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

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

Monomer Symmetry-Regulated Defect Engineering: In Situ Preparation of Functionalized Covalent Organic Frameworks for Highly Efficient Capture and Separation of Carbon Dioxide

Developing crystalline porous materials with highly efficient CO2 selective adsorption capacity is one of the key challenges to carbon capture and storage (CCS). In current studies, much more attention has been paid to the crystalline and porous properties of crystalline porous materials for CCS, while the defects, which are unavoidable and ubiquitous, are relatively neglected. Herein, for the first time, we propose a monomer-symmetry regulation strategy for directional defect release to achieve in situ functionalization of COFs while exposing uniformly distributed defect-aldehyde groups as functionalization sites for selective CO2 capture. The regulated defective COFs possess high crystallinity, good structural stability, and a large number of organized and functionalized aldehyde sites, which exhibit one of the highest selective separation values of all COF sorbing materials in CO2/N2 selective adsorption (128.9 cm3/g at 273 K and 1 bar, selectivity: 45.8 from IAST). This work not only provides a new strategy for defect regulation and in situ functionalization of COFs but also provides a valuable approach in the design and preparation of new adsorbents for CO2 adsorption and CO2/N2 selective separation