Solvent-Free Synthesis of C=N Linked Two-Dimensional Covalent Organic Frameworks.

Covalent organic frameworks (COFs) are an emerging class of porous crystalline polymers with well-defined structures and tunable functionalities, which have fascinating applications in a wide range of fields. However, the synthetic procedures of COFs are mainly confined to the solvothermal synthesis method which usually requires harsh experimental conditions. In this work, an effective solvent-free synthesis method to construct a series of two-dimensional (2D) COFs including imine-linked, azine-linked, β-ketoenamine-linked, which avoids the complicated solvent screening process and most of the disadvantages of solvothermal methods is developed. The crystallinity and porosity of these COFs are comparable to those prepared by traditional solvothermal routes. What's more, the advantages of the solvent-free method enable the production of gram-scale of those 2D COFs through a one-pot reaction, demonstrating high industrial application potentials.