Development of high permeability nanofiltration membranes through porous 2D MOF nanosheets

Abstract

High-performance nanofiltration membrane is of great importance to alleviate the worldwide freshwater crisis. Recent studies have shown that the performance of nanofiltration membranes can be enhanced by optimizing the properties of the substrates. Substrates with large pores are favorable to mass transfer but difficult to prepare highly selective polyamide layers on them by interfacial polymerization reaction. Here we employed porous two-dimensional (2D) aluminum-metal organic framework (Al-MOF) nanosheets to tune the commercial Nylon microfiltration substrate, and then prepared polyamide nanofiltration membranes by interfacial polymerization. 2D Al-MOF nanosheets were chosen for the tuning material except for their obvious advantages of easy synthesis and structural stability, the most important thing was their high porosity, which provided additional water transport channels. The morphologies as well as the separation properties were analyzed systematically. The best-performing Nylon-2.5 TFC membrane achieved an ultrahigh permeability (42.4 L m−2 h−1 bar−1), 13 times that of a control (PES-0) TFC membrane prepared on commercial PES substrate under the same interfacial polymerization conditions while ensuring the high rejection of Na2SO4 (97.0%). Our work provides insights for optimizing substrate properties to prepare high-performance nanofiltration membranes.