Liquid Metal Catalysts: A Unified Framework for Homogeneous and Heterogeneous Catalysis

Catalysis plays a fundamental role in most chemical transformations. However, traditional heterogeneous solid and homogeneous molecular catalysis systems generally suffer from limitations, such as coking, sintering, and thermal instability, to perform catalytic chemical transformations at high temperatures and pressures for long time periods. Liquid metal catalysts (LMCs) were proposed as an alternative class of heterogeneous catalysts that operate with low-melting-point metals such as Ga and In as a liquid solvent. In this liquid state, continuous active-site regenerability inherent to liquid systems provides inherent resistance against coking and sintering. Furthermore, liquid metals can serve as tunable liquid bases for atomic dispersion and alloying of active catalytic metals in a precise manner and can regulate their electronic structure and coordination environment. This review addresses key underlying principles of liquid metal catalysis, specifically dynamic interfaces and electronic flexibility, and assesses the advantages and challenges of top-down and bottom-up synthesis of LMCs, along with suitable operando tools that can be employed to monitor the activity of dynamic interfaces. Prospective future research opportunities for LMC applications in thermocatalysis, electrocatalysis, and photocatalysis, including designs based on single-atom or high-entropy alloys in liquid metals, are also discussed.