Forwarding the Molecular Design of Heterogeneous Catalysts
Tanja Cuk
ACS Central Science (First Reactions), 2018. DOI: 10.1021/acscentsci.8b00492.
Catalysis research has long been divided between homogeneous and heterogeneous catalysis. In homogeneous catalysis, reactivity arises from molecular catalysts in a homogeneous solution, while in heterogeneous catalysis reactivity comes from sites on a surface. The main advantage of homogeneous catalysis is the ability to design reaction sites within molecularly defined catalysts in order to achieve high catalytic activity, measured in the number of product molecules evolved per site per second (turnover frequency, TOF). However, homogeneous catalysis suffers from degradation of the molecular catalysts during the reaction, leading to a low number of total product molecules evolved (turnover number, TON). In comparison, heterogeneous catalysis has incredibly high TONs—so much so that discrete TONs are often impractical to report. A new, promising area of research is intended to combine the benefits of both homogeneous and heterogeneous catalysis by tethering the molecular catalyst onto a solid surface to achieve tunability, high TOFs, and high TONs.