Construction of modularized catalytic system for transfer hydrogenation: Promotion effect of hydrogen bonds

The construction of enzyme-mimicking catalysts is a crucial route for achieving green chemical transformations; however, integrating multiple sites into one catalyst is challenging. Herein, a facile method is reported to combine different active sites by constructing a modularized catalytic system. A modularized catalytic system composed of covalent organic frameworks (COFs) and Cu2Cr2O5 exhibits remarkable efficiency in the transfer hydrogenation of cinnamaldehyde, with a selectivity of over 99% towards cinnamyl alcohol, surpassing the reaction rate of Cu2Cr2O5 by more than fourfold. The results of the mechanistic study and density functional theory calculations suggest that the enhanced activity of the modularized catalytic system is derived from the hydrogen bonds between the COFs and isopropyl alcohol, which promote isopropyl alcohol dehydrogenation and hydride transfer. In addition, the modularized catalytic system is efficient for various saturated and unsaturated aldehydes and could be replaced by different submodules. This study demonstrates the efficiency of a modularized catalytic system for mimicking the functions of enzymes in catalysis.