Rapid Synthesis of Covalent Organic Frameworks with a Controlled Morphology: An Emulsion Polymerization Approach via the Phase Transfer Catalysis Mechanism

Covalent organic frameworks (COFs) with a periodic network of permanent porosity and ordered structures have witnessed enormous potential in many applications. However, the synthesis of COFs with controllable morphologies under mild conditions remains a critical issue. Herein, we report a novel strategy to synthesize β-ketoenamine-linked COFs by emulsion polymerization via phase transfer catalysis for the first time. This new approach employs commercially available pyridinium surfactants as emulsifiers for emulsion polymerization, which function as both catalysts and morphological regulators. By controlling the interfacial interaction in the emulsion, the TpPa-COF can be prepared into different morphologies, i.e., spheres, bowls, and fibers. Furthermore, the COF emulsion can be directly used to prepare a film by applying an electric field, providing a new route to prepare COF films. This phase transfer catalysis method also allows the synthesis of the TpPa-COF on a gram scale. The strategy is fast, facile, and effective in improving the morphology and particle size, providing a prospective route for the green preparation of functional COFs.