Elucidation of Macrocycle-Derived Covalent Organic Framework Film Formation through Interfacial Linker Exchange

Over the past decade, postsynthetic linker exchange (PLE) has emerged as a promising strategy for fabricating high-quality covalent organic frameworks (COFs), leveraging the principles of dynamic covalent chemistry (DCC). However, the synthetic challenges posed by the complex parent entities used in PLE, such as COFs and cages, often limit their broader applicability. Herein, for the first time, we demonstrate a facile 'macrocycle-to-COF' transformation from simple and scalable trianglimines via the PLE method at the liquid-liquid interface under ambient conditions. The interfacially grown free-standing COF films (ICOFs) possessed high crystallinity (crystalline domain size up to 47.9 ± 0.5 nm) and excellent porosity (specific BET surface area up to 2244 ± 12 m2 g-1). The interfacial dynamics and mechanistic aspects of the PLE-guided imine macrocycle-to-COF transformation were elucidated using a combination of in situ tensiometry, optical microscopy of the interface, and ex situ spectroscopic techniques. The macrocycle-derived COF film exhibited excellent solvent permeance. Thus, our study expands the synthetic scope of functional, processable COF materials and provides mechanistic insights into the crystalline framework formation at the liquid-liquid interface.