Turing Membranes Regulated by Intermolecular Hydrogen Bonding for Molecular Sieving

Membrane technology has garnered broad concern for its high process efficiency. This study presents an approach to control the microstructure and permselectivity of nanofiltration (NF) membranes by incorporating 18-crown-6 (18C6) or diaza-18-crown-6 (DA18C6). The hydrogen-bonding interactions between crown ethers and piperazine (PIP) decelerate the PIP diffusion during interfacial polymerization, forming thinner polyamide (PA) layers. Furthermore, the constrained PIP diffusion amplifies the differential diffusion kinetics between PIP and trimesoyl chloride, triggering diffusion-driven instability that generates nanoscale striped Turing patterns on the membrane surface. Computational analysis reveals DA18C6’s stronger hydrogen-bonding interactions with PIP compared to 18C6, resulting in its superior diffusion inhibition capability. Increasing hydrogen bond density or strength enhances the inhibitory effect of crown ethers on PIP diffusion and facilitates more distinct Turing structures. The crown ether-incorporated PA layers exhibit improved hydrophilicity and microporosity. Benefiting from the optimized physicochemical properties, the modified NF membrane exhibits noticeably enhanced water permeance while sustaining high Na2SO4 rejection. A 115% increase in water permeance is achieved with DA18C6 regulation. Particularly, DA18C6-regulated membranes demonstrate narrowed pore size distribution for precise molecular sieving. This work presents a straightforward strategy utilizing crown ethers for fine-tuning the membrane microstructure and provides fundamental insights into diffusion-mediated membrane fabrication.