Deciphering the Growth Kinetics of Monolayer and Multilayer Covalent Organic Framework Membranes at Liquid-Liquid...

Interfacial synthesis is a promising strategy for fabricating ordered covalent organic framework membranes, yet the mechanisms driving their structural regulation remain elusive. Here, we employed coarse-grained molecular dynamics simulations combined with a dynamic bond model to elucidate the growth mechanisms of covalent organic framework membranes at liquid-liquid interfaces. By systematically varying monomer solubility and catalyst affinity to the oil phase, we constructed a qualitative phase diagram illustrating the observed formation regimes of oligomers, monolayer membranes, few-layer membranes, and multilayer membranes. Our results indicate that membrane thickness is closely associated with the reactant distribution: increasing monomer solubility in the organic phase or limiting catalyst penetration into the oil phase favors monolayer formation. High crystallinity is favored by a synergistic balance among adequate interfacial energy, moderate catalyst penetration, and moderate monomer solubility. Furthermore, balancing reaction reversibility to facilitate defect repair or utilizing lower monomer concentrations significantly enhances structural order. These results help understand the growth mechanism of covalent organic framework membranes at the liquid-liquid interface.