Poly(β-ketoenamine) membranes with interconnected microporosity for high-performance fluid separations

Thin-film composite (TFC) membranes fabricated via interfacial polymerization are a pivotal enabler for energy-efficient fluid separations. However, achieving both a high separation efficiency and solvent stability is challenging, as it requires the critical and precise tuning of the film microporosity and internal molecular interactions. Here, we present a molecular linkage engineering approach to designing high-microporosity and structurally rigid poly(β-ketoenamine) membranes. By integrating a three-dimensional (3D) shape-persistent triptycene scaffold (2,6,14-triaminotriptycene, TAT) and a hydroxyl-pendant trialdehyde linker (1,3,5-triformylphloroglucinol, Tp), the resultant TAT-Tp membranes exhibit an extraordinary surface area of 620.21 m²·g⁻¹, far exceeding those of traditional polyamide and polyimine counterparts. The high density of β-ketoenamine linkages promotes the creation of intra- and intermolecular hydrogen-bonding networks, thereby imparting remarkable structural stability and inducing ordered local regions. These improved structural attributes, coupled with high microporosity, endow these membranes with dual-function superiority: 99.1% desalination efficiency and 99.2% methyl orange rejection in methanol. Furthermore, the membranes exhibit a remarkable solvent resistance, retaining structural integrity after 30-d exposure to diverse solvents. Experiments and simulations reveal the critical role of substantially interconnected ultramicroporous voids within the rigid crosslinked networks in achieving this superior performance. This work provides a framework for engineering resilient poly(β-ketoenamine) TFC membranes for high-efficient multitasking fluid separations.