(713f) Reversible Polycondensation-Termination Growth of 2D Covalent Organic Frameworks with Controlled Morphologies

The well-defined nanopores existing in Covalent organic frameworks (COFs) can precisely control the transport of molecules through them and make these materials promising for separations, gas storage, sensing, and catalysis. However, such applications are compromised by the low crystallinity and poor morphology control of COFs. Herein we introduce a new strategy called Reversible Polycondensation-Termination (RPT). With the RPT strategy, the spherical, fibrous, and centimeter-dimensions membranous COFs with highly ordered structures can be obtained by tuning the monomer concentrations, solvent species, and substrates. And we are able to fabricate a microreactor by depositing a thin COF film loading with metal nanocatalysts on the inner wall of a coiled copper capillary. This microreactor can efficiently reduce the nitrophenol in the continuous flow, and the catalytic activities are increased by more than one order of magnitude when compared with the same reaction carried in a batch setup. We also find that COF films demonstrate a fast and repeatable color change while exposing to water and organic vapors. The RPT strategy may lead to the controlled synthesis of COFs or even other polycondensates possessing a greater structural hierarchy, and thus be more favorable in catalysis, sensing, and other applications.