Transversal nanochannel-enabled MXene laminated membranes for superior oil-water separation: A fluid mosaic cytomembrane inspired approach

Abstract

Transition metal carbide and nitride materials (MXenes) have been greatly appreciated for their facilely exfoliated and hydrophilic two-dimensional (2D) layered structure to fabricate laminated membranes for oil separation. However, the denser slits and longer interlayer transport of traditional MXene membranes usually result in the poor permeability and antifouling performance. Herein, a novel approach was developed by synthesizing ultra-thin MXene and ferroferric oxide doped molybdenum disulfide (FM) and subsequently embedding FM into MXene laminates. This method yielded additional transversal nanochannels that enable lateral transport in a manner akin to that of a mosaic transport protein. Additionally, the incorporation of FM resulted in the creation of extremely irregular surfaces that form extensive membrane structures, reminiscent of tightly packed phospholipid bilayers. The incorporation of flower-like FM composites with MXene laminates endowed the resultant membrane with improved interface hydrophilicity, intensive surface roughness and enhanced permeability. These effects synergistically contributed to an exceptionally high pure water flux of the resultant membrane (3.12 × 104 L m−2 h−1), surpassing that of the control membrane (6.15 × 103 L m−2 h−1) without FM by over 5-fold. Furthermore, the optimum membrane exhibited enhanced permeance to oil mixtures (3.75 × 103 L m−2 h−1) and emulsions (4.25 × 102 L m−2 h−1), with separation of over 99% remaining. Impressively, the permeability of severely fouled membranes could be restored by 99% under visible light, highlighting the admirable photocatalytic self-cleaning ability enabled by MXene and FM. The underlying mechanisms that account for the superior antifouling performance and self-cleaning ability of the laminated membrane were also elucidated by the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory. The facile fabrication strategy employing transversal transport laminates provides a remarkable approach for water purification and other fluidic separation applications.