Amino acid-bonded Ti3C2Tx MXene nanofiltration membranes with superior antifouling property for enhanced water purification

MXene nanosheets have been identified as promising building blocks for high-performance nanofiltration (NF) membranes in water purification. Herein, we report a series of amino acid-bonded Ti3C2Tx MXene membranes with enhanced NF performance and antifouling properties via glycine (Gly), l-glutamic acid (L-Glu), l-lysine (L-Lys) or l-cysteine (L-Cys) modification. The physicochemical properties, separation performances and anti-fouling behaviors of the pure Ti3C2Tx MXene membrane, Gly-, L-Glu-, L-Lys- and L-Cys-bonded Ti3C2Tx MXene membranes were comparatively investigated. The stable Ti–N bonds were found between the amino acids and the MXene nanosheets and different amino acids lead to different properties of the corresponding membranes. While maintaining ultra-high rejections to various organic dyes, all the amino acid functionalized membranes exhibited enhanced water permeability (7.17–13.11 L m−2 h−1·bar−1) compared with that of the pure MXene membrane. Importantly, the Gly-bonded membrane showed the optimal separation performance with high salt rejections of 86.28 %, 81.36 %, 72.88 % and 66.82 % to MgSO4, MgCl2, Na2SO4 and NaCl, respectively, and the membrane also exhibited superior anti-fouling property with a flux recovery rate of 80.59 % to bovine serum albumin (BSA). The separation mechanism was further revealed which may offer a simple yet efficient way for enhancing 2D MXene-based NF membranes.