Separation of monovalent metal ions is essential for metal extraction and mining such as lithium salt production for battery manufacturing and other industrial applications, but it is challenging. In this study, we develop a cation selective and thermally regenerable metal-organic framework (MOF) for efficient separation of monovalent metal ions. Specifically, a crosslinked poly(N-isopropylacrylamide-co-acryloylamidobenzo-18-crown-6) functionalized MOF-808 (pNCE/MOF-808) preferentially adsorb Na⁺ and K⁺, leaving Li⁺ behind at ambient temperature, due to the size-match effect, ion dehydration effect, and stability constant of cation-benzo-18-crown-6 complex. It shows high adsorption capacity of 1.04 mmol g^-1 and excellent selectivity up to 29.4 for Na⁺/Li⁺ and 34.4 for K⁺/Li⁺ in the mixed solution contained 0.5 M LiCl, 0.5 M NaCl, and 0.5 M KCl. Importantly, pNCE/MOF-808 with adsorbed Na⁺ and K⁺ ions could be efficiently regenerated at mild temperature (e.g., 45°C) in water. This work firstly provides an effective way to functionalize MOFs with thermoresponsive property for high ion selectivity and chemical-free regeneration. pNCE/MOF-808 holds promise for further development for environmentally friendly monovalent ion separations such as lithium ion purification.

一价金属离子的分离对于金属提取和开采（例如电池制造和其他工业应用中的锂盐生产）至关重要，但具有挑战性。在这项研究中，我们开发了一种阳离子选择性和可热再生的金属有机骨架（MOF），用于有效分离一价金属离子。具体而言，交联的聚（N-异丙基丙烯酰胺-co-acryloylamidobenzo-18-crown-6）官能化的MOF-808（pNCE / MOF-808）优先吸附Na ⁺和K ⁺，在室温下由于Li ⁺残留Li ⁺阳离子-苯并-18-冠-6配合物的尺寸匹配效应，离子脱水作用和稳定性常数。显示出1.04 mmol g ^-1的高吸附容量混合溶液中含有0.5 M LiCl，0.5 M NaCl和0.5 M KCl，对Na ⁺ / Li ^+的选择性高达29.4，对K ⁺ / Li ^+的选择性高达34.4 。重要的是，具有吸附的Na ⁺和K ⁺离子的pNCE / MOF-808可以在温和的温度下（例如45°C）在水中高效再生。这项工作首先提供了一种有效的方法来对具有热响应特性的MOF进行功能化，以实现高离子选择性和无化学物质的再生。pNCE / MOF-808有望进一步开发环保单价离子分离技术，例如锂离子纯化。