Tailoring Tröger's base membrane structures for high-efficiency mono-/divalent ion separation

Efficient ion-selective membranes are critical for numerous industrial applications, yet achieving simultaneous cation and anion separation remains a significant challenge. Tröger's base (TB) materials, featuring angstrom-scale channels, have emerged as a promising platform for precise ion separation. Herein, two trifunctional monomers, 1,3,5-tris(4-aminophenyl) benzene (TPB) and tris(4-aminophenyl) amine (TPA), were selected to fabricate crosslinked TB membranes. By tuning the TPA doping ratio (0, 50, 100 mol%), three distinct membranes (TPA0, TPA50, TPA100) with progressively reduced pore apertures were fabricated, owing to the more compact molecular architecture of TPA relative to TPB. As a result, TPA100 demonstrates a 4.8-fold enhancement in Li + /Mg 2+ selectivity (157 vs 33) compared to TPA0, along with universal mono-/divalent cations differentiation. Simultaneously, the near-electroneutral channels endow TPA100 with exceptional anion sieving capabilities, achieving high selectivity of 260 for OH − /WO 4 2− . This work not only elucidates the structure-property interplay in TB membranes but also establishes a versatile paradigm for advanced membranes capable of simultaneous cation and anion separation.