Lanthanides are a group of important elements and have been widely used in many fields. Their separation is crucial for technical applications, but it remains a troublesome task due to their subtly different properties. Herein, novel nanoporous sulfonic covalent organic frameworks were synthesized by the Schiff base reaction of 1,3,5-tris(p-formylphenyl)benzene (TFPB) and 2,5-diaminobenzene-1,4-disulfonic acid (DABDA) under mild conditions, which were defined as TFPB-DABDA iCOFs and used for highly selective adsorption separation of lanthanide elements. These iCOFs have uniform morphology, good stability, and excellent adsorption separation ability. The experiment results indicate that the adsorption capacity of TFPB-DABDA iCOFs is highly sensitive to the ionic radius. It means that the larger the size difference between ions, the higher the separation selectivity, especially in the early lanthanides (La³⁺, Ce³⁺, Pr³⁺, Nd³⁺, Sm³⁺, Eu³⁺, and Gd³⁺) and late lanthanides (Tb³⁺, Dy³⁺, Ho³⁺, Er³⁺, Tm³⁺, and Lu³⁺). The separation mechanism of lanthanide elements by TFPB-DABDA iCOFs may be related to the sulfonic acid groups in the ordered channels of the COFs. This work develops a simple and efficient strategy for the synthesis of iCOFs, which shows a promising application of effective adsorption separation of lanthanides.

中文翻译：

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用于选择性吸附和分离镧系元素的纳米孔磺酸共价有机骨架

镧系元素是一族重要的元素，在许多领域都有广泛的应用。它们的分离对于技术应用至关重要，但由于它们的特性略有不同，这仍然是一项棘手的任务。在此，通过 1,3,5-tris( p-甲酰苯基）苯（TFPB）和2,5-二氨基苯-1,4-二磺酸（DABDA）在温和条件下，被定义为TFPB-DABDA iCOFs，用于镧系元素的高选择性吸附分离。这些iCOFs具有均匀的形貌、良好的稳定性和优异的吸附分离能力。实验结果表明，TFPB-DABDA iCOFs 的吸附容量对离子半径高度敏感。这意味着离子之间的尺寸差异越大，分离选择性越高，特别是在早期的镧系元素（La ³⁺、Ce ³⁺、Pr ³⁺、Nd ³⁺、Sm ³⁺、Eu ³⁺和Gd ^{3 +} )和晚期镧系元素(Tb ³⁺、Dy ³⁺、Ho ³⁺、Er ³⁺、Tm ³⁺和Lu ³⁺）。TFPB-DABDA iCOFs 对镧系元素的分离机制可能与 COFs 有序通道中的磺酸基团有关。这项工作开发了一种简单有效的 iCOF 合成策略，显示了镧系元素有效吸附分离的前景广阔的应用。