Issue

Vol. 19 (2027)

Covalent Organic Framework Membranes through Sequential Imine Exchange for Precise Molecular Separation

https://doi.org/10.1007/s40820-026-02287-5
Tingyuan Wang
School of Chemistry and Chemical Engineering, Collaborative Innovation Center of Ecological Civilization, Hainan University, Hainan 570228, People’s Republic of China
Yanan Liu
School of Chemistry and Chemical Engineering, Collaborative Innovation Center of Ecological Civilization, Hainan University, Hainan 570228, People’s Republic of China
Junhao Wu
School of Chemistry and Chemical Engineering, Collaborative Innovation Center of Ecological Civilization, Hainan University, Hainan 570228, People’s Republic of China
Xiaocui Wei
School of Chemistry and Chemical Engineering, Collaborative Innovation Center of Ecological Civilization, Hainan University, Hainan 570228, People’s Republic of China
Zongmei Li
School of Chemistry and Chemical Engineering, Collaborative Innovation Center of Ecological Civilization, Hainan University, Hainan 570228, People’s Republic of China
Fu Zhao
School of Chemistry and Chemical Engineering, Collaborative Innovation Center of Ecological Civilization, Hainan University, Hainan 570228, People’s Republic of China
Yixi Sun
School of Chemistry and Chemical Engineering, Collaborative Innovation Center of Ecological Civilization, Hainan University, Hainan 570228, People’s Republic of China
Chunyang Fan
School of Chemistry and Chemical Engineering, Collaborative Innovation Center of Ecological Civilization, Hainan University, Hainan 570228, People’s Republic of China
Yuhan Wang
School of Chemistry and Chemical Engineering, Collaborative Innovation Center of Ecological Civilization, Hainan University, Hainan 570228, People’s Republic of China
Zhongyi Jiang
School of Chemistry and Chemical Engineering, Collaborative Innovation Center of Ecological Civilization, Hainan University, Hainan 570228, People’s Republic of China

Corresponding Author: Zhongyi Jiang

zhyjiang@tju.edu.cn

Nano-Micro Letters, Vol. 19 (2027), Article Number: 15

Abstract

Covalent organic framework (COF) membranes with high crystallinity hold great promise in precise molecular separation, but often suffer from the intercrystalline defects and thus poor membrane-formation ability. This study reports a sequential imine exchange strategy to fabricate highly crystalline, defect-free COF membranes for precise molecular separation. Two functional amines (aromatic and aliphatic amines) are employed in highly reversible imine exchange reaction to separately conduct crystallization and defect remedy processes according to their different energy gaps. Aromatic amine, which serves as COF framework building unit, undergoes the first-step imine exchange for high crystallinity because of its lower energy gap. Afterward, the hyperbranched aliphatic amine with abundant amino groups undergoes the second-step imine exchange, affording the tight connections between adjacent crystals and the excellent membrane-formation ability. Accordingly, the COF membrane exhibits high permeance (344 L m−2 h−1 bar−1 for water, 462 L m−2 h−1 bar−1 for methanol) and rejection (> 99.9% for Congo red and Alcian blue). Meanwhile, the membrane is endowed with an ultrahigh separation factor (> 528) for mixed dye aqueous solutions and large-scale processability (> 290 cm2). This work offers a new strategy to fabricate highly crystalline and defect-free COF membranes, revealing their large potential in diverse practical applications.


Highlights:
1 A sequential imine exchange strategy is first proposed for the fabrication of highly crystalline and defect-free covalent organic framework (COF) membranes.
2 Sequential exchange of two functional amine monomers with distinct exchange energy gaps enabled controlled crystallization and membrane formation, allowing large-area membrane fabrication (> 290 cm2) within 3 h.
3 The fabricated COF membranes exhibited high permeance (344 L m−2 h−1 bar−1 for water and 462 L m−2 h−1 bar−1 for methanol), high rejection (> 99.9% for Congo red and Alcian blue 8GX), and an ultrahigh separation factor (> 528) for mixed dye aqueous solutions.

