Mechanochemical Synthesis of Boroxine‐linked Covalent Organic Frameworks

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).