Nanoconfinement-engineered ZIF-8/polyelectrolyte gel hybrid membranes for high-efficient antibiotic separation

Rising global demand for antibiotics drives the development of nanofiltration (NF) membrane separation technology. However, traditional NF membranes face structural hurdles in practice, mainly the permeability-selectivity trade-off and poor separation precision for multi-component fermentation broths. We proposed a polyelectrolyte gel confined crystallization strategy to in-situ grow ZIF-8 crystals within a poly (acrylic acid)/polyethyleneimine (PAA/PEI) matrix, constructing a hybrid membrane (PAA/PEI@ZIF-8M) with high hydrophilicity, rigid interconnected pores, and good stability. By precisely controlling crystallization kinetics under nano-confinement, the membrane achieves synergistic integration of ZIF-8 molecular sieving and polyelectrolyte networks, and eliminates interfacial defects. The resultant PAA/PEI@ZIF-8M membrane exhibits a high water permeance of 35.3 L·m −2 ·h −1 ·bar −1 –12-fold improvement over the pristine PAA/PEI membrane, along with high selectivity for chlortetracycline hydrochloride (OTC)/sucrose (∼8.0) and OTC/NaCl (∼5.0). Simultaneously, ZIF-8 nanocrystals in PAA/PEI gel act as anti-deformation pillars, while covalent crosslinking and multiple coordination interactions form a stabilized network, resulting in a good and stable separation performance during long-term running process. Moreover, multistage purification tests confirm industrial feasibility, yielding OTC with 97 % purity and a 2-fold concentration increase, meeting pharmaceutical-grade standards. This strategy establishes a novel paradigm for designing stable and high-performance polyelectrolyte gel NF membranes, advancing sustainable antibiotic production.