Exfoliation-free layered double hydroxides laminates intercalated with amino acids for enhanced CO2 separation of mixed matrix membrane

Harvesting energy from biogas is a potential way to retard the depletion of fossil fuels and fight against global warming simultaneously. Membrane technology holds great promise to achieve cost-effective biogas upgrading, along with advantages of low energy consumption and environmental friendliness, which leads to extensive exploration in fabricating CO2 membranes with high separation performance. In this study, mixed matrix membranes are fabricated by incorporating exfoliation-free layered double hydroxides laminates intercalated with amino acids (Phe with hydrophobic side chains and Glu with hydrophilic side chains) into a low-cost commercial Pebax (poly (amide-b-ethylene oxide)) polymer. Both amino and carboxyl groups can facilitate the transport of CO2 through quadrupole moment interaction, enlarged interlayer spacing and reversible reaction. Particularly, MMM containing 5 wt% AA-LDH exhibits an optimal permeability of 790 Barrer and a promising CO2/CH4 selectivity of 31, which is 64.6% and 83.9% higher than the pristine Pebax membrane, respectively. The distinct advantages in terms of facile fabrication and processability confer the LDH-based membrane with great potential for large-scale CO2 capture and separation. [Display omitted] •Exfoliation-free LDH with intrinsic ordered 2D interlayer channels was prepared.•Amino acids with different hydrophilicity are intercalated into LDH (AA-LDH).•Enlarged d-spacing is conducive to the diffusion of CO2 in interlayer channels.•Basic and acidic groups of amino acids both facilitate the transport of CO2.•AA-LDH based MMMs exhibit largely enhanced gas separation performance.