Mechanochemical Synthesis of Boroxine‐linked Covalent Organic Frameworks

Ehsan Hamzehpoor, Farshid Effaty, Tristan H. Borchers, Robin S. Stein, Xavier Ottenwaelder, Tomislav Friščić, Dmytro F. Perepichka

Abstract: We report a rapid, room-temperature mechanochemical synthesis of 2- and 3-dimensional boroxine covalent organic frameworks (COFs), enabled by using trimethylboroxine as a dehydrating additive to overcome the hydrolytic sensitivity of boroxine-based COFs. The resulting COFs display high porosity and crystallinity, with COF-102 being the first example of a mechanochemically prepared 3D COF, exhibiting a surface area of ca. 2,500 m2 g−1. Mechanochemistry enabled a>20-fold reduction in solvent use and ~100-fold reduction in reaction time compared with solvothermal methods, providing target COFs quantitatively with no additional work-up besides vacuum drying. Real-time Raman spectroscopy permitted the first quantitative kinetic analysis of COF mechanosynthesis, while transferring the reaction design to Resonant Acoustic Mixing (RAM) enabled synthesis of multi-gram amounts of the target COFs (tested up to 10 g).