A new form of interfacial polymerization to synthesize thin-film composite membranes realizes a more sustainable membrane preparation and improved nanofiltration performance. By introducing an ionic liquid (IL) as the organic reaction phase, the extremely different physicochemical properties to those of commonly used organic solvents influenced the top-layer formation in several beneficial ways. In addition to the elimination of hazardous solvents in the preparation, the m-phenylenediamine (MPD) concentration could be reduced 20-fold, and the use of surfactants and catalysts became redundant. Together with the more complete recycling of the organic phase in the water/IL system, these factors resulted in a 50 % decrease in the mass intensity of the top-layer formation. Moreover, a much thinner top layer with a high ethanol permeance of 0.61 L m(-2)  h(-1)  bar(-1) [99 % Rose Bengal (RB, 1017 Da) retention; 1 bar=0.1 MPa] was formed without the use of any additives. This EtOH permeance is 555 and 161 % higher than that for the conventional interfacial polymerization (without and with additives, respectively). In reverse osmosis, high NaCl retentions of 97 % could be obtained. Finally, the remarkable decrease in the membrane surface roughness indicates the potential for reduced fouling with this new type of membrane.

The Back Cover picture shows water purification using a thin‐film composite membrane prepared by using an ionic liquid as organic reactant phase. Water purification and desalination of saltwater receive increasing attention worldwide to meet the growing needs for fresh water. Thin film composite (TFC) membranes are the state‐of‐the‐art membranes in aqueous nanofiltration (NF) and reverse osmosis, the leading desalination technology. The membranes are now also being explored as energy‐saving replacement for distillations and as a waste‐free alternative for extractions and chromatographic separations. However, several environmental and energetic aspects of these TFC membranes, both in the fabrication process as in the membrane performance, are still a concern. The introduction of an ionic liquid during interfacial polymerization can overcome many of these drawbacks. More details can be found in the Full Paper by Mariën et al. on page 1101 in Issue 10, 2016 (DOI: 10.1002/cssc.201600123).