(97e) Thin-Film Composite Membranes Based on Poly(1,3 dioxolane) and Uio-66-NH2 for CO2/N2 Separation

Membrane technology has been pursued in gas separations, such as post-combustion carbon capture, and a key challenge is to fabricate thin film composite (TFC) membranes containing a defect-free selective layer (< 500 nm) with state-of-the-art manufacturing processes. For example, poly(1,3 dioxolane) (PDXLA) has been synthesized via photo-polymerization, which presents the CO₂ permeability of 200 Barrer and CO₂/N₂ selectivity of 60. The highly crosslinked structure makes it hard to be prepared as TFC membranes. Herein, we successfully synthesized high molecular weight PDXLA via reversible addition−fragmentation chain-transfer (RAFT) polymerization. The water-soluble PDXLA remains amorphous with a macular weight of 200 kDa. We successfully coated PDXLA selective layer (as thin as 140 nm) on the gutter layer of polydopamine (PDA) modified polydimethylsiloxane (dPDMS). The TFC membranes exhibited CO₂ permeance of 700 GPU and CO₂/N₂ selective of 35 at room temperature. Given the mixed matrix materials as a promising avenue for achieving the dual objective of high selective and permeance, the metal-organic frameworks (UiO-66-NH₂) were incorporated into the PDXLA selective layer. The smooth mixed matrix selective layer benefited from hydrogen bonding between amine in UiO-66-NH₂ and PDXLA. The effect of UiO-66-NH₂ size (25 to 160 nm) on the separation performance of PDXLA membranes was also investigated. For example, adding 5 mass% of UiO-66-NH₂ (25 nm) increases CO₂ permeance from 700 to 880 GPU and CO₂/N₂ selectivity from 35 to 70, in contrast, adding 5 mass% of UiO-66-NH₂ (160 nm) increases CO₂ permeance from 700 to 890 GPU and CO₂/N₂ selectivity from 35 to 52. This showcases the smaller particles with strong interaction potential benefits of fabricating high-performance TFC membranes.