Functionalized ligands mediated microenvironment of Pd@UiO-66-X catalysts for ethanol upgrading to n-butanol

The upgrading of ethanol to produce n-butanol and other >C4 alcohols is a promising reaction. However, the development of efficient catalysts for this reaction has been slow. In this study, we prepared a series of Pd@UiO-66-X catalysts using ligands functionalized with electron-donating groups (–NH2 and –CH3) and electron-accepting groups (–H and –NO2). These functional groups play two roles in mediating the microenvironment of the Pd metal. Firstly, they regulate the electronic properties of the Pd metal, and secondly, they alter the hydrophilicity/hydrophobicity surrounding the Pd metal. The intrinsic electronic properties of the Pd metal significantly influence ethanol conversion, while the hydrophilicity/hydrophobicity surrounding the Pd metal is an extrinsic factor. As a result, the Pd@UiO-66-CH3 catalyst with a hydrophobic microenvironment around the electron-rich Pd metal exhibits the highest ethanol conversion and n-butanol yield among all the Pd@UiO-66-X catalysts. It also achieves an impressive >C4 alcohols yield of up to 47.7 %, which is the highest reported to date.