Detection of Hydrogen Spillover Over Pt Catalysts Supported on UiO‐66‐NO 2 Under Practical Conditions and the Corresponding Ligand Effect

Abstract

The existence and the roles of hydrogen spillover in heterogeneous catalysts under practical conditions are still under debate. This is particularly true for metal catalysts supported on metal‐organic frameworks (MOFs). Here, we prepared a Pt/UiO‐66‐NO 2 catalyst and a Pt/UiO‐66‐NH 2 catalyst by an impregnation method. The Pt particles were mainly on the external surface of UiO‐66‐NO 2 and UiO‐66‐NH 2 , which excludes the atomic‐scale intimacy between the functional groups and most of the Pt particles. We observed that the nitro groups in Pt/UiO‐66‐NO 2 were substantially reduced to amino groups above 270 °C under 1.0 MPa H 2 . Since the reduction of aromatic nitro compounds over the Pt catalysts is easy to occur, the observation not only provides an evidence for the existence of hydrogen spillover in the metal catalysts supported on the UiO‐66‐type MOFs under practical conditions but also demonstrates that the occurrence of hydrogen spillover in the catalysts requires high temperature. The Pt/UiO‐66‐NO 2 and Pt/UiO‐66‐NH 2 catalysts reduced at 300 °C behaved similarly in several hydrogenation reactions, which differed from that of the Pt/UiO‐66‐NO 2 catalysts reduced at 200 °C. Hence, we propose an indirect ligand effect of spillover hydrogen. It affects the catalytic performances of supported metal catalysts by affecting the functional groups of the supports.