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

Abstract

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 2 -to NH 2 -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.

Arylene Ethynylene-Functionalized Bithiazole-Based Zinc Polymers for Ultraefficient Photocatalytic Activity

“…High-resolution TEM (HR-TEM) illustrated curved streaks with a lattice parameter of 0.369 nm that belongs to the interlayer distance of PAE (Figure 3c). 41 Meanwhile, selected area electron diffraction (SAED) pattern is shown in Figure 3d as well. The plane (100) is presented in the inset, and its intensity integrates to more than 360°.…”

Droplet microfluidics: from proof-of-concept to real-world utility?

“…These features, allied with the ability to vary the chemical payload of individual droplets, enable a range of complex synthetic processes to be performed in high-throughput. 81 The utility of droplets for producing monodisperse nanocrystalline materials has recently been showcased through the generation of a wide range of materials, including metal nanoparticles (such as Au, 82 Ag 83 and Pd 84 ) ceramic nanomaterials, 85 nanocomposites, 86 quantum dots, 87 organic nanomaterials, 88 metal-organic frameworks 89 and perovskite nanoparticles. 90 In all cases, care has been paid to developing systems that can cope with extreme conditions, such as high temperatures and aggressive reagents.…”

Approaches and challenges in the synthesis of three-dimensional covalent-organic frameworks

“…The first synthesis of 3D COFs, reported in 2007 again by Yaghi and coworkers, brought a new dimension to the field 32 . There have since been many reports describing new 2D COF structures 33,34 , novel synthetic strategies such as microwave synthesis 35 , flow synthesis [36][37][38] , and vapor-assisted synthesis 39,40 , and construction and modification of 2D COFs towards applications including catalysis 41,42 , membrane fabrication 43 , and gas storage 44 . In comparison, there have been only a handful of new 3D COF structures reported, and little beyond structural explorations and preliminary applications.…”