Effects of metal size on supported catalysts for CO₂ hydrogenation

Catalytic CO2 conversion is an important way to realize the artificial carbon cycle, and loaded catalysts are promising candidates for the reaction. Modulating the catalytic performance of loaded catalysts by varying the metal size to maximize the CO2 conversion efficiency is a popular area of research but remains challenging because of the complicated precise synthesis of catalysts and the enigmatic elaboration of mechanisms at the molecular level. In this review, the structure-activity relationships of efficient CO2 conversion are discussed in detail, with special emphasis on single-atom and ultra-small nanocluster catalysts. We first discuss the dependence of the electronic and geometric structure of metals on their size and discuss the potential impact of these changes on catalytic performance. We then summarize the previous representative literature, using size effects in CO2 hydrogenation as a clue, and focusing mainly on how size effects affect product selectivity and activity in catalytic processes rather than synthesis. Finally, we present the challenges and prospects of this field.