Carbon Capture Membranes Based on Amorphous Polyether Nanofilms Enabled by Thickness Confinement and Interfacial Engineering

Abstract

Thin-film composite membranes are a leading technology for post-combustion carbon capture, and the key challenge is to fabricate defect-free selective nanofilms as thin as possible (100 nm or below) with superior CO 2 /N 2 separation performance. Herein, we developed high-performance membranes based on an unusual choice of semi-crystalline blends of amorphous poly(ethylene oxide) (aPEO) and 18-crown-6 (C6) using two nanoengineering strategies. First, the crystallinity of the nanofilms decreases with decreasing thickness and completely disappears at 500 nm or below because of the thickness confinement. Second, polydimethylsiloxane is chosen as the gutter layer between the porous support and selective layer, and its surface is modified with bio-adhesive polydopamine (<10 nm) with an affinity toward aPEO, enabling the formation of the thin, defect-free, amorphous aPEO/C6 layer. For example, a 110 nm film containing 40 mass % C6 in aPEO exhibits CO 2 permeability of 900 Barrer (much higher than a thick film with 420 Barrer), rendering a membrane with a CO 2 permeance of 2200 GPU and CO 2 /N 2 selectivity of 27 at 35 °C, surpassing Robeson's upper bound. This work shows that engineering at the nanoscale plays an important role in designing highperformance membranes for practical separations.

Scalable and Highly Porous Membrane Adsorbents for Direct Air Capture of CO2

“…Therefore, the l values from eq are the only way to indicate the PEI layer thickness, which increases from 38 to 293 nm as the loading increases from 18 to 62%. Figure b shows that the pore wall can significantly influence the polymer chain dynamics of the thin PEI films, , consistent with the improved thermal stability of the Solupor-confined PEI (Figure a).…”

“…ρ L (g/cm 3 ) is the density of n -decane (0.73 g/cm 3 ), and V MA (cm 3 ) is the volume of the sorbent sample. Pure-gas CO 2 permeance was determined using a constant-pressure and variable-volume apparatus at 15 psig and 35 °C …”

“…Pure-gas CO 2 permeance was determined using a constant-pressure and variable-volume apparatus at 15 psig and 35 °C. 37 Characterization of DAC Performance by TGA. The CO 2 sorption capacity of the membrane adsorbents was determined using TGA.…”

Low-Loading Mixed Matrix Materials: Fractal-Like Structure and Peculiarly Enhanced Gas Permeability

“…Pure-gas CO 2 and N 2 at desired flow rates were mixed in situ to obtain a binary gas mixture before being introduced to the permeation cell. Helium was used as a sweep gas on the permeate side, and the gas composition was measured by 3000 Micro GC (Inficon Inc., Syracuse, NY) . The uncertainty of the gas permeability was estimated to be less than 10% using an error propagation analysis …”

“…Helium was used as a sweep gas on the permeate side, and the gas composition was measured by 3000 Micro GC (Inficon Inc., Syracuse, NY). 48 The uncertainty of the gas permeability was estimated to be less than 10% using an error propagation analysis. 49 Gas sorption in MMMs was determined using a gravimetric method with an IGA 001 microbalance (Hiden Isochema, Warrington, U.K.) at 35 °C and three pressures (4.5, 7.9, and 11.4 bar).…”