Solvent‐Responsive Porous Organic Cage‐Based Membranes With Switchable Pore Openings for Molecular Sieving and Heavy Metal Recovery

ABSTRACT Porous organic cages are an innovative type of material used in membranes, characterized by their ability to generate high‐quality films, hierarchical porous structures, adjustable porosity, and varied functionalities. These materials with unique structures have garnered significant attention due to their ability to alter pore size in response to solvent or chemical stimuli. Here, solvent‐responsive porous organic cage‐based membrane (PCM) for heavy metal recovery and molecular sieving is demonstrated. PCM dominated membrane were fabricated on PTFE polymer support prepared from 1,3,5‐triformylbenzene and tris(4‐formylphenyl)amine in methanol as solvent at room temperature. PCM exhibits a low penetration of heavy metal ions (∼4%) and enhanced efficiency in rejecting dyes (94.5%) in water compared with methanol as a solvent. These solvent stimuli influence PCM to alter its pore size, which was confirmed using Powder X‐ray diffraction analysis. Investigations into dye removal studies revealed that the pore size of PCM decreased when the solvent transitioned from methanol to water, and this change was reversible. Moreover, the recovery of retained heavy metal ions achieving 52% recovery rate for Ni 2+ ions and 45.4% for Zn 2+ ions. This study presents the use of PCM for extracting heavy metal ions from water by adjusting the pore size via external stimuli.