Mixed-Matrix Membranes Containing Carbon Nanotubes Composite with Hydrogel for Efficient CO₂ Separation

In this study, a carbon nanotubes composite coated with <i>N</i>-isopropylacrylamide hydrogel (NIPAM-CNTs) was synthesized. Mixed-matrix membranes (MMMs) were fabricated by incorporating NIPAM-CNTs composite filler into poly­(ether-<i>block</i>-amide) (Pebax MH 1657) matrix for efficient CO₂ separation. The as-prepared NIPAM-CNTs composite filler mainly plays two roles: (i) The extraordinary smooth one-dimensional nanochannels of CNTs act as the highways to accelerate CO₂ transport through membranes, increasing CO₂ permeability; (ii) The NIPAM hydrogel layer coated on the outer walls of CNTs acts as the super water absorbent to increase water content of membranes, appealing both CO₂ permeability and CO₂/gas selectivity. MMM containing 5 wt % NIPAM-CNTs exhibited the highest CO₂ permeability of 567 barrer, CO₂/CH₄ selectivity of 35, and CO₂/N₂ selectivity of 70, transcending 2008 Robeson upper bound line. The improved CO₂ separation performance of MMMs is mainly attributed to the construction of the efficient CO₂ transport pathways by NIPAM-CNTs. Thus, MMMs incorporated with NIPAM-CNTs composite filler can be used as an excellent membrane material for efficient CO₂ separation

High-Performance Composite Membrane with Enriched CO₂‑philic Groups and Improved Adhesion at the Interface

A novel strategy to design a high-performance composite membrane for CO₂ capture via coating a thin layer of water-swellable polymers (WSPs) onto a porous support with enriched CO₂-philic groups is demonstrated in this study. First, by employing a versatile platform technique combining non-solvent-induced phase separation and surface segregation, porous support membranes with abundant CO₂-philic ethylene oxide (EO) groups at the surface are successfully prepared. Second, a thin selective layer composed of Pebax MH 1657 is deposited onto the support membranes via dip coating. Because of the water-swellable characteristic of Pebax and the enriched EO groups at the interface, the composite membranes exhibit high CO₂ permeance above 1000 GPU with CO₂/N₂ selectivity above 40 at a humidified state (25 °C and 3 bar). By tuning the content of the PEO segment at the interface, the composite membranes can show either high CO₂ permeance up to 2420 GPU with moderate selectivity of 46.0 or high selectivity up to 109.6 with fairly good CO₂ permeance of 1275 GPU. Moreover, enrichment of the PEO segment at the interface significantly improves interfacial adhesion, as revealed by the T-peel test and positron annihilation spectroscopy measurement. In this way, the feasibility of designing WSP-based composite membranes by enriching CO₂-philic groups at the interface is validated. We hope our findings may pave a generic way to fabricate high-performance composite membranes for CO₂ capture using cost-effective materials and facile methods