Reaction induced self-separating metal catalysts – Wonder systems in 21st century catalysis

Abstract

The term Catalysis was first coined in the 19th century and has since been recognized as a fundamental field contributing to the greenness and sustainability of chemical processes. This inspiring field has many wonders. A discovery of the 21st century is reaction-controlled or reaction-induced self-separating (RISS) metal-based catalytic systems, essentially based on coordination compounds, which combine features of the two hemispheres of Catalysis, i.e. homogeneous and heterogeneous catalysis. Specifically, RISS catalytic systems involve homogeneous catalysis with facilitated mass transfer phenomena, and catalyst self-precipitation under ambient conditions, enabling its easy separation and reuse, without requiring energy intensive downstream processes (e.g., cooling bellow ambient temperature or use of precipitation agents to separate metal catalysts). This review discusses the wonders of RISS metal-based catalytic systems and their application in important chemical transformations, how these systems operate (e.g., factors triggering the transition between homogeneous and heterogeneous catalytic features), the types of soluble active metal species formed, and relevant aspects from a practical point of view, such as catalyst recovery yield and reuse. Gaps are identified which merit future research and innovation.