Thin-film composite mixed-matrix membrane with irregular micron-sized UTSA-16 for outstanding gas separation performance

Low-cost, micron-sized particles still pose a barrier to their use in thin-film composite mixed-matrix membranes (TFC-MMMs) owing to their poor interfacial contact with the polymer matrix. Also, the particles are too large to be fabricated into the submicron-thick membranes. Herein, we report high-performing, TFC-MMMs based on a CO₂-philic comb copolymer, poly (tetrahydrofurfuryl methacrylate)–co–poly (poly (oxyethylene methacrylate)) (PTO), and an irregular, micron-sized, CO₂-selective metal-organic framework (MOF), UTSA-16. The PTO comb copolymer matrix exhibited excellent film-forming ability, adhesion properties and showed a good gas separating performance. The PTO comb copolymer also enhanced the dispersibility of UTSA-16 in an environment-friendly solvent mixture (i.e., ethanol/water), which did not adversely damage the underlying porous polymeric support. Despite the micron-scale particle size of UTSA-16, PTO copolymer completely covered the surface of UTSA-16 via strong interactions without any deep pore infiltration and exhibited excellent interfacial contact properties. Consequently, defect-free TFC-MMMs with a polymer thickness of 300 nm were successfully prepared on the porous support. The TFC-MMM with 10% filler loading exhibited excellent CO₂ permeance and selectivity, i.e., CO₂ permeance of 1070 GPU, CO₂/N2 selectivity of 41.0, CO₂/CH₄ selectivity of 17.2, outperforming the TFC-MMMs prepared with commercially available Pebax. All PTO-based MMMs, with the exception of the low content of UTSA-16 (5%), exceeded the gas separation performance required for post-combustion CO₂ capture process.