Liu Qinghua, Liu Ming, Zhang Zhe, Yin Congcong, Long Jianghai, Wei Mingjie, Wang Yong
State Key Laboratory of Materials-Oriented Chemical Engineering, and College of Chemical Engineering, Nanjing Tech University, Nanjing, 211816, Jiangsu, China.
School of Environmental Science and Engineering, Nanjing Tech University, Nanjing, 211816, Jiangsu, China.
Nat Commun. 2024 Oct 25;15(1):9221. doi: 10.1038/s41467-024-53625-3.
Covalent organic frameworks (COFs) have emerged as promising platforms for membrane separations, while remaining challenging for separating ions in a fast and selective way. Here, we propose a concept of COF membranes with vertically aligned nanorods for efficient separation of rare metal ions. A quaternary ammonium-functionalized monomer is rationally designed to synthesize COF layers on porous substrates via interfacial synthesis. The COF layers possess an asymmetric structure, in which the upper part displays vertically aligned nanorods, while the lower part exhibits an ultrathin dense layer. The vertically aligned nanorods enlarge contact areas to harvest water and monovalent ions, and the ultrathin dense layer enables both high permeability and selectivity. The resulting membranes exhibit exceptional separation performances, for instance, a Cs permeation rate of 0.33 mol m h, close to the value in porous substrates, and selectivities with Cs/La up to 75.9 and 69.8 in single and binary systems, highlighting the great potentials in the separation of rare metal ions.
共价有机框架（COFs）已成为膜分离领域颇具前景的平台，但以快速且选择性的方式分离离子仍具有挑战性。在此，我们提出了一种具有垂直排列纳米棒的COF膜概念，用于高效分离稀有金属离子。通过合理设计一种季铵官能化单体，经由界面合成在多孔基底上制备COF层。COF层具有不对称结构，上部呈现垂直排列的纳米棒，而下部则为超薄致密层。垂直排列的纳米棒扩大了接触面积以截留水和单价离子，超薄致密层则实现了高渗透性和选择性。所得膜展现出优异的分离性能，例如，铯的渗透速率为0.33 mol m⁻² h⁻¹，接近多孔基底中的值，在单体系和双体系中铯/镧的选择性分别高达75.9和69.8，突显了其在稀有金属离子分离方面的巨大潜力。
