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. 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.