Keywords

Covalent organic framework Molecular separation Dynamic imine chemistry
Wang, Tingyuan, Yanan Liu, Junhao Wu, Xiaocui Wei, Zongmei Li, Fu Zhao, Yixi Sun, Chunyang Fan, Yuhan Wang, and Zhongyi Jiang. 2026. “Covalent Organic Framework Membranes through Sequential Imine Exchange for Precise Molecular Separation”. Nano-Micro Letters 19 (July):15. https://doi.org/10.1007/s40820-026-02287-5.
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References
  1. L. Wang, M.S.H. Boutilier, P.R. Kidambi, D. Jang, N.G. Hadjiconstantinou et al., Fundamental transport mechanisms, fabrication and potential applications of nanoporous atomically thin membranes. Nat. Nanotechnol. 12(6), 509–522 (2017). https://doi.org/10.1038/nnano.2017.72
  2. J.R. Werber, C.O. Osuji, M. Elimelech, Materials for next-generation desalination and water purification membranes. Nat. Rev. Mater. 1(5), 16018 (2016). https://doi.org/10.1038/natrevmats.2016.18
  3. H. Wang, J. Zhao, Y. Li, Y. Cao, Z. Zhu et al., Aqueous two-phase interfacial assembly of COF membranes for water desalination. Nano-Micro Lett. 14(1), 216 (2022). https://doi.org/10.1007/s40820-022-00968-5
  4. J. Kim, J.F. Kim, Z. Jiang, A.G. Livingston, Advancing membrane technology in organic liquids towards a sustainable future. Nat. Sustain. 8(6), 594–605 (2025). https://doi.org/10.1038/s41893-025-01570-4
  5. Z. Sun, Y. Liao, Y. Zhang, S. Sun, Q. Kan et al., Sustainable carbon materials in environmental and energy applications. Sustain. Carbon Mater. 1(1), e007 (2025). https://doi.org/10.48130/scm-0025-0002
  6. D.W. Burke, Z. Jiang, A.G. Livingston, W.R. Dichtel, 2D covalent organic framework membranes for liquid-phase molecular separations: state of the field, common pitfalls, and future opportunities. Adv. Mater. 36(1), 2300525 (2024). https://doi.org/10.1002/adma.202300525
  7. G. He, R. Zhang, Z. Jiang, Engineering covalent organic framework membranes. Acc. Mater. Res. 2(8), 630–643 (2021). https://doi.org/10.1021/accountsmr.1c00083
  8. Y.-H. Jin, M.-H. Li, Y.-W. Yang, Covalent organic frameworks for membrane separation. Adv. Sci. 12(5), 2412600 (2025). https://doi.org/10.1002/advs.202412600
  9. B. Fan, J. Yu, X. Wang, Y. Si, P. Tang, Flexible high-aspect-ratio COF nanofibers: defect-engineered synthesis, superelastic aerogels, and uranium extraction applications. Nano-Micro Lett. 18(1), 142 (2026). https://doi.org/10.1007/s40820-025-01984-x
  10. Z. Kang, H. Guo, L. Fan, G. Yang, Y. Feng et al., Scalable crystalline porous membranes: current state and perspectives. Chem. Soc. Rev. 50(3), 1913–1944 (2021). https://doi.org/10.1039/d0cs00786b
  11. K. Liu, C. Yin, J. Gao, Y. Wang, Temperature-swing synthesis of highly crystalline covalent organic framework films for fast and precise molecular separations. Angew. Chem. Int. Ed. 64(12), e202422333 (2025). https://doi.org/10.1002/anie.202422333
  12. K. Dey, M. Pal, K.C. Rout, S. Kunjattu H, A. Das et al., Selective molecular separation by interfacially crystallized covalent organic framework thin films. J. Am. Chem. Soc. 139(37), 13083–13091 (2017). https://doi.org/10.1021/jacs.7b06640
  13. N. Ali Khan, R. Zhang, X. Wang, L. Cao, C.S. Azad et al., Assembling covalent organic framework membranes via phase switching for ultrafast molecular transport. Nat. Commun. 13(1), 3169 (2022). https://doi.org/10.1038/s41467-022-30647-3
  14. L. Cao, H. Wu, Y. Cao, C. Fan, R. Zhao et al., Weakly humidity-dependent proton-conducting COF membranes. Adv. Mater. 32(52), 2005565 (2020). https://doi.org/10.1002/adma.202005565
