Pt, Ir, Ru, and Rh Nanoparticles Supported on ZIF-67 Nanocubes for Evaluation of Hydrogen Spillover Ability of Noble Metals

The hydrogen spillover phenomenon offers a great potential for enhanced performance in heterogeneous catalysis involving hydrogenation. Despite this, the current applications of hydrogen spillover are usually only for demonstrative purposes and the appropriate metal elements are often chosen by trial-and-error screening. Therefore, herein we systematically study and rigorously compare the hydrogen spillover abilities of various metal nanoparticles (NPs) supported on ZIF-67 nanocubes (NCs) by analyzing the hydrogenolysis of ZIF-67 at elevated temperatures. In this investigation, we make our ultimate efforts to ensure that all factors influencing the hydrogen spillover and thus hydrogenolysis are constant, which is crucial to objectively compare the hydrogen spillover abilities of the studied metals. Finally, a controllable synthetic procedure is devised to anchor presynthesized 2 nm metal NPs onto the exterior surfaces of ZIF-67 NCs. On the basis of this protocol, we have successfully determined the relative ability of hydrogen spillover for a series of 2 nm noble metal NPs: Pt > Ir > Ru > Rh. It is important to recognize that the ZIF-67 NCs serve effectively as a detector (or a receiver) of the dissociated hydrogen, which can measure the amount of hydrogen atoms produced during the hydrogen spillover. Therefore, the findings of this study could guide the rational choice of metal materials in other catalytic hydrogenation reaction systems. Moreover, the hydrogen spillover abilities of a wide variety of metal elements with defined particle sizes can also be determined via devising similar procedures in future investigations.