Enhanced dehydration performance of hybrid membranes by incorporating lanthanide-based MOFs

Metal-organic frameworks (MOFs) with high hydrolytic stability are highly needed to prepare polymer-MOFs hybrid membranes working in aqueous solution media. In this study, [Eu(BTB)(H2O)2·solvent]n (abbreviated as EuBTB), a kind of lanthanide-based two-dimensional MOFs, was utilized to prepare hybrid membranes for organic solvent dehydration owing to their hydrolytic stability arising from the relatively strong coordination bond between lanthanide ions and oxygen-containing groups. The detailed structure and properties of the hybrid membranes were well characterized. The hybrid membranes exhibited high mechanical strength and swelling resistance due to the strong interfacial interaction benefiting from the well complexation of EuBTB and sodium alginate (SA) through carboxylic groups. The horizontally aligned lamellar EuBTB could render ordered channels with the diameter of 0.5-0.8 nm. Each Eu3+ in EuBTB could coordinate two water molecules and serves as carriers to facilitate the transportation of water molecules. Moreover, the incorporated EuBTB could render decreased crystallinity. Accordingly, the hybrid membranes exhibited superior permeability and selectivity for ethanol dehydration. Especially, the membrane containing 5 wt% EuBTB exhibited an optimum performance with permeation flux of 1996 g/m2 h and separation factor of 1160 for 90 wt% ethanol aqueous solution at 350 K. Meanwhile, the hybrid membranes showed good long-term stability. This study may offer a generic and efficient approach to prepare MOFs-based hybrid membranes with high performance and stability for water-selective separation.