Boosting Ion Exclusion of Two Dimensional TMD Lamellar Membranes via In-plane Engineering Strategy

Abstract Transition metal dichalcogenide (TMD) derived stratiform membranes exhibit sub-nanometer scale interlayer distances and exceptional anti-swelling property in water environments but they are frustrated in ion rejections. Herein, the in-plane regulating concept to improve ion exclusion of TMD laminates was proposed. We demonstrate this concept using flexible and hydrophilic polyvinyl alcohol (PVA) polymers as the intercalators to implant TMDs. The resulting TMD/PVA membranes show obviously decreasing ion permeation. Taking the TaS2/PVA membrane as an example, its monovalent, divalent and trivalent ion transport rates reduce by 87, 131 and 168 times respectively compared with the pristine TaS2 membrane. Additionally, the ion permeation behaviors of TMD/PVA membranes reveal long-term and cyclic stability. For the practical desalination process under the forward osmosis mode, the TaS2/PVA membrane shows an extraordinarily high water flux of 3.9 L m-2 h-1 together with a promising NaCl rejection of 98.7%, which is superior to the existing two dimensional membranes.