(378a) Two-Dimensional-Material Mixed-Matrix Membranes for Gas Separation

Two-dimensional (2D) materials, with atomic thickness and micrometer lateral size, are emerging building blocks for separation membranes. Extraordinary molecular separation properties for purifying water and gases have been demonstrated by developing 2D-material membranes, which attract a huge surge of interest during last a few years. As a prominent characteristic of 2D-material membranes, inter-layer space has been proved to play a significantly important role in molecular transport.

We introduced mixed-matrix approach to develop 2D-material membranes for gas separation, with particular focus on tailoring sub-nanosized interlayer spaces between nanosheets for fast and selective transport of gases. Two typical 2D-materials will be demonstrated in this presentation: graphene oxide (GO)¹ and MXene². First, membranes with fast and selective CO₂ transport channels of GO laminates were proposed based on the construction of hydrogen bonding between GO nanosheets and PEBAX chain. Notably, incorporating only 0.1 wt% GO could double the CO₂ permeability and CO₂/N₂ selectivity of pristine PEBAX membrane, transcending the 2008 Robeson upper-bound. Our explorations (e.g., TEM, positron annihilation and sorption) found that molecular-sieving of the interlayer spaces and CO₂-philic pathways of the GO laminates play critical roles in the enhancement of gas transport properties. Second, borate and amine intercalated MXene membranes with ultra-thin skin layer (~20 nm) were fabricated by a facile spin-casting assisted assembly technique. With finely tuned interlayer spacing and introduced CO₂-falicitate transport groups, the intercalated MXene membranes show excellent CO₂ separation performance that overcomes the CO₂/CH₄ upper-bound. The transport mechanism was also understood by analyzing the coefficients of sorption and diffusion. Our results demonstrate that 2D-material mixed-matrix membranes offer exciting opportunities for efficient gas separation.

References:

1. Angew. Chem. Int. Ed.54, 578-582 (2015).
2. Adv. Funct. Mater. 28, 1801511 (2018).