Enhanced catalytic performance of palladium nanoparticles in MOFs by channel engineering

Summary: The embedding of metal nanoparticles in MOFs is highly relevant in catalysis research. The MOF matrix prevents the NMP agglomeration. Furthermore, the MOF can easily be functionalized to design an optimal chemical environment for the benefit of a catalytic reaction. We report on a series of metal@MOF materials, namely Pd@CuBTC and Pd@CuBTC-Cnip, consisting of the structural prototype CuBTC (= [Cu3BTC2]; BTC = benzene-1,3,5-tricarboxylate). Pd NPs were incorporated by rapid “bottle-around-the-ship” encapsulation. Regulation of the microenvironment around the Pd NPs by using alkoxy-functionalized fragmented linkers H2Cnip (n = 3, 6, 10) allows to adjust the hydrophobicity. These modifications significantly improve the catalytic activity for alkene hydrogenation compared with Pd@CuBTC. Our work suggests that the “channel engineering,” i.e., the introduction of hydrophobic alkyl chains to the MOF linkers, increases the interactions with non-polar substrates, leading to a facilitated substrate diffusion in the host, which is an efficient way to optimize the metal@MOF catalysts.