Electronic Effects of Embedding Redox-Active Sites within Zirconium-Based Metal–Organic Frameworks

Abstract

Metal–Organic Frameworks (MOFs) have the capacity to immobilize and host a wide variety of catalysts and electrocatalysts. Therefore, it is important to understand the way catalysts behave once embedded in these frameworks, as well as the inherent electronic contributions of the frameworks themselves. Herein, a zirconium-based MOF, UiO-67-Mn(bpy)(CO)3Br, is utilized as a platform for studying the electronic effects of immobilizing Mn(bpy)(CO)3Br. The Mn(bpy)(CO)3Br units serve as redox-active sites and facilitate the migration of electron density through the framework. This research reveals that, under electrochemical conditions, there is significant electronic interaction between the Mn(bpy)(CO)3Br sites, which modulates the energy of the carbonyl stretching modes as more of the framework is reduced. Moreover, a framework-based reduction is observed at a more negative potential than the reduction of Mn(bpy)(CO)3Br. This reduction further alters the electronic environment of Mn(bpy)(CO)3Br and suggests that there is inherent redox activity within UiO-type frameworks to be considered when analyzing these systems.