Pushing Rubbery Polymer Membranes To Be Economic for CO₂ Separation: Embedment with Ti₃C₂T MXene Nanosheets

Sustainable and energy-efficient molecular separation requires membranes with high gas permeability and selectivity. This work reports excellent CO₂ separation performance of self-standing and thin-film mixed matrix membranes (MMMs) fabricated by embedding 2D Ti₃C₂T MXene nanosheets in Pebax-1657. The CO₂/N₂ and CO₂/H₂ separation performances of the free-standing membranes are above Robeson's upper bounds, and the performances of the thin-film composite (TFC) membranes are in the target area for cost-efficient CO₂ capture. Characterization and molecular dynamics simulation results suggest that the superior performances of the Pebax-Ti₃C₂T membranes are due to the formation of hydrogen bonds between Ti₃C₂T and Pebax chains, leading to the creation of the well-formed galleries of Ti₃C₂T nanosheets in the hard segments of the Pebax. The interfacial interactions and selective Ti₃C₂T nanochannels enable fast and selective CO₂ transport. Enhancement of the transport properties of Pebax-2533 and polyurethane when embedded with Ti₃C₂T further supports these findings. The ease of fabrication and high separation performance of the new TFC membranes point to their great potential for energy-efficient CO₂ separation with the low cost of $29/ton separated CO₂.