Embedding Ag+@COFs within Pebax membrane to confer mass transport channels and facilitated transport sites for elevated desulfurization performance

In this study, covalent organic frameworks (COFs) are utilized as carriers to immobilize metal ions in facilitated transport membranes for organic solvent separation for the first time. SNW-1, a kind of COFs with high amount of amino groups, were loaded with Ag+ ions and then incorporated into Pebax matrix to prepare hybrid membranes. Under optimal conditions, 48.11 wt% of Ag+ was loaded onto SNW-1 through a facile approach, which greatly intensified the mass transfer of unsaturated penetrant molecules (thiophene) by pi-complexation. The channels within SNW-1 decreased the mass transport resistance and imparted the molecular sieving ability. The organic nature of SNW-1 optimized the interfacial affinity between filler and polymer, and rendered appropriate free volume properties. The membranes displayed simultaneously enhanced permeation flux and selectivity in pervaporation gasoline desulfurization. Especially, when the content of Ag+@ SNW-1 was 9 wt%, the optimum performance towards thiophene concentration of 1312 ppm under 60 degrees C, was achieved with permeation flux of 16.35 kg/(m(2) h) and enrichment factor of 6.8, which was increased by 78.5% and 30.0%, respectively, compared with pure Pebax membranes. In addition, the anti-swelling property of the membranes was improved and the membranes possessed superior long-term stability. This study demonstrates that COFs are superior carriers to immobilize metal ions within facilitated transport membrane for efficient liquid separation.