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

Abstract 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 CO 2 separation. The PMA strategy allows a facile control over the assembly mode between polyethyleneimine (PEI) and TpPa‐SO 3 H, 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 CO 2 permeances of 1371 GPU and CO 2 /N 2 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.