Biomimetic Mineralization-Inspired Polymer–Inorganic Nanohybrid Membranes for CO2 Separation

Hybrid membranes composed of continuous polymer phase and filler phase have been extensively studied for energy-efficient gas separation, especially for CO₂ separation, gasoline desulfurization, and alcohol dehydration, etc. The multiphase characteristics of composite membranes provide more degree of freedom to manipulate multiple interactions, tailor multiscale structures and integrate multiple functionalities, compared to pristine polymer membranes. Inspired by the silica formation process mediated by silica deposition vesicle (SDV) in diatoms or sponges, silica nanoparticles (SiO₂) were in-situ formed within poly(ether-block-amide) (Pebax® MH 1657) bulk matrix through the controlled biomimetic mineralization, using either protamine or cysteamine as inducer/catalyst. The free volume of the hybrid membrane could be tailored by varying doping conditions (e.g. the concentration of silicon precursor, mineralization time and pH value). In particular, nanohybrid membrane prepared by cysteamine as inducer exhibited simultaneously high CO₂ permeability, high CO₂/CH₄ selectivity and high mechanical stability. The as-prepared membrane displayed an optimum CO₂ performance with permeation flux of 138 Barrer and the selectivity of 46 for CO₂/CH₄ mixtures.