Stimuli-responsive metal-organic polyhedra-based hydrogel membrane for switchable separations toward CO₂/H₂.

Abstract

Carbon capture is essential for producing blue hydrogen and syngas. However, designing a single membrane with dual CO₂-selective and H₂-selective separations has long been considered impractical because these modes rely on fundamentally different mechanisms. We report a stimuli-responsive membrane that overcomes this limitation by integrating two functional materials. A zirconium metal-organic polyhedron (Zr-MOP) polymerized hydrogel membrane was fabricated via a stepwise molecular-level blending and polymerization strategy, achieving excellent filler dispersion, strong interfacial compatibility, and good solution processability. The Zr-MOP cages reinforce the hydrogel hydrogen-bond network, enabling high CO₂-philic performance with a CO₂/H₂ separation factor of 44 and CO₂ permeability of 7025 Barrer. Upon dehydration, membrane shrinkage induces cage rearrangement and exposure of molecular sieving windows, switching the separation behavior to a highly H₂-selective mode with an H₂/CO₂ separation factor of 798. This transition is reversible and can be further regulated by pH stimuli. This work introduces a strategy for membranes with switchable and inverted separation functions.