2D layered double hydroxide membranes with intrinsic breathing effect toward CO2 for efficient carbon capture

2D material membranes with well-defined interlayer nanochannels hold great promise for precise molecular separation, where the size and surface chemical property of the channel determine the separation efficiency. The currently reported 2D material membranes for efficient CO2 separation are primarily built by introducing crosslinkers or intercalators into the interlayer channel. In this study, we demonstrate a novel 2D material membrane with inherent CO2-selective transport channels based on layered double hydroxide (LDH). The intrinsic breathing effect of LDH toward CO2 enables the spontaneous incorporation of CO2 molecules into the interlayer nanochannels and subsequent conversion/transport in the form of CO32- species which are released as CO2 at the downstream side of membrane. Moreover, the intercalated CO32- ions with an ionic radius of 0.136 nm narrow down the nanochannel size from 0.7 nm to 0.3 nm by electrostatic interaction with LDH layers, conferring the membrane a distinct molecular sieving ability for CO2/CH4 separation. The unique breathing effect and size-sieving effect jointly contribute to the high membrane separation performance with CO2 permeance of 150 GPU and CO2/CH4 selectivity of 33. This study is anticipated to extend the materials and strategies for design of the CO2 preferential transport channels in membranes.