调串联设计吸附剂材料和多功能装置系统的重要性，整合材料设计需求、当地用水需求和能源效率，以充分利用大气湿度的未开发能力。