Coordination engineering in single-site catalysts: General principles, characterizations, and recent advances

Summary

Single-site catalysts (SSCs) have long been considered to be promising candidates for heterogeneous catalysis due to the maximum exposure of metal sites at the catalytic interface and the well-defined active-site structure. Regulating the coordination environment of single-metal centers via the coordination engineering strategy is crucial to optimizing the geometric and electronic structure of active sites, thereby promoting the overall catalytic performance of SSCs. In this review, the unique features of up-to-date synthetic strategies for the preparation of SSCs are systematically summarized. The key role of advanced microscope and spectroscopy techniques in structure-performance relationship study is concisely introduced, with special emphasis on combining in situ characterizations and theoretical calculations during real-time catalysis. Then, we classify various coordination regulation strategies reported in the last decade into four basic categories, including first-shell coordination, second-/higher-shell coordination, unsaturated coordination, and dual-site collaboration engineering. Also, an in-depth discussion of the general principles and regulation mechanisms is provided. Lastly, recent advancements in state-of-the-art SSCs are overviewed under the different forms of metal-substrate interactions, along with challenges and perspectives in the emerging field.