Intensified synthesis and post-synthetic modification of covalent organic frameworks using a continuous flow of microdroplets technique

Covalent organic frameworks (COFs) are two-dimensional/three-dimensional crystalline polymeric materials with diverse molecular backbones and topologies and are strong candidates for numerous applications. However, the ready availability of these materials is a challenge. The key issues are slow production rates, harsher and longer reaction conditions, and a need for post-synthetic modification to obtain desired molecular functionalities. Only a few studies, including those using microfluidic techniques, have focused on refining these factors, but these reports lack synthetic continuity and scalability. Herein, we present a fast, intensified and continuous synthesis and post-synthetic modification of β-ketoenamine-linked COFs by confining organic building units into moving microdroplets in a transparent capillary. This study introduces a one-step, facile approach to serially modify NO-toNH-substituted COFs in a fraction of the time, effort and cost of traditional methods. These results may stimulate the development of novel COFs with unique chemistries and functions for various applications.