Large-Scale and Rapid Processing of 3D COFs via 3D-Controlled Reaction–Diffusion Zones

Abstract

Covalent organic frameworks (COFs) are an emerging class of two-dimensional (2D) or three-dimensional (3D) porous structures. Most COFs are typically prepared via solvothermal methods involving long reaction times (>12 h) that generally result in unprocessable powders, significantly hindering their straightforward integration into devices and applications. Current processing methods for 2D COFs have not been implemented for 3D COFs, probably due to the lack of preassembly mechanisms among the 3D COF precursors during synthesis. Here, we report a pioneering synthetic environment that achieves two objectives: precise control over the reaction time of 3D COF precursors through controlled diffusion, ensuring the absence of turbulent mixing, and the ability to fine-tune the specific reaction zone where the reaction and controlled diffusion of the 3D COF precursors will occur. We further demonstrate that controlling these two features in 3D creates an unparalleled synthetic environment, allowing for a rapid one-pot synthesis of 3D COFs, with their formation occurring in less than a minute. Additionally, this approach yields self-standing 3D COF fibers on a centimeter scale, showcasing the versatility and potential of the approach presented for scalable production of 3D COFs as well as for their seamless integration into devices and patterning strategies.

Continuous flow synthesis and post-synthetic conversion of single-crystalline covalent organic frameworks

“…Compared to the highest yielding reaction conditions reported for the batch synthesis of 2D COF single crystals the flow synthesis approach offers a 2–3-fold increase in framework production rate and similar to the recent reports of 3D COF synthesis in microfluidic systems. 5,31 PXRD confirmed the high crystallinity of the yellow CF-TAPB-DMPDA COF with a sharp diffraction at 2.78 2 θ degree angles corresponding to the (100) facet of a primitive hexagonal lattice (Fig. 3b and S22†).…”

“…5,29,30 Recently, high quality 3D-COF fibers with micrometer particle sizes were realized in a continuous microfluidic synthesis approach with reaction times of just a few seconds showing promise of this strategy in the scaling of COF preparation. 31…”

Covalent Organic Framework-Based Materials for Advanced Lithium Metal Batteries

“…Conjugated 3D COFs remain scarce primarily because of the exacting synthesis conditions required for their direct construction from building blocks. The lack of efficient preassembly mechanisms among 3D COF precursors during synthesis likely hinders the development of a streamlined process specifically designed for the synthesis and processing of 3D COFs. − …”