PdAu Nanoparticles Supported by Diamine-Containing UiO-66 for Formic Acid Dehydrogenation

Diamine-containing UiO-66 (UiO-66-(NH2)(2)) was utilized as a support to load PdAu nanoparticles (NPs) through a double-solvent strategy for the catalytic application in the dehydrogenation of formic acid. A variety of characterization results demonstrate that tiny PdAu NPs (below 1.1 nm) are successfully encapsulated inside the cavities of the Zr-based metal-organic frameworks (Zr-MOFs). The resultant Pd0.8Au0.2/UiO-66-(NH2)(2) catalyst affords a turnover frequency (TOF) value of 3660 h(-1) for hydrogen generation from formic acid at 323 K and could also work well at room temperature with a TOF of 980 h(-1), much higher than that of the reference catalyst derived from the monoamine-containing UiO-66 support and other MOF-supported Pd-based catalysts reported in the literature. In addition, Pd0.8Au0.2/UiO-66-(NH2)(2) exhibits very high stability against aggregation and can be easily recycled seven times without obvious loss in catalytic activity. The excellent catalytic activity and stability of Pd0.8Au0.2/UiO-66-(NH2)(2) should be mainly attributed to the presence of a higher concentration of amino groups throughout the whole frameworks of the Zr-MOFs, which can coordinate with the precursors of Pd/Au species during the process of catalyst preparation and can also efficiently inhibit the aggregation of the subsequently formed nanoparticles confined inside the cavities of UiO-66-(NH2)(2). This work demonstrates that the choice of suitable supports and preparation strategies plays a critical role in fabricating highly efficient and stable supported Pd-based NP catalysts for formic acid dehydrogenation.