No abstract

A porous organic polymer with aminopyridine functionalities was designed to fabricate a stable, atomically dispersed Ir catalyst. This Ir-based SAC exhibits excellent catalytic activity during the liquid phase hydrogenation of CO 2 to formate, with a turnover number as high as 25,135 representing the best performance yet for a heterogeneous conversion of CO 2 to formate. The chemical structure of the Ir SAC is analogous to that of a homogeneous mononuclear complex catalyst, representing an intermediary between heterogeneous and homogeneous catalysis.

The catalytic performance of Cu/ZnO/Al 2 O 3 (CuZnAl) catalyst for CO 2 hydrogenation to methanol was investigated over a period of 720 h time-on-stream, which showed that the space time yield of CH 3 OH was decreased by 34.5% during the long-term testing. Different characterization techniques, including X-ray diffraction (XRD), scanning electron microscopy, high resolution transmission electron microscopy, X-ray photoelectron spectroscopy (XPS), and N 2 O adsorption experiments, were applied to study the deactivation reasons. XRD and N 2 O adsorption experiments indicated that there were no obvious changes in Cu particle size after the CuZnAl catalyst was exposed to reaction atmosphere for 720 h, while agglomeration took place on ZnO particles. XPS results revealed that part of the metallic Cu was oxidized to Cu 2+ . The CuZnAl catalyst deactivation was proved to be due to the comprehensive effect of Cu oxidation and ZnO species agglomeration during CO 2 hydrogenation to methanol.