Sonochemical precursor engineering for scalable covalent organic framework synthesis.

Abstract

Covalent organic frameworks (COFs) are promising functional materials, yet scalable synthesis of highly crystalline COFs remains a persistent challenge because existing synthetic strategies primarily focus on direct framework formation. Here, we introduce sonochemical precursor engineering (SPE), a two-step processing strategy in which mild bath sonication generates amorphous precursors that are subsequently crystallized by vapor-assisted framework development. Using this approach, three representative imine- and β-ketoenamine-linked COFs were obtained with high crystallinity at scales approaching 10 g, and the representative TFP-TAT framework exhibited well-defined porosity and excellent chemical and hydrothermal stability. Structural characterization confirms that sonication generates amorphous precursors, which subsequently evolve into highly crystalline COFs while preserving the intended framework structure. Computational, spectroscopic, and photoelectrochemical analyses demonstrate that the synthesized COFs retain their intrinsic structure-property relationships, which are further validated through photocatalytic hydrogen evolution. By decoupling precursor formation from framework crystallization, this work provides a practical route toward gram-scale production of highly crystalline COFs and broadens the processing toolbox available for COF synthesis.