(285c) Tuning Nano-Confinement of Ionic Liquid Membranes for Highly Efficient CO2 Capture from Flue Gas

Membrane separation has attracted significant attention for CO₂ capture from flue gas because of its low energy consumption. Among all the membranes, facilitated transport membrane (FTM) is one of the promising candidates for highly efficiently separating low-concentration CO₂ from other inert gas, especially with the aid of water vapor. However, the loss of active species incorporated within FTM is always an issue. Amino acid ionic liquids (AAILs) may serve as an ideal active species for CO₂ transport due to their negligible vapor pressure, excellent thermal stability, and amino functional group in cation that can reversibly react with CO₂. In order to apply ionic liquid into membrane, we designed and fabricated a nano-confined structure utilizing a single-walled carbon nanotube and nitrogen-doped graphene oxide quantum dot (SWCNT/N-GOQD) to fix AAIL. The nano-confined space, modified by trapped N-GOQDs in SWCNT mesh, ensures excellent mechanical stability of infiltrated AAIL. Moreover, the confined space determines the formation of AAIL membrane selective layer and regulates the transport behavior of different gas components through AAIL membrane. The influence of temperature, relative humidity, and feed pressure on AAIL membrane separation performance was evaluated. Rationally designed AAIL membranes with regulated confinement effect exhibited excellent CO₂ separation performance with CO₂ permeance >1500 GPU and CO₂/N₂ selectivity >1000 for simulated natural gas flue gas separation. Separation performance of a 1,000-cm² AAIL membrane with stage cut was also evaluated, demonstrating enrichment of CO₂ from 4% to 95% (dry-base purity) with excellent stability over 100 h. We expect this “nano-confined” platform might provide new opportunities for developing membranes with high selectivity for highly efficient CO₂ capture from flue gas.