In-situ formation of metal-polyphenol networks in MXene membranes for efficient molecular/ion sieving

This study proposes a bio-inspired in-situ cross-linking strategy to address the critical issue of swelling and structural instability in MXene two-dimensional (2D) lamellar membranes. By anchoring gallic acid (GA) onto MXene nanosheets via hydrogen bonding and subsequently coordinating cross-linking with Al 3+ ions, a robust three-dimensional GA-Al network is constructed between the nanosheets. This approach effectively transforms the inherently swellable, loosely stacked MXene assembly into a coordination-crosslinked reinforced lamellar architecture, successfully yielding structurally stable MXene/GA-Al composite membranes with excellent separation performance. The GA-Al network significantly suppressed interlayer swelling (the dry-wet d-spacing difference is only 1.2 Å), enabling precise sub-nanometer channel tuning, mitigating interlayer defects, and improving surface hydrophilicity. The optimized membrane achieved over 99% rejection of Congo red (CR), a pure water permeability of 120.0 L m −2  h −1 bar −1 , and outstanding separation factors of 1105 and 1403 for CR/NaCl and CR/Na 2 SO 4 mixed solutions, respectively. These results outperform most documented 2D lamellar and nanofiltration membranes. This work offers a new design paradigm for developing high-performance, anti-swelling 2D lamellar separation membranes.