  15. Y. Yang, B. Liang, J. Kreie, M. Hambsch, Z. Liang et al., Elastic films of single-crystal two-dimensional covalent organic frameworks. Nature 630(8018), 878–883 (2024). https://doi.org/10.1038/s41586-024-07505-x
  16. J.W. Colson, W.R. Dichtel, Rationally synthesized two-dimensional polymers. Nat. Chem. 5(6), 453–465 (2013). https://doi.org/10.1038/nchem.1628
  17. F. Yang, J. Guo, C. Han, J. Huang, Z. Zhou et al., Turing covalent organic framework membranes via heterogeneous nucleation synthesis for organic solvent nanofiltration. Sci. Adv. 10(50), eadr9260 (2024). https://doi.org/10.1126/sciadv.adr9260
  18. J.L. Fenton, D.W. Burke, D. Qian, M. Olvera de la Cruz, W.R. Dichtel, Polycrystalline covalent organic framework films act as adsorbents, not membranes. J. Am. Chem. Soc. 143(3), 1466–1473 (2021). https://doi.org/10.1021/jacs.0c11159
  19. Z. Ou, B. Liang, Z. Liang, F. Tan, X. Dong et al., Oriented growth of thin films of covalent organic frameworks with large single-crystalline domains on the water surface. J. Am. Chem. Soc. 144(7), 3233–3241 (2022). https://doi.org/10.1021/jacs.1c13195
  20. M.E. Belowich, J.F. Stoddart, Dynamic imine chemistry. Chem. Soc. Rev. 41(6), 2003 (2012). https://doi.org/10.1039/c2cs15305j
  21. S.J. Rowan, S.J. Cantrill, G.R.L. Cousins, J.K.M. Sanders, J.F. Stoddart, Dynamic covalent chemistry. Angew. Chem. Int. Ed. 41(6), 898–952 (2002). https://doi.org/10.1002/1521-3773(20020315)41:6%3c898::AID-ANIE898%3e3.0.CO;2-E
  22. C. Qian, A. Qiu, Q. Huang, J. Liu, Q. Gao et al., Dynamic imine exchange enables access to nanoporous covalent organic frameworks with high crystallinity for the heck reaction. ACS Appl. Nano Mater. 7(8), 9668–9677 (2024). https://doi.org/10.1021/acsanm.4c01275
  23. G. Shreeraj, A. Giri, A. Patra, Pushing the boundaries of covalent organic frameworks through postsynthetic linker exchange. ChemNanoMat 10(1), e202300398 (2024). https://doi.org/10.1002/cnma.202300398
  24. B. Yu, R.-B. Lin, G. Xu, Z.-H. Fu, H. Wu et al., Linkage conversions in single-crystalline covalent organic frameworks. Nat. Chem. 16(1), 114–121 (2024). https://doi.org/10.1038/s41557-023-01334-7
  25. W. Zhang, L. Chen, S. Dai, C. Zhao, C. Ma et al., Reconstructed covalent organic frameworks. Nature 604(7904), 72–79 (2022). https://doi.org/10.1038/s41586-022-04443-4
  26. T. Ma, E.A. Kapustin, S.X. Yin, L. Liang, Z. Zhou et al., Single-crystal X-ray diffraction structures of covalent organic frameworks. Science 361(6397), 48–52 (2018). https://doi.org/10.1126/science.aat7679
  27. J. Han, J. Feng, J. Kang, J.-M. Chen, X.-Y. Du et al., Fast growth of single-crystal covalent organic frameworks for laboratory X-ray diffraction. Science 383(6686), 1014–1019 (2024). https://doi.org/10.1126/science.adk8680
  28. S. Wang, Y. Yang, H. Zhang, Z. Zhang, C. Zhang et al., Toward covalent organic framework metastructures. J. Am. Chem. Soc. 143(13), 5003–5010 (2021). https://doi.org/10.1021/jacs.0c13090
  29. W. Li, Z. Bie, C. Zhang, X. Xu, S. Wang et al., Combinatorial synthesis of covalent organic framework ps with hierarchical pores and their catalytic application. J. Am. Chem. Soc. 145(35), 19283–19292 (2023). https://doi.org/10.1021/jacs.3c04995
  30. X.-L. Wang, L.-T. Zhang, S. He, X.-X. Chen, X.-C. Huang et al., Dynamic imine exchange reactions for facile synthesis of imine-linked covalent organic frameworks. Chem. Mater. 35(23), 10070–10077 (2023). https://doi.org/10.1021/acs.chemmater.3c02092
