Synergistic Covalent/Hydrogen-Bonded Dual-Network Architectures: Self-Healing Meets High-Performance CO2 Separation Membranes

Abstract

Ion gel membranes exhibit high efficiency and environmental friendliness for CO₂/N₂ separation, but their poor mechanical strength and inability to self-heal after physical damage hinder their industrial application. To overcome these limitations, we propose an efficient one-pot method for preparing dual-network (DN) ion gel membranes with enhanced gas separation and self-healing properties. This method involves constructing dual self-healing networks: the first network (FN), formed through a Schiff base reaction between O,O’-bis(2-aminopropyl)poly(propylene glycol)-block-poly(ethylene glycol)-block-poly(propylene glycol) (H₂N–PPG-PEG-PPG-NH₂) and 1,3,5-benzenetricarboxaldehyde (BTC), and the second network (SN), consisting of polyurethane (PU) featuring a quadruple hydrogen-bonded cross-linked network. By optimizing the ratio of the two networks to 5:2 and adjusting the ionic liquid content ([EMIM]TFSI) to 60 wt %, the resulting DN membrane demonstrates exceptional CO₂ gas separation performance, with a CO₂ permeability (P_CO2) of 726 Barrer and a selectivity (α_CO2/N2) of 23. This underscores the potential of this process for effective gas separation applications. Furthermore, compared to conventional ion gel membranes, the DN membranes exhibit significant improvements in mechanical properties and self-healing capabilities, while maintaining high CO₂ permeability and selectivity.