Polyphenol-modified MXene membrane with Ag nanoparticles intercalation for high-performance nanofiltration

Lamellar membranes fabricated through the layer-by-layer stacking of two-dimensional nanosheets hold great promise in the field of nanofiltration (NF) owing to the existence of abundant nanochannels that function as excellent nanofilters. However, the NF performance of these lamellar membranes is severely limited by the irregularity of the nanochannels and the stacking defects of the nanosheets. To address this issue, a facile approach was proposed in this study, which involved the modification of lamellar MXene membranes intercalated with Ag nanoparticles (Ag@MXene) using tea polyphenols (TPs). Upon the TP modification, the initial wrinkles present in the MXene nanosheets were flattened, which effectively reduced the stacking defects and increased the regularity of the nanochannels. Consequently, the water permeability of the TP-modified Ag@MXene (Ag@MXene-TP) membrane significantly increased up to 137.7 Lm−2 h−1·bar−1, a value that was three times the permeability of the pristine MXene membrane. Importantly, the Ag@MXene-TP membrane maintained a high dye rejection rate, with values of 95.85% for Rhodamine B and 97.30% for Congo Red. Molecular dynamics simulations further elucidated the underlying mechanism for the water permeability enhancement. It was found that the adsorption of TPs on the MXene surface prevented the aggregation of MXene nanosheets by shielding the electrostatic attraction between the MXene nanosheets and the Ag nanoparticles. In addition, the enhanced regularity of the nanochannels was also found to cause largely reduced water transport resistance. This pre-modification strategy of MXene nanosheets with TPs provides a new way to build MXene-based nanochannels with improved regularity for high-performance NF membranes.