Adjusting interlayer interactions and proton-conduction pathways of 2D covalent organic frameworks through the
Jianjian Yang1, Weidong Fan1, Xiaofei Wei1
1Shandong Key Laboratory of Intelligent Energy Materials, State Key Laboratory of Heavy Oil Processing, School of Materials Science and Engineering, China University of Petroleum (East China), Qingdao 266580, China.
National Science Review
|September 10, 2025
Summary
This study introduces a new method to create 3D channels in 2D covalent organic frameworks (COFs) using rotaxane structures. This enhances proton conduction pathways, leading to significantly improved conductivity in materials like CD-TpAzo.
Area of Science:
- Materials Science
- Chemistry
- Nanotechnology
Background:
- Covalent organic frameworks (COFs) show promise for proton conduction.
- Existing 2D COFs have limited 1D channels, hindering continuous proton transfer due to anisotropic grain interactions.
- The π-π stacking interactions in 2D COFs restrict efficient proton conduction pathways.
Purpose of the Study:
- To engineer 3D proton-transfer pathways within 2D COFs.
- To overcome the limitations of 1D channels in conventional 2D COFs.
- To enhance proton conductivity by reducing interlayer interactions and facilitating guest doping.
Main Methods:
- Incorporation of rotaxane structures, specifically interlocking α-cyclodextrin (CD) molecules, into a 2D COF (CD-TpAzo).
- Modification of interlayer stacking energy through the rotaxane architecture.
- Doping with phosphoric acid (H₃PO₄) to create proton conduction pathways.
Main Results:
- The stacking energy of 2D layers in CD-TpAzo was reduced from 154.2 to 55.2 kJ mol⁻¹.
- CD-TpAzo facilitated easier H₃PO₄ doping into its 3D channels and interlayers.
- CD-TpAzo@H₃PO₄-10 showed an eight-fold decrease in H⁺ spin-lattice relaxation time compared to TpAzo@H₃PO₄-10.
- Anhydrous proton conductivity of CD-TpAzo@H₃PO₄-18 reached 0.78 S cm⁻¹ at 150°C, surpassing pure H₃PO₄ (0.47 S cm⁻¹).
Conclusions:
- The rotaxane strategy effectively creates 3D channels in 2D COFs, enabling efficient proton conduction.
- Reduced interlayer interactions are key to facilitating guest doping and enhancing proton transfer.
- The developed COF materials exhibit superior anhydrous proton conductivity, suitable for advanced applications.
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