Precisely regulating the Brønsted acidity and catalytic reactivity of novel allylic C–H acidic catalysts

Due to the lack of effective active centers, the catalytic performances of covalent organic frameworks (COFs) materials are rarely reported. In this work, on the basis of the acidic 1,1,3,3-tetratriflylpropene structure proposed by List et al. (Angew. Chem. Int. Ed. 2017, 56, 1411–1415), a series of allylic C–H acids with varied acidic strengths were theoretically designed by altering the terminal functional groups. The acidity of allylic C–H acids was found to be closely related to the electron-withdrawing capacity of terminal substituent groups. Furthermore, the probe molecule approaches and ethanol dehydration reactions were theoretically performed to evaluate the diverse acidity of allylic C–H acids as well as establish the structure–reactivity correlations of such catalytic systems. Moreover, benefiting from allylic C–H acids can be perfectly embedded into the framework structures of COFs, the versatile catalytic performances for these promising porous materials may be realized in the foreseeable future. This work may open up an avenue on the directed design and/or modification of these novel organic solid acid catalysts for practical applications.