Desalination using conventional pressure-driven membranes for filtration has a number of drawbacks, including the need to overcome high osmotic pressures, which is technically challenging and energy demanding. Membrane pervaporation is a promising technique but, to date, membranes for this purpose have suffered from low desalination productivity and poor operational stability with concentrated brine feeds. Now, researchers in the Schools of Chemistry and Chemical Engineering at the University of Sydney, University of New South Wales and University of Cambridge, UK, have shown that the incorporation of defective aluminium fumarate metal–organic frameworks (MOFs), known as MIL-53s, into polyvinyl alcohol pervaporation membranes effectively promotes freshwater production from concentrated brines, with salt rejection of >99.999% (Liang W., Li L., Hou J., Shepherd N.D., Bennett T.D., D’Alessandro D.M., Chen V. Chem. Sci. 2018, 9, 3508–16). The engineering control of defects in MOF structures was achieved by facile microwave synthesis techniques to produce materials with hierarchical porosity. This work provides evidence that topological engineering of MOF surfaces is related to their physical and chemical behaviour in a polymeric matrix, opening up the possibility of MOF defect engineering to realise selective separations, drug delivery, catalysis and sensing within a polymeric matrix.