High-efficiency CO2 separation using hybrid LDH-polymer membranes

Membrane-based gas separation exhibits many advantages over other conventional techniques; however, the construction of membranes with simultaneous high selectivity and permeability remains a major challenge. Herein, (LDH/FAS) n -PDMS hybrid membranes, containing two-dimensional sub-nanometre channels were fabricated via self-assembly of unilamellar layered double hydroxide (LDH) nanosheets and formamidine sulfinic acid (FAS), followed by spray-coating with a poly(dimethylsiloxane) (PDMS) layer. A CO 2 transmission rate for (LDH/FAS) 25 -PDMS of 7748 GPU together with CO 2 selectivity factors (SF) for SF(CO 2 /H 2 ), SF(CO 2 /N 2 ) and SF(CO 2 /CH 4 ) mixtures as high as 43, 86 and 62 respectively are observed. The CO 2 permselectivity outperforms most reported systems and is higher than the Robeson or Freeman upper bound limits. These (LDH/FAS) n -PDMS membranes are both thermally and mechanically robust maintaining their highly selective CO 2 separation performance during long-term operational testing. We believe this highly-efficient CO 2 separation performance is based on the synergy of enhanced solubility, diffusivity and chemical affinity for CO 2 in the sub-nanometre channels. Membrane-based gas separation exhibits many advantages over other conventional techniques but the construction of membranes with simultaneous high selectivity and permeability remains a major challenge. Here, the authors propose a layered double hydroxide (LDH)-polymer hybrid membrane, which shows improved CO 2 permselectivity.