Understanding the roles of variable Pd(II)/Pd(0) ratio supported on conjugated poly-azobenzene network : from characteristic alteration in properties to their cooperation towards visible-light-induced selective hydrogenation

Selective hydrogenation of organic functionalities at environmentally benign conditions using visible light is of great industrial and economic significance. Herein we report visible-light-induced rapid, almost quantitative and selective hydrogenation of olefins to respective mono-reduced products using cooperative performance of Pd(0) nanoparticles (NPs) and Pd(II) ions evenly distributed on a newly synthesized conjugated mesoporous poly-azobenzene network. Role of variable Pd(0)/Pd(II) ratio on the properties of polymeric networks and their overall catalytic abilities is critically investigated. This is the first proposed example of cooperative hydrogenation by simultaneous activation of H-2 and unsaturated substrates using Mott-Schottky heterojunction between Pd NPs and the semiconducting polymer, with the help of Pd(II)-site-mediated eta-coordination. A control over selective mono-reduction of diene with identical double bonds was also obtained. The catalytic activity retained for other non-olefinic functionalities as well. (C) 2020 Elsevier Inc. All rights reserved