Water-Assisted Microwave Synthesis of Imide-Linked Covalent Organic Frameworks in Minutes

Abstract

Solvothermal synthesis has been dominant for covalent organic frameworks (COFs) in the past decades. However, it requires high temperatures, harmful organic solvents, sealed pressurized reactors, and a long reaction time (from days to weeks). Herein, we report a solid-state strategy to synthesize imide-linked COFs rapidly. Utilizing water-assisted microwave synthesis, the process is remarkably fast, with one COF synthesized in merely 1 min. This method eliminates the need for toxic organic solvents and significantly shortens the reaction time. Using the water-assisted microwave method, we synthesized four previously reported COFs. The crystallinity and porosity of these COFs are comparable to or better than those made by the reported procedures. The generality of our synthetic method is shown in the preparation of three new imide-linked COFs. Finally, a microwave-synthesized COF@CNT composite acts as an excellent cathode material for lithium-ion batteries, showing a specific capacity of 154 mAh g^-1 at an ultrahigh current density of 10 A g^-1 (equivalent to 26 C), which can maintain a specific capacity of 128.59 mAh g^-1 after 10,000 cycles. This excellent stability and durability under extreme operational conditions make the material highly suitable for applications requiring rapid charging and discharging. The speed, ease, and generality of this water-assisted microwave method, together with improved material quality, enable the rapid discovery of functional imide-linked COFs.