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

Abstract

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 H2 and unsaturated substrates using Mott-Schottky heterojunction between Pd NPs and the semiconducting polymer, with the help of Pd(II)-site-mediated η-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.