Organic-inorganic hybrid two-dimensional membranes with enhanced solvent flux and stability

Abstract

Two Dimensional membranes, which are usually constructed by inorganic nanosheets, have shown great potentials in efficient separation of low-molecular-weight chemicals. In this study, a novel type of organic–inorganic hybrid two-dimensional membrane is designed and prepared by co-assembly of a two-dimensional organic building block, Dopa thin-walled microcapsule, and a typical inorganic nanosheet, MXene. The introduction of MXene not only increases the distance between adjacent Dopa microcapsules and improves the solvent flux of the membrane, but also improves the structural stability by modulating the chelation strength of MXene with the Dopa microcapsules. The optimal Dopa/MXene composite membrane shows good performance in the field of organic solvent nanofiltration (OSN), with a flux of 723 L m−2 h−1 bar−1 for methanol and reactive black rejection of more than 90%. All the Dopa/MXene hybrid membranes show better stability than MXene lamellar membranes and MXene/Dopa hybrid membranes (where Dopa microcapsule is inserted into MXene membrane), demonstrating the advantages of organic species in enhancing interfacial adhesion. More interestingly, since the chelation between Dopa and MXene mainly depends on the presence of TiO2 in MXene, the oxidation of MXene, which often raises concerns of instability, herein is found to further increase the rejection and stability of Dopa/MXene hybrid membranes with only slight decrease of solvent flux.