Ultrathin ionic COF Membrane via Polyelectrolyte-Mediated Assembly for Efficient CO₂ Separation

Fabricating ultrathin covalent organic framework (COF) membranes toward high-permeance molecular separations is highly desired yet challenging. Herein, a polyelectrolyte-mediated assembly (PMA) strategy is developed to fabricate ultrathin ionic COF membrane for efficient CO₂ separation. The PMA strategy allows a facile control over the assembly mode between polyethyleneimine (PEI) and TpPa-SO₃H, yielding PEI-bridged ultra-large COF nanosheets which are readily processed into COF membranes with thickness down to 8 nm. The resulting COF membranes exhibit a high CO₂ permeances of 1371 GPU and CO₂/N₂ selectivity of 33 for stimulated flue gas. This PMA strategy may open up a new avenue to fabricating ultrathin 2D material membranes for diverse applications.