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Ultrapermeable Thin Film Composite Membranes Enhanced via Doping MOF Nanosheets
preprintsubmitted on 07.01.2020, 23:35 and posted on 09.01.2020, 11:40 by Min Liu, Ke Xie, MITCHELL NOTHLING, Lianhai Zu, qiang fu, PAUL WEBLEY, GREG QIAO
Thin film composite (TFC) membranes have attracted increasing interest to meet the demands of industrial gas separation. However, the development of high performance TFC membranes within their current configuration faces two key challenges: (i) the thickness-dependent gas permeability of polymeric materials (mainly polydimethylsiloxane (PDMS)) and (ii) the geometric restriction effect due to the limited pore accessibility of porous substrates. Here we demonstrate for the first time that the incorporation of trace (~1.8 wt%) amounts of amorphous metal-organic framework (aMOF) nanosheets into the gutter layer of TFC assemblies can simultaneously address these two limitations, with experimental evidence revealing the creation of rapid gas diffusion pathways along horizontal direction. Leveraging this strategy, we successfully fabricated a novel TFC membrane, consisting of a PDMS/aMOF gutter and an ultrathin (~54 nm) poly(ethylene glycol) top selective layer via surface-initiated atom transfer radical polymerization (ATRP). The complete TFC membrane exhibits excellent processability and the highest CO2 permeance (1,990 GPU with a CO2/N2 ideal selectivity of 39) yet observed for a TFC membrane employing a PDMS gutter layer. This study reveals an avenue for the design and fabrication of a new TFC membrane system with unprecedented gas separation performance.