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Vol. 18 (2026)

COF Scaffold Membrane with Gate-Lane Nanostructure for Efficient Li+/Mg2+ Separation

https://doi.org/10.1007/s40820-025-01972-1
Zixuan Zhang
Joint School of National University of Singapore and Tianjin University, International Campus of Tianjin University, Binhai New City, Fuzhou 350207, People’s Republic of China
Yan Kong
Key Laboratory for Green Chemical Technology of Ministry of Education, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, People’s Republic of China
Runlai Li
College of Polymer Science and Engineering, State Key Laboratory of Polymer Materials Engineering, Sichuan University, Chengdu 610065, People’s Republic of China
Xiaolin Yue
Key Laboratory for Green Chemical Technology of Ministry of Education, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, People’s Republic of China
Hao Deng
Joint School of National University of Singapore and Tianjin University, International Campus of Tianjin University, Binhai New City, Fuzhou 350207, People’s Republic of China
Yu Zheng
Key Laboratory for Green Chemical Technology of Ministry of Education, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, People’s Republic of China
Sui Zhang
Department of Chemical and Biomolecular Engineering, National University of Singapore, 4 Engineering Drive 4, Singapore 117585, Singapore
Runnan Zhang
Key Laboratory for Green Chemical Technology of Ministry of Education, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, People’s Republic of China
Zhongyi Jiang
Joint School of National University of Singapore and Tianjin University, International Campus of Tianjin University, Binhai New City, Fuzhou 350207, People’s Republic of China

Corresponding Author: Runnan Zhang

runnan.zhang@tju.edu.cn

Nano-Micro Letters, Vol. 18 (2026), Article Number: 126

Abstract

Due to complex ion–ion and ion–membrane interactions, creating innovative membrane structures to acquire favorable ion mixing effect and high separation performance remains a big challenge. Herein, we design covalent organic framework (COF) scaffold membrane with gate-lane nanostructure for efficient Li+/Mg2+ separation. COF nanosheets, serving as the scaffold, are intercalated by polyethyleneimine (PEI) to form the permeating layer. Subsequently, PEI on the surface reacts with 1,4-phenylene diisocyanate to form the polyurea gating layer. The gating layer, bearing tailored smaller pore size, affords high rejection to co-ions (Mg2+) and thus high Li+/Mg2+ selectivity. The permeating layer, with asymmetric charge and spatial nanostructure for creating individual lanes of Li+ and Cl−, facilitates Li+ transport and thus high Li+ permeability. The optimum COF scaffold membrane exhibits the permeance of 11.5 L m−2 h−1/bar−1 and true selectivity of 231.9 with Li+ enrichment of 120.2% at the Mg2+/Li+ mass ratio of 50, exceeding the ideal selectivity of 80.5 and outperforming all ever-reported positively charged nanofiltration membranes. Our work may stimulate the further thinking about how to design the hierarchical membrane structure to achieve favorable ion mixing effect and break the membrane permeability–selectivity trade-off in chemical separations.


Highlights:
1 Covalent organic framework (COF) scaffold membranes with gate-lane nanostructure were prepared.
2 The gating layer affords high rejection to Mg2+ and thus high Li+/Mg2+ selectivity. The permeating layer bearing Li+ lanes and Cl− lanes facilitates Li+ transport and thus high Li+ permeability.
3 The COF scaffold membrane exhibits the true selectivity of 231.9 with Li+ enrichment of 120.2% at the Mg2+/Li+ mass ratio of 50, exceeding the ideal selectivity of 80.5.

Keywords

Covalent organic framework Polyethyleneimine Scaffold membrane Lithium/magnesium nanofiltration separation Ion mixing effect
Zhang, Zixuan, Yan Kong, Runlai Li, Xiaolin Yue, Hao Deng, Yu Zheng, Sui Zhang, Runnan Zhang, and Zhongyi Jiang. 2026. “COF Scaffold Membrane With Gate-Lane Nanostructure for Efficient Li+/Mg2+ Separation”. Nano-Micro Letters 18 (January):126. https://doi.org/10.1007/s40820-025-01972-1.
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