  31. J. Yuan, X. You, N. Ali Khan, R. Li, R. Zhang et al., Photo-tailored heterocrystalline covalent organic framework membranes for organics separation. Nat. Commun. 13(1), 3826 (2022). https://doi.org/10.1038/s41467-022-31361-w
  32. D. Shi, H. Li, X. Yu, Z. Zhang, Y.D. Yuan et al., Intercrystalline channels at subnanometer scale for precise molecular nanofiltration. J. Am. Chem. Soc. 145(29), 15848–15858 (2023). https://doi.org/10.1021/jacs.3c02711
  33. D. Shi, F. Huang, K. Xue, X. Shi, N. Zhu et al., Scalable metal-organic framework membranes through nonclassical crystallization for molecular separation. Sci. Adv. 11(49), eadz5237 (2025). https://doi.org/10.1126/sciadv.adz5237
  34. S.-Y. Ding, J. Gao, Q. Wang, Y. Zhang, W.-G. Song et al., Construction of covalent organic framework for catalysis: Pd/COF-LZU1 in suzuki–miyaura coupling reaction. J. Am. Chem. Soc. 133(49), 19816–19822 (2011). https://doi.org/10.1021/ja206846p
  35. Z. Miao, G. Liu, Y. Cui, Z. Liu, J. Li et al., A novel strategy for the construction of covalent organic frameworks from nonporous covalent organic polymers. Angew. Chem. Int. Ed. 58(15), 4906–4910 (2019). https://doi.org/10.1002/anie.201813999
  36. M. Wang, T.-Y. Ma, Z.-H. Wu, Y. Liu, S. Li et al., Construction of local-ion trap in phase-reversed mixed matrix COF membranes for ultrahigh ion selectivity. Angew. Chem. Int. Ed. 64(22), e202504990 (2025). https://doi.org/10.1002/anie.202504990
  37. H. Li, Z. Zhou, T. Ma, K. Wang, H. Zhang et al., Bonding of polyethylenimine in covalent organic frameworks for CO2 capture from air. J. Am. Chem. Soc. 146(51), 35486–35492 (2024). https://doi.org/10.1021/jacs.4c14971
  38. W. Zhang, Z. Lu, C. Chen, P. Vannatta, C. Yang et al., Expanded synthesis of 3D covalent organic frameworks via linker exchange for efficient photocatalytic aerobic oxidation. Small 21(18), e2502316 (2025). https://doi.org/10.1002/smll.202502316
  39. M. Ciaccia, S. Di Stefano, Mechanisms of imine exchange reactions in organic solvents. Org. Biomol. Chem. 13(3), 646–654 (2015). https://doi.org/10.1039/c4ob02110j
  40. K.T. Tan, S. Ghosh, Z. Wang, F. Wen, D. Rodríguez-San-Miguel et al., Covalent organic frameworks. Nat. Rev. Methods Primers 3(1), 1 (2023). https://doi.org/10.1038/s43586-022-00181-z
  41. C. Fan, H. Wu, J. Guan, X. You, C. Yang et al., Scalable fabrication of crystalline COF membranes from amorphous polymeric membranes. Angew. Chem. Int. Ed. 60(33), 18051–18058 (2021). https://doi.org/10.1002/anie.202102965
  42. H. Fan, J. Gu, H. Meng, A. Knebel, J. Caro, High-flux membranes based on the covalent organic framework COF-LZU1 for selective dye separation by nanofiltration. Angew. Chem. Int. Ed. 57(15), 4083–4087 (2018). https://doi.org/10.1002/anie.201712816
  43. G. Cheng, C. Sui, W. Hao, J. Li, Y. Zhao et al., Ultra-strong Janus covalent organic framework membrane with smart response to organic vapor. Small 20(34), 2401635 (2024). https://doi.org/10.1002/smll.202401635
  44. J.Á. Martín-Illán, L. Sierra, A. Guillem-Navajas, J.A. Suárez, S. Royuela et al., β-ketoenamine-linked covalent organic frameworks synthesized via gel-to-gel monomer exchange reaction: from aerogel monoliths to electrodes for supercapacitors. Adv. Funct. Mater. 34(40), 2403567 (2024). https://doi.org/10.1002/adfm.202403567
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