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Pyrophosphoric Acid-Mediated Hydrogen-Bond Crosslinking: Design and Performance Breakthrough in High-Selectivity H2
Fengting Yao1, Mengfan Pei2, Ziheng Li1
1State Key Laboratory of Fine Chemicals, R&D Center of Membrane Science and Technology, School of Chemical Engineering, Ocean and Life Sciences, Dalian University of Technology, Panjin, Liaoning, China.
Small (Weinheim an Der Bergstrasse, Germany)
|July 30, 2026
Summary
A new hydrogen-bond crosslinking strategy using pyrophosphoric acid (PPA) overcomes the permeability-selectivity trade-off in polymer membranes for hydrogen (H₂) separation. This method enhances H₂ permeability and selectivity, surpassing the 2015 Robeson upper bound.
Area of Science:
- Materials Science
- Chemical Engineering
- Polymer Science
Background:
- Polymer membranes for hydrogen (H₂) separation face a critical permeability-selectivity trade-off, limiting their efficiency.
- Existing membranes struggle to balance high gas flux with precise molecular sieving capabilities.
Purpose of the Study:
- To engineer chain packing in polyimides (PI) for ultra-selective H₂ separation.
- To develop a supramolecular strategy to decouple the permeability-selectivity conflict in membrane technology.
Main Methods:
- Utilized a hydrogen-bond crosslinking strategy with pyrophosphoric acid (PPA) to modify 6FDA-TFMB polyimides (PI).
- Incorporated hydroxyl-rich PPA into rigid, non-coplanar PI with trifluoromethyl side groups.
- Employed collaborative simulation and experimental validation to analyze membrane structure and performance.
Main Results:
- Achieved a 4% compression of polymer chain spacing in the PI₂-PPA₁-60°C membrane, creating a graded chain-spacing architecture.
- Demonstrated exceptionally high H₂ permeability (167.24 Barrer) and significantly enhanced H₂/CH₄ (708.51) and H₂/N₂ (443.56) selectivity.
- The membrane performance surpassed the 2015 Robeson upper bound for H₂ separation.
Conclusions:
- The hydrogen-bond crosslinking strategy effectively engineers polymer chain packing for improved H₂ separation.
- This approach provides a viable solution to the inherent permeability-selectivity trade-off in membrane-based gas separations.
- The developed membranes show promising potential for advanced industrial H₂ purification applications.
