Pushing Rubbery Polymer Membranes to Be Economic for CO₂ Separation: Embedment with Ti₃C₂T_x 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_x 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_x membranes are due to the formation of hydrogen bonds between Ti₃C₂T_x and Pebax chains, leading to the creation of the well-formed galleries of Ti₃C₂T_x nanosheets in the hard segments of the Pebax. The interfacial interactions and selective Ti₃C₂T_x nanochannels enable fast and selective CO₂ transport. Enhancement of the transport properties of Pebax-2533 and polyurethane when embedded with Ti₃C₂T_x further supports these findings.