Controllable Switch of Thermodynamic and Kinetic Growing Paths in Two-Dimensional Covalent Organic Frameworks

Based on dynamic covalent chemistry (DCC), the synthesis of covalent organic frameworks (COFs) is generally thought to be under thermodynamic control. However, the kinetically governed synthesis of COFs under unbalanced conditions has rarely been reported so far. For the first time, we found that the dedicated switch between thermodynamic and kinetic paths in the synthesis of two-dimensional (2D) COFs, implemented by modifying experimental parameters, would lead to products with disparate stacking profiles and macro-properties. In this study, we successfully synthesized several thermodynamic and kinetic COFs by modulating the solubility of monomers and sheet intermediates in the COF synthesis system through changing the length of alkyl side chains on monomers and the reaction temperature. Further, the transformation from kinetic to thermodynamic products was realized by a second solvothermal treatment under modified conditions. These results could provide an unprecedented approach to the structural and functional design of COFs.