Solvation‐Mediated Assembly for Large‐Scale Synthesis of Covalent Organic Framework Membranes

Covalent organic framework (COF) membranes featuring rigid frameworks and ordered channels have surmounted the dilemma of ion permeability and selectivity trade-off for traditional polymeric membranes. However, it remains a challenge regarding the scale-up synthesis of COF membranes and the understanding of dynamic formation mechanisms therein. We report a solvation-mediated assembly (SMA) approach to synthesize large-scale freestanding COF membranes with ∼2400 cm² and a tensile strength of ∼65 Mpa. The solvation-mediated nucleation, elongation, crystallization, and assembling processes are visualized via the in situ heating liquid transmission electron microscopy, which integrated with multiscale simulations provide elaboration on the solvation interactions during membrane formation. The as-prepared membranes demonstrate selective ion separation for high-salt water reclamation and rare-earth ions recovery, endowing potential for the practical application of COF membranes.