Mixed matrix membranes incorporated with polydopamine-coated metal-organic framework for dehydration of ethylene glycol by pervaporation

Abstract In order to solve the issue of incompatibility between metal-organic frameworks (MOFs) and polymer matrix, mixed-matrix membranes (MMMs) on the basis of a hydrophilic polymer poly(vinyl alcohol) (PVA) and a MOF with hydrophilic sulfonic acid group (SO 3 H-MIL-101-Cr) coated by a thin and uniform polydopamine (PD) layer were prepared for separation of organic solvent from aqueous solutions by taking ethylene glycol (EG) as an example. The PD layer can control the thickness effectively on the surface of SO 3 H-MIL-101-Cr through a self-polymerization of dopamine and enhance the compatibility between MOF and PVA due to the formation of hydrogen bond between the abundant amine groups in PD and the hydroxyl in PVA matrix. As a result, the prepared SO 3 H-MIL-101-Cr@PD-PVA MMM exhibits a largely improved water permeability of 7.05×10 −5  g m −1  h −1  kPa −1 (the water flux is 540 g m −2  h −1 ) and the selectivity is as high as 68.1 (the separation factor is 2864) for EG aqueous solution (water content: 10 wt%) separation at 343 K. Compared with those in pure PVA membrane, the water permeability and selectivity were increased by 483% and 567% respectively. To the best of our knowledge, this separation performance is superior to those in all of the reported membranes so far. Therefore, this interfacial modification of MOF fillers may be an effective way to enhance the PV separation performance of MMMs, which can be conveniently extended to prepare other kinds of membranes with advanced properties.