Modulation on interlayer channels of LDH/polymer hybrid membranes for efficient CO2 separation

Two-dimensional (2D) nanosheets with thickness of one to several atoms serve as ideal building units for separation membranes. Assembling 2D nanosheets into layered stacks with well-defined spacing as molecular separation channels is still a huge challenge. Herein, we report the construction of ultrathin membranes with layered double hydroxides (LDHs) nanosheets, polyacrylic acid (PAA) and polyethyleneimine (PEI) alternately deposited on porous substrates based on layer-by-layer assembly. The chemical tuning of PEI leads to an accurate regulation of interlayer spacing in angstrom scale, resulting in selective nanochannels for CO 2 permeation. The laminar membranes with CO 2 transport-facilitated channels exhibit excellent gas separation performance and exceed the limit of the state-of-the-art membranes with CO 2 permeance of 1068 GPU (1 GPU = 1 × 10 -6 cm 3 (STP) cm −2 s −1 cmHg −1 ), CO 2 /N 2 and CO 2 /CH 4 selectivity of 126 and 330 respectively. It is revealed the as-prepared nanofilms with strong adsorption enthalpy overcome the energy barrier of CO 2 molecules entering into and diffusing through the nanochannels. The strategy demonstrated in this work would open up new avenues for effective CO 2 separation and capture in recycling of carbon resources.