Multi‐Stage Structured PPTA/PPy@UiO‐66‐NH 2 /PEMs Composite Membranes for Organic Wastewater Treatment

ABSTRACT A poly(p‐phenylene terephthalamide) (PPTA)‐based solvent‐resistant composite nanofiltration membrane (PPMU membrane), namely PPTA/Polypyrrole@UiO‐66‐NH 2 /Polyelectrolyte Multilayers (PPTA/PPy@UiO‐66‐NH 2 /PEMs), was successfully fabricated via a two‐step strategy. First, polypyrrole (PPy) nano separation layers were in situ polymerized on PPTA surfaces using chemical vapor deposition (CVD). Subsequently, polyelectrolyte multilayer (PEM) membranes were constructed via layer‐by‐layer self‐assembly (LBL) on PPTA/PPy surfaces, with UiO‐66‐NH 2 metal–organic frameworks (MOFs) introduced to optimize membrane performance. Experimental results demonstrate that the PPMU(M5) composite nanofiltration membrane maintains high permeation flux while significantly enhancing rejection of small‐molecule dyes and inorganic salt ions. The rejection rates for CR, MB, and MO dye solutions are 99.70%, 94.59%, and 93.25%, respectively, while those for Na 2 SO 4 , MgSO 4 , and CaCl 2 reach 99.12%, 95.29%, and 85.09%, respectively. Additionally, the membrane exhibits excellent solvent resistance, retaining stable separation performance after immersion in organic solvents for one month. To address the low flux of PPTA/PPy nanofiltration membranes, the high porosity of UiO‐66‐NH 2 was leveraged to optimize mass transfer channels, while the LBL method was used to regulate surface charge and microstructure. This approach overcomes the traditional trade‐off between flux and rejection in nanofiltration membranes, achieving both high flux and high rejection. The strategy provides a new design paradigm for solvent‐resistant nanofiltration (SRNF) membranes in treating complex organic wastewater.