Design of ultrathin cross-linked poly(ethylene oxide) selective layer for high-performance CO₂ capture

Cross-linked poly(ethylene oxide) (PEO) is a highly promising membrane material for CO2 capture, as it allows fast and selective CO2 transport. However, the facile fabrication of an ultrathin cross-linked PEO selective layer for thin-film composite (TFC) membrane to achieve high CO2 separation performance remains challenging. To address this issue, we reported the design of a soluble high-permeability cross-linked PEO polymer and the fabrication of it into an ultrathin CO2-selective layer through a simple coating technique. The as-synthesized cross-linked PEO polymer contains abundant poly(dimethylsiloxane) (PDMS) segments, leading to highly improved free volume and affinity towards CO2, which result in high CO2 diffusivity, solubility, and consequently high CO2 permeability (528 Barrer). TFC membranes with an ultrathin selective layer (similar to 128 nm) were successfully fabricated using the PEO polymer, leading to superior CO2 capture performance (CO2 permeance = 2650 GPU, CO2/N-2 = 20) for CO2/N-2 mixture separation in a long-term stability test, exceeding the target performance for carbon capture. Given their high separation performance, excellent stability, and scalable fabrication route, our PEO-based membranes hold great promise for post-combustion CO2 capture.