Challenge and Chance of Single Atom Catalysis: The Development and Application of the Single Atom Site Catalysts Toolbox.

ConspectusSingle atom catalysis has garnered widespread attention in the past decade. In general, single atom catalysis refers to a catalytic process involving the participation of single atom sites. A single atom site refers to an active site with only one metal atom playing the main role in the catalysis process. This metal atom is usually coordinated by other atoms in the active site and anchored on the support. Heterogeneous catalysts in which all active sites are single atom sites are referred to as single atom site catalysts (SASCs). Owing to their distinctive active site architecture, single atom catalysis has shown ultrahigh atomic utilization efficiency and unique catalytic activity and selectivity in many systems such as thermal catalysis, electrocatalysis, and environmental catalysis.However, the preparation of SASCs poses significant challenges as metal species tend to sinter and agglomerate during high-temperature treatment. In the past decade, we have challenged the controllable preparation of SASCs based on more than ten years of experience in nanomaterial synthesis. Several representative SASC preparation strategies have been proposed by our group, such as pyrolysis of MOFs with metal ions doped in the skeleton, M@ZIF-8 with a metal precursor fixed by the host-guest interaction, and M/N-rich support precursors. Additionally, "top-down" strategies starting from metal nanoparticles have been established. Based on these synthetic strategies, a systematic SASCs toolbox has been successfully built.In addition to the SASCs, we have expanded the toolbox to include the dual-atom-site catalysts (DASCs) (including active sites with dual active metal atoms or including dual kinds of single atom sites) and nanosingle-atom-site catalysts (NSASCs) (catalysts with both single atom sites and nanoparticle/cluster sites). With the help of a variety of "tools" in the toolbox, single atom catalysis has shown its application value in many important processes such as bulk chemical catalysis, fine chemical catalysis, energy catalysis, and environmental catalysis. Based on laboratory-scale research, we further explored the feasibility of single atom catalysis in industrial catalysis and successfully applied single atom catalysis to industrial-level automobile exhaust purification, which will soon achieve commercialization.This Account provides a concise overview of the evolution of single atom catalysis, summarizes the preparation strategies for SASCs pioneered by our group over the past decade, and highlights the SASCs toolbox developed through these strategies. We also showcase the practical applications of the SASCs toolbox in key catalytic fields, highlight our progress in advancing the industrialization of single atom catalysis (particularly for automobile exhaust purification), and discuss the future prospects of single atom catalysis in industrial applications.