Mechanochemical Transition from a Hydrogen-Bonded Organic Framework to Covalent Organic Frameworks

We reported the directed structural transformation of a hydrogen-bonded organic framework (HOF) to covalent organic frameworks (COFs) via a mechanochemical drive for the first time. The X-ray single crystal structure confirmed that the hydrogen bonds afford a 3-connected amine building unit forming a HOF, namely, HOF-TPPA, with a hcb topology. The topological similarity between HOF and the targeted COFs facilitates the transition from HOF-TPPA to COFs (isotopological COF-TPPA-1, COF-TPPA-2, and COF-TPPA-3) under the mechanical grinding. Furthermore, the as-synthesized COFs exhibited broad light absorption, superior chemical stability, and excellent photocatalytic hydrogen evolution performance (45.429 mmol g–1 h–1). This work not only produced a series of novel large-channel two-dimensional multicomponent COFs but also provided new guidance for the green and efficient synthesis, as well as the functionalized applications of COFs.